Numerical simulation on the impacting and comminuting of coal based on LS-DYNA
numerical analysis method
numerical analysis methodNumerical analysis methods are techniques used to approximate the solutions of mathematical problems that cannot be solved analytically. These methods involve the use of numerical algorithms and computers to obtain approximate solutions. Here are some common numerical analysis methods:1.Interpolation:Interpolation is a method used to estimate the value of a function at a point based on the known values of the function at other points. There are various types of interpolation, such as linear interpolation, polynomial interpolation, and spline interpolation.2.Integration:Integration is the process of calculating the area under a curve. Numerical integration methodsapproximate the integral by dividing the region into small subintervals and calculating the area of each subinterval.3 Differentiation:Differentiation is the process of calculating the slope ofa curve at a point. Numerical differentiation methodsapproximate the derivative by calculating the slope of the line connecting two points on the curve.4.ODEs and PDEs:Ordinary differential equations (ODEs) and partial differential equations (PDEs) are equations that describe the evolution of a system over time or in multiple dimensions. Numerical methods are used to solve these equations, such as Euler's method, Runge-Kutta method, and finite element method.5.Simulation:Simulation is a technique used to model the behavior of a system or process. Numerical simulation methods use mathematical models and numerical algorithms to simulate the behavior of the system and predict its output.6Optimization:Optimization is the process of finding the best solution to a problem. Numerical optimization methods use algorithms such as gradient descent, Newton's method, and genetic algorithms to find the最优 solution.These are just some examples of numerical analysis methods. Numerical analysis is a broad field that encompasses many other techniques and applications. The choice of numerical method depends on the specific problem being solved and the desiredaccuracy and efficiency of the solution.。
海上作战体系仿真建模技术
第39卷第1期2017年2月指輝控制与仿真C o m m a n d C o n tro l &S im u la tio nYol. 39 No. 1Feb.2017文章编号：1673-3819( 2017) 01-0073-04海上作战体系仿真建模技术初阳，季蓓，窦林涛(江苏自动化研究所，江苏连云港222061)摘要:针对当前海上作战仿真模型体系不健全、建模方法单一等问题，本文从作战体系仿真对仿真模型的需求入 手进行分析，建立了海上作战仿真模型体系，并从多分辨率建模、多视图模型描述、模型全生命周期管理等三个方面 对体系对抗条件下的作战体系仿真建模技术进行研究，有效地支持了联合战役战术仿真推演系统的研发。
关键词：体系对抗；作战仿真；装备体系论证中图分类号:T P391. 9;E917 文献标志码：A D0I:10.3969/j.issn.1673-3819.2017.01.016Research on Simulation and Modeling Technologiesfor Warfare System of Systems at SeaCHU Yang，JI B e i，DOU Lin-tao(Jiangsu A utom ation Research In s titu te，Lianyungang 222061，C h in a)A b s t r a c t：A im m in g at the problem that cu rre n t sim u la tio n m odel system is not perfect and the m odeling m ethod is s in g le，fro m the com bat system s im u la tio n on dem and sim u la tio n m odel of a n a lysis，th is paper establishes a naval com bat sim u la tio n m odel system，and fro m the view po int of the m u lti-re s o lu tio n m o d e lin g，m u lti view m odel d e scrip tio n and m o d e llin g of whole life cycle management three aspects，research on system s im u la tio n m odeling technology u n der the system atic confrontation co n d itio n has m a d e，and e ffe ctive ly support fo r the Jo in t T a ctica l S im ulatio n System Research and developm ent.K e y w o r d s：system atic counterm easure;op erational s im u la tio n；equipm ent system dem onstration目前，由于一体化联合作战理论尚不成熟，联合战役作战下的体系对抗模型，尤其是适用于海上作战体系的模型尤为缺乏，主要体现在:海上作战体系需求与仿真建模需求无法一致转换；面向体系对抗仿真的模型体系构建困难；模型数量、种类繁多，没有形成统一的模型描述、开发标准和管理规范等。
impact造句
impact造句1、air impact moulding machine.2、Brinell impact hardness tester.3、impact (evaluation) report.4、impact cell mill.5、4.2.3.1 impact identification.6、Impact heat distortion temperature and low; temperature impact strength.7、That should lessen its impact.8、His impact reflected anonymous dedication.9、Cases having great impact nationwide.10、The impact has been lethal.11、Might they impact worker morale?12、The impact of "Griffinization" is twofold.13、Will implementing reliability negatively impact performance?14、Measuring impact in philanthropy is not easy.15、The word "Ilousy" has lost its impact.16、The impact on Indian society is grim.17、Equivalent Static Force of Ship Impact to Bridge Based on impact Numeric Simulati on-Fundamental Formula.18、It can impact on the relationship and that will impact on your children.19、Eco-tax Impact on Economic Life: A dynamic CGE analysis of the impact of Eco-tax.20、The effects of impact Angle, particle velocity, erodent size and impact time were de monstrated.21、Among the five steps the impact identification, impact prediction and impact evalu ation are most important. For each step there are different methods and considerations.22、Impact detecting resistors (141), (143) of an impact detecting circuit (104) detectac ounter electromotive force of a step motor (105) generated due to an impact.23、The effects of impact energy and impact times on the green density, the maximal impact force and the withdraw force of specimen were investigated.24、Don't try to quantify the impact of each individual kaizen.25、Where should we look for the impact of kaizen?26、Every kind of life style can impact on our body.27、DOI and CrossRef and their impact on scientific periodical publishing.。
翻译原文
20TH INTERNATIONAL SYMPOSIUM ON BALLISTICSORLANDO, FL, 23–27 SEPTEMBER 2002NUMERICAL SIMULATION OF THE PENETRATIONPROCESS OF GEOPENETRATORS INTO PREDAMAGEDCONCRETE TARGETSN. Heider11Ernst-Mach-Institut, Eckerstr. 4, 79104 Freiburg, GermanyTandem warhead systems consist of two components: a precursor shaped charge and a following kinetic energy (KE) projectile containing a high explosive filling. They are designed to penetrate hardened structures especially targets with concrete layers. The performance of the KE projectile depends strongly on the target damage due to the shaped charge jet penetration. At the moment there are no detailed reliable data about the damage available. This paper therefore analyses in a parametric way the influence of target damage (formation of crater hole as well as concrete material damage) on the achievable KE penetration performance. The simulations are based on an explicit modeling of the shaped charge jet crater with the crater profile deduced from experimental results. The crater shape and the damage level (reduced compressive strength of the concrete afterloading from the shaped charge jet) are varied parametrically. The numerical model is validated with experiments of KE projectiles intoplain concrete targets without pre damage. INTRODUCTIONA principal sketch of a tandem warhead system is shown in fig.1. The sequence of events during the impact of the tandem warhead is as follows:∙ Initiation of precursor shaped charge with jet formation∙ Interaction of jet with target (crater formation and damage of concrete around the crater)∙ Penetration of the following KE projectile into the pre damaged concrete target.A complete simulation of the tandem warhead function including the shaped charge jetpenetration is given in [1]. The theoretical description of the performance of the two tandem warhead components as a single weapon is already very good (within numerical as well as analytical modeling). Some uncertainties still exist for the tandem system especially concerning the interaction of the KE projectile with the damaged target. The analytical and empirical modeling of the tandem system therefore requires some better understanding of the target damage and its influence on the time history of the KE projectile penetration process. Due to the lack of detailed experimental and theoretical data on the damage distribution within the target it seems a reasonable approach to analyze the penetration process with the help of parametric variations of the relevant parameters describing the crater and the degree of damage in the concrete target material. This method allows the separate investigation of the influence of these physical parameters on the penetration depth of the KE projectile and a detailed understanding of the involved processes.Fig.1 Components of tandem warhead system Fig.2 Parameterization of carter ProfileEXPERIMENTAL BASISThe simulation model is based on experimental results of concrete penetration with shaped charge jets and KE projectiles.The explicit modeling of the damaged concrete target requires information about typical crater profiles created by the impact of the shaped charge jet. The crater profiles are taken from experiments where shaped charges were fired against concrete targets at a stand off of 3 calibers. The crater profiles are not very sensitive to stand off as soon as the maximum penetration depth as a function of stand off is reached. Even at high stand off values of 20calibers the crater profiles are still similar to the corresponding ones at 3 calibers. The tests have been performed with 80 mm caliber charges with aluminum liners and point initiation. Typical crater profiles have the following characteristics:Biconical profile (see fig.2)Spall crater at shaped charge jet impact surfaceErosion crater reaching to the final depth.The explicitly modeled crater profiles are derived from these data.The KE projectile penetration into undamaged concrete targets was used as avalidation case for the simulation model including the concrete material description.The following penetrator design was used:Caliber 60mmLength 508mmMass 6039gThe target consisted of two concrete blocks of diameter 96cm, length 1m and a steel casing. The concrete compressive strength was 35N/mm2 . The experimental results were (see [2] and [3] for experimental details and interpretation of penetration depth within cavity expansion theory):Impactvelocity 509m/secPenetration depth 114.5cmFig.3 shows the front and rear side of the target after impact of the KE projectile.Fig.3 KE projectile impact test: front and rear side of concrete target The corresponding