ansys-FLOTRAN层流和湍流分析算例

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ansys fluent中文版流体计算工程案例详解

ansys fluent中文版流体计算工程案例详解ANSYS Fluent是一种流体计算动力学软件，可用于解决各种流体力学问题。

本文将详细介绍ANSYS Fluent中文版的流体计算工程案例，包括案例的基本背景、模拟过程和结果分析。

这些案例旨在帮助用户深入了解ANSYS Fluent的使用方法和流体计算工程实践。

一个典型的案例是流体在管道中的流动。

该案例背景是，一根长直管道内有水流动，管道的直径为0.1米，长度为10米。

水的初始速度为1 m/s，管道的壁面是光滑的，管道两端的压差为100Pa。

现在需要使用ANSYS Fluent模拟该流体流动过程，并进一步分析不同参数对流动的影响。

首先，在ANSYS Fluent中创建一个新的仿真项目，并选择“仿真”模块。

在界面上点击“新建”按钮，在弹出的对话框中填写相应的参数，例如案例名称、计算器类型和尺寸单位。

点击“确定”后，进入模拟设置页面。

首先，需要定义获得流动场稳定解所需的物理模型和求解方法。

在“物理模型”选项卡中，选择“连续相”和“非恒定模型”。

在“湍流模型”中选择某种适合的模型，例如k-ε模型。

在“重力”选项卡中，定义流体的密度和重力加速度。

接下来，在“模型”选项卡中，定义管道的几何和边界条件。

选择“管道”作为流体领域的几何模型，并定义长度、直径和内壁面的润滑系数。

在“边界”选项卡中，定义管道两端的入口和出口条件，例如速度和压力。

将管道两端的压力差设置为100Pa，在入口处设置水的初始速度为1 m/s。

在出口处选择“出流”边界条件。

完成几何和边界条件的定义后，点击“模拟”选项卡进入模拟设置界面。

在“求解控制”中，设置计算时间步长和迭代次数。

选择合适的网格划分方法，并进行网格划分。

点击“网格”选项卡，选择合适的网格类型，并进行网格划分。

在划分网格后，可以使用“导入”按钮导入网格文件，并进行网格优化。

完成设置后，点击“计算”按钮开始进行模拟计算。

在计算过程中，可以实时观察流体场的变化情况，并通过Fluent Post-processing工具进行结果分析。

ANSYS流体第4章flotran流体分析典型工程实例

第4 章FLOTRAN流体分析典型工程实例ANSYS程序中的FLOTRAN CFD流体分析是一个用于分析二维及三维流体流动场的先进工具。

本章重点通过实例讲解介绍FLOTRAN CFD流体分析在工程上的一些典型应用。

本章要点如何解决流体力学问题FLOTRAN流体分析典型工程实例本章案例三维U型管道速度场的数值模拟实际生活中射流现象的数值模拟4.1 如何解决流体力学问题在流体力学的研究中，常用的方法有理论研究方法、数值计算方法和实验研究方法。

理论研究方法的特点是：能够清晰、普遍地揭示出流动的内在规律，但该方法目前只局限于少数比较简单的理论模型。

研究更复杂更符合实际的流动一般采用数值计算方法，它的特点就是能够解决理论研究方法无法解决的复杂流动问题，如常见的航空工程、气象预报、水利工程、环境污染预报、星云演化过程等。

实验研究方法的特点就是结果可靠，但其局限性在于相似准侧不能全部满足、尺寸限制、边界影响等。

数值计算方法和实验研究方法相比，它所需的费用和时间都比较少，并且有较高的精度，但它要求对问题的物理特性有足够的了解（通过实验方法了解），并能建立较精确的描述方程组（通过理论分析）。

对于流体力学的数值模拟常采用的步骤如下。

（1）建立力学模型通过流动分析，采用合理的假设与简化，建立力学模型。

假设与简化：连续介质与不连续介质；理想流体与粘性流体；不可压缩流体与可压缩流体；定常流动与非定常流动。

（2）建立数学模型根据力学模型，建立描述力学模型的数学方程组，并利用无量钢化、量纲分析、引进新的物理参数、经验或半经验公式等方法对基本方程组进行简化，得到相应流动的求解方程组，再根据具体的流动条件确定流动的初始条件和边界条件。

