A wind tunnel simulation of the dynamic processes involved in sand dune formation on the western
Fluid-Structure Interaction and Dynamics
Fluid-Structure Interaction and Dynamics Fluid-structure interaction (FSI) is a complex and fascinating field that involves the interaction between deformable structures and surrounding fluids. This interaction can lead to a wide range of dynamic behaviors and phenomena, making it a crucial area of study in various engineering disciplines. From flutter in aircraft wings to the movement of blood in the human body, FSI plays a significant role in understanding and predicting the behavior of systems where fluids and structures interact. One of the key challenges in FSI is accurately modeling and simulating the interaction between the fluid and structure. This requires a deep understanding of the physics involved, as well as advanced computational tools and techniques. Computational fluid dynamics (CFD) and finite element analysis (FEA) are commonly used to model and simulate FSI problems, allowing engineers to predict how a structure will deform under the influence of fluid forces, and how the fluid flow will be affected by the presence of the structure. In addition to modeling and simulation, experimental testing is also crucial in validating FSI models and understanding the real-world behavior offluid-structure systems. Wind tunnel tests, water tank tests, and other experimental techniques can provide valuable insights into the dynamics of FSI systems, helping engineers to refine their models and improve the performance and safety of structures exposed to fluid forces. From a practical standpoint, FSI has numerous applications in various industries, including aerospace, automotive, civil engineering, and biomechanics. In aerospace, FSI is critical for designing aircraft wings that can withstand aerodynamic forces and vibrations, while in automotive engineering, FSI is used to optimize the performance of vehicle bodies and components under different flow conditions. In civil engineering, FSI is essential for designing bridges, dams, and other structures that are exposed to wind, water, and other fluid forces, while in biomechanics, FSI is used to study the flow of blood in arteries and veins, and its impact on the cardiovascular system. Despite its importance and widespread applications, FSI remains a challenging and evolving field, with many open research questions andopportunities for innovation. Researchers and engineers continue to explore new techniques for modeling and simulating FSI systems, as well as developing advancedmaterials and structures that can better withstand fluid forces. By advancing our understanding of FSI, we can improve the performance, efficiency, and safety of a wide range of engineering systems, leading to better designs and solutions that benefit society as a whole. In conclusion, fluid-structure interaction is a fascinating and important field that plays a crucial role in understanding and predicting the behavior of systems where fluids and structures interact. By combining advanced modeling and simulation techniques with experimental testing and practical applications, engineers can gain valuable insights into the dynamics of FSI systems and develop innovative solutions to complex engineering challenges. As we continue to push the boundaries of FSI research, we can unlock new opportunities for improving the performance and safety of structures exposed to fluid forces, leading to a more sustainable and resilient built environment.。
矩形截面高层建筑立面上面风压极值的尺度折减系数
第49卷第3期2021年3月同济大学学报（自然科学版）JOURNAL OF TONGJI UNIVERSITY（NATURAL SCIENCE）Vol.49No.3Mar.2021论文拓展介绍矩形截面高层建筑立面上面风压极值的尺度折减系数全涌1，王翔1，张正维2（1.同济大学土木工程防灾国家重点实验室，上海，200092；2.奥雅纳工程咨询（上海）公司，上海，200031）摘要：通过一系列刚性模型测压风洞试验，研究了矩形截面高层建筑立面面风压极值的变化特征，并与我国建筑结构荷载规范GB50009—2012中的相关规定进行了对比，分析了受压面的面积、水平尺度及竖向尺度的影响，给出了更合理的尺度参数。
试验结果表明，随受压面尺度的增加，面风压极值逐渐减小，当足尺面积达到50m2时，面风压正极值的尺度折减系数在0.9左右，而负极值的尺度折减系数在0.8左右。
我国建筑结构荷载规范对围护结构风荷载的尺度折减方法将导致面风压极值的低估，尤其是面风压正极值。
以作用面面积、对角线长度和宽度作为尺度参数描述面风压极值折减系数的变化规律都不合理，建议采用以受压面的水平尺度b、竖向尺度h和整个建筑迎风面宽度B确定的综合尺度参数（b0.85h0.15/B）来描述建筑立面上面风压极值的尺度折减系数的变化规律。
关键词：围护结构；面风压；尺度折减系数；高层建筑；面积平均法中图分类号：TU312.1文献标志码：A Size Reduction Factor of Extreme Area-Averaging Wind Pressure on Claddings of High-Rise Buildings with Rectangular SectionQUAN Yong1，WANG Xiang1，ZHANG Zhengwei2（1.State Key Laboratory of Disaster Reduction in Civil Engineering，Tongji University，Shanghai200092，China；2.Arup International Consultants（Shanghai）Co.，Ltd.，Shanghai 200031，China）Abstract：By conducting a series of wind pressure measurement wind tunnel tests，the characteristics of the extreme area-averaging wind pressures on the cladding of a building with a rectangular cross-section were studied. The test results were compared with relevant standards of Load Code for the Design of Building Structures（GB50009—2012）.The influence of areal size，horizontal scale and vertical scale of forced areas were discussed，and more reasonable scale parameters were suggested for size reduction coefficients（SRCs）of area-averaging wind pressure.The results indicate that extreme wind pressure gradually declines with the size of forced areas increasing. When the full-scale area reaches about50m2，the SRC of positive extreme area-averaging wind pressure is close to about0.9，while that of negative extreme area-averaging wind pressure is close to about0.8.The wind-load reduction method of building structure load code in China will lead to an underestimation of wind pressure extreme value，especially in the most unfavorable positive pressure.It is not appropriate to describe the variation of the reduction coefficient by taking the area of acting surface as the size parameter.It is，therefore，suggested that comprehensive size parameters，b0.85h0.15/B，of the horizontal dimension，b，vertical dimension，h，of the acting surface and the width，B，of the windward surface of the whole building be used to determine the SRCs of the surface wind pressure extremum of the cladding.Key words：cladding；area-averaging wind pressure；size reduction factor；high-rise building；area-averaging method为了简化起见，工程设计中常常有人直接采用测点风压的最不利值进行围护结构设计，这默认受压面上不同位置处的风压时程是同步变化的。
用动网格模拟超音速飞机投弹过程