results from the simulation are shown in fig.4 with the configurationat the time of impact and after the penetrator came to rest. The calculated penetration depth is 119 cm and agrees very well the experimental value of 114.5cm.Fig.4 Simulation: KE penetrator at impact and at end of penetrationSIMULATION MODELThe simulation model consists of the damaged target and the KE penetrator. Theperformance of the shaped charge jet is not explicitly modeled. Instead the crater profile andthe damage area around the crater are modeled explicitly. The simulation model used forthis application is based on the erosion crater because the radius of the spall crater issignificantly bigger than the radius of the KE projectile and thus has no influence on the KEprojectile penetration. The crater used in the simulations is thus characterized by twodiameters corresponding to target surface and the final penetration depth. These twoparameters can be varied to study the influence of crater diameter on the penetration process.As no date are available about the damage produced in the concrete target due to thepenetration of the shaped charge jet, the damaged region around the crater and the amount ofstrength reduction are additional variation parameters. The damaged area was assumedcylindrical with a certain depth and radius and a constant degree of damage within this area.These are three further variation parameters.The presented model parameters are deduced from experiments if possible and in theother cases are varied in a range that seems to be reasonable and interesting for he physicalunderstanding.The simulation contains the three materials: original concrete target, damaged concretetarget and the high strength steel penetrator case. The high strength steel is described with aJohnson Cook model for the deviatoric strength behavior. Very important is the material description of concrete. For this purpose the RHT model, developed at EMI is used .Concrete has the following experimental material properties:∙ Tensile strength is 1/10 of compressive strength∙ Shear strength is pressure dependent∙ Damage development (failure surface depends on damage due to preloading)∙ Porosity and existence of micro cracks between mortar and aggregatesThe description of these phenomena requires a complex model for the characterization of concrete. The EMI RHT model includes the static as well as the dynamic range and thus can be used for the penetration processes of KE penetrators.The following gives a short summary of the main properties of the model:∙ Porous equation of state∙ Limit surfaces pressure dependent (elastic, failure and residual strength)∙ Limit surfaces depend on all 3 invariants of stress tensor∙ Strain rate effectsFig.5 shows the schematic location of the different limit surfaces in the stress space especially the change of the failure surface due to damage development. Damage occurs as soon as the failure surface in the stress space is reached during a loading process. In the uniaxial compression test damage occurs in the stress strain diagram in the region following the maximum compression stress. The material behavior is then characterized by macroscopic crack development. The following phenomena have to be described:∙ Reduction of the failure surface with increasing damage (material with a complete damage can not sustain any tensile stresses any more)∙ Reduction of elastic constantsIn the following the presented modeling parameters are varied and their influence on the KE penetration depth is analyzed.SIMULATION RESULTSThe simulation variants analyzed are shown in fig.6. The reference case is simulation 1 with the original undamaged concrete target. Varied is the crater profile (simulation 2 and 7)and the damaged area around the crater (spatial extend and damage level, simulations 3 to 6 and 8 to 12). In addition a simulation 13 was performed with a semi infinite target to get information about the influence of the target size on the penetration performance.Influence of the crater diameter: fig.7 shows the penetration depth of the KE projectile as a function of the crater radius on the impact surface. The penetration depth from the simulation in the undamaged target is 1198mm (the corresponding experimental value is 1145mm). Modeling of the eroded crater profile (without damage in the region around the crater) gives an increase to 1251mm (crater radius 11.2mm) or 1404mm (crater radius22.4mm). Small hole diameters (compared with the projectile diameter) lead only to a small increase of the performance of the penetrator. Only hole diameters approaching half of the penetrator caliber significantly increase the penetration depth.Influence of strength reduction: fig.8 shows the penetration depth as a function of time for several simulations. Here the reference configuration 1 is compared with the simulation 6 where the model shows only a strength reduction (from 35MPa for the original concrete to10MPa for damaged concrete) but no crater hole in the target. The penetration depth increases from 1198mm to 1377mm. The increase is nearly as high as for simulation 2 with the crater profile modeled (penetration depth for simulation 2 is 1404mm). The strength reduction with a spatial extension of 2 penetrator calibers around the impacting projectile thus leads already to a significant performance increase.Combination of crater profile and strength reduction: fig.8 contains the simulations 1,3 and 4. This corresponds to the situation where crater profile and strength reduction occur together. The penetration depth increases from 1198mm (reference case) to 1458mm (simulation 3 with small damage area) and finally to 1467mm (simulation 4 with bigger damage area). Comparison with the former results shows that the combined effect leads to a relatively small additional increase of penetration.Material damage or crater hole alone give already most of the achievable performance gain. The combination shows an overmatch for the simulated configuration. Variation of the damage level from 10MPa to 5MPa gives an additional penetration depth increase (simulation 4 - 1467mm compared with simulation 5 - 1490mm). It is important to note that there is no linear addition of the contributions fromdamage and crater hole to the total penetration. The whole target damage in front of the penetrator determines the performance independent by which effect it is caused. If there is already a significant damage due to eroded material an additional material damage has only minor influence. On the other hand material damage alone is sufficient to increase the penetration depth significantly.Fig.6 Simulated crater profiles and damaged target areasInfluence of spatial extension of damage zone: the radial as well as the axial extension of the damage zone is varied. For the axial extension the two values of 637mm and 1000mm were selected. The crater hole profile itself was not changed. The dependence of the penetration on the radial extension of the damaged area is shown in fig.9. There is a sort of plateau formation at a radial distance of around 2 projectile calibers with a penetration increase of around 250mm. The 2 significantly lower values at the radial distance at 50mm correspond to the axial damage extension of 637mm.This shows the importance of the radial as well as the axial extension of the damaged target regions on the penetration.Fig.5 Schematic representation of Fig.7 KE projectile penetration aslimit surfaces of concrete a function of crater radiusFig.8 Time history of KE Fig.9 KE projectile penetration asprojectile penetration a function of damage radius Influence of target dimension: a final simulation 13 was done which modeled a target with semi infinite extension (simulated with corresponding boundary conditions). The penetration is 1104mm and has to be compared with the value of 1198mm from the reference simulation 1. It gives an impression of the expected variation of performance of KE projectiles in real targets where different impact conditions are found. The decrease of penetration is due to the higher confinement and the reduced effects from the target boundaries.SUMMARYThe performance of the precursor shaped charge in a tandem warhead systems leads to a weakening of target (formation of crater hole and material damage). The development of engineering codes for the description of the tandem system requires a detailed understandingof the separated effects. Therefore a finite element model was developed that is based on experimental results and includes an explicit modeling of the crater profile and damaged region around the crater. The model allows the parametric analysis of the target weakening on the penetration of the KE projectile.Following conclusions can be drawn:∙ The penetration depth increase of the penetrator is not a linear combination of eroded crater and damage around the crater. In the analyzed parameter range both effects alone lead nearly to the final penetration depth.∙ Penetration increases slowly with crater diameter and reaches significant contributions at crater diameter larger than half of the penetrator caliber.∙ The damage area (radial and axial extend) influences the penetration depth with the effects being strongly pronounced when the damage area is significantly larger than the penetrator caliber.REFERENCES1. N. Heider, S. Hiermaier, Numerical Simulation of the Performance of Tandem Warheads,Proceedings of the 19th International Symposium on Ballistics, 807-815, 20012.N. Heider, U. Günther, Modern Geopenetrators and Relevant Revision of Concrete Penetration Models, Proceedings of the 5th International Symposium on Structures Under Shock and Impact (SUSI), 807-815, 19983.K. Kleinschnitger, C. Mayrhofer, E, Schmolinske, Modellversuche mitKE-Penetratoren gegen Betonziele, Internal EMI Report E 8/94, 19944.W. Riedel, Beton unter dynamischen Lasten Meso-und makromechanische Modelle und ihre Parameter, Dissertation Universität der Bundeswehr, 143-166, 2000。
平头弹撞击角度对2A12-T4铝合金板失效特性影响的数值模拟