描写流体运动的两种方法：拉格朗日方法和欧拉方法。

（3）求解方法●准确解法：解析解●近似解法：近似解、数值解●实验解法：相似解（4）求解结果速度分布、压力分布、合力、阻力、能量耗散等物理量的求解结果。

ANSYS-FLOTRAN分析指南F5-FLOTRAN层流和湍流分析算例

第五章FLOTRAN层流和湍流分析算例一、问题描述二、分析方法及假定三、几何尺寸及流体性质四、分析过程第1步：进入ANSYS第2步：设置分析选择第3步：定义单元类型第4步：生成分析区域的几何面第5步：定义单元形状第6步：划分有限元网格第7步：生成并应用新的工具栏按钮第8步：施加边界条件第9步：求解层流第10步：观察层流分析的结果第11步：确定流体粘性如何影响流场特性第12步：进行湍流分析第13步：对新的出口区划分网格第14步：施加湍流分析的载荷第15步：改变FLOTRAN分析选项和流体性第16步：进行求解第17步：将流体速度结果以向量图和路径图的方式进行显示第18步：绘制压力等值线图第19步：退出ANSYS问题描述该算例是一个二维的导流管分析，先分析一个雷诺数为400的层流情况，然后改变流场参数再重新分析，最后再扩大分析区域来计算其湍流情况。

该算例所用单位制为国际单位制。

分析区域图示如下：分析方法及假定用FLUID141单元来作二维分析，本算例作了如下三个分析：·雷诺数为400的假想流的层流分析·降低流体粘性后（即增大雷诺数）的假想流的层流分析·雷诺数约为260000的空气流的湍流分析分析时假定进口速度均匀，并且垂直于进口流场方向上的流体速度为零。

在所有壁面上施加无滑移边界条件（即所有速度分量都为零）；假定流体不可压缩，并且其性质为恒值，在这种情况下，压力就可只考虑相对值，因此在出口处施加的压力边界条件是相对压力为零。

第一次分析时，流场为层流，着可以通过雷诺数来判定，其公式如下：第二次分析时，将流体粘性降低到原来的十分之一（雷诺数相应增大）后再在第一次分析的基础上重启动分析对于内流来说，当雷诺数达到2000至3000时，流场即由层流过渡到湍流，故第三次分析（空气流，雷诺数约为260000）时，流场是湍流。

对于湍流分析，上图所示的导流管的后端应加长，以使流场能得到充分发展。

流体动力学(CFD)分析.

Page 12
Intro-12
层流分析
T-2. FLOTRAN 分析的种类
Objective
层流中的速度场都是平滑而有序的，高粘性流体（如石油等）的低速流动就通常是层流。
Page 13
Intro-13
紊流分析
T-2. FLOTRAN 分析的种类
Objective
紊流分析用于处理那些由于流速足够高和粘性足够低从而引起紊流波动的流体流动情况，ANSYS中的二方程紊流模型可计及在平均流动下的紊流速度波动的影响。如果流体的密度在流动过程中保持不变或者当流体压缩时只消耗很少的能量，该流体就可认为是不可压缩的，不可压缩流的温度方程将忽略流体动能的变化和粘性耗散。
Page 8
Intro-8
第一章
FLOTRAN 计算流体动力学(CFD)分析概述
Page 9
Intro-9
目标
Module Objective
在完成本章学习后，我们应该对流体动力学分析的基本概念有所了解，并知道它的基本分类。
Lesson Objectives
第一讲、FLOTRAN CFD 分析的概念第二讲、 FLOTRAN 分析的种类第三讲、层流分析第四讲、紊流分析第五讲、热分析第六讲、可压缩流分析第七讲、非牛顿流分析第八讲、多组份传输分析
六、 FLOTRAN分析过程中应处理的问题
七、对一个FLOTRAN分析进行评价
八、验证结果
Page 3
目录
Guidelines
第三章 FLOTRAN设置命令
一、FLOTRAN求解控制命令
二、FLOTRAN执行及输出控制命令稳态控制参数设置
三、FLOTRAN执行及输出控制命令瞬态控制参数设置

ansysFLUENT湍流模型PPT课件

– 只有非常简单的流动才能预测出这些尺度（如充分发展的管流或粘度计里的流动
对一般问题，我们需要导出偏微分输运方程组来计算涡粘系数
湍动能k 启发了求解涡粘模型的物理机理
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A Pera Global Company © PERA China
涡粘模型
涡粘系数类似于动量扩散效应中的分子粘性
涡粘系数不是流体的属性，是一个湍流的特征量，随着流体流动的位置而改变。
– 模型参数通过试验数据校验过，如管流、平板流等 – 对大多数应用有很好的稳定性和合理的精度 – 包括适用于压缩性、浮力、燃烧等子模型
SKE 局限性:
– 对有大的压力梯度、强分离流、强旋流和大曲率流动，模拟精度不够。
– 难以准备模拟出射流的传播 – 对有大的应变区域（如近分离点），模拟的k 偏大
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Fully turbulent region (log law region)
y is the normal distance
Upper limit of log
from the wall.
law region depends
on Reynolds number
近壁面处无量纲的速度分布图
对平衡的湍流边界层来说，半对数曲线的线性段叫做边界层一致性定
Eddy viscosity
– 雷诺应力模型 (RSM): 求解六个雷诺应力项（加上耗散率方程）的偏微分输运方程组
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A Pera Global Company © PERA China
涡粘模型
量纲分析表明，如果我们知道必要的几个尺度（如速度尺度、长度尺度），涡粘系数就可以确定出来
– 例如，给定速度尺度和长度尺度，或速度尺度和时间尺度，涡粘系数就被确定，RANS方程也就封闭了