⽤动⽹格模拟超⾳速飞机投弹过程J O U R N A L A R T I C L E S B Y F L U E N T S O F T W A R E U S E R SWorking closely with the U.S. Air Force Munitions Directorate, Jacobs Sverdrup engineers have developed a method to accurately simulate the behavior of stores (such as munitions) as they are released from transonic aircraft. The separation of stores is a challenging problem that cost manyaircraft during the period when flight testing was the only way to evaluate alternative designs.Computational fluid dynamics (CFD) simulations of munitions separation are challenging because the rapid movement requires continual modification of the mesh, which drives the demand forcomputational resources. Jacobs Sverdrup engineers have overcome this problem by using an unstructured dynamic mesh technique. The ability to dynamically change an unstructured mesh greatly increases the speed of grid generation at each time step of the calculation. Comparing the CFD results with wind tunnel testing for one case studied showed that this method was able to accurately predict the location and velocity of the center of gravity, the angular orientation and its rate of change, and surfacepressure profiles after release. The ability to simulate separation events willsubstantially reduce design time and cost and will allow engineers to evaluate many more potential designs,presenting the opportunity for substantial performance improvements.The aerodynamic behavior of munitions or other objects as they are released from aircraft is criticalboth to the accurate arrival of the munitions at the target and the safety of the releasing aircraft. The challenge is especially great for objects that are dynamically unstable, such as fuel tanks and some modern, agile munitions in the event of control failure. In the distant past, separation testing was accomplished solely using flight tests. This approach was very time-consuming, often requiring years to certify a weapon. It was also expensive and occasionally led to the loss of an aircraft due to unexpected behavior of the store being tested. In the 1960s, methods of predicting store separation in wind tunnel tests were developed. These tests have proven so valuable that they are now the primary design tool used. However, wind tunnel tests are still expensive,have long lead times, and suffer from limited accuracy in certain situations, such as wheninvestigating stores released from within weapons bays or the ripple release of multiple moving objects.In addition, because very small-scale models must often be used, scaling problems can reduce accuracy.Dynamic Meshing Models Store Separation f rom Transonic AircraftJA212Figure 1: Perspective view of the wing/pylon/store geometryBy Deryl O. Snyder Aerospace Engineer,Jacobs Sverdrup, Inc.Eglin Air Force Base, FloridaThe advent of simulationIn recent years, engineers have begun using modeling and simulation to reduce certification cost and evaluate additional designs in order to increase the margin of safety for flight-testing. A CFD simulation provides fluid velocity, pressure, temperature, and other variables, as appropriate, throughout the solution domain for problems with complex geometries and boundary conditions. As part of the analysis, an engineer may change the geometry of the system or the boundary conditions, and observe the effect of the changes on fluid flow patterns or distributions of other variables. The use of CFD for modeling store separation began by combining traditional steady-state solutions with empirical or semi-empirical approaches. The methodology became more useful with the innovation of Chimera overset (overlapping) grid approachesthat made it possible to perform unsteady, full field simulations with or without viscous effects. Until recently, CFD has not reached its full potential for modeling transonic separation events because of the large amount of time required to perform simulations. The grid must be generated, assembled and recalculated at each time step of the simulation. Fine grids and small time steps are often required for accuracy and stability, which increases computationaltime. The most time-consuming aspect of the Figure 2: Surface meshes for coarse, nominal, and fine gridssimulation is usually the grid generation and assembly. This is especially true for complex store geometries, and in particular, for the case of stores released from weapons bays. These bays often contain intricate geometric features that affect the flow field.Unstructured dynamic meshing approach To improve on these methods, Sverdrup engineers set out to develop an unstructured dynamic meshapproach for store separation simulations. Grid generation time with unstructured meshes is reduced because the user's input is largely limited to the generation of a surface mesh. Also, because there are no overlapping grid regions, fewer grid points are required. The Sverdrup computational approach consists of three distinct components: a flow solver, a six-degree-of-freedom (6DOF) trajectory calculator, and a dynamic mesh algorithm. The FLUENT flow solver from Fluent Incorpor, Lebanon, New Hampshire, is used to solve the governing fluid dynamic equations at each time step. From this solution, the aerodynamic forces and moments acting on the store are computed by integrating the pressure over the surface. The forces and moments are used to compute the movement of the store by the 6DOF trajectory code. This code integrates the Newton-Euler equations of motion within FLUENT as a user-defined function (UDF) that is dynamically linked with the FLUENT solver at run time. A local remeshing algorithm is used to accommodate the moving body in the discretized computational domain. Finally, the unstructured mesh is modified to account for store movement via the dynamic mesh algorithm. When the motion of the body is small, a localized smoothing method is used. When the motion of the moving body is large, poor quality cells, based on volume or skewness criteria, are agglomerated and locally remeshed.Validating the new methodThis approach was demonstrated on a genericwing/pylon/store geometry for which benchmark experimental data was available. The wing is a 45-degree clipped delta with a 25-foot root chord length. The ogive-flat pylon extends 2 feet below the wing leading edge. The store consists of a tangent-ogive forebody, a clipped tangent-ogive afterbody, and a cylindrical centerbody. Fluent' preprocessor, Gambit, was used to generate triangle surface meshes from CAD geometry files. The meshes were imported into Fluent's meshing preprocessor, TGrid, for generation of the tetrahedral volume mesh. The automated meshing tools in GAMBIT and TGrid made it possible to create all three meshes in just a few hours. Nonpermeable wall boundary conditions were used for the wing, pylon, and store surfaces. A pressure far field condition was used at the upstream and downstream domain extents, a symmetry plane was used at the wing root, and the downstream boundary was assigned a pressure outlet condition. The initial condition used for the separation analysisFigure 3: Comparison of numerical (blue) and experimental (shadow) separation eventswas a fully converged steady-state solution. Time steps