平头弹撞击角度对2A12-T4铝合金板失效特性影响的数值模拟胡静;邓云飞;崔亚男;张银波【摘要】利用有限元软件ABAQUS建立模拟模型,开展38CrSi钢弹体撞击2A12-T4铝合金板数值模拟研究,分析撞击过程中弹体撞击角度对弹道姿态及靶体失效特性的影响.基于数值仿真和实验结果,分析靶体的失效特性,确立不同撞击条件下靶体主要失效模式的转变规律,以及由此对靶体抗撞击性能的影响.研究结果表明:弹体的弹道极限速度随其撞击角度的增大先减小后增大,弹道极限速度在撞击角度约为15°时达到最小值;弹体撞击角度对靶体失效模式存在很大影响,随着弹体撞击角度的增大,靶体主要失效模式由剪切破坏逐渐过渡到撕裂破坏,靶体的撕裂程度不断加剧;弹体初始撞击角度和速度对其在撞击过程中的弹道姿态存在影响,在弹道极限速度附近表现尤为显著.%A simulation model was established using finite element software ABAQUS,and the numerical simulations of 38CrSi steel projectile impacting 2A12-T4 aluminum alloy plates were conducted, then the influences of impact angles of projectile on the failure characteristics of target and ballistic attitude of projectile were analyzed.Based on numerical simulation and experimental results,the failure characteristics of the target were analyzed,the change laws of the dominant failure modes under different impact conditions,as well as the influences on the impact resistance of target because of that were established.The results show that with the increases of impact angles the ballistic limit velocity decreases,and then increases,and the ballistic limit reaches the minimum when the impact angle is about 15 degrees. In addition,the impact angle ofprojectile impacting greatly influences the failure mode of target,with the projectile angle increases,the dominant failure mode of target changes from shearing to tearing,and also increasing the degree of tearing the target.The initial impact angle and velocity of projectile have great influences on the trajectory attitude of the projectile during the impacts,especially in the vicinity of the ballistic limit velocity.【期刊名称】《中国机械工程》【年(卷),期】2018(029)009【总页数】6页(P1050-1054,1062)【关键词】撞击;2A12-T4铝合金板;平头弹体;失效模式【作者】胡静;邓云飞;崔亚男;张银波【作者单位】中国民航大学航空工程学院,天津,300300;中国民航大学航空工程学院,天津,300300;中国民航大学航空工程学院,天津,300300;中国民航大学航空工程学院,天津,300300【正文语种】中文【中图分类】O385;O3470 引言弹靶撞击属于经典的冲击动力学问题，撞击结果受到多种因素的影响，如弹靶材料力学性能、靶体结构、弹体几何形状、弹体撞击角度与速度等。
Experimental and numerical investigations on the influence o
can occur, e.g. either occasionally paired with an overload (mixed mode overload) or permanently in terms of a mixed mode block loading as a combination of normal and shear stresses. By means of this change, the lifetime is influenced as well. Only few investigations of such mixed mode loading change effects on the lifetime are described in the literature [e.g. 3–6]. Within the scope of this paper, firstly the influence of mixed mode loading changes in terms of mixed mode (Mode ICMode II) overloads and block loadings, which are interspersed into a Mode I baseline level loading, is experimentally investigated. Secondly, a detailed elastic– plastic finite element analysis of the fatigue crack growth after mixed mode overloads, which are interspersed into a Mode I baseline level loading, is presented in order to understand the mechanisms of the load interaction effects.
船舶结构碰撞试验及简化数值计算方法
本文网址：/cn/article/doi/10.19693/j.issn.1673-3185.03193期刊网址：引用格式：卢安格, 王子棠, 孔祥韶, 等. 船舶结构碰撞试验及简化数值计算方法[J]. 中国舰船研究, 2024, 19(2): 128–139.LU A G, WANG Z T, KONG X S, et al. Ship structure collision experiments and simplified numerical calculation meth-od[J]. Chinese Journal of Ship Research, 2024, 19(2): 128–139 (in Chinese).船舶结构碰撞试验及简化数值计算方法扫码阅读全文卢安格1，王子棠1，孔祥韶*1，李樱2，陈三桂2，吴卫国31 武汉理工大学 船海与能源动力工程学院，湖北 武汉 4300632 中国舰船研究设计中心，湖北 武汉 4300643 武汉理工大学 绿色智能江海直达船舶与邮轮游艇研究中心，湖北 武汉 430063摘 要:［目的］采用流固耦合计算方法虽能较好地模拟船舶碰撞过程，但计算时间较长，为此，提出一种简化的数值计算方法。
［方法］以某船的局部舱段为对象，开展多工况水上碰撞试验。
采用力传感器和基于高速摄影技术非接触测量的方法获得到碰撞力及碰撞船的运动时程数据，通过对碰撞接触力和加速度响应等数据进行分析，并针对试验过程开展任意拉格朗日−欧拉（ALE ）流固耦合数值计算分析，提出将碰撞过程中水域对撞击船的影响简化为等效质量，将对被撞船的影响简化为等效阻力，以面力的形式作用于被撞船非撞击侧用以阻碍被撞船运动的简化方法，然后基于此简化方法开展不涉及水域与结构耦合过程的数值计算。
［结果］结果显示，采用简化计算方法得到的各工况的碰撞力峰值与试验值间的误差均在5%以内，且该方法所需要的计算时长远小于ALE 流固耦合算法。
包钢长材厂蓄热式加热炉数值模拟
包钢长材厂蓄热式加热炉数值模拟！刘中兴1冯猛1伍永福1张鹏1!2戈春刚2(1.内蒙古科技大学内蒙古自治区白云鄂博矿多金属资源综合利用重点实验室，2.包钢长材厂)摘要以包钢长材厂蓄热式加热炉为研究对象，利用A n sy s软件采用湍流模型、P- 1辐射模型等，模拟了采用交错燃烧组织方式加热炉内各物理场分布情况。
发现该种燃烧方式下，炉内流动涡流运动明显加强，有利于燃烧的混合和组织。
但出口附近的回流造成燃烧短路，高温烟气不易达到炉膛中心，易造成炉内温度不均匀，氧气浓度相对较高不利于钢坯生产，因此该平顶、平底炉型采用交错换向燃烧有待于进一步实践验证。
关键词蓄热式加热炉数值模拟物理场高温空气燃烧技术Numerical simulation on the long materitil factoryof Baogangd regenerative furnaceLiu Zhongxing1Feng Meng1Wu Yongfu1Zhang Peng1，2Ge Chungang2(1. Inner Mongolia University of Science and Technology，2.Long Material Factory of Baogang)Abstract The regenerative heating furnace of tlie long material factory was taken as the research obje c t，used the m odel of '- $ turbulence model and P -1radiation model using Ansys software，andsimulated the distribution of the physical field in the furnace with staggered combust is found that the flow vortex motion in the furnace is obviously enhanced under And it is also conducive to the mixing and organization of the combustion. But the reflow caused bycombustion short circuit near the exit. High temperature f lue gas is not easy to reach the center of thefurnace and cause t he furnace t uneven temperature distribution. Oxygen concentration is relativelyhigh，which is unfavorable to billet production. Therefore，the flat roof and flat hearth type adoptedstaggered reversing combustion need to be further verified.Keywords regenerative furnace numerical simulation physical field high temperature air combustion加热炉是工业加热的关键设备，广泛应用于 国民经济的各行各业。
电杆基础冲刷及防护措施效果的数值分析
收稿日期:２０２３￣０８￣１１ꎮ基金项目:江西省自然科学基金资助项目(２０２３２ＡＣＢ２０４０３１㊁２０２２４ＡＣＢ２０４０１９)ꎻ江西省水利科技计划资助项目(２０２３２５ＺＤＫＴ０７)ꎻ江西省水利科学院开放研究基金资助项目(２０２１ＳＫＳＧ０２)ꎮ作者简介:钟念龙(２０００ )ꎬ男ꎬ硕士生ꎬ研究方向为水工结构可靠度与风险分析ꎮ㊀∗通信作者:蒋水华(１９８７ )ꎬ男ꎬ教授ꎬ博士ꎬ博士生导师ꎬ研究方向为水工岩土工程可靠度与风险分析ꎮＥ￣ｍａｉｌ:ｓｊｉａｎｇａａ＠ｎｃｕ.ｅｄｕ.ｃｎꎮ钟念龙ꎬ万怡国ꎬ陈东ꎬ等.电杆基础冲刷及防护措施效果的数值分析[Ｊ].南昌大学学报(工科版)ꎬ２０２４ꎬ４６(１):１１￣２０.ＺＨＯＮＧＮＬꎬＷＡＮＹＧꎬＣＨＥＮＤꎬｅｔａｌ.Ｎｕｍｅｒｉｃａｌａｎａｌｙｓｉｓｏｆｔｈｅｓｃｏｕｒｉｎｇｏｆｅｌｅｃｔｒｉｃｐｏｌｅｆｏｕｎｄａｔｉｏｎｓａｎｄｔｈｅｅｆｆｅｃｔｉｖｅｎｅｓｓｏｆｐｒｏｔｅｃ￣ｔｉｖｅｍｅａｓｕｒｅｓ[Ｊ].ＪｏｕｒｎａｌｏｆＮａｎｃｈａｎｇＵｎｉｖｅｒｓｉｔｙ(Ｅｎｇｉｎｅｅｒｉｎｇ＆Ｔｅｃｈｎｏｌｏｇｙ)ꎬ２０２４ꎬ４６(１):１１￣２０.电杆基础冲刷及防护措施效果的数值分析钟念龙１ꎬ万怡国２ꎬ陈东３ꎬ陈永清３ꎬ李嵩３ꎬ黄河４ꎬ蒋水华１∗(１.南昌大学工程建设学院ꎬ江西南昌３３００３１ꎻ２.江西省水利科学院ꎬ江西南昌３３００２９ꎻ３.江西省天然气集团有限公司管道分公司ꎬ江西南昌３３０２００ꎻ４.中铁水利水电规划设计集团有限公司ꎬ江西南昌３３００２９)㊀㊀摘要:目前考虑一定坡度下基础局部冲刷的研究很少ꎬ并且缺乏探讨山洪灾害下电杆防护措施的效果研究ꎮ基于ＦＬＯＷ￣３Ｄ软件对电杆基础冲刷进行三维数值模拟ꎬ分别对水头(４~６ｍ)㊁坡度(１０ʎ~２０ʎ)㊁电杆距坡脚距离(６~９ｍ)和初始流速(１~３ｍ ｓ－１)４个变量进行了参数敏感性分析ꎬ对照工况的水头㊁坡度㊁电杆距坡脚距离和初始流速分别设置为４ｍ㊁２０ʎ㊁６ｍ和２ｍ ｓ－１ꎬ通过控制变量法进行试验ꎮ随后在对照工况基础上分别设置牺牲桩群和杆前分流板ꎬ计算电杆基础的最大冲刷深度和水流冲击电杆的压力ꎬ并对比分析２种防护措施的防护效果ꎮ结果表明:随着水头㊁坡度和初始流速的增大及电杆距坡脚距离的减小ꎬ电杆基础的最大冲刷深度和水流冲击电杆的压力均随之增大ꎮ在水头㊁坡度㊁电杆距坡脚距离和初始流速分别取６ｍ㊁２０ʎ㊁６ｍ和３ｍ ｓ－１的工况下ꎬ电杆基础的最大冲刷深度和水流冲击电杆的压力最大ꎻ设置牺牲桩和分流板均可降低水流冲击电杆的压力ꎬ其中设置牺牲桩降低冲击压力的幅度更大ꎻ设置牺牲桩可有效降低电杆基础的最大冲刷深度ꎬ相比之下ꎬ设置分流板只能降低电杆前侧基础的冲刷深度ꎬ但对电杆后侧基础的防护效果不明显ꎮ关键词:电杆基础ꎻ山洪模拟ꎻ局部冲刷ꎻ防护措施ꎻ防护效果中图分类号:Ｘ４３㊀㊀㊀㊀文献标志码:Ａ㊀㊀㊀㊀文章编号:１００６￣０４５６(２０２４)０１￣００１１￣０１０ＮｕｍｅｒｉｃａｌａｎａｌｙｓｉｓｏｆｔｈｅｓｃｏｕｒｉｎｇｏｆｅｌｅｃｔｒｉｃｐｏｌｅｆｏｕｎｄａｔｉｏｎｓａｎｄｔｈｅｅｆｆｅｃｔｉｖｅｎｅｓｓｏｆｐｒｏｔｅｃｔｉｖｅｍｅａｓｕｒｅｓＺＨＯＮＧＮｉａｎｌｏｎｇ１ꎬＷＡＮＹｉｇｕｏ２ꎬＣＨＥＮＤｏｎｇ３ꎬＣＨＥＮＹｏｎｇｑｉｎｇ３ꎬＬＩＳｏｎｇ３ꎬＨＵＡＮＧＨｅ４ꎬＪＩＡＮＧＳｈｕｉｈｕａ１∗(１.ＳｃｈｏｏｌｏｆＩｎｆｒａｓｔｒｕｃｔｕｒｅＥｎｇｉｎｅｅｒｉｎｇꎬＮａｎｃｈａｎｇＵｎｉｖｅｒｓｉｔｙꎬＮａｎｃｈａｎｇ３３００３１ꎬＣｈｉｎａꎻ２.ＪｉａｎｇｘｉＡｃａｄｅｍｙｏｆＷａｔｅｒＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇꎬＮａｎｃｈａｎｇ３３００２９ꎬＣｈｉｎａꎻ３.ＰｉｐｅｌｉｎｅＢｒａｎｃｈꎬＪｉａｎｇｘｉＰｒｏｖｉｎｃｉａｌＮａｔｕｒａｌＧａｓＧｒｏｕｐＣｏ.ꎬＬｔｄ.ꎬＮａｎｃｈａｎｇ３３０２００ꎬＣｈｉｎａꎻ４.ＣｈｉｎａＲａｉｌｗａｙＷａｔｅｒＣｏｎｓｅｒｖａｎｃｙ＆ＨｙｄｒｏｐｏｗｅｒＰｌａｎｎｉｎｇａｎｄＤｅｓｉｇｎＧｒｏｕｐＣｏ.ꎬＬｔｄ.ꎬＮａｎｃｈａｎｇ３３００２９ꎬＣｈｉｎａ)Ａｂｓｔｒａｃｔ:Ａｔｐｒｅｓｅｎｔꎬｔｈｅｒｅａｒｅｌｉｍｉｔｅｄｓｔｕｄｉｅｓｃｏｎｓｉｄｅｒｉｎｇｔｈｅｌｏｃａｌｓｃｏｕｒｏｆｆｏｕｎｄａｔｉｏｎｓｕｎｄｅｒａｃｅｒｔａｉｎｓｌｏｐｅꎬａｎｄｔｈｅｒｅｉｓａｌａｃｋｏｆｒｅｓｅａｒｃｈｏｎｔｈｅｅｆｆｅｃｔｏｆｐｒｏｔｅｃｔｉｏｎｍｅａｓｕｒｅｓｆｏｒｅｌｅｃｔｒｉｃｐｏｌｅｓｕｎｄｅｒｔｈｅｍｏｕｎｔａｉｎｆｌｏｏｄｄｉｓａｓｔｅｒ.Ｉｎｔｈｉｓｓｔｕｄｙꎬｔｈｅｔｈｒｅｅ￣ｄｉｍｅｎｓｉｏｎａｌｎｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎｏｆｔｈｅｓｃｏｕｒｏｆａｎｅｌｅｃｔｒｉｃｐｏｌｅｆｏｕｎｄａｔｉｏｎｈａｓｂｅｅｎｃｏｎｄｕｃｔｅｄｕｓｉｎｇＦＬＯＷ￣３Ｄｓｏｆｔｗａｒｅꎬａｎｄｔｈｅｓｅｎｓｉｔｉｖｉｔｙａｎａｌｙｓｉｓｏｆｆｏｕｒｐａｒａｍｅｔｅｒｓꎬｉｎｃｌｕｄｉｎｇｗａｔｅｒｈｅａｄ(４－６ｍ)ꎬｓｌｏｐｅ(１０ʎ－２０ʎ)ꎬｄｉｓｔａｎｃｅｂｅｔｗｅｅｎｐｏｌｅａｎｄｓｌｏｐｅｆｏｏｔ(６－９ｍ)ａｎｄｉｎｉｔｉａｌｖｅｌｏｃｉｔｙ(１－３ｍ ｓ－１)ꎬｈａｓｂｅｅｎｃａｒｒｉｅｄｏｕｔ.Ｍｅａｎｗｈｉｌｅꎬｔｈｅｗａｔｅｒｈｅａｄꎬｓｌｏｐｅꎬｄｉｓｔａｎｃｅｂｅｔｗｅｅｎｐｏｌｅａｎｄｓｌｏｐｅｆｏｏｔａｎｄｉｎｉｔｉａｌｖｅｌｏｃｉｔｙｗｅｒｅｔａｋｅｎａｓ４ｍꎬ２０ʎꎬ６ｍꎬａｎｄ２ｍ ｓ－１ꎬｒｅｓｐｅｃｔｉｖｅｌｙꎬａｓｔｈｅｒｅｆｅｒｅｎｃｅｃｏｎｄｉｔｉｏｎ.Ｆｉｎａｌｌｙꎬｔｈｅｃｏｎｔｒｏｌｖａｒｉａｂｌｅｍｅｔｈｏｄｗａｓｕｓｅｄｔｏｃｏｎｄｕｃｔｎｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎｅｘｐｅｒｉｍｅｎｔｓ.Ｓｕｂｓｅｑｕｅｎｔｌｙꎬｏｎｔｈｅｂａｓｉｓｏｆｔｈｅｒｅｆｅｒｅｎｃｅｃｏｎｄｉｔｉｏｎꎬｔｈｅｓａｃｒｉｆｉｃｉａｌｐｉｌｅｓａｎｄａｓｐｌｉｔｔｅｒｐｌａｔｅｉｎｆｒｏｎｔｏｆｔｈｅｐｏｌｅｗｅｒｅｒｅｓｐｅｃｔｉｖｅｌｙｓｅｔｕｐꎬｔｈｅｍａｘｉｍｕｍｓｃｏｕｒｉｎｇｄｅｐｔｈｏｆｔｈｅｐｏｌｅｆｏｕｎｄａｔｉｏｎａｎｄｔｈｅｗａｔｅｒｐｒｅｓｓｕｒｅｉｍｐａｃｔｉｎｇｔｈｅｐｏｌｅｗｅｒｅｃａｌｃｕｌａｔｅｄꎬａｎｄｔｈｅｐｒｏｔｅｃｔｉｖｅｅｆｆｅｃｔｓｏｆｔｈｅｓｅｔｗｏｐｒｏｔｅｃｔｉｖｅｍｅａｓｕｒｅｓｗｅｒｅｃｏｍｐａｒｅｄａｎｄａｎａｌｙｚｅｄ.Ｔｈｅｒｅｓｕｌｔｓｓｈｏｗｅｄｔｈａｔ:ｔｈｅｍａｘｉｍｕｍｓｃｏｕｒｉｎｇｄｅｐｔｈｏｆｔｈｅｐｏｌｅｆｏｕｎｄａｔｉｏｎａｎｄｔｈｅｐｒｅｓｓｕｒｅｏｆｗａｔｅｒｉｍｐａｃｔｉｎｇｔｈｅｐｏｌｅｉｎｃｒｅａｓｅｗｉｔｈｔｈｅｉｎｃｒｅａｓｅｉｎｗａｔｅｒ第４６卷第１期２０２４年３月㊀㊀㊀㊀㊀㊀南昌大学学报(工科版)ＪｏｕｒｎａｌｏｆＮａｎｃｈａｎｇＵｎｉｖｅｒｓｉｔｙ(Ｅｎｇｉｎｅｅｒｉｎｇ＆Ｔｅｃｈｎｏｌｏｇｙ)Ｖｏｌ.４６Ｎｏ.１Ｍａｒ.２０２４㊀ｈｅａｄꎬｓｌｏｐｅａｎｄｉｎｉｔｉａｌｖｅｌｏｃｉｔｙａｓｗｅｌｌａｓｔｈｅｄｅｃｒｅａｓｅｉｎｄｉｓｔａｎｃｅｂｅｔｗｅｅｎｐｏｌｅａｎｄｓｌｏｐｅｆｏｏｔ.Ｗｈｅｎｔｈｅｗａｔｅｒｈｅａｄꎬｓｌｏｐｅꎬｄｉｓｔａｎｃｅｂｅｔｗｅｅｎｐｏｌｅａｎｄｓｌｏｐｅｆｏｏｔａｎｄｉｎｉｔｉａｌｆｌｏｗｒａｔｅｗｅｒｅｓｅｔｔｏ６ｍꎬ２０ʎꎬ６ｍꎬａｎｄ３ｍ ｓ－１ꎬｒｅｓｐｅｃｔｉｖｅｌｙꎬｔｈｅｍａｘｉｍｕｍｓｃｏｕｒｉｎｇｄｅｐｔｈｏｆｔｈｅｐｏｌｅｆｏｕｎｄａｔｉｏｎａｎｄｔｈｅｐｒｅｓｓｕｒｅｏｆｗａｔｅｒｉｍｐａｃｔｉｎｇｐｏｌｅｗｅｒｅｔｈｅｌａｒｇｅｓｔ.Ｔｈｅｓｅｔｔｉｎｇｏｆｓａｃｒｉｆｉｃｉａｌｐｉｌｅｓａｎｄｓｐｌｉｔｔｅｒｐｌａｔｅｃａｎｒｅｄｕｃｅｔｈｅｐｒｅｓｓｕｒｅｏｆｗａｔｅｒｉｍｐａｃｔｉｎｇｔｈｅｐｏｌｅꎬａｎｄｔｈｅｓａｃｒｉｆｉｃｉａｌｐｉｌｅｃａｎｒｅｄｕｃｅｔｈｅｉｍｐａｃｔｐｒｅｓｓｕｒｅｍｏｒｅｇｒｅａｔｌｙ.Ｋｅｙｗｏｒｄｓ:ｐｏｌｅｆｏｕｎｄａｔｉｏｎꎻｓｉｍｕｌａｔｉｏｎｏｆｍｏｕｎｔａｉｎｆｌｏｏｄꎻｌｏｃａｌｓｃｏｕｒꎻｐｒｏｔｅｃｔｉｖｅｍｅａｓｕｒｅｓꎻｐｒｏｔｅｃｔｉｖｅｅｆｆｅｃｔｉｖｅｎｅｓｓ㊀㊀山洪是我国发生频率较高的地质灾害之一ꎮ据统计ꎬ在１９４９ ２０１５年间ꎬ全国范围内发生的５３０００余次山洪灾害共导致约６万人死亡ꎻ自２０００年以来ꎬ在每年的洪涝灾害中ꎬ有７０％以上的死亡人数是由山洪造成的[１]ꎮ持续的降雨是导致山洪发生的直接原因ꎬ每当雨季来临ꎬ山洪发生的频率将急剧提高ꎬ常造成大量的生命㊁经济和环境损失ꎮ另一方面ꎬ配电网设施的安全对社会经济发展及人民生活质量具有重要的影响ꎬ持续的洪水会对配电网设施安全运行造成严重的威胁ꎮ因此ꎬ研究洪水对电杆基础的冲刷及洪水对电杆的冲击作用ꎬ并选择有效可靠的防护措施降低配电网设备损失对保障人民生活正常用电具有重要的现实意义ꎮ许多学者已经对电杆在不同灾害环境下的破坏机理进行了深入研究ꎮＤａｒｅｓｔａｎｉ等[２]通过设计实验和逻辑回归分析ꎬ提出了一组参数化的脆弱性模型ꎬ可有效考虑风㊁风暴潮和海浪等多种因素对木质电杆的影响ꎬ并发现电杆底部破裂和基础失稳是主要破坏模式ꎮ严屹然等[３]使用蒙特卡洛方法和模型构建ꎬ评估了地震和滑坡对输电杆塔的损毁概率ꎬ并提出了相应的风险防控措施和应急决策建议ꎮ电杆基础局部冲刷与其他冲刷研究较为相似ꎬ在该领域ꎬ许多学者的研究已经较为深入ꎮ钭锦周等[４]基于ＦＬＯＷ￣３Ｄ软件模拟了单桩基础的局部冲刷ꎬ设置不同的试验进行对比分析ꎬ得到了流速和桩径变化对基础冲刷深度的影响规律ꎮ张曙光等[５]基于ＦＬＯＷ￣３Ｄ软件模拟桥墩附近局部冲刷ꎬ预测了与实测相符合的局部冲刷坑形态和最大冲坑深度ꎮ王鑫等[６]基于Ｆｌｕｅｎｔ软件ꎬ并采用Ｍｉｘｔｕｒｅ两相流方法模拟风力机基础冲刷ꎬ得到了风力机基础冲刷规律ꎮ李火坤等[７]采用ＦＬＯＷ￣３Ｄ数值模拟方法ꎬ建立尾矿库溃坝模型ꎬ得到了溃口冲刷程度随时间的变化规律ꎮ此外ꎬ保护基础免受局部冲刷是防护的关键ꎬ目前国内外许多学者在基础防冲刷措施研究方面取得了有益的成果ꎮＰａｎｄｅｙ等[８]开展了不同直径和深度位置下环箍减小圆柱桥墩冲刷的试验ꎬ发现环箍直径为墩柱直径的１.５~２.５倍并且位于河床表面时ꎬ环箍对桥墩的防护最好ꎮＷａｎｇ等[９]研究了一种新型防护措施 防冲圈 ꎬ阐述了护环高度和直径对防护效果的影响ꎮＶａｌｅｌａ等[１０]提出了一种新的碎石放置设计ꎬ发现新的设计不仅大幅度减小了冲刷的深度和体积ꎬ而且降低了碎石材料的使用量ꎮ杨少鹏等[１１]提出一种护圈与人工草相结合的防冲措施并开展了水槽试验ꎬ发现同时采用护圈和人工草ꎬ可大幅降低河床的冲刷程度ꎮ柏涛[１２]对不同墩柱间距㊁防冲板安装高程及数量下的串联桥墩冲刷进行了物理模型试验ꎬ得出防冲板安装高程是影响冲刷深度的主要因素ꎮ综上ꎬ尽管国内外在基础冲刷方面的研究成果较多ꎬ但是大多数研究的情况是水平河床或海面ꎬ未考虑斜坡水流冲刷ꎬ对易发山洪的区域研究较少ꎬ并且缺乏针对电杆基础的冲刷研究ꎮ考虑到进行现场模型试验的成本较高ꎬ并且泥沙被水流激起时ꎬ水流浑浊难以观察试验现象ꎮＦＬＯＷ￣３Ｄ是一款经过验证的计算流体力学软件ꎬ能够较准确地模拟水动力学和泥沙运移过程ꎬ具有快速㊁方便地改变各种边界条件以及可视化展示各种流场流动现象的优点ꎬ有助于系统分析单因素变量对局部冲刷的影响ꎬ深入了解局部冲刷机理ꎮ因此ꎬ本文基于ＦＬＯＷ￣３Ｄ软件对电杆周围基础冲刷进行了三维数值模拟ꎬ得到了不同水头㊁坡度㊁初始流速和电杆距坡脚距离下电杆基础的最大冲刷深度及洪水对电杆的冲击力ꎬ并进一步分析２种防护措施的防护效果ꎬ以期对电杆基础防护提供一定的理论依据ꎮ１㊀电杆基础冲刷数值模型１.