ansys fluent中文版流体计算工程案例详解

ansys fluent中文版流体计算工程案例详解ANSYS Fluent是一种用于计算流体力学的软件，通过数值模拟的方式进行流体分析和设计。

在实际应用中，需要使用流体计算工程案例来验证仿真结果的准确性和可靠性。

下面将介绍一些常见的应用案例。

1.汽车空气动力学设计。

在汽车设计中，空气动力学是一个非常重要的因素。

使用ANSYS Fluent可以对汽车外形进行流体分析，如气流、气压、气动力等。

通过对气流的模拟，可以优化车身外形设计，提高汽车的性能和燃油经济性。

2.船舶流场分析。

船舶的流体设计是提高船舶速度和燃油经济性的重要因素。

使用ANSYS Fluent可以对船舶外形和水动力性能进行分析。

通过模拟船舶在水中的流动情况，可以优化船体外形和螺旋桨设计，提高航行效率。

3.风力发电机设计。

风力发电机是一种通过风力发电的机械设备。

通过ANSYS Fluent对风场进行数值模拟，可以预测风力发电机的性能和稳定性。

通过分析叶片的气动力学特性，可以优化叶片的设计，提高风力发电机的发电效率。

4.石油钻井液流分析。

石油钻井过程中，需要注入液体来冷却钻头并加速岩屑的排除。

使用ANSYS Fluent对液体的流动情况进行数值模拟，可以预测液体的流动速度和压降，优化钻井液的配比，提高钻井效率。

5.医用注射器设计。

医用注射器是一种常见的医疗器械。

通过使用ANSYS Fluent分析注射器的流场，可以优化注射器的设计。

通过预测注射器注射药液时的速度和压降，可以优化注射器的内部结构和开孔位置，提高注射的精度和安全性。

总之，ANSYS Fluent可以应用于各种流体力学领域，帮助工程师们进行流体力学设计与分析，取得更高效准确的结果。

这些案例都为设计和实施各种流体系统提供了指导，可以大大提高工作效率。

Ansys Flotran做的一个三维流场分析实例

【原创】Ansys Flotran做的一个三维流场分析实例(入门级，CFD高手莫入) 三维, Ansys, CFD, Flotran, 流场三维, Ansys, CFD, Flotran, 流场1、打开Main menu下的Preference对话框，进行如图所示的设置(设置的目的是让后面只显示与Flotran有关的菜单和命令，使得工作更方便):317552-Preference-embed.jpg (57.63 KB)1评分次数nwpuyl收藏分享评分回复引用订阅报告道具TO Pzhjberry初级会员帖子67 积分5 仿真币-2 阅读权限20发表于2004-9-2 14:28 | 只看该作者回复：【原创】Ansys Flotran做的一个三维流场分析实例2、建模。

使用第三方CAD软件(如本例)或用Ansys自带的前处理器生成如图所示的几何模型。

方形盒子表示要求解的流场域，机翼有一定后掠角。

本例近似模拟风洞中的吹风模型。

317556-geomodel-embed.jpg (42.43 KB)回复引用报告道具 TOPzhjberry初级会员发表于2004-9-2 14:30 | 只看该作者回复：【原创】Ansys Flotran做的一个三维流场分析实例3、选择单元类型，如下图所示：317559-element-embed.jpg (74.12 KB)帖子67 积分5仿真币-2阅读权限20回复引用报告道具 TOPzhjberry初级会员帖子67 积分5发表于 2004-9-3 08:30 | 只看该作者回复：【原创】Ansys Flotran 做的一个三维流场分析实例4、划分网格。

首先进行网格设置，如下图所示。

318022-setmesh-embed.jpg (111.43 KB)仿真币-2阅读权限2回复引用报告道具 TOPzhjberry发表于2004-9-3 08:31 | 只看该作者回复：【原创】Ansys Flotran做的一个三维流场分析实例设置完成以后，单击Mesh按钮，选择实体准备网格划分。