of three sizes, 0.01 sec., 0.002 sec and 0.0004 sec., were evaluated for each of three grid refinements used.The results showed that CFD performed very well in modeling a separation event at Mach 1.2 at an altitude of 38,000 feet. The center of gravity location matched very closely with the experimental data for all three grid refinements The store moved rearward and slightly inboard as it fell. The CFD results slightly underpredicted the rearward acceleration. The pitch and yaw angles of the store calculated by the simulation also agreed well with the experimental results. The roll angle is especially difficult to modelbecause the moment of inertia about the roll axis is much smaller than that of the pitch and yaw axes. Consequently the roll is very sensitive to errors in aerodynamic force prediction. In this case, the store initially pitched nose-up in response to the moment produced by the ejectors. Once free of the ejectors, the nose-down aerodynamic pitching moment reversed the trend. The store yawed initially outboard until about 0.55 seconds, after which it began turning inboard. The store rolled continuously outboard throughout the first 0.8 seconds of the separation. This trend was underpredicted by the simulation and the curve tended to diverge from the experiments after approximately 0.3 seconds.Experimental surface pressure data was also available from the wind tunnel tests. The data was compared with the simulation along axial lines of the store body at four circumferential locations and three instants in time. The agreement between the simulation and experiments was exceptional. Of particular interested was the 5 degree circumferential location line at t=0.0 because it is located in the small gap between the pylon and store. The simulation did a good job of capturing the deceleration near the leading edge of the pylon.All in all, this study showed that CFD with unstructured dynamic meshing can be a powerful tool for modeling transonic store separation. The simulation captured the experimental location, velocity, orientation and angular rate trends. Surface pressure distributions were also in excellent agreement with the experiments at the three times at which they were compared during the separation event. This new approach offers the ability to obtain accurate store separation predictions with quick turn-around times. Grid generation can be accomplished in a matter of hours, and runs such as the nominal grid case examined in this study can be completed overnight on a desktop workstation. The use of unstructured tetrahedral meshes and a fully parallelized, accurate and stable solver allows for small grids and relatively large time steps without anexcessive computational burden.Figure 4: Rigid boundary layer mesh attached to the store。
WIND TUNNEL HOMEWORK
Technical capabilities of (Auto) wind tunnels"Wind tunnel" from the English "wind tunnel", the first "wind tunnel" designed to study aircraft's aerodynamic performance.Follow The development of the global automobile industry, it is widely used in the design and development of new vehicles being. By simulating the flow of air relative sunshine precipitation and other traffic environment to design cars to find the most fuel efficient, safest and most beautiful shape for parts to obtain the safest, most durable performance. Automotive design generally includes hand-painted preliminary design renderings, making clay models, making the kind of car, wind tunnel tests, crash test, road test, vehicle crash test and other processes.Wind tunnel mainly by wind tunnel cave, drive systems and measurement and control system components, in the form of various parts of the tunnel due to type.1 A caveIt has a test section of the model can be measured and observed necessary. Upstream of the test section has improved airflow evenly straight, lower and stable segment airflow turbulence intensity and flow rate of contraction accelerated to the desired section or nozzle. Reduce the flow rate test section downstream, reducing energy loss diffuser and exhaust air flow towards the outer section of the wind tunnel or reflux back into the inlet section of the wind tunnel. Sometimes in order to reduce the noise inside and outside the tunnel, in a stable section and exhaust ports, etc. equipped with muffler。
浅谈CFD技术在建筑风环境模拟中的应用
浅谈CFD技术在建筑风环境模拟中的应用摘要近年来，建筑的风环境越来越多地引起人们的重视。
风是构成环境，尤其是室外环境的重要因素之一，风和城市环境、建筑环境有着密不可分的关系，并对城市规划、建筑设计和结构设计等领域起着很大的影响。
然而人们对风环境的掌握十分困难，传统的模拟手段费时、费力，且结果收集存在误差。
近些年来，CFD技术越来越多的被各行业的技术人员用来作数字化模拟的手段，其不可替代的优势必将使建筑模拟技术实现新的飞跃。
关键词：建筑风环境CFD技术AbstractIn recent years, more and more people pay attention to building wind environment. Wind is one of the important factors constituting the outdoor environment, wind and the urban environment, the built environment has a close relationship, and urban planning, architectural design and structural design field plays a big impact. However, it is very difficult to master the wind environment, The traditional analog means consuming and laborious. In recent years, more and more of the technical staff of the various industries used CFD technology as a means of digitized analog, its irreplaceable advantages will make the building simulation technology to achieve a new leap.Keywords: Building wind environmentCFD technology0.引言人、自然、建筑、城市一直是紧密相关的概念，而风与他们都有关系。
风洞测试实验 英文
Stanislav Pospíšil, Miloš Drdácký, Zuzana Slížková, Jaroslav Lesák, Dagmar Knotková Institute of Theoretical and Applied Mechanics, AS CR
ห้องสมุดไป่ตู้
2 Current status – CWT, BLWT
CLIMATIC WIND TUNNEL
• rain-250 mm/h
•sand conc. - 10 g/m3 in a 10 m2 section • -25 ° C to +50 ° C and relative humidity from 30% to 100% •flow speed can be set from 90 km/h to 140 km/h. • snow mantle (15 cm/h) on the 200 m2 floor of the test chamber.
• Gothic pinnacles from one of the most important late medieval Gothic churches, St. Barbara’s in Kutná Hora (Bohemia), were exposed to accelerated clima for a period of four days in order to test the efficiency of hydrophobic surface coating • Usually individual effects are analysed
高速列车头型长细比对气动噪声的影响