１㊀模型建立ＦＬＯＷ￣３Ｄ依据临界切应力来判断泥沙是否起动ꎬ临界希尔兹数θｃｒ是一个无量纲参数ꎬ用Ｓｏｕｌｓｂｙ￣Ｗｈｉｔｅｈｏｕｓｅ公式[１３]进行计算:θｃｒ＝０.３１＋１.２ｄ∗＋０.０５５[１－ｅｘｐ(－０.０２ｄ∗)](１)式中:ｄ∗＝ｄ５０ρ(ρｓ－ρ)｜ｇ｜μ２éëêêùûúú１３ꎬ为一个无量纲参数ꎻρ为流体密度ꎻρｓ为泥沙密度ꎻｄ５０为泥沙颗粒中值粒２１ 南昌大学学报(工科版)２０２４年㊀径ꎻμ为动力黏滞系数ꎻ｜ｇ｜为重力加速度的绝对值ꎮ对于有一定坡度的斜面ꎬ可以将临界希尔兹数计算公式修正为包含休止角的计算表达式:θᶄｃｒ＝θｃｒｃｏｓψ ｓｉｎβ＋(ｃｏｓ２βｔａｎ２φ－ｓｉｎ２ψｓｉｎ２β)０.５ｔａｎφ(２)式中:θᶄｃｒ为修正后的临界希尔兹数ꎻβ为河床坡度ꎻφ为泥沙休止角ꎻψ为水流方向与上坡方向之间的夹角ꎮ采用Ｍａｓｔｂｅｒｇｅｎ和ＶａｎＤｅｎＢｅｒｇ理论[１４]来计算泥沙的夹带提升速度:ｕｌｉｆｔ＝αｉｎｓｄ０.３∗(θｉ－θᶄｃｒ)１.５｜ｇ｜ｄ５０(ρｓ－ρ)ρ(３)θｉ＝τ｜ｇ｜ｄ５０(ρｓ－ρ)(４)式中:ｕｌｉｆｔ为提升速度ꎬｕｌｉｆｔ将用于计算被转换为悬沙的泥沙量ꎻαｉ为泥沙携带系数ꎬ默认值０.０１８ꎻｎｓ为法向向量ꎻθｉ为希尔兹数ꎻρ为流体密度ꎻτ为局部切应力ꎮ另外本文使用ＶａｎＲｉｊｎ公式[１５]计算单宽输沙率:Φ＝βＶＲｄ－０.３∗θｉθᶄｃｒ－１.０æèçöø÷２.１ｃｂ(５)式中:βＶＲ为推移质系数ꎬ其默认值为０.０５３ꎻｃｂ为泥沙体积分数ꎮ１.２㊀数值模型构建山洪一般发生在山区沟谷中ꎬ由于地势差ꎬ导致洪水水量集中ꎬ冲刷破坏力强ꎮ电杆广泛地分布在我国山区中ꎮ本试验研究洪水从山坡冲下ꎬ冲击山下单根电杆的过程ꎮ模型设置山坡高度为３ｍꎬ宽度为３ｍꎬ电杆高度为１０ｍꎬ入土深度为１.７ｍꎬ电杆直径Ｄ为０.３５ｍꎬ电杆基础长宽均为１.２ｍꎬ模型示意图见图１ꎮ图１㊀模型设置示意图Ｆｉｇ.１㊀Ｄｉａｇｒａｍｏｆｍｏｄｅｌｓｅｔｕｐ计算区域的选择会影响模型建立的合理性ꎬＳａｒｋｅｒ[１６]的研究结果表明ꎬ墩柱会影响下游１２Ｄ位置范围内水流的流动ꎮ为保证墩柱不受下游出口边界的影响ꎬ刘慧芳[１７]取水流出口处距墩柱的距离为１５Ｄꎬ横向取８倍墩柱直径ꎮ因此ꎬ本文适当延长计算区域使得距离略大于１５Ｄꎬ将模型横向宽度设为３ｍꎬ略大于８倍的电杆直径ꎮ实际计算中ꎬ先计算一段长为１５ｍ的无摩擦的进口段ꎬ使得流速充分发展ꎬ选取充分发展区段作为电杆的计算区域ꎮ划分的网格粗密程度对计算精度会有显著影响ꎮ网格设置粗一些可以提高计算效率ꎬ但是如果设置过粗就无法完整地将模块外形构建出来ꎬ反之ꎬ网格设置过密ꎬ虽然可以计算得更为准确ꎬ但是计算效率会大大降低ꎮ同时还须考虑计算机设备等条件限制选择相对合理的网格密度[１８]ꎮ此外ꎬ在ＦＬＯＷ￣３Ｄ构建模型的过程中ꎬ往往会使用多个ｓｔｌ模块组成想要的模型ꎬ如果网格不够精细可能会在ＦＡＶＯＲ之后在２个部件之间引入间隙ꎮ图２给出了利用ＦＡＶＯＲ识别的３种网格大小(０.０２㊁０.０５㊁０.１ｍ)下的电杆和基础ꎬ识别的物体为深色ꎮ这３种网格进行ＦＡＶＯＲ计算的耗时分别为１００㊁１８㊁１１ｓꎮ这表明网格划分得越密ꎬ电杆和基础形状越精细ꎬ相应的计算时间会成倍增长ꎮ黄佳丽等[１９]考虑计算效率等因(ａ)网格尺寸为０.０２ｍ(ｂ)网格尺寸为０.０５ｍ(ｃ)网格尺寸为０.１ｍ图２㊀不同网格尺寸下电杆及基础识别情况Ｆｉｇ.２㊀Ｉｄｅｎｔｉｆｉｃａｔｉｏｎｏｆｐｏｌｅｓａｎｄｆｏｕｎｄａｔｉｏｎｓｗｉｔｈｄｉｆｆｅｒｅｎｔｇｒｉｄｓｉｚｅｓ３１第１期㊀㊀㊀㊀㊀钟念龙等:电杆基础冲刷及防护措施效果的数值分析素ꎬ采用不同相邻网格尺寸比进行试验ꎮ结果表明ꎬ当相邻网格尺寸比在１.０~２.０之间时ꎬ计算结果没有明显差别ꎮ也就是说ꎬ在这个范围内选择较大的网格尺寸比可以提高计算效率ꎬ但不会对计算结果产生较大影响ꎮ因此ꎬ本文主要考虑电杆周围基础冲刷和水流冲击电杆的压力ꎮ综合权衡计算精度和效率ꎬ在坡脚前方２ｍ处至电杆基础后方２ｍ范围内加密网格ꎬ网格尺寸取０.０５ｍꎬ其余地方根据１ ２网格比ꎬ设置网格尺寸为０.１ｍꎬ均选用正立方体网格单元ꎮ考虑水头㊁初始流速㊁电杆距坡脚距离及防护措施变化时ꎬ共离散约４６２万个网格ꎮ在考虑坡度变化时ꎬ由于要控制坡高不变ꎬ坡度越小ꎬ坡面越长ꎬ则相应的计算区域就会越大ꎬ网格数量越多ꎮ坡度为１０ʎ时ꎬ共离散约４９６万个网格ꎻ坡度为１５ʎ时ꎬ共离散约４７３万个网格数量ꎻ坡度为２０ʎ时ꎬ共离散约４６２万个网格ꎮ以２０ʎ坡模型为例ꎬ模型网格划分示意图如图３所示ꎮ单位：m图３㊀网格划分图Ｆｉｇ.３㊀ＤｉａｇｒａｍｏｆｍｅｓｈｇｅｎｅｒａｔｉｏｎＦＬＯＷ￣３Ｄ每个结构化网格块的６个面都要设置边界条件ꎬ默认情况下为对称边界Ｓꎮ本模拟试验计算区域入口设置为速度边界Ｖꎬ用以调整入流处水流的初始流速ꎮ出口处设置为自由出流边界Ｏꎬ保证水流自由出流ꎮ左右边界保持默认设置为对称边界Ｓꎮ上部设置为压力条件边界Ｐꎬ体积分数为０ꎬ即为空气ꎬ下部设置为围墙边界Ｗꎮ为了降低计算量ꎬ在足够长的无摩擦段获得流速充分发展的流体后ꎬ坡面入口处设置为网格边界Ｇꎮ在Ｇｅｎｅｎａｌ模块设置整个计算模型运行时间为４０ｓꎬ单一不可压缩流体ꎬ双精度条件ꎬ将ｏｎｅｆｌｕｉｄ㊁ｆｒｅｅｓｕｒｆａｃｅ作为流体体积(ＶＯＦ)计算对象ꎮ然后在Ｐｈｙｓｉｃｓ板块中构建物理模型ꎬ设置重力加速度为－９.８１ｍ ｓ－２ꎬ负号代表重力方向竖直向下ꎮ设置水流为黏性流ꎮ本文研究对象为山洪水流的紊流流动ꎬ在坡度变化区域水流运动急剧变化ꎬ水面形态复杂ꎬ故使用ＲＮＧｋ￣ε模型[２０]ꎮ设置泥沙模型ꎬ电杆地基不同地区情况不同ꎬ有些地方直接采用回填土埋深ꎬ有些地方会采用混凝土浇筑ꎬ再用土回填ꎮ本试验模拟直接采用土回填的情况ꎮ本次试验选用粒径为０.２４ｍｍ的泥沙颗粒ꎬ泥沙模型参数取值如表１所示ꎮ接着在Ｆｌｕｉｄｓ模块设置水流的系数ꎬ设置水流密度为１６８９ｋｇ ｍ－３ꎬ黏滞度为固定值２.３８ˑ１０－５ꎬ压缩系数为４.６５ˑ１０－５ꎮＦＬＯＷ￣３Ｄ采用尼古拉兹糙率尺寸Ｋｓ来表示粗糙程度ꎬ其与曼宁系数的转换公式如式(６)所示ꎮ如材料曼尼系数为０.０１４ｍ１/６ꎬ转化为尼古拉兹糙率尺寸为０.００２ｍꎬ路面及坡面均采用０.００２ｍꎮ沙面粗糙度设置为２.５ｄ５０ꎬ即０.０００６ｍꎮ在ｏｕｔｐｕｔ板块设置每０.２ｓ获取１次数据ꎬ并提取所需要的数据(泥沙㊁压力㊁水流数据等)ꎮ在Ｎｕｍｅｒｉｃｓ板块设置初始时间步长为０.０１ｓꎮＫｓ＝ｎ０.０３８９æèçöø÷６(６)式中:Ｋｓ为尼古拉兹糙率尺寸ꎬ单位为ｍꎻｎ为曼宁系数ꎬ单位为ｍ１/６ꎮ表１㊀泥沙模型参数取值Ｔａｂ.１㊀Ｖａｌｕｅｓｏｆｓｅｄｉｍｅｎｔｍｏｄｅｌｐａｒａｍｅｔｅｒｓ模型参数参数取值模型参数参数取值最大填料分数０.６４河床荷载系数０.０５３理查森－扎基系数乘数１.０休止角/(ʎ)３２填料沉积物河床的粗糙度１夹带系数０.０１８临界希尔兹数０.０５密度/(ｋｇ ｍ－３)２６５０１.３㊀试验内容为研究不同变量(水头㊁坡度㊁电杆距坡脚距离㊁初始流速㊁防护措施)对电杆基础最大冲刷深度及洪水对电杆冲击力的影响ꎬ设置对照工况进行敏感性分析ꎬ设置情况如表２所示ꎮ采用控制变量法ꎬ改变其中一种变量的值ꎬ其他变量保持不变ꎬ与对照工况进行对照ꎮ对照工况下水头为４ｍꎬ坡度为２０ʎꎬ电杆距坡脚距离为６ｍꎬ洪水初始流速为２ｍ ｓ－１ꎬ表２㊀敏感性分析对照组设置Ｔａｂ.２㊀Ｓｅｔｔｉｎｇｓｏｆｃｏｎｔｒｏｌｇｒｏｕｐｓｆｏｒｓｅｎｓｉｔｉｖｉｔｙａｎａｌｙｓｉｓ变量设置参数１参数２参数３水头/ｍ４５６坡角/(ʎ)１０１５２０电杆距坡脚距离/ｍ６.０７.５９.０初始流速/(ｍ ｓ－１)１２３防护措施无措施添加牺牲桩添加分流板４１ 南昌大学学报(工科版)２０２４年㊀无防护措施ꎮ除常规物理量外ꎬ本文还研究了添加不同防护措施对试验结果的影响ꎮ基础防冲刷措施有很多ꎬ根据防护原理ꎬ基础冲刷防护措施可分为实体抗冲防护和减速不冲防护[２１]ꎮ本文根据实际情况并借鉴桥墩防冲刷措施研究经验选择了如下２种防护措施:牺牲桩和分流板ꎮ牺牲桩是设置在基础上游的桩群ꎬ属于实体抗冲防护ꎬ可以根据当地斜坡坡向㊁河流位置等条件确定牺牲桩的设置位置ꎮ牺牲桩可以有效降低水流的动能ꎬ在桩后形成尾流区ꎬ从而减小基础的最大冲刷深度ꎬ其作用与抛石防护类似ꎮＭｅｌｖｉｌｌｅ等[２２]认为影响牺牲桩防护效果的因素包括牺牲桩数目㊁位置分布㊁间距㊁牺牲桩距墩柱的距离ꎮ通过实验分析得出牺牲桩数目为５ꎬ并且按顶角为３０ʎ的等腰三角形分布ꎬ桩间距为Ｄꎬ顶角桩距离墩柱为２.５Ｄ时ꎬ牺牲桩防护效果最好ꎮ魏凯等[２３]通过试验指出ꎬ牺牲桩直径越大ꎬ防护效果越好ꎬ菱形截面牺牲桩比方形和圆形截面牺牲桩的防护效果更好ꎮ因此ꎬ本文共设５个牺牲桩ꎬ截面为菱形ꎬ直径均为０.１４ｍꎬ高度为１ｍꎬ按顶角为３０ʎ的等腰三角形分布ꎬ桩间距ＳＰ＝Ｄ＝０.３５ｍꎬ顶角上的桩距电杆距离ＳＸ＝２.５Ｄ＝０.８７５ｍꎬ牺牲桩分布位置如图４所示ꎮ分流板有墩前分流板和墩后分流板２种ꎬ本文只模拟墩前分流板对电杆基础的防护效果ꎮ分流板可以改变墩柱周围流场ꎬ减小马蹄涡和墩柱周围的床层剪力作用ꎬ在一定程度上降低水流动能ꎬ降低最大冲刷深度ꎮＷｕ等[２４]试验研究表明在一定高度下ꎬ墩柱前方长度取１.３３Ｄ的分流板对减小基础最大冲刷深度的作用最大ꎬＡｋｉｌｌｉ等[２５]利用粒子图像测速技术指出ꎬ不同厚度分流板并不会改变流态ꎮ因此本文根据文献[２４￣２５]ꎬ设置分流板长度Ｌ＝１.３３Ｄ＝０.４７ｍꎬ高出地面高度ｈ＝１ｍꎬ厚度为０.１ｍꎮ分流板的几何布置如图５所示ꎮ图４㊀牺牲桩位置分布Ｆｉｇ.４㊀Ｌｏｃａｔｉｏｎｄｉｓｔｒｉｂｕｔｉｏｎｏｆｓａｃｒｉｆｉｃｉａｌｐｉｌｅｓ１.４㊀模型验证电杆基础冲刷类似于单桩基础冲刷ꎬ对比上述对照工况条件下数模所得流场与Ｍｅｌｖｉｌｌｅ经典试验[２６]结果以验证本文模型的准确性ꎮ图６(ａ)为经典试验平面流线图ꎬ图６(ｂ)为数值模拟获得的平面流线图ꎮ对比可以看出ꎬ数值模拟电杆基础杆前绕流及电杆后的尾涡与经典试验结果基本一致ꎬ从而验证了模型的有效性ꎮD Lh图５㊀电杆周围分流板及局部冲刷几何示意图Ｆｉｇ.５㊀Ｓｋｅｔｃｈｏｆｓｐｌｉｔｔｅｒｐｌａｔｅａｎｄｌｏｃａｌｓｃｏｕｒｇｅｏｍｅｔｒｙａｒｏｕｎｄｔｈｅｐｏｌｅ(ａ)试验流场流线图(ｂ)数值模拟流线图图６㊀桩基础局部冲刷流速对比图Ｆｉｇ.６㊀Ｃｏｍｐａｒｉｓｏｎｏｆｌｏｃａｌｓｃｏｕｒｖｅｌｏｃｉｔｉｅｓｆｏｒｐｉｌｅｆｏｕｎｄａｔｉｏｎ２㊀数值模拟结果分析㊀㊀根据上述给定条件ꎬ采用ＦＬＯＷ￣３Ｄ软件对电杆基础冲刷进行数值模拟ꎬ得到了电杆基础最大冲刷深度及洪水对电杆的冲击力随时间变化曲线ꎮ以对照工况为例ꎬ该工况计算耗时１４.５３ｈꎬ其余工况计算时间与对照工况相差不大ꎮ电杆基础最大冲刷深度每１ｓ记录１次数据ꎬ而洪水对电杆的冲击力每０.２ｓ记录１次数据ꎮ电杆基础的冲刷程度采用５１ 第１期㊀㊀㊀㊀㊀钟念龙等:电杆基础冲刷及防护措施效果的数值分析最大冲刷深度来表征ꎮ２.１㊀常规物理量对冲刷深度影响图７分别调查了水头㊁坡度㊁初始流速㊁电杆距坡脚距离等变量对电杆基础最大冲刷深度ｈｍａｘ的影响ꎮ由图７(ａ)可知ꎬ４㊁５㊁６ｍ水头工况下ꎬ水流分别在第７㊁６㊁５秒到达了电杆基础处ꎮ在计算至第４０秒时ꎬ４㊁５㊁６ｍ水头工况下基础最大冲刷深度分别为０.７１２㊁０.８２３㊁０.９４０ｍꎬ其中６ｍ水头工况下基础最大冲刷深度是４ｍ水头工况下的１.３２倍ꎮ由图７(ｂ)可知ꎬ１０ʎ和１５ʎ斜坡工况下水流在第７秒到达了电杆基础处ꎬ而２０ʎ斜坡工况下水流在第６秒到达了电杆基础处ꎮ在计算至第４０秒时ꎬ１０ʎ㊁１５ʎ㊁２０ʎ斜坡工况下基础最大冲刷深度分别为０.５８９㊁０.６７１㊁０.７１２ｍꎬ其中２０ʎ斜坡工况下基础最大冲刷深度是１０ʎ斜坡工况下的１.２１倍ꎮ由图７(ｃ)可知ꎬ电杆距坡脚距离７.５ｍ和９.０ｍ工况下水流在第８秒到达了电杆基础处ꎬ而电杆距坡脚距离６ｍ工况下水流在第７秒到达了电杆基础处ꎮ在计算至第４０秒时ꎬ电杆距坡脚距离６.０㊁７.５㊁９.０ｍ工况下基础最大冲刷深度分别为０.７１２㊁０.６４９㊁０.６０６ｍꎬ其中电杆距坡脚距离６.０ｍ工况下基础最大冲刷深度是电杆距坡脚距离９.０ｍ工况下的１.１７倍ꎮ由图７(ｄ)可知ꎬ初始流速１㊁２㊁３ｍ ｓ－１工况下ꎬ水流分别在第９㊁７㊁６秒到达了电杆基础处ꎮ在计算至第４０秒时ꎬ初始流速１㊁２㊁３ｍ ｓ－１工况下基础最大冲刷深度分别为０.５２７㊁０.７１２㊁０.７４２ｍꎬ其中初始流速３ｍ ｓ－１工况下基础最大冲刷深度是初始流速１ｍ ｓ－１工况下的１.４１倍ꎮ可以看出ꎬ基础最大冲刷深度会出现几处降低的点ꎬ这是因为本文记录的时间间隔短ꎬ在某些时刻被水流冲起的土会重新降落回基础冲刷坑里ꎬ导致冲刷坑深度降低ꎮｔ/ｓ(ａ)水头对冲刷深度的影响ｔ/ｓ(ｂ)坡度对冲刷深度的影响6.09.0ｔ/ｓ(ｃ)电杆距坡脚距离对冲刷深度的影响ｔ/ｓ(ｄ)初始流速对冲刷深度的影响图７㊀不同变量取值对冲刷深度的影响Ｆｉｇ.７㊀Ｉｎｆｌｕｅｎｃｅｓｏｆｄｉｆｆｅｒｅｎｔｖａｌｕｅｓｏｆｆｏｕｒｖａｒｉａｂｌｅｓｏｎｔｈｅｓｃｏｕｒｄｅｐｔｈ表３给出了计算历时至第４０秒时不同变量对应的电杆基础的最大冲刷深度ꎮ综上ꎬ随着水头的提高ꎬ坡度的加大ꎬ初始流速的增大ꎬ电杆距坡脚距离的缩小ꎬ洪水会更快到达电杆基础位置ꎬ电杆周围基础的最大冲刷深度会增大ꎮ６１ 南昌大学学报(工科版)２０２４年㊀表３㊀计算历时至第４０秒电杆基础最大冲刷深度Ｔａｂ.３㊀Ｃｏｍｐａｒｉｓｏｎｏｆｍａｘｉｍｕｍｓｃｏｕｒｄｅｐｔｈｏｆｐｏｌｅｆｏｕｎｄａｔｉｏｎａｔａｃｏｍｐｕｔａｔｉｏｎｄｕｒａｔｉｏｎｏｆ４０ｓ变量参数取值４０ｓ时电杆基础最大冲刷深度/ｍ水头/ｍ４０.７１２５０.８２３６０.９４０坡度/(ʎ)１００.５８９１５０.６７１２００.７１２电杆距坡脚距离/ｍ６.００.７１２７.５０.６４９９.００.６０６初始流速/(ｍ ｓ－１)１０.５２７２０.７１２３０.７４２由于电杆限制了水流通过的空间ꎬ过水面积被压缩ꎬ引起流速和压力增大ꎮ此外ꎬ电杆引起的湍流起伏对基础泥沙夹带也起着重要作用ꎬ在电杆前部形成的加速流动和马蹄涡ꎬ导致电杆周围的泥沙向下游运移ꎬ降低了电杆基础埋深ꎮ并且随着水头提高ꎬ坡度加大ꎬ初始流速增大ꎬ电杆距坡脚距离缩小ꎬ水流到达电杆基础的速度会增大ꎬ进而电杆周围水流加速流动和马蹄涡加剧ꎬ导致电杆基础冲刷更严重ꎮ此外ꎬ电杆基础周围最大冲刷深度随着时间呈现先快速增加后缓慢增加的趋势ꎮ水流冲刷电杆基础的过程可分为２个阶段:侵蚀阶段和稳定阶段ꎮ在侵蚀阶段ꎬ基础冲刷深度随时间迅速增大ꎻ而在稳定阶段ꎬ冲刷深度增长速度缓慢下降ꎬ从而图７的变化关系曲线出现拐点ꎮ出现拐点的原因主要与泥沙基础物理性质和水流条件有关ꎮ在侵蚀阶段ꎬ一方面水流对泥沙基础施加的冲击力较大ꎬ另一方面泥沙还没有形成稳定的底床结构ꎬ因而泥沙被迅速剥蚀和搬运ꎬ导致冲刷深度快速增大ꎮ然而ꎬ随着时间的推移ꎬ泥沙基础颗粒逐渐排列整齐ꎬ并形成一定密实度的底床结构ꎮ这时ꎬ底床结构开始对水流冲击产生抵抗作用ꎬ进而阻碍了侵蚀进一步发展ꎬ但是仍会有部分表层泥沙被水流带走ꎮ因此ꎬ当底床结构趋于稳定时ꎬ冲刷深度增长速度会逐渐减缓ꎮ２.２㊀不同变量对水流冲击电杆压力的影响图８分别调查了水头㊁坡度㊁初始流速㊁电杆距坡脚距离等对水流冲击电杆压力Ｐ的影响ꎮ由图８(ａ)可知ꎬ在４ｍ水头工况下水流冲击电杆压力在１６ｓ后约为５.３７ｋＮꎬ在５ｍ水头工况下水流冲击电杆压力在１５ｓ后约为１０.７９ｋＮꎬ６ｍ水头工况下水流冲击电杆压力在１８ｓ后约为１７.１４ｋＮꎬ是４ｍ水头工况下的３.１９倍ꎮ由图８(ｂ)可知ꎬ１０ʎ斜坡工况下水流冲击电杆压力在３２ｓ后约为５.１２ｋＮꎬ１５ʎ斜坡工况下水流冲击电杆压力在２６ｓ后约为５.３１ｋＮꎬ２０ʎ斜坡工况下水流冲击电杆压力在１６ｓ后大约为５.３７ｋＮꎬ是１０ʎ斜坡工况下的１.０５倍ꎮ由P /k N㊀㊀ｔ/ｓ(ａ)水头对水流冲击电杆压力的影响P /k N㊀㊀ｔ/ｓ(ｂ)坡度对水流冲击电杆压力的影响P /k N㊀㊀ｔ/ｓ(ｃ)电杆距坡脚距离对水流冲击电杆压力的影响７１ 第１期㊀㊀㊀㊀㊀钟念龙等:电杆基础冲刷及防护措施效果的数值分析P /k N㊀㊀ｔ/ｓ(ｄ)初始流速对水流冲击电杆压力的影响图８㊀不同变量取值对水流冲击电杆压力的影响Ｆｉｇ.８㊀Ｉｎｆｌｕｅｎｃｅｓｏｆｄｉｆｆｅｒｅｎｔｖａｌｕｅｓｏｆｆｏｕｒｖａｒｉａｂｌｅｓｏｎｔｈｅｉｍｐａｃｔｐｒｅｓｓｕｒｅｏｆｗａｔｅｒｆｌｏｗｏｎｔｈｅｐｏｌｅ图８(ｃ)可知ꎬ电杆距坡脚距离９.０ｍ工况下水流冲击电杆压力在３５ｓ后约为５.１０ｋＮꎬ电杆距坡脚距离７.５ｍ工况下水流冲击电杆压力在２５ｓ后约为５.３１ｋＮꎬ电杆距坡脚距离６.０ｍ工况下水流冲击电杆压力在１６ｓ后约为５.３７ｋＮꎬ是电杆距坡脚距离９.０ｍ工况下的１.０５倍ꎮ由图８(ｄ)可知ꎬ初始流速为１ｍ ｓ－１工况下水流冲击电杆压力在２３ｓ后约为１.９９ｋＮꎬ初始流速为２ｍ ｓ－１工况下水流冲击电杆压力在１６ｓ后约为５.３７ｋＮꎬ初始流速为３ｍ ｓ－１工况下水流冲击电杆压力在２６ｓ后约为８.２０ｋＮꎬ是初始流速为１ｍ ｓ－１工况下的４.１２倍ꎮ表４比较了不同变量对应的水流对电杆的冲击压力ꎮ表４㊀不同变量对应的水流对电杆的冲击压力Ｔａｂ.４㊀Ｉｍｐａｃｔｐｒｅｓｓｕｒｅｓｏｆｗａｔｅｒｆｌｏｗｏｎｔｈｅｐｏｌｅｆｏｒｄｉｆｆｅｒｅｎｔｖａｌｕｅｓｏｆｆｏｕｒｖａｒｉａｂｌｅｓ参数参数取值压力稳定时各工况压力大小/ｋＮ水头/ｍ４５.３７５１０.７９６１７.１４坡度/(ʎ)１０５.１２１５５.３１２０５.３７电杆距坡脚距离/ｍ６.０５.３７７.５５.３１９.０５.１０初始流速/(ｍ ｓ－１)１１.９９２５.３７３８.２０㊀㊀综上ꎬ水流冲击电杆的压力随着时间的增加而逐渐变得稳定ꎬ随着水头的提高ꎬ坡度的加大ꎬ初始流速的增大ꎬ电杆距坡脚距离的缩小ꎬ水流冲击电杆的压力越大ꎮ这是由于随着时间的延长ꎬ电杆基础的冲坑形状和深度会逐渐稳定ꎬ电杆受压面积趋于定值ꎬ水流也逐渐变得平稳ꎬ进而水流冲击电杆的压力趋于稳定ꎮ水头提高ꎬ坡度加大ꎬ初始流速增大ꎬ电杆距坡脚距离缩小ꎬ导致水流到达电杆前的动能增大ꎮ水流的动能会在冲击电杆时转化为对电杆的压能ꎬ导致电杆受到的压力增大ꎮ２.３㊀防护措施对试验结果的影响防护措施对电杆基础的冲刷深度影响如图９(ａ)所示ꎬ防护措施对水流冲击电杆压力的影响如图９(ｂ)所示ꎮ其中由于在添加分流板工况下ꎬ以电杆处横断面为分界线前后侧基础冲刷程度差异过大ꎬ所以将此工况下电杆基础最大冲刷深度分为两㊀㊀ｔ/ｓ(ａ)防护措施对电杆基础的冲刷深度影响P /k N㊀㊀ｔ/ｓ(ｂ)防护措施对水流冲击电杆压力的影响图９㊀不同防护措施对试验结果的影响Ｆｉｇ.９㊀Ｉｎｆｌｕｅｎｃｅｏｆｄｉｆｆｅｒｅｎｔｐｒｏｔｅｃｔｉｖｅｍｅａｓｕｒｅｓｏｎｔｈｅｒｅｓｕｌｔｓ８１ 南昌大学学报(工科版)２０２４年㊀部分来分析ꎮ由图９(ａ)可知ꎬ计算至第４０秒时ꎬ无措施工况下电杆基础的最大冲刷深度为０.７１２ｍꎮ添加分流板工况下ꎬ电杆前侧基础的最大冲刷深度为０.６２１ｍꎬ电杆后侧基础的最大冲刷深度为１.２６ｍꎮ添加牺牲桩工况下电杆基础的最大冲刷深度为０.５８６ｍꎮ由图９(ｂ)可知ꎬ无措施工况下水流冲击电杆压力在１６ｓ后约为５.３７ｋＮꎮ添加分流板工况下水流冲击电杆压力在２６ｓ后约为２.５５ｋＮꎬ比无措施工况下减小了５３％ꎮ添加牺牲桩工况下水流冲击电杆压力在２５ｓ后约为０.７６ｋＮꎬ比无措施工况下减小了８６％ꎮ计算至第４０秒ꎬ不同防护措施工况下电杆周边的流速ｖ分布云图如图１０所示ꎬ水流在电杆前流速骤降并产生绕流ꎮ通过图１０(ａ)与１０(ｂ)对比可知ꎬ添加分流板工况下电杆前侧及左右两侧的流速较无措施工况下略微降低ꎬ后侧流速有所提高ꎮ添加分流板工况下电杆两侧的水流流速明显大于其余地方流速ꎬ表明水流接触到分流板时产生了加速绕流ꎮ因分流板发挥的分流作用ꎬ导致电杆前侧的水流量减小ꎬ最终加速的水流作用到电杆后侧基础ꎬ因Y /m v /（m ·s -1）3.01.5019.718.421.08.506.384.252.120Ｘ/ｍ㊀㊀(ａ)无措施工况下流速分布v //（m ·s -1）Y /m3.01.5019.718.421.08.506.384.252.120Ｘ/ｍ㊀㊀(ｂ)添加分流板工况下流速分布v //（m ·s -1）Y /m3.01.5019.718.421.08.506.384.252.120Ｘ/ｍ㊀㊀(ｃ)添加牺牲桩工况下流速分布图１０㊀不同防护措施下电杆周边流速分布云图Ｆｉｇ.１０㊀Ｃｏｎｔｏｕｒｏｆｖｅｌｏｃｉｔｙｄｉｓｔｒｉｂｕｔｉｏｎａｒｏｕｎｄｔｈｅｐｏｌｅｕｎｄｅｒｄｉｆｆｅｒｅｎｔｐｒｏｔｅｃｔｉｖｅｍｅａｓｕｒｅｓ此添加分流板工况下电杆前侧基础的冲刷深度会小于电杆后侧ꎮ通过图１０(ａ)与１０(ｃ)对比可知ꎬ添加牺牲桩工况下电杆基础周围流速较无措施工况下明显降低ꎬ说明牺牲桩群消耗了水流的大部分动能ꎬ因此ꎬ添加牺牲桩工况下电杆基础的最大冲刷深度会减小ꎮ此外ꎬ分流板和牺牲桩均能减小水流的动能ꎬ因此ꎬ添加防护措施工况下的水流对电杆的冲击压力会降低ꎮ综上ꎬ添加牺牲桩可有效减小基础的冲刷深度ꎬ添加分流板能够一定程度减小电杆前侧基础冲刷深度ꎬ而对电杆后侧基础防护作用不明显甚至会加大基础冲刷程度ꎮ添加牺牲桩和分流板均能有效减小水流冲击电杆压力ꎬ其中添加牺牲桩降低冲击压力的效果要比添加分流板更明显ꎮ３㊀结论㊀㊀１)电杆基础周围最大冲刷深度随时间增长呈现先快速增加后缓慢增加的趋势ꎮ随着水头的提高ꎬ坡度的加大ꎬ初始流速的增大ꎬ电杆距坡脚距离的缩小ꎬ洪水会更快到达电杆基础位置ꎬ电杆周围基础的最大冲刷深度会增大ꎮ２)水流冲击电杆的压力会随时间的增长而逐渐变得稳定ꎬ随着水头的提高ꎬ坡度的加大ꎬ初始流速的增大ꎬ电杆距坡脚距离的缩小ꎬ水流冲击电杆的压力会增大ꎮ３)添加牺牲桩能够有效减小基础的冲刷深度ꎬ而添加分流板对电杆后侧基础的防护作用不明显ꎬ甚至会加大基础的冲刷程度ꎬ但是能有效减小电杆前侧基础的冲刷深度ꎮ添加防护措施能有效减小水９１ 第１期㊀㊀㊀㊀㊀钟念龙等:电杆基础冲刷及防护措施效果的数值分析。
弹丸侵彻钢纤维混凝土数值模拟
C AM E O 凯模C A E 案例库w w w .c a m e o .o r g .c n文章编号:1009-3443(2005)05-0459-05弹丸侵彻钢纤维混凝土数值模拟纪 冲, 龙 源, 万文乾(解放军理工大学工程兵工程学院,江苏南京210007)摘 要:为了对弹丸侵彻钢纤维混凝土问题进行数值模拟研究,在有限元计算中引入了Holmquist-Johnson-Co ok 累积损伤材料模型以描述钢纤维混凝土的非线性变形及断裂特性,弹丸作为刚体处理。
侵彻深度计算结果与在 14.5m m 弹道炮上所获得的试验结果相吻合,并很好地模拟了在侵彻过程中钢纤维混凝土靶的成坑、层裂现象。
在此基础上分析了钢纤维混凝土这种新型复合材料抗侵彻性能的影响因素。
计算结果表明,HJC 本构模型用来描述钢纤维混凝土的侵彻问题是可行和有效的。