ANSYS CFD管道流体分析经典算例 Fluid

Fluid #2: Velocity analysis of fluid flow in a channel USING FLOTRAN Introduction:In this example you will model fluid flow in a channelPhysical Problem:Compute and plot the velocity distribution within the elbow. Assume that the flow is uniform at both the inlet and the outlet sections and that the elbow has uniform depth.Problem Description:T he channel has dimensions as shown in the figureThe flow velocity as the inlet is 10 cm/sUse the continuity equation to compute the flow velocity at exitObjective:T o plot the velocity profile in the channelT o plot the velocity profile across the elbowYou are required to hand in print outs for the aboveFigure:IMPORTANT: Convert all dimensions and forces into SI unitsSTARTING ANSYSC lick on ANSYS 6.1in the programs menu.S elect Interactive.T he following menu comes up. Enter the working directory. All your files will be stored in this directory. Also under UseDefault Memory Model make sure the values 64 for Total Workspace, and 32 for Database are entered. To change these values unclick Use Default Memory ModelMODELING THE STRUCTUREG o to the ANSYS Utility Menu (the top bar)Click Workplane>W P Settings…The following window comes up:o Check the Cartesian and Grid Only buttonso Enter the values shown in the figure aboveGo to the ANSYS Main Menu (on the left hand side of the screen) and click Preprocessor>Modeling>Create>Keypoints>On Working PlaneCreate keypoints corresponding to the vertices in the figure. The keypoints look like below.Now create lines joining these key points.M odeling>Create>Lines>Lines>Straight lineT he model looks like the one below.Now create fillets between lines L4-L5 and L1-L2.C lick Modeling>Create>Lines>Line Fillet. A pop-up window will now appear. Select lines 4 and 5. Click OK. The following window will appear:T his window assigns the fillet radius. Set this value to 0.1 m.Repeat this process of filleting for Lines 1 and 2.The model should look like this now:N ow make an area enclosed by these lines.M odeling>Create>Areas>Arbitrary>By LinesS elect all the lines and click OK. The model looks like the followingT he modeling of the problem is done.ELEMENT PROPERTIESSELECTING ELEMENT TYPE:Click Preprocessor>Element Type>Add/Edit/Delete... In the 'Element Types' window that opens click on Add... The following window opens.∙Type 1 in the Element type reference number.∙Click on Flotran CFD and select 2D Flotran 141. Click OK. Close the Element types window.∙So now we have selected Element type 1 to be solved using Flotran, the computational fluid dynamics portion of ANSYS. This finishes the selection of element type.DEFINE THE FLUID PROPERTIES:∙Go to Preprocessor>Flotran Set Up>Fluid Properties.∙On the box, shown below, set the first two input fields as Air-SI, and then click on OK. Another box will appear. Accept the default values by clicking OK.∙Now we’re ready to define the Material PropertiesMATERIAL PROPERTIESW e will model the fluid flow problem as a thermal conduction problem. The flow corresponds to heat flux, pressurecorresponds to temperature difference and permeability corresponds to conductance.Go to the ANSYS Main MenuClick Preprocessor>Material Props>Material Models. The following window will appearA s displayed, choose CFD>Density. The following window appears.F ill in 1.23 to set the density of Air. Click OK.Now choose CFD>Viscosity. The following window appears:N ow the Material 1 has the properties defined in the above table so the Material Models window may be closed.MESHING: DIVIDING THE CHANNEL INTO ELEMENTS:G o to Preprocessor>Meshing>Size Cntrls>ManualSize>Lines>All Lines.I n the window that comes up type 0.01 in the field for 'Element edge length'.N ow Click OK.Now go to Preprocessor>Meshing>Mesh>Areas>Free. Click the area and the OK. The mesh will look like thefollowing.BOUNDARY CONDITIONS AND CONSTRAINTSG o to Preprocessor>Loads>Define Loads>Apply>Fluid CFD>Velocity>On lines. Pick the left edge of theouter block and Click OK. The following window comes up.E nter 0.1 in the VX value field and click OK. The 0.1 corresponds to the velocity of 0.1 meter per second of air flowingfrom the left side.R epeat the above and set the Velocity to ZERO for the air along all of the edges of the pipe. (VX=VY=0 for all sides)O nce they have been applied, the pipe will look like this:∙Go to Main Menu>Preprocessor>Loads>Define Loads>Apply>Fluid CFD>Pressure DOF>On Lines.∙Pick the outlet line. (The horizontal line at the top of the area) Click OK.∙Enter 0 for the Pressure value.∙Now the Modeling of the problem is done.SOLUTIONG o to ANSYS Main Menu>Solution>Flotran Set Up>Execution Ctrl.∙The following window appears. Change the first input field value to 300, as shown. No other changes are needed. Click OK.G o to Solution>Run FLOTRAN.W ait for ANSYS to solve the problem.C lick on OK and close the 'Information' window.POST-PROCESSINGP lotting the velocity distribution…Go to General Postproc>Read Results>Last Set.Then go to General Postproc>Plot Results>Contour Plot>Nodal Solution. The following window appears:∙Select DOF Solution and Velocity VSUM and Click OK.∙This is what the solution should look like:∙Next, go to Main Menu>General Postproc>Plot Results>Vector Plot>Predefined.The following window will appear:∙Select OK to accept the defaults. This will display the vector plot to compare to the solution of the same tutorial solved using the Heat Flux analogy. Note: This analysis is FAR more precise as shown by the followingsolution:∙Go to Main Menu>General Postproc>Path Operations>Define Path>By Nodes∙Pick points at the ends of the elbow as shown. We will graph the velocity distribution along the line joiningthese two points.∙The following window comes up.∙Enter the values as shown.∙Now go to Main Menu>General Postproc>Path Operations>Map onto Path. The following window comes up.∙Now go to Main Menu>General Postproc>Path Operations>Plot Path Items>On Graph.∙The following window comes up.∙Select VELOCITY and click OK.∙The graph will look as follows:。