高速列车头型长细比对气动噪声的影响安翼;莫晃锐;刘青泉【摘要】高速列车的头尾车外形对气动噪声具有重要的影响.工程实践中随着车速的增加,车辆头部越来越细长,日本高速磁悬浮列车实践中甚至出现了具有极端长细比的头部形状.本文以讨论头型长细比对列车气动噪声的影响规律为出发点,应用非线性声学求解器(NLAS)和FW–H声学比拟法的混合算法,在3种运行速度下对基于CRH380A高速列车头型概化的4种不同头型长细比的模型车的气动噪声进行了数值模拟.给出了不同头型长细比列车的流场特征、气动阻力和气动噪声.结果表明,列车的气动总阻力随头型长细比的增大而减小,且头型长细比对列车总气动阻力的影响随运行速度的增加而增强.而头型长细比对气动噪声的影响呈现出较为复杂的影响,并不存在单调的影响关系;综合考虑气动阻力和气动噪声,长细比最大的头型综合性能较优,但差异并不显著,因此在不考虑微气压波等因素的条件下,简单增加车头长细比并不一定能带来明显的气动噪声性能提升.%In the high-speed train design, the nose shape is a crucial control factor influencing not only aerodynamic performance but also the aerodynamic noise. In the engineering practice, the nose shape becomes more and more slender along with the increasing of the design speed, e.g. the Japanese high-speed maglev train L0 series even has a 15 m long slender nose (the slenderness ratio reach to 8.8). This study aims to discuss the influence of the slenderness ratio of the nose shape on the aerodynamic noise. The hybrid numerical method of nonlinear acoustics solver (NLAS) and Ffowcs Williams-Hawkings (FW-H) acoustic analogy method is employed to study the aerodynamics noise characteristics. The numerical method is validated with a standard windmirror test case and a set of acoustics wind tunnel experiments of the CRH380A train. The shape of the CRH380A train is chosen as a bench mark, and four different nose shapes of different slenderness ratio under different running speed situation are studied with numerical simulation. The flow field, aerodynamic drag, and the aerodynamic noise are obtained and discussed. The result shows that the total drag decrease with the increase of the slenderness ratio, and this effect enhances when the train speed increases. However, the influence of the slenderness ratio on the aerodynamic noise is much complex as no simple trend is observed. Considering both the aerodynamic and aeroacoustics characteristics, the train with the most slender nose shape is the best while this advantage is not notable compared with the second-best. Thus, simply increase the slenderness does not necessarily result in better aerodynamic noise performance if the effect of tunnel boom is not considered.【期刊名称】《力学学报》【年(卷),期】2017(049)005【总页数】12页(P985-996)【关键词】高速列车;气动噪声;气动阻力;头型长细比【作者】安翼;莫晃锐;刘青泉【作者单位】中国科学院力学研究所流固耦合系统力学重点试验室,北京100190;中国科学院力学研究所流固耦合系统力学重点试验室,北京100190;北京理工大学宇航学院力学系,北京100081【正文语种】中文【中图分类】O354.1;TB533+.2;U260.16;U266近年来，我国的高速铁路迅速发展，已成为我国最主要的城际客运系统之一，更高速的磁悬浮列车也正在研发中.随着列车运行速度的不断提升，噪声问题日显突出，成为影响高速列车可持续发展的关键问题之一.高速列车的噪声主要由机械噪声和气动噪声组成[1]，气动声学理论指出，气动噪声的声功率与速度的6～8次方成正比[2]，而机械噪声则与速度的低次幂相关.研究表明[34]，当列车运行速度超过300km/h时，气动噪声将显著增强，并主导列车的总体噪声.高速列车的气动噪声主要来自于头尾车、转向架、受电弓和车体[5]，其中头尾车产生的气动噪声是其主要来源之一[6].Mellet等[7]分析了不同时速下的TGV-Duplex和ICE3高速列车的大量噪声实测数据，发现头尾车噪声占全车噪声的比重随着列车速度的提高而快速增长，当运行速度达到300km/h以上时，头尾车辐射的噪声超过其余八节车厢辐射的噪声，且头车的噪声比尾车噪声还要显著.由于高速列车头尾车的几何外形决定着周围流动的附着、边界层的发展和分离，以及列车尾部的流动分离和所产生的非定常尾流[8]，头尾车气动噪声的产生与其几何形状密切相关[9].Kitagawa和 Nagakura[10]分析了日本新干线高速列车的气动噪声组成以及声源位置，发现光滑的车体表面可以有效地减少车体上部产生的气动噪声.Torii和Ito[11]对新干线列车噪声源的研究发现，对列车鼻形的改进可以降低标准测点处(距离轨道中心线25m，距地面高3.5m)约2dB(A)的噪声级，同时可有效减少列车在隧道中的压力波.Maeda等[12]和Ido等[13]通过风洞实验进行了一系列长细比下的高速列车头型的气动阻力测试，发现列车的气动阻力随着头型长细比的增大而有效降低.喻华华[14]曾在不同来流速度条件下，对CRH380高速列车的5种备选头型的气动噪声进行了风洞测试，结果表明，在相同长细比条件下，当头型满足流线型设计要求时，其不同横截面形状的车鼻对列车总体气动噪声的影响较为有限.王成强等[15]应用基于NLAS(nonlinear acoustics solver)的CAA模拟方法对高速列车的气动噪声进行了数值模拟研究.潘忠和陆森林[16]发现表面声功率级和脉动压力级最大值都出现在鼻锥、雨刷器等表面曲率变化较大的部位.高速列车的头车和尾车具有一致的外形设计，一般为复杂的三维曲面 [17]，其横截面存在明显形状或面积变化的区段称为车鼻，通常由此确定了头型最主要的几何特性[18].车鼻外形由众多参数决定，为头型特征结构的气动噪声特性研究带来了困难，实际研究中，常定义车头鼻形部位长度与后部车身断面等效半径之比为头型的长细比[19]，其与车鼻横截面形状分布一起，成为头型设计的重要参数.实践中，日本在 2015年试验的下一代磁悬浮列车L0系采用了长达15m的车鼻，而其车厢断面仅为3.1m×2.9m，长细比高达8.8，对列车功能和使用模式的设计都产生了影响.而在我国高速磁悬浮列车发展中，长细比在气动外形设计中的位置也是一个值得思考的问题.高速列车头型的长细比对列车气动性能有着显著的作用和影响，然而，至今关于头型长细比对列车气动噪声影响的研究还较少，仍缺乏深刻的规律性认识.为此，本文将通过数值模拟方法，以我国自行设计的CRH380A高速列车为对象，参考飞行器设计中的优化技术[2022]，针对特定的车鼻横截面形状函数，探讨其分布区间的改变，即头型长细比的变化，对不同运行速度下高速列车气动噪声的影响，以期为合理进行头型降噪设计提供科学依据.本文采用计算流体力学/计算气动声学 (hybrid CFD/CAA)的混合方法对高速列车的气动噪声进行数值模拟.将计算区域分为非线性声源区(近场流动区)和线性声传播区，分别采用相应的计算方法求解.虽然大涡模拟(LES)和脱体涡模拟(DES)类方法以及FW-H方法已经逐渐用于噪声计算[23]，但其计算量很大.考虑到本文研究对象为细长流线体，其流动的不稳定性较弱，本文选用由Batten等[24]提出的计算量较低的非线性声学求解器(non-linear acoustics solver,NLAS)作为近场流动的求解算法.即首先使用cubic k-ε RANS模型求解Navier-Stokes方程，获得流动的统计定常解，然后运用非线性声学求解器(NLAS)求解流动的非定常时空演化和压力脉动，获得近场流场和噪声声源信息.而对于远场噪声的预测则采用声比拟法实现，即采用FW-H方程[25]，通过在控制面的积分得到远场噪声.由于近场部分求解的是脉动量，避免了LES等方法直接使用流动量造成的数值误差，同时对流项影响较小，NLAS对网格的需求也远低于LES和DES等方法.非线性声学求解器是由Batten等[2627]提出的一种求解统计定常状态流动中声的产生与传播的数值算法，其控制方程是从Navier-Stokes方程的扰动推导而来，称之为非线性扰动方程(NLDE)[24]，其形式为式中，ρ为密度，u为速度，e为能量，τ为切应力，p为压强，δ为delta函数. 忽略密度扰动，对上述方程组取时间平均，可以消去时间演变项和所有线性通量项，得到其中，Ri中的物理量对应于标准雷诺应力张量和湍流的热通量项，通过RANS方法可以求得这些未知项.远场声压的预测基于Farassat[28]给出的FW-H方程的时域积分解这里，Qi=(ρ∞−ρ)vi+ρui，Li=pˆni+ρui(uj−vj)nj；ρ∞和c∞分别为远场未受扰动流体介质的密度和声速，ui和vi分别表示当地流体速度和物体表面速度；ˆni和ˆri分别为物面单位法向矢量n和单位发射矢量(x−y)/r在3个方向的分量，r=|x−y|为观测点与声源之间的距离，其中x和y分别表示观测点和声源的位置矢量.符号[]ret代表在延迟时间τ=t−r/c∞下取值，其中t和τ分别为声源发出声波的时间和声波到达观测点的时间；Mr=viˆri/c∞为声源与观测点方向上的马赫数.首先用经典的汽车后视镜噪声算例做验证.Hold等[29]和Siegert等[30]对放置于平板上的汽车后视镜简化模型的气动噪声进行了风洞实验.如图1所示，后视镜简化模型由1/2圆柱与1/4球体拼接组成，竖直放置于平板上，圆柱直径和高度以及1/4球体的直径均为0.2m.将圆柱的下底面圆心设为坐标原点，流场中设置了两个压力探点，探点a位于半圆柱下游表面的边缘，坐标为(0.0,0.117,0.085)，探点b位于下游尾流的平板表面处，坐标为(0.3978,0.0,0.14181).本文采用与Siegert[30]实验相同的后视镜模型及几何配置，运用非线性声学求解器(NLAS)数值计算后视镜简化模型的近场流动与压力脉动.采用六面体结构网格离散求解空间，流动求解域范围为x ∈ [−5D,15D]，y ∈ [0,10D]，z ∈[−5D,5D]，网格量约4.9×105. 来流速度U∞ =200km/h，瞬态计算的时间步长△t=2×10−5s，约为5.6×10−3T0，其中，T0=D/U0≈ 3.6× 10−3s 为流场以平均流速传播一个特征长度D所需的时间.数值求解时，后视镜模型和底部平板采用绝热的无滑移固壁条件，其它边界处为来流速度200km/h、参考温度298.5K和参考压力99530Pa的远场边界条件.计算可解析的信号最高频率fmax=1/(2∆t)=25000Hz.图2为探点a与探点b处声压级的数值计算结果与Siegert实验结果的对比.结果显示，在探点a处，数值结果低估了约40～400Hz频段内的声压级，但其余频段的声压级与实验结果吻合很好；而在探点b处，数值计算结果与实验结果在40～2000Hz的频段内整体上有着较好的吻合，在60～100Hz频段处，NLAS较为理想地预测了探点b处声压谱的峰值特征，但峰值频率的预测结果较实验结果偏低，整体上数值结果和实验测量结果符合良好.其次应用在同济大学的气动--声学风洞中开展的1:8模型试验结果做验证[14].该风洞在喷口速度160km/h试验段背景噪声SPL(A)为61dB，截止频率为50Hz.模型试验使用CRH 380A三编组模型，为突出头型影响，去除转向架并将其和车厢连接处填充光滑.试验中测点在距模型7.5m处平行于车长方向布置，有4组测点采集了噪声数据，试验共研究了200,230和250km/h三种风速.本文对三种风速条件下的噪声频谱和分布进行了研究，典型工况(250km/h，中间测点)的计算和试验测量结果的比较如图3所示.图中可以看出，模拟结果和试验测量结果在200Hz以上区域吻合良好，低频部分有差异.差异可能主要由风洞低频背景噪声所引起，但总体上在列车噪声所关注的频率范围，本文的数值方法给出了较好的结果.总体上验证了所采用数值方法的有效性和准确性.基于CRH380A高速列车的基本头型，抽象简化出代表列车主体结构特征的细长结构体，作为本文研究的列车几何模型，模型列车为头车、单节中间车厢和尾车组成的三节车体编组.由于车体复杂部件对流场有一定影响[3132]，本文去掉车厢间隙、受电弓和转向架等非光顺曲面结构以突出头部形状的影响，并将CRH380A高速列车的车鼻横截面形状作为初始的分布函数.将列车车鼻看作是其二维横截面沿长度方向的分布，则可使用函数S(l)表征其形状，S(l)为距离车头鼻尖l位置处的横截面形状函数，设其相对应的面积为A(l)，其中，l∈[0,ln]，ln为车鼻长度，其一般应小于单节车体的总长度.当确定车鼻横截面形状函数S(l)和其分布区间[0,ln]后，头型的最主要几何外形即可确定，其长细比λ=ln/r，其中为头型后部断面的等效半径值.为研究头型长细比对气动噪声的影响，采用了4种具有不同长细比的头型，它们对应的列车几何模型如图4.CRH380A的头型ln为12m，长细比λ0约为6.36，A,B,C,D四种列车模型对应的头型长细比分别为：λA=0.75λ0，λB=1.0λ0，λC=1.25λ0，λD=1.5λ0.简化列车模型的单节车体长Ls=26m，宽W≈3m，高H≈3.5m，取列车下底面面心为计算域原点，从而车体长度在x轴上的范围为[−39m,39m].数值计算区域长度范围为x∈[−4.5Ls,10.5Ls]，宽y∈ [−4Ls,4Ls]，高z∈ [−h,4L s]，其中h=0.371m为车体底面距离地面的高度.计算网格为四面体非结构网格，壁面附近区域的网格分辨率约为，在车体的尾流区域对网格进行了加密，当地网格分辨率约为.列车车体壁面边界层采用了棱柱网格，按照NLAS计算原理，第一层网格取在对数区，其高度对应的y+≈150，模型的计算网格总量约为5.8×106(见图5).数值求解时，列车车体为绝热的无滑移固壁条件，地面采用不可滑移的运动固壁条件，其运动速度与来流速度一致，其他边界处为参考温度298.5K和参考压力101325Pa的均匀来流的远场边界条件.近场流动的非定常计算使用隐式的双重时间步(dualtime-stepping)方法，瞬态计算的时间步长∆t=5×10−5s. 计算可解析的信号最高频率fmax=1/(2∆t)=10000Hz.计算采用了250km/h,350km/h,500km/h三种运行速度，对应的马赫数 Ma分别为0.204,0.286和0.408.由于上述马赫数之间的差异较大，并处于弱可压缩区间，近场流动的数值求解统一采用了可压缩形式的控制方程，同时，通过预处理方法调节控制方程的Jacobi系数矩阵特征值u−c,u+c和u的大小，以减小声速u±c和流体质点速度u之间的差异，减少控制方程系数矩阵的特征值分散，使问题的刚性降低以提高收敛速度.求解过程中，首先使用cubic k-ε RANS模型求得流动的定常解，进行脉动重建后运用非线性声学求解器(NLAS)进行非定常流动演进，并在预设噪声面上采集压力脉动.在这一求解步，开始收集声源信息之前流动经过了额外的0.5s的非定常演变，以消除脉动重建所造成的人为影响，获得统计稳定的非定常流动.