关键词:钢纤维混凝土;侵彻;数值模拟;侵彻深度;韧度中图分类号:O 385;E 932.2文献标识码:ANumerical simu lation of projectile penetrating intosteel fiber reinforced concreteJ I Chong , LON G Yuan , W AN Wen -qian(Enginee ring Institute o f Co rps of Engineers,P L A U niv.of Sci.&T ech.,N anjing 210007,China)Abstract :Kinetic energ y projectile penetra ting into steel fiber reinfo rced co ncrete (SFRC )target w as simulated by the finite element metho d,w here the pro jectile w as considered to be rigid.To describe nonlinear deforma tio n and fracture cha racteristics o f SFRC ,Holmquist -Johnso n -Cook constitutiv e rela tions and damage model w ere incorporated into com putatio ns.The num erical results o f penetration depth w ere in goo d ag reem ent w ith recent ex perimental results obtained fro m 14.5mm gun.The crater fo rm atio n ,spall o f SFRC target in the process o f penetra tion w ere simula ted v ery w ell .The influence facto rs of anti -penetra tio n properties o f SFRC w ere studied .The feasibility and v alidity of applying the H JC concrete model to simulating such pro blem as penetratio n in SFRC w ere co nfirmed.Key words :SFRC (steel fiber reinfo rced concrete);penetration;numerical simulatio n;penetratio n depth;toughness index 收稿日期:2005-01-26.基金项目:北京理工大学爆炸科学与技术国家重点实验室开放基金资助项目(KFJJ 03-5).作者简介:纪 冲(1981-),男,博士生.联系人:龙 源,教授,博士生导师;研究方向:爆破器材及爆炸作用;E-mail :Long -yuan @s oh . 钢纤维混凝土SFRC (steel fiber reinfo rced concrete)是在素混凝土中掺入乱向分布的钢纤维后所形成的一种新型多相复合材料。
供热管道泄漏流场声源特性及其变化规律
消防理论研究供热管道泄漏流场/声源特性及其变化规律张曼\张立申％王随林\李仲博，王海鸿％张威\穆连波；(1.北京建筑大学环境与能源工程学院，北京100044; 2.北京市热力集团有限责任公司，北京100022)摘要：以供热管道泄漏喷射为研究对象，建立管道泄漏致噪的计算流体力学C'F D/计算声学C A混合数值模型，采用Flu—e n t与b A coustics搞合数值模拟，分析管内压力、温 度等因素对热水管道泄漏流场及声源特性的影响结果表明，泄 漏源附近流场呈非对称扇形结构，热水管道泄漏声能主要集中在低频段(0〜20 H z),平均声压级随管内压力的升高而增大，随水 温的升高而有所降低模拟结果与文献实验结果相对偏差小于7.99%,可为基于声波法的供热管道泄漏检测提供理论基础关键词：热水管道；泄漏声源；C F D/C A;流场特性；声源特性中图分类号：X956;T U995.3 文献标志码：A文章编号：1009—0029(2021)03-0312-07随着城市集中供热的发展，供热管网规模和规格不断 增大。
2018年我国城市集中供热面积达到87.8亿集中供热管道长度为371120 km。
由于管路老化、腐蚀、焊 缝缺陷及其他自然或人为损坏等，管道泄漏事故频繁发生。
直埋管线非开挖泄漏检测与定位困难，抢修时间长，影响正常供热和城市基础设施安全，势必会造成能源浪费、经济损失及不良社会影响。
为了保障城市供热管网安 全高效运行，开展供热直埋管道非开挖泄漏检测与精准定位的研究具有重要意义。
管道泄漏检测方法包括基于硬件和软件的方法。
声 波检测法具有动态无损检测的优点，是一种很有前景的管 道泄漏检测方法。
国内外学者基于声波检测原理对管道 泄漏检测与定位进行了研究。
Mostafapour等基于管壁泄 漏声发射技术，结合小波变换、数字滤波和互相关分析开 发了一种适用于城市埋地高压燃气管道的泄漏检测与定位算法，以布置在各向同性、均匀弹性介质的圆柱壳体中 的埋地输气管道泄漏声源理论模型进行了实验验证。
【16】Numerical simulation of blasting-induced rock fractures(1)
School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798, Singapore Received 3 January 2007; received in revised form 3 December 2007; accepted 4 December 2007 Available online 20 February 2008
Abstract In the present study, the Johnson–Holmquist (J–H) material model is implemented into the commercial software LS-DYNA through user-subroutines to simulate the blasting-induced rock fractures. The J–H model consists of strength models for both intact and fully fractured materials, a polynomial equation of state, and a damage model that represents the material from an intact state to a fully fractured state. Influences of the key parameters in smooth blasting, viz., loading rate, distance from a free face, earth stress, and preexisting joint planes, etc., on fracture patterns are explored. According to the simulation results, the rock fracture pattern is significantly influenced by the loading rate. Fracture control techniques, namely, notched borehole and charge holder with slits are also simulated. Effectiveness of the fracture control techniques is demonstrated. The numerical simulation in the present study reproduces some of the well-known phenomena observed by other researchers. It has the potential to be applied in practical blast control and gas and hydraulic fracturing engineering. r 2007 Elsevier Ltd. All rights reserved.
无冷凝器及再沸器的热集成蒸馏塔技术进展
第34卷第9期2006年9月 化 学 工 程CHE M I CAL E NGI N EER I N G (CH I N A ) Vol .34No .9Sep.2006作者简介:李娟娟(1981—),女,硕士生,主要从事过程模拟研究;陆恩锡,通讯联系人,教授,博导,电话:(020)87114867,E 2mail:ceenxilu@scut .edu .cn 。
无冷凝器及再沸器的热集成蒸馏塔技术进展李娟娟,陆恩锡,张 翼(华南理工大学传热强化与过程节能教育部重点实验室,广东广州 510640)摘要:蒸馏塔内部热集成技术系指同一塔内通过精馏段和提馏段之间的热量集成。
介绍了内部热集成蒸馏塔的结构、特点、节能原理以及发展概况。
该项技术被认为是最具节能潜力的新型蒸馏技术之一,与传统蒸馏塔相比,内部热集成蒸馏塔节能可达到30%—60%。
近年来,塔内部热集成技术研究呈现加速发展的势态,国外学者已成功地完成了中试,并开始工业化应用的研究。
关键词:蒸馏;内部热集成;热力学效率中图分类号:T Q 021.8 文献标识码:A 文章编号:100529954(2006)0920001204Techn i cal progress of distill ati on colu mns withoutcondensers and reboilersL I Juan 2juan,L U En 2x i ,ZHANG Y i(The Key Lab of Enhanced Heat Transfer &Energy Conservati on ofM inistry of Educati on,South China University of Technol ogy,Guangzhou 510640,Guangdong Pr ovince,China )Abstract:The internally heat integrated distillati on technol ogy refers t o the heat integrati on of the sa me colu mn bet w een the rectifying and stri pp ing secti ons .The devel opment,configurati on,energy 2saving p rinci p le and app licati on of heat integrated columns were p resented .This technol ogy is considered as one of the most effective methods f or saving energy in distillati on colu mns .The saved energy is expected t o reach t o 30%260%,compared with the conventi onal colu mns .Recently the research f or heat integrated columns exhibits the tendency of s peeding up.The p il ot p lant experi m ent is successfully comp leted in abr oad .And the research for commercial facility is in p r ogress .Key words:distillati on;internally heat integrated;ther modyna m ic efficiency 蒸馏过程是最重要的化工单元过程之一,它又是一类高能耗的单元过程。
Numerical simulations of low-velocity impact
Numerical simulations of low-velocity impacton an aircraft sandwich panelM.Meoa,*,A.J.Morris a ,R.Vignjevic a ,G.MarengobaStructures and Materials Group,College of Aeronautics,Cranfield University,Bedford MK430AL,UKbGKN Aerospace Services,Cowes,Isle of Wight PO316RH,UKAbstractThe potential hazards resulting from a low-velocity impact (bird-strike,tool drop,runway debris,etc.)on aircraft structures,such as engine nacelle or a leading edge,has been a long-term concern to the aircraft industry.Certification authorities require that exposed aircraft components must be tested to prove their capability to withstand low-velocity impact without suffering critical damage.This paper describes the results from experimental and numerical simulation studies on the impact and penetration damage of a sandwich panel by a solid,round-shaped impactor.The main aim was to prove that a correct mathematical model can yield sig-nificant information for the designer to understand the mechanism involved in the low-velocity impact event,prior to conducting tests,and therefore to design an impact-resistant aircraft structure.Part of this work presented is focused on the recent progress on the materials modelling and numerical simulation of low-velocity impact response onto a composite aircraft sandwich panel.It is based on the application of explicit finite element (FE)analysis codes to study aircraft sandwich structures behaviour under low-velocity impact conditions.Good agreement was obtained between numerical and experimental results,in particular,the numerical simulation was able to predict impact damage and impact energy absorbed by the structure.Ó2003Elsevier Ltd.All rights reserved.Keywords:Sandwich panel;Barely visible impact damage;Low-velocity impact1.IntroductionSandwich constructions are becoming more common in a wide variety of structural applications,largely be-cause of their relative advantages over other structural materials in terms of improved stability,high stiffness to weight and strength to weight ratios.Sandwich constructions provide an efficient solution to increase bending stiffness without significant increase in structural weight.The sandwich is generally made by bonding CFRP facesheets to honeycomb,Nomex or foam cores.These structures can carry both in-plane and out-of-plane loads and remain stable under com-pression without a significant weight penalty.The potential applications for sandwich structures are substantial.Transport aircraft components,helicopter blades,shields for space applications,are some of thecurrent applications.The main restriction to the appli-cation of sandwich structures in aircraft industry is due to lack of understanding of low-speed impact-damage mechanisms,and the effect of such damage,including penetration damage,on structural performance.Sandwich constructions are being considered for ap-plication to aircraft primary structures,where durability and damage tolerance is a primary consideration,therefore,understanding the adverse effect of in-service impact events (impact damage and penetration damage)has become critical.Low-velocity impact can be attributable to a number of fairly common discrete sources of damage (DSD)such as bird-strike,hail stone,tool drops,debris thrown up from runways,etc.These events may induce overall and localized damage in sandwich structures (fiber breaks,resin cracking,facesheet-core delamination,core crush,puncture,etc.)The failure characteristics of sandwich structures are significantly different from conventional laminated structures.Typical damage modes to be assessed include*Corresponding author.Tel.:+44-1234750111x5220;fax:+44-1234752149.E-mail address:m.meo@cranfi (M.Meo).0263-8223/$-see front matter Ó2003Elsevier Ltd.All rights reserved.doi:10.1016/pstruct.2003.09.035Composite Structures 62(2003)353–360/locate/compstructpenetration and delamination within the sandwich facesheet,and additional modes such as core crushing and composite facesheet debonding.The present paper presents the results of an experi-mental and analytical study into low-velocity impact on a sandwich engine nacelle panel.The test panel is rep-resentative of the structure that will be used in a fan cowl door of an underwing engine nacelle of a large commercial aircraft.The objectives of the study was to understand the impact-damage mechanism,the load distribution in the composite facesheets of the sandwich panel,and to de-termine panel failure mechanisms.The impact-damage condition simulated in the experimental study corre-sponds to barely visible impact damage (BVID).Ex-perimental data was generated using a steel ball indentor to create the impact damage.The analytical study con-sists of finite element analyses of the low-velocity impact of a 3D sandwich panel.Test results with respect to dent depth and delamination area are compared with finite element analysis results.Finally,the present paper de-scribes the panel failure characteristics in the presence of BVID and facesheet intra-ply strains and sandwich plastics