ANSYS／FLOTRAN流体动力学(CFD)分析

Intro-9
目标
Module Objective
在完成本章学习后，在完成本章学习后，我们应该对流体动力学分析的基本概念有所了解，并知道它的基本分类。有所了解，并知道它的基本分类。
第一讲、第一讲、FLOTRAN CFD 分析的概念第二讲、第二讲、 FLOTRAN 分析的种类第三讲、层流分析第四讲、第四讲、紊流分析第五讲、第五讲、热分析第六讲、第六讲、可压缩流分析第七讲、第七讲、非牛顿流分析第八讲、多组份传输分析第八讲、
ANSYS培训教程 – 版本 5.5 – XJTU MSSV By: Haich Gao (011001) Intro-4
2001年10月1日
目录
设置命令（第三章 FLOTRAN设置命令（续）设置命令
Guidelines
十三、设定FLOTRAN自由度松弛系数设定自由度松弛系数十四、设定FLOTRAN流体性质松弛因子十四、设定流体性质松弛因子十五、设置FLOTRAN分析的自由度限值十五、设置分析的自由度限值十六、选择FLOTRAN各自由度相应的求解器十六、选择各自由度相应的求解器十七、十七、对FLOTRAN各求解器的控制各求解器的控制十八、设置FLOTRAN湍流模型的一些常数十八、设置湍流模型的一些常数十九、重新设定FLOTRAN各分析参数的值十九、重新设定各分析参数的值二十、控制FLOTRAN面积积分的阶次二十、控制面积积分的阶次二十一、二十一、FLOTRAN多组份疏运分析的设置及控制多组份疏运分析的设置及控制二十二、定义FLOTRAN的重启动（续算）控制的重启动（二十二、定义的重启动续算）二十三、设置并执行一个零迭代FLOTRAN分析二十三、设置并执行一个零迭代分析

ansys中的FLOTRAN分析

一个典型的FLOTRAN分析有如下七个主要步骤：1. 确定问题的区域。

2. 确定流体的状态。

3. 生成有限元网格。

4. 施加边界条件。

5. 设置FLOTRAN分析参数。

6. 求解。

7. 检查结果。

第一步：确定问题的区域用户必须确定所分析问题的明确的范围，将问题的边界设置在条件已知的地方，如果并不知道精确的边界条件而必须作假定时，就不要将分析的边界设在靠近感兴趣区域的地方，也不要将边界设在求解变量变化梯度大的地方。

有时，也许用户并不知道自己的问题中哪个地方梯度变化最大，这就要先作一个试探性的分析，然后再根据结果来修改分析区域。

这些在后面章节中都有详述。

第二步：确定流体的状态用户在此需要估计流体的特征，流体的特征是流体性质、几何边界以及流场的速度幅值的函数。

FLOTRAN能求解的流体包括气流和液流，其性质可随温度而发生显著变化，FLO TRAN中的气流只能是理想气体。

用户须自己确定温度对流体的密度、粘性、和热传导系数的影响是否是很重要，在大多数情况下，近似认为流体性质是常数，即不随温度而变化，都可以得到足够精确的解。

通常用雷诺数来判别流体是层流或紊流，雷诺数反映了惯性力和粘性力的相对强度，详见第四章。

通常用马赫数来判别流体是否可压缩，详见第七章。

流场中任意一点的马赫数是该点流体速度与该点音速之比值，当马赫数大于0.3时，就应考虑用可压缩算法来进行求解；当马赫数大于0.7时，可压缩算法与不可压缩算法之间就会有极其明显的差异。