随后，在时间上继续推进0.5s以便在噪声面上记录近场流动的压力脉动，脉动信号的采集时长足够FW-H远场积分的需求.最后进行压力脉动的FW-H积分以获得远场兴趣点处的噪声信息.流场特征决定了列车的气动噪声，为此我们首先分析了列车周围的流场特征.结果显示不同模型在不同速度下的流场表现出基本相似的特征.图6所示为B头型在350km/h运行速度下，列车周围流场不同剖面的流线.流线使用当地流向速度U与自由来流速度U∞的差值∆U进行渲染，为清晰对比当地流向速度与自由来流速度的相对大小，将速度差∆U的取值范围限定在[−10m/s,10m/s]的区间中.可见，在列车头车位置，流体从鼻尖驻点沿车鼻表面开始加速，且车鼻近地表面处的流体加速较快，在较短的距离内，当地流体的流向速度便超过了来流速度.而在车鼻表面的其他位置，流体随着曲面截面的扩张不断加速，并在车鼻截面达到最大时达到了局部的最高速度，随后，流体沿着具有固定截面形状的车体发展，当地流向速度趋近于来流速度.当流动发展到尾车附近时，车体上表面流体在尾车车鼻顶部存在加速段，随后速度快速下降，进入尾流区.在车体后部的两侧位置，靠近车体表面的流体流向速度在较长距离内都低于来流速度，它们与车体上表面的流体一起，汇聚进入车体尾部的尾流.根据Powell等的涡声理论，旋涡与势流以及旋涡之间的相互作用是流动致声的重要机制，涡不仅是流体运动的肌腱，同时也是流动产声的引擎.为此，分析了流动中的涡结构.流场中的涡湍流结构可通过 Q判据较好地表征和展现，Q被定义为：Q=(ΩijΩij− SijSij)/2,其中,以及.当流场中某处的Q值大于零时，表示当地流体微元的旋转运动主导了拉伸和剪切等形变运动.图7为运行速度350km/h时，不同头型长细比的列车周围流场的Q判据等值面，Q的取值为(U∞/H)2，其中U∞=350km/h为来流速度，H≈3.5m为车体高度.Q判据等值面由当地压力p与来流压力p∞=101325Pa的差值∆p渲染和着色，为更清楚对比，∆p的取值限制在区间[−100Pa,100Pa]内.根据图7所示的计算结果，4种车型的Q判据等值面具有相似的空间外形，主要存在于车体表面附近和尾流区域，由此可知，细长列车体流动中的主要声音产生区域为车体表面和尾流区.不同车型的Q判据等值面上的压力分布规律也具有一致性：头车车鼻位置具有高于来流压力的压力状态，随着流体沿着车鼻表面的加速流动，车鼻后部的流体速度高于自由来流速度，导致其当地压力低于自由来流的压力.随后，中间车体的压力逐渐趋于自由来流的压力值，当流体运动到列车尾部时，局部的加速导致当地压力快速下降，而当加速的流体进入尾流区域，其压力再次迅速上升.不同长细比的头型具有相异的车鼻长度和不同的截面变化率，导致当地流体的加速和减速状态存在差异，在压力分布上，表现为车头和车尾位置压力状态的空间差异.为了更清楚地了解列车周围的涡结构，图8给出了模型B尾流区域的Q判据等值面的局部视图.从中可以看出，列车尾流中存在明显的涡列对，并伴随着一系列的环状涡，环状涡从车体尾部开始发展，沿着尾流逐步扩张并随之破碎，尾涡结构的发展及破碎行为将产生可观的气动噪声.而尾涡中的压力分布整体上是从车体尾部向下游方向降低，逐步恢复到自由来流的压力状态，但其局部的压力状态是十分复杂的，比如，同一环状涡的不同位置，其压力值存在较大的差异.近场流动中压力脉动p′的空间分布特征如图9所示，p′为各位置的瞬时压力p与时均压力¯p的差，即p′=p−¯p.从车体中纵剖面处的压力脉动灰度描述(图9(a))可知，列车表面的压力脉动呈现出沿车体表面正负压力交替分布的偶极子声源特性，而尾流区的压力脉动是在体空间内正负交替分布的，表现出四极子声源特性.图9(b)给出了近场压力脉动的三维空间描述，从中可以清晰地看出，列车表面和尾流中近场压力脉动在空间分布上的正负交替特征.高速列车头尾车外形的变化将影响周围流动的发展和分离，不仅影响列车的气动噪声，同样影响其气动性能，特别是阻力性能，列车气动噪声的优化不应以气动阻力的过度增加为代价.为此，分析了A,B,C,D四种列车模型在不同运行速度下的阻力系数，如图10所示.在三种运行速度下，头车和尾车阻力系数都随着长细比λ的增大而减小，这可能是由于长细比的增大，导致车鼻处的横截面变化率降低，从而使周围流动的稳定性增强，分离减弱.但头、尾车气动阻力的明显下降段发生在[λA,λC]区间，当λ＞λC时，头尾车阻力系数的下降趋势将显著减弱.中间车厢的阻力系数与头型长细比之间没有呈现出明确的规律，由于C型车与D型车在头尾车阻力上差异很小，而前者的中间车厢阻力系数较小于后者，从而C型车有着最小的总阻力.与模型A相比，在250km/h的运行速度下，模型B,C,D的总阻力分别降低2.31%,8.56%,7.70%，在350km/h的运行速度下，总阻力分别下降2.50%,8.95%,8.01%，而在500km/h时，其总阻力分别下降2.81%,9.36%,8.45%.可见，在一定程度上，头型长细比增大有利于气动阻力的减小，但当长细比增大到一定程度时，气动阻力反而有所增大；而且头型长细比对列车气动阻力的影响随着运行速度的增加而增强.远场噪声的求解基于近场声源面的 FW-H积分，由于湍动能的主要集中区域是气动噪声的主要声源区，本文选取最大湍动能的1%等值面作为近场声源面的参照，最终所选取的声源面位置如图11所示，声源面长度范围为[−45m,60m]，宽度为[−3m,3m]，高度区间为[0,5.5m].高速列车铁路沿线噪声的评估通常基于距离轨道中心线25m、高度3.5m处的声压级，为探讨列车沿线的噪声特性，沿列车长度方向设置了如图12所示的声压探点，探点总数为13个，各探点在x方向上的间距为10m，从车头向车尾方向依次编号，其中P7探点与列车车体中点对齐.图13为模型B的3个沿线探点P1,P7和P13在3种运行速度下的声压级频谱.可以看出，其气动噪声分布在很宽的频率范围内，并不存在明显的主峰，随着运行速度的提高，各探点位置的声压级在整个频段内都相应地增加.4种车型的沿线噪声总声压级 (overall sound pressure level,OASPL)随运行速度的变化如图14，各型列车沿线噪声在车长方向上的分布具有相似的特征，列车的沿线噪声从车体前部向尾部方向上升，并且前部探点的总声压级趋于线性增长.随着运行速度的增大，各探点的总声压级相应增大，同时，越靠近车体尾部，探点的总声压级的增加幅度越大，这可能是由于速度的增大，使得列车后部产生了更高强度的尾流流动.图15给出了列车沿线噪声总声压级与头型长细比之间的关系，总体上讲，4种头型中列车沿线噪声总声压级从高到低依次为A,C,B,D，且A与C具有相近的沿线噪声声压级，而B和D具有相近的声压级.同时，4种头型沿线噪声的差异随着运行速度的提高而减少，也就是说，头型对列车气动噪声的影响随着列车速度的增大而减弱.为更全面地比较头型对列车远场噪声声压级和方向性的影响，围绕列车车体设置了如图16所示的远场压力探点，探点位于距离地面3.5m的水平面内，沿半径为150m的圆周等间隔分布，间隔角度∆θ=15°，圆周的圆心与列车的中心具有相同的x和y坐标值.沿列车周向分布远场压力探点的总声压级分布如图16所示，总声压级的圆周分布在列车两侧是对称的，声压级从高到低依次为A,C,B,D，其中，B和D的声压级在车头位置(θ=0°)存在小的差异，但在整个圆周上都是十分接近的，这与前面的沿线噪声结果一致.本文基于简化的列车细长体模型，在250km/h,350km/h,500km/h三种运行速度下，探讨了头型长细比分别为0.75λ0，1.0λ0，1.25λ0和1.5λ0四种头型的列车气动性能和气动噪声特性，得到如下主要结论：(1)列车头尾车的气动阻力随着头型长细比的增大而减少，但当头型长细比超过其一定值后，其对气动阻力的影响将减弱；且头型长细比对列车总气动阻力的影响随运行速度的增加而增强.在本文研究中，C、D两种头型列车的头尾车气动阻力差异较小，整体上长细比为1.25λ0的C型车在四种车型中具有最低的气动总阻力. (2)不同长细比的各型列车，其沿线噪声在车长方向上的分布具有相似的特征，列车的沿线噪声从车体前部到尾部逐渐上升，并且前部探点的总声压级趋于线性增长.。
基于CFD技术的气流温度传感器数值校准虚拟风洞初探
doi:10.11823∕j.issn.1674-5795.2021.02.11基于CFD技术的气流温度传感器数值校准虚拟风洞初探王玉芳,赵俭(航空工业北京长城计量测试技术研究所,北京100095)摘㊀要:在气流温度传感器风洞校准试验中,由于试验成本高㊁校准试验环境与实际使用环境差距大等原因,有必要构建气流温度传感器数值校准虚拟风洞,实现极限非常规校准工况的气流温度传感器误差修正及虚拟校准,并通过气流温度传感器的虚拟校准数值风洞获取仿真结果,尽可能地减少实物校准的工况数量,同时也从理论层面为气流温度传感器的设计与校准提供补充㊂本文介绍了气流温度校准技术国内外发展现状,分析了气流温度传感器数值校准虚拟风洞实现思路及方法,探讨了如何利用CFD技术在计算机平台上建立虚拟仿真风洞以模拟真实的校准环境,为建立国产化气流温度传感器数值校准虚拟风洞提供技术参考㊂关键词:CFD技术;气流温度传感器;风洞校准试验;数值校准虚拟风洞中图分类号:TB9㊀㊀㊀㊀文献标识码:A㊀㊀㊀㊀文章编号:1674-5795(2021)02-0091-04Preliminary Study on Numerical Calibration of Virtual Wind Tunnel of AirflowTemperature Sensor Based on CFD TechnologyWANG Yufang,ZHAO Jian(Changcheng Institute of Metrology&Measurement,Beijing100095,China)Abstract:In the wind tunnel calibration test of air temperature sensor,due to the high test cost and the gap between the calibration test en-vironment and the actual use environment,it is necessary to build the virtual wind tunnel for the numerical calibration of the air temperature sen-sor,and realize the error correction and virtual calibration of the air temperature sensor under the extremely abnormal calibration condition.The virtual calibration of the numerical wind tunnel of the air temperature sensor is obtained.The simulation results can reduce the working conditions of the real calibration as much as possible,and provide a supplement for the design and calibration of the air temperature sensor from the theoreti-cal level.The development of air temperature calibration at home and abroad is introduced.The realization idea and method of virtual wind tunnel for the numerical calibration of air temperature sensor are analyzed.How to establish virtual simulation wind tunnel on computer platform by Com-putational Fluid Dynamics(CFD)technology is discussed to simulate the real calibration environment,which provides technical reference for the establishment of the virtual wind tunnel for the numerical calibration of domestic air temperature sensor.Key words:CFD technology;airflow temperature sensor;wind tunnel calibration test;numerical calibration of virtual wind tunnel0㊀引言气流温度是武器装备研制㊁生产㊁试验中需要准确测量的重要参数,为武器装备的性能评价㊁状态监控等提供数据支撑,对武器装备的技术指标验证和可靠性评价起到至关重要的作用㊂涡轮入口温度T3∗的不断提高是航空发动机研制技术向前推进的重要标志㊂美国高性能涡轮发动机技术计划(IHPTET)中提出实现T3∗达到2273~2473K的目标㊂据计算,涡轮入口温度测量误差达到8K,引入的效率计算误差将可达到1%,因此随着涡轮入口温度的逐步提高,对气流温度测量校准的要求也越来越高[1]㊂航空发动机内流温度的计量需要充分考虑气流速度和压力所带来的影响㊂由于目前主要使用冷却式测温耙进行航空发动机高温气流测量,气流的速度㊁压力和环境温度等参数对测量结果影响非常大,如果不能在相应条件下对温度传感器进行校准,将带来几十甚至上百摄氏度的测量误差[2]㊂随着航空发动机技术的发展,气流温度传感器的需求量不断增大,且要求其测温范围更大㊁测量精度更高,并能够在苛刻条件下工作㊂由于目前气流温度传感器校准风洞试验成本高且无法模拟极端工况,有必要构建温度传感器与热校准风洞相结合的虚拟校准数值风洞㊂随着计算机软硬件技术的迅速发展以及计算流体力学的日益成熟,在计算机上建立气流温度传感器数值校准虚拟风洞已成为可能㊂从理论层面模拟现有气流温度传感器风洞校准所达不到的工况,为后续扩展风洞工况范围极限提供技术参考具有重要意义,且能够节约大量试验经费㊂1㊀气流温度校准国内外现状目前,航空工业计量所拥有国内最完备的气流温度校准风洞群,该套校准风洞群从1976年开始建立,气流温度范围为室温至1973K,气流速度覆盖亚声速范围㊂同时,航空工业计量所对气流温度传感器的校准技术及其稳态与动态性能进行了大量研究,负责起草了JJF1049-1995‘温度传感器动态响应校准“等计量技术规范㊂但是由于工况众多,传感器结构形式也多种多样,目前还无法编制出完备的传感器性能手册㊂此外,目前所建立的校准风洞均为常压风洞,校准数据对压力的修正缺乏可靠的试验验证,得到的校准结果与实际情况有所差异㊂同时,随着航空发动机技术的发展,需要用于试验的气流温度不断提高,现有热校准风洞的温度上限无法完全满足高温气流温度传感器的校准需求㊂随着我国武器装备自主化研制的推进,气流温度传感器的校准工作量呈几何级增长,目前的校准风洞存在数量少㊁校准费用高㊁自动化程度低等问题[3]㊂受试验条件所限,我国尚无法对气流温度探针在复杂使用环境下进行校准试验,导致气流温度测量结果存在一定误差㊂由于热风洞技术能力不足,气流温度传感器的校准技术研究受到限制,且在实际的气流温度校准过程中,存在试验过程复杂㊁试验费用较高㊁试验数据提取受限等问题㊂近年来,NASA在气流温度传感器校准技术研究中逐步引入了数值模拟手段,采用数值虚拟风洞技术,在实流校准的基础上将压力㊁速度㊁温度等因素外推修正,扩展了气流温度传感器校准技术的应用范围㊂俄罗斯也对气流温度传感器校准技术进行过详细的研究,并将相关的传感器性能曲线进一步总结为经验公式,以便传感器的设计或使用人员查看㊂英国的P.Smout和S.Cook等人基于剑桥大学惠特尔实验室的变压力风洞,在变压力条件下对气流温度传感器的校准技术进行了研究,并将校准结果与所建立的理论模型进行了对比㊂Robert