strain that illustrate load redistribution around the impact damage.2.Impact testingDuring the lifetime of a civil transport aircraft,the chances of low-velocity impact on a fan cowl door are reasonably high.The impact damage resulting from these low-speed impact event on sandwich structures correspond usually to barely visible impact damage.The damaged site typically exhibits very little surface dam-age,and usually,the performance of the damaged sandwich panel structure are not significantly degraded by the presence of BVID [1–3,9–20].The main objective of the test programme was to investigate the behaviour and the damage resulting from low-velocity impact on a fan cowl door sandwich structures in order to demonstrate the damage tolerance of this structural solution.A sandwich panel,representative of the materials and manufacturing processes used on the A330-Trent 700engine nacelle modified fan cowl doors,was tested.The test panels dimensions were 0.381m long and 0.3048m wide.The Nomex core used in the sandwich panel was a 0.00635m thick HRH-10-1/8-4.0Aramid fiber/phenolic resin Nomex.Facing skins were made of four plies of carbon epoxy AS4/8552prepeg on both sides of the core with lay-up sequence of [90/45/45/90].The test was done by dropping a suitable tup and mass arrangement from a defined height onto the required impact location of the test panels,in order to achieve the required impact en-ergy.During the tests,the panel was placed on a cylin-drical ring with an outer radius of 0.1016m at the impact locations.The impactor tup diameters was 16mm with a cylindrical mass attached to achieve the ki-netic energy specified by test requirements.The tup was made of 1018Steel.Details of the test rig and impact locations are shown in Fig.1and the impact test re-quirement are summarised in Table 1.Before the impact tests,the panel was subjected to a C-scan examination in order to clear the presence of manufacturing defects.The panel was tested at ambient conditions.After the completion of the tests,the panel was again subjected to another C-scan examination to assess the area affected by the impact damage.Impact dent depth was also recorded at the end of the impact test.The results are summarised in Table 2and the C-scan image of the impact damage location is shown in Fig.2.The scan,alongside optical examination,evidenced the presence of matrix cracking and fiber breakage in the damagedarea.Fig.1.Details of impact test rig and impact locations.354M.Meo et al./Composite Structures 62(2003)353–3603.Analytical modelDuring impact of a projectile on a sandwich panel,the target experiences localized deformation in the vi-cinity of the point of impact as well as overall structural deformation.Classical beam,plate,and shell theories generally do not account for the local deformation near the impact site.The localized deformation in a sandwich panel were estimated from a large-scale numerical analysis of the dynamic contact problem and by intro-ducing contact law that accounts for the effect of in-elastic deformation and damage induced in the impact zone.The sandwich panel was analyzed using the LS-DYNA3D finite element code.Mesh sensitivity studies were performed.A finer mesh was employed in the im-pact location in order to better capture the damaged state of the sandwich panel.The final finite element model of the undamaged panel is shown in Fig.3.The panel was modelled as a combination of solid and shell elements.A four-node Belytschko-Tsai shell element was used for modelling the composite facing skin while eight node solid element were employed to model honeycomb core.A total of 55,605elements were used.Load was applied to the model by specifying an initial velocity of the impactor.The impacting speed assumed was 30.5m/s.Simple support boundary conditions were specified at the bottom of the support ring.An elasto-plastic with isotropic hardening constitutive material model was assumed for the impactor and support ring.Surface contact algorithm were introduced into the model to simulate contact between the impacting body and the top facing composite skin and bottom facing composite skin sandwich and support ring.The model-ling of the contact-impact problem is governed by the fact that the impacting body and the target must not penetrate each other.This condition was achieved by using the symmetric penalty method and a symmetric surface-to-surface algorithm was assumed.The major difficulty in solving the contact problem is the assign-ment of the value of the penalty (normal)stiffness which affects the accuracy and stability of the solution.The use of an excessively high value of the penalty stiffness may lead to numerical errors.The penalty algorithm has the main drawback that an increase of the penalty stiffness reduces the stable time increment,since the penalty springs increase the overall stiffness acting on the in-terface nodes.On the other hand,smaller values of the penalty stiffness could lead to wrong solutions,leading to excessive interpenetration and incorrect estimates of the stick regions.In order to use the right value of penalty stiffness factor for the master and slave surface,several runs were conducted.The values assigned to our finite element model was 0.2.4.Honeycomb core material propertiesThe stress–strain curve of the Nomex core material is shown schematically in Fig.3.The compressive stress–strain curve for honeycomb cores can be divided into three distinct regions:(1)At low strains (0.5–5%)a lin-early elastic region,(2)a region corresponding to pro-gressive crushing at nearly constant stress level (the Ôplateau stress’r pl ),and (3)a region of rapidly increas-ing stresses with further deformation due to the fact that the cell walls are forced into contact with each other.For high density honeycombs,the linearly elastic region ends when the honeycomb cell walls start fracturing.Table 1Impact test requirements Required drop energy (J)Mass of tup (kg)Tup diameter (mm)Drop height (m)85160.16Table 2Impact test results Dent depth (mm)Area of delamination (mm 2)1.48396.5Fig.2.C-scan image ofdamage.Fig.3.Finite element model.M.Meo et al./Composite Structures 62(2003)353–360355The initiation of elastic buckling does not cause a complete loss of stiffness since after the initial fracture of the cell walls is observed,a sudden drop from a collapse stress to a steady crush strength occurs as shown in Fig.4.Small oscillations may occur about the mean stress value due to consecutive local buckling.TheÔdensifica-tion strain’e D typically ranges from50%to80%.The area under the stress strain curve up to densification is the useful energy that can be absorbed per unit volume. It is given approximately byW v¼r plÁe Dð1ÞThe honeycomb material properties are shown in Table 3.posite material propertiesThe damage of composite laminates due to transverse impact loading generally consists of several modes such as matrix tensile cracking,matrix compressive/shear failurefiber matrix debonding,fiber breakage(tensile or compressive),delamination,etc.Among these damage modes,delamination is the most important mode. However,visible delamination was not observed in the tests.Therefore,the carbon epoxy AS4/8552composite laminate was modelled as an orthotropic material with damage occurring by matrix cracking,compressive failure andfiber breakage.The Chang and Chang failure criterion[4,5]was utilized by the model to predict matrix cracking,compressive failure andfiber breakage of the laminate.For matrix cracking failure,two different failure criteria are used depending on whether transverse normal stress,r22,is in tension or in compression.The failure index,e m is defined in terms of transverse tensile strength,Y t,transverse compressive strength Y c,and in-plane shear strength S,and is expressed ase2m¼ðr22=Y cÞ½ðY c=2SÞ2À1 þðr22=SÞ2þ sðs12=SÞ2for r22<0ð2Þande2m¼ðr22=Y tÞ2þðs12=SÞ2for r22>0ð3ÞMatrix failure is assumed to occur when the failure index e m exceeds unity.Fiber–matrix shearing failure is assumed to be de-pendent on a combination of axial stress,r11and shear stress s12and is expressed as follows:e2s¼ðr11=X tÞþðs12=S2Þforr11>0andðr11=X tÞ<ðs12=SÞ2ð4Þe2s¼ðr11=X cÞþðs12=SÞ2forr11<0andðr11=X cÞ<ðs12=SÞ2ð5Þwhere e s is the failure index forfiber–matrix shearing, X t is the tensile strength along thefiber direction and X c is the compressive strength along thefiber direction. Fiber–matrix shearing dominated failure occurs when the failure index e s exceeds unity.Fiber breakage failure occurs in tension due to the combination of axial stress and shear stress while the failure in compression is governed by buckling and ex-pressed in terms of only axial stress.The criterion for fiber breakage failure is expressed as follows:e2f¼ðr11=X tÞþðs12=SÞ2for r11>0ð6Þe2f¼ðr11=X cÞþðs12=SÞ2for r11<0ð7ÞThe geometrical data and lay-up sequence are given in Table4.The ply material properties shown in Table5.Table4Ply lay-up and geometrical dimensions of the plateLay-up sequence No.of plies Thickness(mm)[90,45,45,90]40.3Table3Mechanical properties of honeycomb coreModuli parameter Strength parametersYoung modulus compacted material,E z1GPa Stabilised compression,Z c(plateau stress)7.76MPaPoisson’s ratio compacted material,m0.25In-plane shear,S L(expansion direction) 2.66MPa Transverse modulus,E z414MPa In-plane shear,S R(ribbon direction) 1.38MPaShear modulus direction of expansion,G L89MPa Yield stress fully compacted material 3.19MPaShear modulus ribbon direction,G R44MPaDensification strain0.8356M.Meo et al./Composite Structures62(2003)353–360Table 5Mechanical properties of laminate Moduli parameterStrength parametersLongitudinal modulus,E x (GPa)47Longitudinal tension,X t (MPa)247Transverse modulus,E y (GPa)47Longitudinal compression,X c (MPa)151Shear modulus,G xy (GPa)14Transverse tension,Y t (MPa)247Poisson’s ratio,m xy0.054Transverse compression,Y c (MPa)151In-plane shear,S (MPa)99Fig.5.Strain energy honeycomb and compositeskin.Fig.6.