第三步：生成有限元网格用户必须事先确定流场中哪个地方流体的梯度变化较大，在这些地方，网格必须作适当的调整。

例如：如果用了紊流模型，靠近壁面的区域的网格密度必须比层流模型密得多，如果太粗，该网格就不能在求解中捕捉到由于巨大的变化梯度对流动造成的显著影响，相反，那些长边与低梯度方向一致的单元可以有很大的长宽比。

为了得到精确的结果，应使用映射网格划分，因其能在边界上更好地保持恒定的网格特性，映射网格划分可由命令MSHKEY,1或其相应的菜单Main Menu>Preproce ssor > -Mes hing-Mesh>-entity-Mapped来实现。

ANSYS／FLOTRAN流体动力学分析

ANSYS／FLOTRAN流体动力学分析
使用ANSYSFLOTRAN进行流体动力学分析时，首先需要建立一个几何模型。

可以使用ANSYS的几何建模工具或其他CAD软件进行建模，并将几何模型导入到FLOTRAN中。

然后，需要定义流体材料属性、边界条件和初始条件。

可以选择不同的材料模型，如理想气体、压缩流体或多相流体，并指定相应的物理参数。

边界条件定义了流体流动的入口和出口条件，例如速度、压力或温度。

初始条件是指流体的初始状态，包括速度、压力和温度。

在建立完几何模型和定义边界条件后，可以进行网格生成。

网格的质量对计算结果的准确性和稳定性至关重要，因此需要根据具体问题进行调整。

ANSYSFLOTRAN提供了丰富的网格生成工具，并支持结构化和非结构化网格。

完成网格生成后，可以设置求解器参数并开始求解。

ANSYSFLOTRAN 使用数值方法离散化方程，并通过迭代求解获得流动场的数值解。

求解器可以自动适应计算速度和精度，并提供详细的收敛信息。

求解完成后，可以进行后处理分析。

ANSYSFLOTRAN提供了多种后处理工具，如流线、压力和温度分布图、剪切应力等。

此外，还可以对结果进行比较和优化，以寻找最佳设计方案。

总之，ANSYSFLOTRAN是一种强大的流体动力学分析工具，可用于模拟和分析各种流体流动问题。

它提供了丰富的功能和工具，帮助工程师更好地理解和优化流体流动的行为。

学会使用ANSYSFluent进行流体力学模拟和分析

学会使用ANSYSFluent进行流体力学模拟和分析流体力学是研究流体运动和相互作用的科学。

在工程学领域，流体力学广泛应用于模拟和分析各种工程问题，如气体和液体流动、热传递、质量传递等。

而ANSYSFluent是一种常用的流体力学模拟和分析软件，可以帮助工程师和科研人员进行流体力学模型的建立、仿真和结果分析。

本文将介绍如何学会使用ANSYSFluent进行流体力学模拟和分析。

第一章：ANSYSFluent简介ANSYSFluent是面向工程领域的一款强大的计算流体力学软件。

它提供了广泛的模型和分析工具，可以模拟和分析各种流体力学问题。

ANSYSFluent具有友好的界面，简单易用，同时也具备高级的功能和定制性。

该软件在汽车、航空、化工等领域得到了广泛的应用。

第二章：流体力学模拟流程在使用ANSYSFluent进行流体力学模拟和分析之前，我们需要先了解整个模拟流程。

首先，我们需要定义几何模型，可以通过导入CAD模型或手动构建几何体。

然后，对几何模型进行网格划分，将其离散成小的单元。

接下来，设置流体材料的物性参数，如密度、粘度和热传导系数。

然后，定义流体动力学模型，如流动方程和边界条件。

最后，进行求解和后处理，通过数值方法求解流体力学方程，并分析结果。

第三章：几何建模在ANSYSFluent中，我们可以使用多种方法进行几何建模。

一种常用的方法是通过导入CAD模型，可以直接打开各种常见格式的CAD文件。

另一种方法是使用Fluent的几何建模工具，可以手动构建几何体。

该工具提供了创建基本几何体（如圆柱、球体等）、布尔操作（如并集、交集等）和边界设置等功能，可以方便地生成复杂的几何体。

第四章：网格划分网格划分是流体力学模拟中的重要环节。

好的网格划分可以提高计算精度和计算效率。

在ANSYSFluent中，我们可以使用多种方法进行网格划分。

一种常用的方法是结构化网格划分，它将几何体划分成规则的网格单元。

另一种方法是非结构化网格划分，它允许在几何体中创建任意形状的网格单元。

ANSYS湍流动能湍流耗散率ke计算公式V

(8-8)
已知湍流强度和长度尺度,计算 k-omega
指标
公式
平均速度velocity magnitude
湍流强度intensity
水力直径Hydraulic Diameter
特征长度
L=dh
湍流长度尺度Length Scale
l = 0.07L
(8-3)
湍流动能turbulent kinetic energy
公式
变量 u_arg I mu_t/mu rho V mu k
omega
计算过程 2
0.02 100 1000