Rhodes 研究团队采用有限元数值分析的方法建立了高温气流温度传感器的误差修正模型,并根据NACA的George Glawe等人的早期试验数据对误差修正模型进行了验证㊂美国㊁俄罗斯等国都建立有比较完备的系列风洞校准或试验设备,可以利用风洞实现实际的发动机内流工况,并在此基础上进行大量试验工作,与数值模拟技术充分结合,形成了可靠的研究基础㊂由此可见,国际上已广泛利用数值模拟手段对气流温度校准技术进行补充和修正㊂2㊀气流温度传感器数值校准虚拟风洞实现思路气流温度传感器数值校准虚拟风洞实现的基本思路是:通过数字化虚拟仿真手段,结合计算流体力学仿真技术和有限元技术,构建气流温度传感器在典型校准工况下的不同测试场景,最终实现对气流温度传感器的性能评估及校准工作㊂首先,通过参数化建模技术对典型的校准风洞及气流温度传感器进行几何建模,结合几何装配技术,构建气流温度校准数字化场景几何模型;之后通过自动网格划分技术对流体域及固体域进行离散;再通过数值仿真技术对校准场景中的流动㊁传热等进行系统分析,得到校准场景中典型参数(气流速度㊁压力㊁温度等)的分布规律;通过对仿真结果的后置处理,重构场景的模型并显示所关注参数的空间分布图㊁报表等,进而实现气流温度传感器校准场景的全数字化展示㊂平台后台采用数据库技术,可以储存典型的校准风洞模型㊁气流温度传感器模型库㊁分析结果数据库㊁试验数据库等,便于进行设计经验的复用及校准场景的再现㊂气流温度传感器数值校准虚拟风洞实现的基本思路如图1所示㊂3㊀实现方法及途经数值校准虚拟风洞是CFD数值模拟技术和高性能计算机软硬件技术紧密结合的产物,包括硬件系统和软件系统两大部分:硬件系统是软件系统的运行平台和物质基础,主要包括高性能计算机㊁高性能可视化服务器㊁海量存储设备和外围输入输出设备,以及连接各设备的网络等;软件系统包括前置处理系统㊁流场求解器㊁CFD数据可视化系统㊁网络数据库系统㊂数值校准虚拟风洞虚拟平台的实现途径为:针对典型校准风洞及气流温度传感器的几何结构特点,采用参数化模块建模方案,预先定制一系列基础模型数图1㊀气流温度传感器数值校准虚拟风洞实现的基本思路据(例如:传感器型号模型库㊁典型风洞试验段模型库等),通过对基础结构模型的搭配组合形成完整的数值校准虚拟风洞几何模型㊂通过对数值校准虚拟风洞几何模型进行计算网格的自动划分及CFD 求解,得到数值校准虚拟风洞内部的流场及温度场分布数据,根据用户需求对分析数据进行提取并与实验结果进行相应的对比处理等,最终形成对气流温度传感器性能的整体评价㊂根据上述分析流程,采用先进的计算机软件开发技术进行封装及定制,采用Java 语言开发数值校准虚拟风洞仿真软件平台的前端用户界面㊁数据库及后置处理部分,并结合UG,FLUENT 等商业软件的二次开发定制技术,最终形成数值校准虚拟风洞虚拟平台㊂上述对校准风洞及气流温度传感器参数化的分析流程包含几何模型的参数化㊁网格划分的参数化㊁计算模型的参数化等,各个阶段既有联系又相对独立㊂根据前述各关键技术的实现路线及方法,深入研究相关软件的二次开发技术,采用编程的方式创建各处理进程所需的批处理命令流,同时构建自动化驱动程序㊁相关的接口程序,以实现计算流程的完全自动化㊂将上述得到的自动化计算流程封装到相应的功能模块,然后开发图形化的用户输入及控制界面,如图2所示㊂设计并开发针对计算结果及相关模型的处理程序,用于转化数据格式㊁提取数据㊁以图表形式显示计算结果,以便进行对比分析㊂采用上述气流温度传感器数值校准虚拟风洞,基于计算流体力学原理和数值化仿真手段,选择合适的湍流模型,结合一定的数值算法和图形显示技术,将气流温度传感器在校准风洞中的吹风结果形象直观地显示出来,建立数值校准虚拟风洞平台㊂相较传统的实验方法,数值校准虚拟风洞平台具有价格低廉㊁数据信息丰富㊁可方便地模拟各种不同工况等优点㊂基于数值校准虚拟风洞平台,可以实现以下功能:①在气流温度传感器校准试验前可利用数值校准虚拟风洞平台进行数值计算,在一定程度上指导试验;②可通过数值校准替代部分试验,节约经费;③可利用数值校准虚拟风洞平台对试验时达不到的工况进行数值计算,达到补充试验的目的㊂图2㊀气流温度传感器数值校准虚拟风洞软件界面4 气流温度传感器数值校准仿真方案气流温度传感器数值校准主要具有以下特点:①气流温度传感器的尺寸形式多样化,与风洞流场相比,尺寸差异也较大;②气流温度传感器内部流动包含较大畸变,感温探球附近的速度几乎滞止为零;③若考虑时间常数的校准,在仿真计算中需要进行非定常计算;④仿真计算中涉及到流固耦合㊁传热㊁流动等多种形式的计算㊂气流温度传感器数值校准的这些特点给数值模拟提出了巨大的技术挑战㊂目前,对于非定常可压缩流动问题,广泛采用的方法是在N-S方程的基础上添加非定常源项进行求解,但由于气流温度传感器数值校准仿真是一个复杂的流动过程,针对此类问题一般采用流体网格法进行求解(fluid-in-cell method),流体网格法属于欧拉差分法中的一种,欧美简称它为FLIC法,苏联称它为大粒子法㊂流体网格法是在质点网格法(PIC)的基础上将单一网格元作为一个大粒子而发展起来的,它和PIC法的不同之处在于在第二步的计算中不计算质点的位移,而是计算连续流体的迁移,即先计算得出通过网格边界的质量输运量,从而得到每个网格的新密度,再计算得出通过网格的质量所携带的动量和能量的输运量,最后计算得到每个网格的新速度和能量㊂该方法的突出特点是对于复杂的流动问题,消耗比较适中的计算时间就可以得到相当准确的解,特别适用于包含大流动畸变的单种物质的流动问题㊂根据文献资料[4-10],大型的管路及管网系统的模拟通常采用流体网格法,而对精细的流场模拟通常采用三维高精度的CFD方法㊂由于气流温度传感器数值校准涉及复杂的流路及局部精确的流场㊁温度场,如果全部采用三维非稳态数值模拟技术,计算规模庞大,实施难度较大㊂因此采用流体网格计算技术与三维CFD数值模拟技术结合的方式,即:大部分计算域采用流体网格方法,将各个典型部件使用元件表示,将各个部件连接的部分使用节点表示;对于需要进行精细化仿真的局部结构采用三维CFD技术模拟,综合计算得到流量㊁压力和温度等典型参数㊂5 结论对气流温度传感器进行校准,既是获取其稳态与动态性能的必要手段,也是对传感器测量结果进行修正的必要依据㊂随着我国自主化研制技术的推进,对气流温度的测试校准提出了更高要求,为解决目前气流传感器校准中存在的费用高㊁可视化程度低㊁极端工况无法校准等问题,满足自主研制气流温度传感器试验的测试计量需求,支撑 中国制造 ,搭建数值校准虚拟风洞虚拟平台具有非常重要的战略意义㊂实现气流温度传感器数值校准虚拟风洞需要同时研究参数化建模技术㊁多物理场耦合技术㊁网格自动生成技术㊁数值仿真技术㊁数据库技术等,并须结合气流温度校准专业实际需求,专业跨度广,技术难度大,有待进一步探索㊂参考文献[1]赵俭.高温气流温度测量与校准技术[J].计测技术,2018, 38(6):42-47.[2]乔渭阳.高温气流温度的测量[J].工业仪表与自动化装置, 1989(1):7-10.[3]杨永军.温度测量技术现状和发展概述[J].计测技术, 2009,29(4):67-70.[4]Song X G,Park J H,Kim S G,et al.Performance comparison and erosion prediction of jet pumps by using a numerical method [J].Mathematical&Computer Modelling,2011,57(2):245 -253.[5]Yimera I,Beckerb H A,Grandmaisonb E W.The strong-jet/ weak-jet problem:new experiments and CFD[J].Combustion and Flame,2001,124(3):481-502.[6]bdulaziz A M.Performance and image analysis of a cavitating process in a small type venturi[J].Experimental Thermal& Fluid Science,2014,53:40-48.[7]Kumar P,Bing M.A CFD study of low pressure wet gas mete-ring using slotted orifice meters[J].Flow Measurement&In-strumentation,2010,22(1):33-42.[8]Cruz Maya J A,F Sánchez Silva,Quinto Diez P.A new corre-lation to determine the discharge coefficient of a critical Venturi nozzle with turbulent boundary layer[J].Flow Measurement and Instrumentation,2006,17(5):258–266.[9]Ghassemi H,Fasih H F.Application of small size cavitating venturi as flow controller and flow meter[J].Flow Measurement and Instrumentation,2011,22(5):406-412. [10]Singh R K,Singh S N,Seshadri V.Study on the effect of ver-tex angle and upstream swirl on the performance characteristics of cone flowmeter using CFD[J].Flow Measurement&Instru-mentation,2008,20(2):69-74.收稿日期:2020-12-19;修回日期:2021-03-29基金项目:工信部两机技术基础科研项目(J2019-Ⅷ-0006-0617)作者简介王玉芳(1976-),女,高级工程师,博士,主要研究方向为航空发动机测试计量㊁动态温度及流速计量测试㊁计算流体力学㊂2005年毕业于北京理工大学机电工程学院,同年于航空工业计量所工作至今㊂主持参与了航空基金㊁技术基础等多项科研项目,先后发表学术论文20余篇,编译撰写国外航空发动机测试及校准译文集系列㊁民用航空发动机参数溯源链手册等专业书籍㊂。
汽车风洞试验中的雷诺数阻塞和边界层效应问题综述
万方数据 万方数据 万方数据 万方数据２００９（Ｖ０１．３１）Ｎｏ．７庞加斌，等：汽车风洞试验中的雷诺数、阻塞和边界层效应问题综述・６１３・不受边界层系统运行的影响，较喷口法更加稳定。
因此汽车风洞中通常采用驻室法测量风速。
图５ＩＶＫ风洞的风速测量标定系数ｋ取值比较２．４静压梯度和水平浮力修正‘最后，风洞的空间限制还会引起试验段的静压力分布不均匀，即静压力梯度。
在真实路面上，汽车周围大气的压力是均匀的，不存在压力梯度，而在风洞中模型前后的静压力梯度很难等于零，由此在模型上产生“水平浮力”，相当于阻力测量误差为ＡＣｏｎ＝堡Ａｕ・生ｄｘ式中△ｃ鲫为考虑水平浮力影响的阻力系数修正量，ｄｅｐ／以为静压梯度系数，％为压力系数，茗以喷口为零点的轴向坐标（顺风向为正），‰为模型的体积，４肼为模型的正投影面积。
试验段的静压力梯度是汽车风洞流场品质优劣的重要指标。
边界层效应及其控制３．１汽车风洞试验的边界层效应汽车风洞试验有别予其他风洞试验的关键在于边界层问题。
在实际路面上行驶的汽车，空气和路面等速相对车辆运动，气流在路面上没有边界层；而在风洞中汽车静止，运动的气流在同样静止的风洞地板上形成边界层。
大量试验证明：随着边界层位移厚度的增加，阻力系数测量值减小；在位移厚度６‘＝０—１０ｍｍ范围内，气动阻力系数与边界层位移厚度之间总体呈线性递减的关系，线性递减系数的大小主要与汽车底盘的高度有关，底盘越低，线性递减系数越大。
对普通轿车线性递减系数大约为０．００２ｍｍ。
¨ｌｔｌ３Ｊ。
而边界层对升力系数以及升力矩测量的影响非常复杂，已经很难用经验公式修正了。
汽车风洞的边界层主要通过模型前方来流的边界层和车辆底部边界层来影响试验数据，图６为汽车风洞的边界层问题示意图。
层）（ａ）来流边界层风洞地板路面实际来流剖而（通过台理的控制．汽乍风洞中能够模拟均匀的肛Ｌ速刮而）ｌ定地板汽车底部边界层Ｉ实际路喃ｉ汽乍底龈边界层ｆ未宽分发展）（充分发展）ｌ（穆蝴系统可漠拗｝匕ｊ盘界层篙其辆漏衙缪殇钐钐钐钐钐易黝（”汽车模型底部边界层图６汽车风涧的边界层问题示意图图６（ａ）为典型的风洞静止地板形成的边界层，靠近地面的气流速度低；同时汽车底部的边界层发展也将和实际不同，如图６（ｂ）所示。
The E80 Wind Tunnel Experiment：在E80风洞实验-精选文档
Actual Lift is icated…
• For a gas, we have to simultaneously conserve the mass, momentum, and energy in the flow. • Newton's laws of motion are statements concerning the conservation of momentum. • Bernoulli's equation is derived by considering conservation of energy. • The simultaneous conservation of mass, momentum, and energy of a fluid (while neglecting the effects of air viscosity) are described by Euler Equations. • If we include the effects of viscosity, we have the Navier-Stokes Equations.
The E80 Wind Tunnel Experiment
the experience will blow you away by Professor Duron Spring 2019
The Experiment
• Objectives – To familiarize the student with the basic operation and instrumentation of the HMC wind tunnel – To examine the lift and drag forces on airfoil shapes in a flow field, and obtain a qualitative relationship between lift and drag coefficients – To understand the significance of the Reynolds Number, and use Reynolds Number matching to utilize the wind tunnel for modeling of a submersible design problem.