(a)Final overall deformation,(b)localized deformation,(c)honeycomb plastic strain.M.Meo et al./Composite Structures 62(2003)353–3603576.Results and discussionThe structural response of sandwich panel to foreign object damage is distinct from that of laminated com-posites.Impact response and energy absorption of sandwich composites is largely by crushing of the sandwich core[6–8].This is confirmed by Fig.5,where the strain energy of the honeycomb is eight times higher than the impact energy absorbed by the composite laminate.The target experienced localized deformation in the vicinity of the point of impact as well as overall struc-tural deformation as shown in Fig.6a–b.The contact laws defining the contact force versus indentation relationship during impact are significantly different for laminated and sandwich composites.The indentation is defined as the relative displacement be-tween the indentor and sandwich panel.Fig7a–b show transverse displacement(m)at impact location and projectile displacement versus time.The duration of the impact is0.0004s since the impactor starts bouncing back as shown in Fig.7b.Once the ball is bounced back, no permanent deformation can occur therefore the re-sults will just show the elastic motion of the structure (Fig.7a).In order to reach a state of static equilibrium tofind thefinal dent depth,there was the need to in-troduce some artificial mechanism to damp out the vi-bration present inside the material.Dynamic relaxation was used.Damping was applied to all the nodes so as to achieve zero velocity for all them.Thefinal dent depth is 1.52mm.The contact law is typically a nonlinear function displaying different loading and unloading characteris-tics(Fig.8).Thefinal damaged state is shown in Fig.9.In par-ticular,failure indicator of tensile matrix mode(crack-ing)is shown.A value of one indicates no damage within the composite plies,while a value less than unity show damage within the composite plies.Since delami-nation is always associated with initial matrix cracking, this failure criteria indicator was assumed comparable with experimental C-scan damage state.The damaged area is354.8mm2.In Table6numerical simulation and experimental results are compared.Good agreement was obtained. Thefinal dent depth was obtained with an error of2.6%.Fig.7.(a)Dent depth––transverse displacement(m)at impact location versus time(b)indentor(projectile)displacement(m)versustime.Fig.8.Impact force versus indentation displacement.358M.Meo et al./Composite Structures62(2003)353–360The delamination area was estimated with an error of 10.5%.7.ConclusionThe present paper describes the results from an ex-perimental and numerical study of impact-under-load responses of composite facesheet sandwich panels sub-jected to low-speed impact damage.The main objective was to understand the load distribution in damaged sandwich structure and to study the failure mecha-nisms of such a structure in the presence of impact damage.The panel is representative of a fan cowl door of a large transport aircraft underwing engine nacelle.The test panel was 0.381m long and 0.3048m wide with thin composite facesheets co-bonded to honeycomb core.Dropped-weight impactor with 16mm diameter steel tups with 5kg mass was used in the present study.The impact energy level used was that required to inflict damage conditions in the test panel correspond to a barely visible impact damage in the impacted composite facesheet.Results from the impact-damage C-scan test indi-cate that significant internal damage occurs at relativelylow-impact energy levels,which can significantly reduce the residual strength of the panel.Dent depth and de-lamination area within the plies were measured experi-mentally.Good agreement was obtained by comparing nu-merical and experimental results,in particular the nu-merical simulation was able to predict dent depth with an error of 2.6%and delamination area with an error of 10.5%.References[1]McGowan DM,Ambur pression response of a sand-wich fuselage keel panel with and without damage.NASA Technical Memorandum 110302.[2]McGowan DM,Ambur DR.Damage-tolerance characteristics ofcomposite fuselage sandwich structures with thick facesheets.NASA Technical Memorandum 110303.[3]Rouse M,Ambur DM,Bodine J,Dopker B.Evaluation of acomposite sandwich fuselage side panel with damage and subjected to internal pressure.NASA Technical Memorandum 110309.[4]Chang FK,Chang KY.A progressive damage model forlaminated composite containing stress concentrations.J Compos Mater 1987;21:834–55.[5]Choi HT,Chang FK.A model for predicting damage in graphite/epoxy laminated composites resulting from low DYNA3d sub-jected to low velocity point impact.J Compos Mater 1992;26:2134–69.[6]Abrate S.Localized impact on sandwich structures with laminatedfacings.Appl Mech Rev 1997;50(2):69–82.[7]Abrate S.Impact on laminated composite materials.Appl MechRev 1991;44(4):155–90.[8]Abrate S.Impact on laminated composites:recent advances.ApplMech Rev 1994;47(11):517–44.[9]Damage tolerance of composite sandwich structures.DOT/FAA/AR-99/91.[10]Horrigan DPW,Aitken RR.Finite element analysis of impactdamaged honeycomb sandwich./pdf/CS503_FEA_of_Impact_Damaged_Honeycomb_Panels.I .[11]Glass DE,Raman VV,Venki VS,Sankaran SN.Honeycomb corepermeability under mechanical loads.NASA/CR-97-206263.[12]McGowan DM,Ambur DR.Damage characteristics and residualstrength of composite sandwich panels impacted with and without compression loading.In:39th AIAA/ASME/ASCE/AHS/ASC Structures,Structural Dynamics and Materials Conference,Ses-sion No.15––Damage Tolerance,Long Beach,CA,April 20–23,1998.[13]Rouse M,Ambur DR,Dopker B,Shah B.Response of compositefuselage sandwich side panels subjected to internal pressure and axial tension.In:AIAA/ASME/ASCE/AHS/ASC 35th Structures,Structural Dynamics,and Materials Conference,Long Beach,CA,April 20–23,1998.[14]Minguet PJ.A model for predicting the behaviour of impactdamaged minimum gage sandwich panels under compression.AIAA 91-1075-CP,1991.p.1112–22.[15]Chang FK,Choi HY,Wang HS.Damage of laminated compos-ites due to low velocity impact.In:Proceedings of the 31st AIAA/ASME/ASCE/AHS/ASC Structures,Structural Dynamics and Materials Conference,Long Beach,CA,1990.[16]Cantwell WJ,Curtis PT,Morton J.Low velocity impact damagetolerance in CFRP laminates containing woven and non-woven posites 1983;14:301–5.[17]Plantema FJ.Sandwich construction.Chinchester:Wiley;1966.Fig.9.Failure indicator of tensile matrix mode (0failed;1elastic).Table 6Comparison of experimental and numerical resultsImpact testsFinite element method Error Dent depth (mm) 1.48 1.52 2.6%Area of delamination (mm 2)396.5354.810.5%M.Meo et al./Composite Structures 62(2003)353–360359[18]Allen HG.Analysis and design of structured sandwich panels.Oxford:Pergamon Press;1969.[19]Krajcinovic D.Damage mechanics.Amsterdam:North Holland/Elsevier;1996.[20]Abbott,R.Damage tolerance evaluation of composite honey-comb structures.In:43rd International SAMPE Symposium,May 31–June4,1998.360M.Meo et al./Composite Structures62(2003)353–360。
空投鱼雷入水载荷
空投鱼雷入水载荷潘光;杨悝【摘要】为了研究空投鱼雷的入水过程,首先分析入水过程中的受力情况进行数值计算;然后使用数值模拟软件Msc.Dytran建立鱼雷入水的有限元模型,计算入水过程中雷体所遭受的冲击压力及其在冲击面上的分布情况,并对不同入水速度和角度下冲击压力峰值、不同头部形状冲击压力峰值特点及鱼雷入水弹道做了分析与讨论,结果表明:鱼雷入水速度和入水角度会对鱼雷壳体所受载荷产生重要影响,研究结果可为预测鱼雷入水冲击载荷提供参考.【期刊名称】《爆炸与冲击》【年(卷),期】2014(034)005【总页数】6页(P521-526)【关键词】爆炸力学;冲击载荷;MSC/DYTRAN;空投鱼雷;入水【作者】潘光;杨悝【作者单位】西北工业大学航海学院,陕西西安710072;西北工业大学航海学院,陕西西安710072【正文语种】中文【中图分类】O383.1;TJ610.2现代鱼雷可通过多种发射方式攻击敌对目标，如飞机空投或舰载发射等，但不管采用何种发射方式，都要经过空中、入水、水下航行至命中目标的全弹道过程。
入水是一个短暂、变化激烈而又复杂的力学过程，在入水的整个过程中，鱼雷将经历撞水、浸水、带空泡航行、全浸湿后转入受控运动等4个阶段。
入水过程中雷体会激起周围流体介质的运动，反过来，流体介质对结构又施加各种反作用力。
入水冲击力有2个分量相当重要：一个是轴向力或阻力，会引起减加速度，可能使雷头变形，破坏鱼雷内部的仪表设备；另一个是法向力或升力，会形成力矩，产生横向角速度，影响弹道，并可能使雷体皱折或断裂。
因此研究空投鱼雷入水冲击力对鱼雷结构的总体设计以及水下弹道设计等方面具有重要的工程意义［1］。
本文中拟基于鱼雷入水动力学模型、动态非线性有限原理论和耦合算法［2］，计算计算鱼雷入水时受到的作用力，建立空投鱼雷入水冲击有限元模型，对不同工况进行数值模拟，以期为预测鱼雷入水冲击载荷提供参考。
1 鱼雷入水受力分析作用在鱼雷上的力可以分成2类：鱼雷重力和流体反作用力，流体反作用力中包括浮力和流体动力［3］。
ResearchPaper-IJMERR
119This article can be downloaded from /currentissue.phpSIMULATION STUDIES ON THE EFFECT OF PROJECTILE NOSE SHAPE IMPACTING ON ALUMINUM PLATESSivaiah A 1*, Nageshwar Reddy V 1 and Syed Altaf Hussain 1*Corresponding Author:Sivaiah A, ***********************In mechanics, an impact is a high force or shock applied over a short period when two or more bodies collide. Such a force or acceleration usually has a greater effect than a lower force applied over a proportionally longer period of time. The effect depends critically on the relative velocity of the bodies to one another. Structural failure due to impact is a common but complex phenomenon. In earlier days the impact problems were primarily confined to the military. As the civilian technology has grown in sophistication, more studies are being carried out to understand the behavior of materials subjected to short duration of loading. The field of impact dynamics is of interest to engineers concerned with design of light weight body amour, safety of nuclear-reactor containment vessels subjected to missile or aircraft impact, protection of spacecraft from meteoroid impact, safe demolition of pre stressed concrete structures and transportation safety of the hazardous materials. In the present work, simulation is performed by impacting aluminum plates of three different thicknesses viz. 0.81 mm, 1.51 mm and 2.05 mm by three different nose projectiles, i.e., blunt, conical and hemispherical with varying kinetic energy in Finite Element Code. Problem is modeled using ANSYS/Explicit Axi-symmetric Model.Keywords:Impact, Projectile velocity, Impact velocity, Residual velocity, Velocity drop INTRODUCTIONIn earlier days, the impact problems wereprimarily confined to the military. As the civiliantechnology has grown in sophistication, morestudies are being carried out to understandthe behavior of materials subjected to shortdynamics is of interest to engineers concerned with design of light weight body amour, safety of nuclear-reactor containment vessels subjected to missile or aircraft impact,protection of spacecraft from meteoroid impact, safe demolition of pre-stressed concrete structures and transportation safety Research Paper120This article can be downloaded from /currentissue.php Impact could be