0.00000101 0.00101 0.0024
单位 m/s 无量纲
kg/m3 m2/s
m2/s2
23.76237624 1/s
单位无量纲
m 无量纲
m mm
已知雷诺数、Y-PLUS, 计算边界层第一层单元高度
变量 u_arg I dh L l k
epsilon
计算过程 10
0.021349141 1 1
0.07 0.068367873
0.041962557
单位 m/s 无量纲
m
m m m2/s2 m2/s3
变量 u_arg I mu_t/mu rho
V
计算过程 2
0.02 100 1000
0.00000101
雷诺数Re 特征长度L yplus dy
平板流 9.95E+06
1 30 8.1951E-05 0.163902002
单位无量纲
m 无量纲
m mm
变量 dh V Re_DH
计算过程 0.056
0.00000101 100

ansys流体分析FLOTRAN

一、FLOTRAN CFD 分析的概念二、 FLOTRAN 分析的种类
1、层流分析 2、紊流分析 3、热分析 4、可压缩流分析 5、非牛顿流分析 6、多组份传输分析
2001年10月1日 2019/2/24
*ANSYS培训教程 – 版本 5.5 – XJTU MSSV By: Haich Gao (011001)
2001年本 5.5 – XJTU MSSV By: Haich Gao (011001)
Intro-16
非牛顿流分析
Objective
T-2. FLOTRAN 分析的种类
应力与应变率之间成线性关系的这种理论并不能足以解释很多流体的流动，对于这种非牛顿流体，ANSYS程序提供了三中粘性模式和一个用户自定义子程序。
2001年10月1日 2019/2/24
*ANSYS培训教程 – 版本 5.5 – XJTU MSSV By: Haich Gao (011001)
Intro-6
目录
第五章
Guidelines
FLOTRAN层流和湍流分析算例
一、问题描述二、分析方法及假定三、几何尺寸及流体性质四、分析过程
第1步：进入ANSYS 第2步：设置分析选择第3步：定义单元类型第4步：生成分析区域的几何面第5步：定义单元形状第6步：划分有限元网格第7步：生成并应用新的工具栏按钮第8步：施加边界条件第9步：求解层流
ANSYS程序中的FLOTRAN CFD分析功能是一个用于分析二维及三维流体流动场的先进的工具，使用 ANSYS 中用于 FLOTRAN CFD分析的FLUID 141和FLUID 142 单元，可解决如下问题：作用于气动翼(叶)型上的升力和阻力超音速喷管中的流场弯管中流体的复杂的三维流动同时，FLOTRAN还具有如下功能：计算发动机排气系统中气体的压力及温度分布研究管路系统中热的层化及分离使用混合流研究来估计热冲击的可能性用自然对流分析来估计电子封装芯片的热性能对含有多种流体的(由固体隔开)热交换器进行研究

ansys fluent 流体数值计算方法与实例

ansys fluent 流体数值计算方法与实例Ansys Fluent 是一种广泛使用的流体数值计算方法,可用于模拟流体流动过程,例如空气动力学、海洋动力学、航空航天等领域。

本文将介绍 Ansys Fluent 的基本概念和数值计算方法,并探讨 Ansys Fluent 在实际工程中的应用实例。

1. Ansys Fluent 的基本概念Ansys Fluent 是 Ansys 公司开发的一款数值计算方法,主要用于模拟流体运动。

它包括三个主要部分:模型建立、求解器和结果后处理。

模型建立部分用于创建流体运动的数学模型,包括流体的物理性质、边界条件、初始条件等。

求解器部分用于对模型进行数值求解,以得到流场的数值解。

结果后处理部分用于对求解得到的流场进行可视化和分析。

2. Ansys Fluent 的数值计算方法Ansys Fluent 的数值计算方法基于有限体积法(Finite Volume Method,FVM)和有限元法(Finite Element Method,FEM)。

在 FVM 中,模型被划分为多个小部分,每个小部分被划分为多个小体积,然后对每个小体积进行求解。

求解器根据流体的物理性质和边界条件计算出每个小体积内的流体速度、压力等物理量,然后将这些物理量代入下一个小体积中,以此类推,最终得到整个模型的解。

在 FEM 中,模型被划分为多个小区域,然后在每个小区域内使用离散化的单元进行求解。

每个单元包含有限个节点和有限个边界面,单元内的物理量可以通过节点和边界面之间的方程进行求解。

3. Ansys Fluent 在实际工程中的应用实例Ansys Fluent 在实际工程中的应用非常广泛,以下是几个实际工程中的应用实例:1. 空气动力学在飞机设计和飞行模拟中,Ansys Fluent 可以用于模拟空气流动,包括气动力学、湍流流动、温度变化等方面。