十字形伞开伞充气过程数值仿真研究
航天返回与遥感第44卷第3期32SPACECRAFT RECOVERY & REMOTE SENSING2023年6月十字形伞开伞充气过程数值仿真研究谢淮刘宇王臻昌飞（北京空间机电研究所，北京100094）摘要十字形降落伞是航空航天减速领域常用的伞型，开伞充气过程是其工作过程中较为复杂的一个阶段。
为了研究十字形伞开伞充气过程中的动力学特性，文章基于任意拉格朗日-欧拉方法对十字形伞开伞过程进行流固耦合仿真计算，并将计算结果与风洞试验结果进行对比。
对比发现：仿真计算得到的十字形伞稳态外形与试验结果一致，且仿真获得的降落伞气动载荷历程曲线与试验结果基本相符，载荷呈现出随着开伞过程逐渐增大，在开伞结束达到最大值后略有降低并逐渐稳定的趋势。
仿真结果还表明，在十字形伞开伞过程中，伞衣的最大应力点位于伞臂的中心区域，充气顺序的先后会影响伞臂的应力分布，降落伞稳定后伞衣应力呈对称分布。
文章采用的仿真方法能较好地模拟十字形伞开伞充气的动力学过程，得到的伞衣应力分布特点及影响因素可为十字形伞的设计与优化提供参考。
关键词十字形降落伞计算流固耦合动力学开伞充气中图分类号: V445文献标志码: A 文章编号: 1009-8518(2023)03-0032-09DOI: 10.3969/j.issn.1009-8518.2023.03.004Numerical Simulation Study of Cruciform ParachuteDeployment and Inflation ProcessXIE Huai LIU Yu WANG Zhen CHANG Fei（Beijing Institute of Space Mechanics & Electricity, Beijing 100094, China）Abstract The cruciform parachute is a commonly used parachute design in the field of aerospace deceleration，and the deployment and inflation stage is a complex stage of its operation. In order to study the dynamics characteristics of cruciform parachute deployment and inflation process, this paper employs the arbitrary Lagrangian-Eulerian method to carry out the fluid-structure interaction simulation calculations on the deployment process of a cruciform parachute. The computed results are compared with wind tunnel test results. The comparison shows that the simulated steady-state shape of the parachute is consistent with the experimental results, and the simulated aerodynamic load history curve of the parachute is largely in agreement with the test results. The load exhibits a gradual increase during the deployment process, reaching its maximum value after the completion of the deployment, followed by a slight decrease and gradual stabilization. The simulation results also show that, during the cruciform parachute deployment process, the maximum stress point of the canopy is located in the central region of the canopy arms, and the inflation sequence affects the stress distribution along the arms. After the parachute stabilizes, the canopy stress exhibits a symmetrical distribution.收稿日期：2023-01-06基金项目：工业和信息化部重点实验室开放基金（KLAECLS-E-202004）引用格式：谢淮, 刘宇, 王臻, 等. 十字形伞开伞充气过程数值仿真研究[J]. 航天返回与遥感, 2023, 44(3): 32-40.XIE Huai, LIU Yu, WANG Zhen, et al. Numerical Simulation Study of Cruciform Parachute Deployment and第3期 谢淮 等: 十字形伞开伞充气过程数值仿真研究 33The simulation method employed in this study effectively simulates the dynamic process of cruciform parachute deployment and inflation, and the characteristics of canopy stress distribution and influencing factors can provide valuable insights for the design and optimization of cruciform parachutes.Keywords cruciform parachute; fluid-structure interaction (FSI); deployment; inflation0 引言降落伞是目前航空航天领域应用最广泛的减速手段[1-2]，根据伞衣结构形式的不同，可以分为平面圆形伞、方形伞、带条伞、环帆伞以及十字形降落伞等。
低速风洞引射短舱动力模拟技术新进展
低速风洞引射短舱动力模拟技术新进展章荣平;王勋年;晋荣超【摘要】引射短舱可以模拟发动机短舱的喷流影响，并部分模拟进气影响，能用于研究发动机短舱与机翼及增升装置的气动干扰特性，且具有研制周期短、造价低等特点，是在风洞中开展飞机/发动机一体化设计研究的一种重要试验技术。
本文介绍了气动中心低速所在引射短舱设计技术和试验技术方面的新进展。
采用商业软件对引射短舱进行了三维流场数值模拟，获得了引射短舱性能和三维流场信息。
对引射短舱内部流场进行了分析和研究，对引射喷嘴数量、位置进行了优化，增加了引射短舱的进气流量，改善了尾喷口流场均匀度，明显提高了引射短舱性能。
发展了空气桥技术，采用有限元方法进行了优化设计，对空气桥和天平进行一体化设计，并进一步发展了空气桥影响修正技术，解决了供气管路对天平测力的影响问题。
发展了高精度流量测量控制技术，采用了数字阀、流量控制单元、短舱内部测量耙等技术，提高了流量的控制测量精度及测量不确定度，流量控制精度达到了0.1%，流量测量不确定度达到了0.3%，引射短舱落压比控制精度优于0.01。
研制了短舱移动支撑装置，能够实现引射短舱的独立支撑，并实现短舱前后和上下位置的变化，用于开展短舱位置优化研究。
最后，介绍了引射短舱的地面性能测试及风洞试验应用，给出了性能测试与数值模拟的对比结果和典型的风洞试验结果，试验结果表明动力影响使得飞机0°迎角升力减小，升力线斜率增大，失速迎角推迟。
%The ejector nacelle has the capability to simulate the effect of jet flow and partly to simulate the effect of inlet flow, so it can be used to study the aerodynamic interference characteristic of engine on wing and high lift systems.Because of the advantages of short testing period and lowcost,the ejector nacelle becomes a key testing technique for aircraft-engine integration research in wind tunnel .This paper presents the recent development in ejector nacelle simulation testing in low speed wind tunnel in China Aerodynamics Research and Development Center (CARDC).The flow field and characteristics of the ejector nacelle are simulated by computational fluid dynamics software.Based on numerical simulation results,the diameter of sonic nozzles and the position of sonic nozzles are optimized,the inlet mass flow is increased,the uniformity of outlet flowfield and the performance of the nacelle are improved.The air bridge technique is developed and optimized by finite element analysis.The rigidity of the air bridge and the balance are matched basing on air bridge and balance assembly numerical simulation.The rigidity effect,the pressure effect,the temperature effect and the mass flow effect of the air bridge are corrected by serial tests.This correction further minimizes residual force of the air bridge.The high accuracy flow measurement and control techniques including the digital valves, the mass control units and the measurement rake are adopted in the ejector nacelle simulationtesting.These techniques improve the precision of the control and the uncertainly of the flow measurement.The precision of the mass flow control is within 0.1%,the uncertainty of the mass flow measurement is 0.3% and the precision of pressure ration 0.01.The moving support system is developed for engine position optimization research.The performance test and wind tunnel test using the ejector nacelle are introduced.The test results show that the effect of the engine increases the slope of liftcurve,increases the stall angle of attack,decreases the zero angle lift coefficient.【期刊名称】《空气动力学学报》【年(卷),期】2016(034)006【总页数】6页(P756-761)【关键词】引射短舱;动力模拟;动力影响;数值模拟;空气桥;流量测量控制;数字阀【作者】章荣平;王勋年;晋荣超【作者单位】中国空气动力研究与发展中心低速空气动力学研究所，四川绵阳621000;中国空气动力研究与发展中心低速空气动力学研究所，四川绵阳621000;中国空气动力研究与发展中心低速空气动力学研究所，四川绵阳621000【正文语种】中文【中图分类】V211.7我国自主研制的大型飞机都采用翼吊涡扇发动机。
风浪联合作用下海上风机动力响应模型试验设计方法
1SSN1672-4305 实验室科学第19卷第6期2016年12月CN12-1352/N LABORATORY SCIENCE Vol. 19 No. 6 Dec. 2016实验研究风浪联合作用下海上风机动力响应模型试验设计方法李玉刚、任年鑫\莫仁杰\李炜2(1.大连理工大学海岸和近海工程国家重点实验室，深海工程研究中心，辽宁大连 116024;2.中国电建集团华东勘测设计研究院有限公司，浙江抗州310000)摘要：海上风机规格越来越大，水深越来越深，其动力响应问题愈发突出，对这一动力敏感性结构的设计，应该避免与波浪和风机产生共振，开展风浪环境荷载与海上风机相互作用的模型试验显得尤为必要。
弹性相似模型是研究整体结构的动力行为的主要手段，将着重从基础结构弹性模型设计方法、风机模型设计方法、风荷载模拟装置、测量方法等方面进行研究。
试验方法为海上风机的动力响应模型试验提供了有益的借鉴。
关键词：海上风机；动力响应；模型试验；相似准则中图分类号：U661 文献标识码：A doi: 10.3969/j.issn.1672-4305.2016.06.001Model test design method of dynamic response for offshoreturbines under the combined action of wind and wavewindL1 Yu-gang1，REN Nian-xin1，MO Ren-jie1，L1 Wei2(1. Deepwater Engineering Research Center，State Key Laboratory of Coastal and Offshore Engineering，Dalian University of Technology，Dalian 116024，China; 2.Powerchina Huadong Engineering，Hangzhou 310000，China)Abstract：Along with the bigger power of the offshore wind turbine and the deeper water，dynamic response problems become more prominent，for the dynamic sensitive structures，designer should avoidresonance phenomena with the wave and wind turbine，therefore，it is necessary to do model researchin cases where interaction between environmental loads and structural behavior.Elastic similarity models are a direct means to study the dynamic behavior of structures，the present paper will focus on theelastic similarity design method of foundation models，the design method of wind turbine model，thewind load simulation device，measuring methods，and the aim is giving an effective reference for thedynamic model test of offshore wind turbine.Key words：offshore wind turbine;dynamic response;model test;scale laws海上风电规模化开发时间较晚,海洋环境的复 杂多变以及相关海洋工程技术经验的匮乏,使得海 上风电相关研究需要更多地依赖模型试验对设计进 行验证,因此相关物理模型试验技术水平决定了研 究与设计工作的有效性和实际价值。
一种用于飞机模型动力模拟风洞试验的空气桥天平的研制
第33卷第3期机电#$%&'()Vol.33,No.3 2020年5月Development&Innovation of M achinery&E lectrical P roducts Ma y.,2020文章编号：1002-6673(2020)03-081-03一种用于飞机模型动力模拟风洞试验的空气桥天平的研制徐越1，",邱俊文1，",李聪1，"，徐铁军！(1.中国航空工业空气动力研究院，黑龙江哈尔滨150001；2.低速高雷诺数气动力航空科技重点实验室，黑龙江哈尔滨150001)摘要：风洞试验是空气动力学研究和飞机设计的必要技术手段，其中测力天平是飞机模型测力试验的核心关键设备之一。
在飞机模型动力模拟风洞试验中(如推力矢量，TPS进排气，滑流试验等)，需要给飞机模型注入高压气体用以驱动动力模拟实验设备，在测力天平上需要安装高压供气管路用来传输高压气，即组成为空气桥天平。
空气桥天平在供气时，由于自身刚度，压力膨胀等原因会对天平测力有干扰影响，需要考虑相关解决措施$研制一台新型六分量内式空气桥天平，用于测量推力矢量风洞试验中飞机的气动载荷。
并研制一套校准装置用于空气桥天平的校准，得到天平工作公式，并修正消除安装波纹管所产生的影响。
关键词：空气桥天平&动力模拟风洞实验&天平校准&波纹管中图分类号：V211.7文献标识码：A doi:10.3969/j.iss/.1002-6673.2020.03.028Development of An Air Bridge Balance for Wind Tunnel Test of Aircraft Model Dynamic SimulationXU Yu1'2,QIUJun-Wen i2,UCo(严,"1.Aviation Industry Corporation of China Aerodynamic Research Institute,Harbin Leilongjiang150001,China；2.Aviation Key Laboratory of Aerdynamics for Low Speed and High Renolds Number,Haibin Heilongjiang150001,China) Abstract:Wind tunnel test is a necessary technical means for Aerodynamics Research and aircraft design,among which the force balance is one of the key equipment for aircraft model force test.In the wind tunnel test of aircraft model dynamic simulation(such as thrust vector, TPS intake and exhaust,slipstream test,etc.),it is necessary to inject high—pressure gas into the aircraft model to drive the dynamic simulation test equipment,and install high—pressure air supply pipeline on the force balance to transmit high—pressure air,that is to say,to form an air bridge balance.When the air bridge balance is supplying air,its own stiffness,pressure expansion and other reasons will interfere with the balance's force measurement,so relevant solutions need to be considered.A new six component internal air bridge balance is developed to measure the aerodynamic load of the aircraft in the thrust vector wind tunnel test.A set of calibration device is developed to calibrate the air bridge balance!the working formula of the balance is obtained!and the influence caused by the installation of bellows is corrected and eliminated.Key words:air bridge balance；dynamic simulation wind tunnel experiment；balance calibration；bellows0引言飞机模型动力模拟风洞试验中的推力矢量技术因其对作战飞机的性能、作战效率和生存能力的极大地提高,已成为许多国家竞相发展的航空关键技术。
A wind tunnel study of turbulent
* Present address: Atmospheric
Environment
Service, Downsview,
Ontario,
M3H 5T4, Canada.