defined as collision of twobodies. The intensity of impact couldbe assmall as the hit of a droplet of rainwater onearth and as high as the collision of twoheavenly bodies such as comets or asteroids.In mechanics, an impact is a high force orshock applied over a short period when twoor more bodies collide. Such a force oracceleration usually has a greater effect thana lower force applied over a proportionallylonger period of time. The effect dependscritically on the relative velocity OBJECTIVE OF THE PROJECT In the present work numerical simulations areperformed on thin aluminium plates of threethicknesses 0.81 mm, 1.51 mm and 2.05 m,subjected to impact by conical, hemispherical and blunt projectiles. Projectiles are impacted normally with velocities in the sub-ordinance range.In modelling the problem in ABAQUS, effect of number of elements on the plate and type of element (triangular, quad) for different projectiles is studied.Impact and residual velocities are measured and energy absorbed by the projectile is calculated. Thicknesses of the plates and impact velocity of the projectile are varied. Mass anddimensions of the projectile are kept constant.Impact velocity is related to the residual velocityand velocity drop. Also variation of absorbedenergy with impact energy is studied.MODELLING OF THE PROBLEM121This article can be downloaded from /currentissue.php distortion in case of conical nosed projectile.For the case of impact by blunt and hemispherical nosed projectiles, quadrilateral elements were employed. An impact zone was created, where the projectile comes in contact with the plate, in which the mesh density was higher and was reduced as the distance from the impact area increased. The aspect ratio of the elements in the impact zone was maintained as unity; however it was allowed to increase elsewhere.Meshing StrategyThe target plate for the case of conical andhemispherical nosed projectiles was modelledwith continuum solid axisymmetric triangular3 noded elements with single integration point.This was done in order to reduce element122This article can be downloaded from /currentissue.php ABACUS INTRODUCTIONTable 4: Number of Elements Along the Thickness in MeshingFigure 5: Step 2 – PlateFigure 6: Step 3 – Entering the Material Properties, Inertia, Boundary Condition for the Figures123This article can be downloaded from /currentissue.php RESULTSFigure 6: Vonmises Stress Contour for Blunt Materials Figure 7: Vonmises Stress Contour for Blunt and Conical MaterialsFigure 9: Vonmises Stress Contour Hemi Spherical Materials Table 5: Residual VelocityBluntConicalHemi Spherical124This article can be downloaded from /currentissue.php CONCLUSION The present study deals with numericalsimulation of normal impact of projectile on thinsingle layered aluminium plates usingcommercial finite element code ABAQUS.Aluminium Plates are subjected to impact bythree different projectiles having conical,hemispherical and blunt noses. Impact andresidual velocities are obtained from the finiteelement code and impact and absorbedenergies are then calculated. The deformationmechanisms resulting from different noseshapes are also studied.Table 5: Velocioty DropBluntConicalHemi125This article can be downloaded from /currentissue.php In case of conical and hemisphericalprojectile the mode of deformation is petalling.They cause failure in the target by ductile holeenlargement. The nose of the projectile firstmade a minute hole in the target along the axisof the trajectory of the projectile and deformedthe target at the centre in shape of crater aroundthe nose of the projectile. In blunt projectileimpact a circular plug of diameter equal to thatof projectile is removed from the plate. Thethickness of plug is found to be same as that ofthe plate. As soon as the projectile comes incontact with the plate a global deformation inform of dishing takes place. The target platekeeps on deforming until the compressive forceapplied by the blunt projectile equals the plasticshear stress of the plate material and shearingof a plug takes place.It is observed from graph of residualvelocities that they follow a quadratic curve;conical projectile penetrated the target moreeasily than the hemispherical and bluntprojectiles, as is evident from the fact that forthe same impact velocity the residual velocityobtained for conical projectile case is more.The residual velocities were found to decreasewith increase in plate thickness for all blunt,conical and hemispherical projectiles.For the same thickness the energyabsorbed by target plate in case ofhemispherical projectile is highest. In case ofconical projectile energy absorbed is lowestand for blunt it lies after hemispherical. Forsame amount of impact energy (164 J) theenergy absorbed by 1.51 mm plate forhemispherical projectile case is around 66.06J and for conical projectile it is 27.63 J. Forthe same impact energy, energy absorbed byblunt projectile is 35.9 J. The absorbedenergies were found to increase with plate thickness; this increment was higher in case of hemispherical projectiles.The velocity drop of projectiles was found to increase with plate thickness, as the velocity is increased the drop in velocity decreases for same thickness and follows a quadratic trend line.REFERENCES 1.Bÿrvik T, Langseth M, Hopperstad O S and Malo K A (2002a), “Perforation of 12mm Thick Steel Plates by 20 mm Diameter Projectiles with Flat,Hemispherical and Conical Noses Part I:Experimental Study”,Int. J. of Impact Engg., Vol. 27, pp. 19-35.2.Bÿrvik T, Langseth M, Hopperstad O S and Malo K A (2002b), “Perforation of 12mm Thick Steel Plates by 20 mm Diameter Projectiles with Flat,Hemispherical and Conical Noses Part II:Numerical Simulations”,Int. J. of Impact Engg., Vol. 27, pp. 37-64.3.Chen X W and Li Q M (2003), “Shear Plugging and Perforation of Ductile Circular Plates Struck by a Blunt Projectile”,Int. J. of Impact Engg., Vol. 28,pp. 513-536.4.Gupta N K, Iqbal M A and Sekhon G S (2008), “Effect of Projectile Nose Shape,Impact Velocity and Target Thickness on the Deformation Behaviour of Layered Plates”,Int. J. of Impact Engg., Vol. 35,pp. 37-60.5.Gupta N K, Ansari R and Gupta S K(2001), “Normal Impact of Ogive Nosed126This article can be downloaded from /currentissue.php Projectile on Thin Plates”,Int. J. of ImpactEngg., Vol. 25, pp. 641-660.6.Iqbal M A, Chakrabarti A and Gupta N K(2010), “3D Numerical Simulations of Sharp Nosed Projectile Impact on Ductile Targets”,Int. J. of Impact Engg., Vol. 37,pp. 185-195.。
数字在日常生活中随处可见的英语作文
数字在日常生活中随处可见的英语作文Title: The Ubiquity of Numbers in Our Daily LivesIn the tapestry of our daily existence, numbers weave an intricate pattern, silently orchestrating the rhythm of our routines and punctuating the milestones of our lives. From the moment we wake up to the last glance at the clock before sleep, these numerical companions guide us through a world where quantification is as essential as the air we breathe.My day typically begins with the shrill alarm of my digital clock, displaying 6:00 AM in bold numerals, a gentle reminder that another 24-hour cycle has dawned. As I reach for my smartphone, the screen lights up, revealing not just the time but also a myriad of notifications –emails (3 unread), messages (7 new), and a weather app forecasting a high of 28 degrees Celsius, guiding my choice of attire for the day. This simple act underscores how numbers influence even the most mundane decisions we make.Stepping into the kitchen, the process of breakfast preparation becomes a symphony of measurements. Two slices of bread, 30 grams of butter, a tablespoon of jam – each portion meticulously quantified, ensuring consistency and flavor. The nutrition label on the cereal box boasts itscontents: 120 calories per serving, 5 grams of fiber, a testament to how numbers inform our dietary choices and health consciousness.As I commute to work, the bus stop displays the arrival times of upcoming buses – 7:15 AM and 7:29 AM. These digits dictate the pace of my morning, deciding whether I have time for a quick coffee or need to hasten my steps. Onboard, the ticket machine spits out a receipt marked $2.50, another transaction quantified, a testament to the financial transactions that grease the wheels of society.At the workplace, numbers take center stage in various guises. As a marketing analyst, my day revolves around data analysis – sales figures, customer demographics, conversion rates. These aren't just abstract concepts; they represent real people making choices, shaping trends, and influencing business strategies. A 10% increase in website traffic translates to tangible outcomes, impacting everything from product development to advertising budgets.Lunchtime sees me scrolling through food delivery apps, comparing prices, ratings (4.7 stars), and estimated delivery times (25 minutes). Even the simple act of nourishment is mediated by a flurry of numerical evaluations, each onepromising satisfaction and convenience.After a long day, exercise offers respite, tracked meticulously by fitness trackers. Steps taken (10,000), calories burned (500), heart rate zones (120-140 bpm) –these metrics transform physical activity into a quantifiable achievement, motivating and monitoring progress.The evening unwinds with entertainment, be it streaming a movie (4K resolution, 2 hours runtime) or delving into a book (Chapter 12, Page 274). Even leisure activities are demarcated by numerical landmarks, guiding our immersion and understanding of stories.Before bed, I check my bank balance (savings: $3,200, checking: $800), a ritualistic dance with financial stability. Bills paid, savings accumulated, each digit a reflection of responsibility and future aspirations.Numbers, in essence, are the universal language that binds our experiences, turning the abstract into the tangible. They measure our achievements, guide our decisions, and quantify our world. In every heartbeat, every step taken, and every dream pursued, numbers are there, silently chronicling our journey, a constant reminder of the intricate dance of life we all partake in.。