Boundary-Layer Meteorology 49: 113-148, 1989. @ 1989 Kluwer Academic Publishers. Printed in the Netherlands.
1. Introduction Over the last two decades, the study of airflow over hills has received considerable attention, because of its importance in a wide range of subjects, including numerical modelling of the atmosphere, pollutant dispersal and wind energy studies. Many studies have restricted attention to the problems of gentle orography and neutrally stratified airflow, including the theoretical work of Jackson and Hunt (1975), Taylor (1977) and Sykes (1980), and the wind tunnel experiments of Kurshudyan et al. (1980), Britter et al. (1981), Pearse et al. (1981) and Teunissen et al. (1982). Field experiments have been described by Mason and Sykes (1979), Bradley (1980), Mason and King (1985), Mason (1986) and Taylor and Teunissen (1987), and reviewed by Taylor et al. (1987). These studier provide some understanding of how a specified upwind mean flow and turbulence
听完风洞技术演讲会感受英语作文
听完风洞技术演讲会感受英语作文英文回答：Last Tuesday, I had the privilege of attending alecture on wind tunnel technology, an event that left me both intellectually stimulated and deeply intrigued. The speaker, Dr. Emily Carter, is a renowned expert in thefield of fluid dynamics, and her knowledge and enthusiasm for the subject were immediately evident.Dr. Carter began her presentation by introducing the fundamental principles of wind tunnel design and operation. She explained how wind tunnels are used to simulate the behavior of fluids, such as air or water, flowing around objects. This simulation allows engineers and scientists to study the effects of different shapes, surfaces, and flow conditions on objects, providing valuable insights into their aerodynamic performance.Dr. Carter went on to describe the various types ofwind tunnels and their specific applications. She discussed low-speed tunnels, used for testing aircraft and automobiles, and high-speed tunnels, employed in the development of spacecraft and missiles. She alsohighlighted specialized wind tunnels designed for research in areas such as turbulence, combustion, and environmental flow.One of the most fascinating aspects of Dr. Carter's lecture was her demonstration of wind tunnel experiments. She showed us how researchers use laser diagnostics and other advanced techniques to visualize and measure the flow of air around objects. This real-time visualization allowed us to observe the complex interactions between the object and the surrounding fluid, providing a deeper understanding of the forces and phenomena involved.Dr. Carter concluded her presentation by discussing the future of wind tunnel technology. She emphasized the importance of computational fluid dynamics (CFD) and other advanced simulation tools in complementing wind tunnel testing. She also highlighted the emerging trend of "smartwind tunnels," which incorporate sensors and feedback systems to optimize the testing process and improve accuracy.Overall, attending the lecture on wind tunnel technology was an enriching and inspiring experience. It not only enhanced my understanding of the subject but also ignited a curiosity to explore the cutting-edge advancements in this field. I am grateful to Dr. Carter for sharing her expertise and passion with us.中文回答：上周二，我有幸参加了关于风洞技术的一场演讲会，这次活动让我既受到了智力的启发，又产生了浓厚的兴趣。
倒角化处理对于矩形高层建筑风荷载特性的影响机理研究
文章编号：1000-4750(2021)06-0151-12倒角化处理对于矩形高层建筑风荷载特性的影响机理研究董 欣1,2，丁洁民1，邹云峰3，左太辉3(1. 同济大学建筑设计研究院(集团)有限公司， 上海 200092；2. 上海防灾救灾研究所， 上海 200092；3. 中南大学土木工程学院，湖南，长沙 410075)摘 要：通过风洞测压试验，对比不同风向下、不同倒角半径的矩形高层建筑表面风压分布、整体风力及斯托罗哈数St ；采用PIV 试验，给出建筑的近尾流流动特性，并从流场作用角度，揭示倒角化处理对于矩形高层建筑风荷载特性的影响机理。
研究表明：临界风向下，在建筑一侧分离的剪切层发生流动再附，形成分离泡；此时，建筑的阻力达谷值，升力和St 达最大值。
相比而言，倒角化矩形高层建筑的临界风向小于无气动措施的工况。
St 主要受到横风向投影宽度和尾流涡对间距的影响，在一定的风向范围内，当倒角半径达一定数值，St 将有所增大。
在建筑的整体阻力方面，倒角化处理将使得建筑尾流涡对尺寸减小；涡对横向流速增大，涡量掺混运动加剧，旋涡强度减弱。
在此作用下，建筑整体阻力降低。
在建筑的整体升力方面，采用倒角化处理后，旋涡脱落的不规则性和随机性增大，脱落强度减弱，这促使建筑整体升力减小；但倒角化处理对于升力的减小效应并非见于所有风向。
关键词：倒角化；矩形高层建筑；PIV ；分离泡；尾流涡对中图分类号：TU973+.213 文献标志码：A doi: 10.6052/j.issn.1000-4750.2020.07.0451EFFECT OF ROUNDED CORNERS ON WIND LOAD CHARACTERISTICSOF RECTANGULAR TALL BUILDINGSDONG Xin 1,2, DING Jie-min 1, ZOU Yun-feng 3, ZUO Tai-hui3(1. Tongji Architectural Design (Group) Co. Ltd, Shanghai 200092, China;2. Shanghai Institute of Disaster Prevention and Relief, Shanghai 200092, China;3. School of Civil Engineering, Central South University, Changsha, Hu’nan 410075, China)Abstract: Through pressure measurement in a wind tunnel, the wind pressure distribution, total forces and Strouhal numbers of rectangular tall buildings with different corner radius under various wind angles were investigated. The near wake characteristics of the rectangular tall buildings with and without rounded corners were observed by PIV experiment, through which the influence mechanism of rounded corners on the wind load characteristics of the buildings was revealed from the perspective of flow field. Results indicated that under critical wind angle, the separated shear layer reattaches on one side face to form a separation bubble. Therefore,the drag force attains a valley value, and the lift forces and Strouhal number reach peak values. Compared with the building without rounded corner, the critical wind angles of those with rounded corners are smaller. The parameters which control the Strouhal number are the transverse projected width and the distance between vortex pairs in the wake. For the rounded-corner buildings of specific rounded radius, the Strouhal number is increased within some wind angles. The drag force is closely related with vortex pairs in the wake. After adopting the收稿日期：2020-07-08；修改日期：2020-11-16基金项目：国家自然科学基金青年基金项目(51408353)；上海市自然科学基金项目(19ZR1421000)；上海市青年科技启明星计划项目(15QB1404800)；国家自然科学基金面上项目(52078504)通讯作者：邹云峰(1984−)，男，湖南隆回人，副教授，工学博士，主要从事结构风工程研究(E-mail: ******************.cn ).作者简介：董 欣(1982−)，女，江苏扬州人，正高级工程师，工学博士，主要从事结构风工程研究(E-mail: ******************);丁洁民(1957−)，男，上海人，研究员，工学博士，主要从事结构工程研究(E-mail: ***********);左太辉(1987−)，男，湖南衡南人，博士生，主要从事结构风工程研究(E-mail: *****************).第 38 卷第 6 期Vol.38 No.6工 程 力 学2021年6 月June2021ENGINEERING MECHANICS151rounded corner, the dimensions of the vortex pairs decrease, while the transverse velocity in the wake increases which implies the intense mixing motion of the fluid and weakened vortex pairs. It gives rise to the decreasing of drag forces. In addition, the irregularity and randomness of vortex shedding are enhanced, while its strength is attenuated by the rounded corner. Then the lift forces are caused to be decreased. However, this decrease tendency is not found for all wind angles.Key words: rounded corner; rectangular tall building; PIV; separation bubble; vortex pair in the wake高层建筑的外形是影响其风荷载特性的重要因素。
舰船空气艉流场试验及仿真技术研究
舰船空气艉流场试验及仿真技术研究胡涛;孙传伟【摘要】开展了SFS2标准舰船模型空气艉流场风洞试验及CFD仿真计算工作，对比分析了国内外试验及仿真结果，给出了飞行甲板上流场的基本分布规律。
结果表明，气流吹过舰体及机库后在飞行甲板上形成了复杂的涡流区，对舰载直升机的飞行安全有直接的影响。
%A wind tunnel experiment and CFD simulations of the SFS2 simplified frigate ship air-wakes have been performed ? respectively, as well as contrast analysis of the test and the simulation results at home and abroad, providing basic flow field distribution characteristics on the flight deck. The results showed that a complex recirculation zone was formed on the flight deck after air blowing through the hull and hangar, which directly impacted on the flight safety of shipborne helicopters.【期刊名称】《直升机技术》【年(卷),期】2016(000)002【总页数】4页(P11-14)【关键词】流场;风洞;飞行甲板;舰载直升机【作者】胡涛;孙传伟【作者单位】南京航空航天大学直升机旋翼动力学国家级重点实验室，江苏南京210016;南京航空航天大学直升机旋翼动力学国家级重点实验室，江苏南京210016【正文语种】中文【中图分类】V211.7舰载直升机着/离舰过程是典型的动态配合过程。
大跨度平屋盖表面风荷载体型系数
型系数的取值建议， 作者考虑了分离泡作用对平屋盖 表面进行 分 区， 但 并 未 给 出 具 体 的 分 区 依 据。 裴 永 等研究了大跨机库的风荷载体型系数 ， 指出气流 流经屋面时二维效应明显， 整个屋面基本处于负 压 忠 我国现行荷载规范中采用一个均匀体型系数 ， 这 区， 对大跨度机库屋面显然是不合适的 。 目前国外有关分离泡结构的研究基本集中于二 维钝体平板， 对大跨屋盖表面分离泡的研究较少， 且 研究内容多为湍流度对于分离泡及其作用下的风压 分布的宏观影响、 风压变化的统一描述， 但并未涉及 到风压特征的细观变化； 国内虽有学者提出平屋盖的 分区体型系数， 但并未给出具体的分区依据， 且体型 系数的计算也基本局限于传统方法。 因此本文通过 基于分离泡作用 机 平屋盖刚性模型风洞测压试验， 理， 对屋盖表面的风压数值、 风压谱特性及相关特性 进行了细致分析， 进而对屋盖表面进行分区， 通过面积 averaged pressure ） 计算分区体型系数， 平均压力 （ area（ GB 并 将 计 算 结 果 与 我 国《建 筑 结 构 荷 载 规 范 》 50009—2001） 、 美 国 规 范 （ ASCE 7—98 ） 、 加拿大规范 （ NBC1995） 以及日本规范（ AIJ2004） 进行对比， 所得结 论可为大跨度平屋盖结构的抗风设计提供参考依据。
Study of shape factors for large-span flat roofs
Dong Xin Ye Jihong
（ The Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education，Southeast University，Nanjing 210096 ，China）