通过 Ansys Fluent,可以分析飞机在不同高度、速度和风速下的气动力学特性,并进行飞行模拟,为飞机的设计和优化提供数值支持。

ansys-fluids流体计算的例子

ANSYS EXERCISE – ANSYS 8.1Flow Over a Flat PlateCopyright 2001-2005, John R. BakerJohn R. Baker; phone: 270-534-3114; email: jbaker@This exercise is intended only as an educational tool to assist those who wish to learn how to use ANSYS. It is not intended to be used as a guide for determining suitable modeling methods for any application. The author assumes no responsibility for the use of any of the information in this tutorial. There has been no formal quality control process applied to this tutorial, so there is certainly no guarantee that there are not mistakes on the following pages. The author would appreciate feedback at the email address above if mistakes are discovered in this tutorial.In this exercise, you will solve the classical flat plate 2-D airflow problem, illustrated below, using ANSYS. The problem is adapted from the textbook, Fundamentals of Fluid Mechanics, by Munson, Young, and Okiishi. The airflow velocity for flow over the flat plate will be solved for, based on the specified velocity and pressure boundary conditions, and the plate dimensions. Step-by-step instructions are provided beginning on the following page.Notes: The fluid is air, with density, ρ=1.23 kg/m3, and dynamic viscosity, μ =1.79E-5 N-s/m2. The plate is 1 m long, as shown, and is very thin. It will be modeled with a thickness of 0.001 m. The plate is modeled in a square field, with edge lengths of 2 m. The 2 m edge length dimensions are arbitrary. These lengths are chosen large enough such that the effects of the flat plate on the flow are captured completely within the square field. Also, the flow velocity in all directions is zero along the sides of the flat plate.The steps that willbe followed, after launching ANSYS, are:Preprocessing:1. Change Preferences2. Change Jobname.3. Define element type. (Fluid141 element, which is a 2-D element for fluid analysis.)4. Define the fluid. (Air – SI Units.)5. Create keypoints.6. Create areas.7. Specify meshing controls / Mesh the areas to create nodes and elements.8. Zoom in to see flat plate region (optional).Solution:9. Specify boundary conditions.10. Specify number of solution iterations.11. Solve.Postprocessing:11. Plot the x-direction velocity (VX) distribution.12. List VX at Nodes.Exit13. Exit the ANSYS program, saving all data._____________________________________________________________________________ Notes:•It is assumed in this tutorial that the user has already launched ANSYS and is working in the Graphical User Interface (GUI).•The menu picks needed to perform all required tasks are specified in italics in the step-by-step instructions below. It is sometimes more convenient to enter certain commands directly at the command line. The method of direct command line entry, however, is not emphasized in this exercise. Primarily, in this exercise, the analysis will be performed using menu picks from the ANSYS Graphical User Interface.SUGGESTION: As you work through this exercise, on the ANSYS Toolbar click on “SAVE_DB” often!At any point, if you want to resume from the previous time the model was saved, simply click on “RESUM_DB” on this same Toolbar. Any information entered since the last save will be lost, but this is a nice feature in the event that you make an input mistake, and are unsure of how to correct it.Note: Most of the required tasks are performed using menu picks from the ANSYS GUI, as specified in italics in the step-by-step instructions below. It is sometimes more convenient, however, to enter certain commands directly at the command line. The command line is seen on the screen.The Main Menu is on the left side of the screen.The method of direct command line entry is used in some cases in this exercise, whenever this method seems more convenient than using menu picks.Often, as an alternative, an input file, known as a “batch file”, is created, which is simply an ASCII text file containing a string of ANSYS commands in the appropriate order. ANSYS can read in this file as if it were a program, and perform the analysis in “batch mode”, without ever opening up the Graphical User Interface. The batch file option is not covered in this exercise.There are a number of ways to model a system and perform an analysis in ANSYS. The steps below present only one method.Preprocessing:1. Change Preferences. Main Menu -> Preferences -> FLOTRAN CFD -> OK2. Change jobname. At the upper left-hand corner of the screen:File -> Change JobnameEnter “flatplate”, and click on “OK”.3. Define element type:Preprocessor -> Element Type -> Add/Edit/DeleteClick on “Add”. The “Library of Element Types” box appears, as shown. Highlight “FLOTRAN CFD”, and “2D FLOTRAN 141”. Click on “OK”, then “Close”.4. Define fluid properties: Preprocessor -> FLOTRAN Set Up ->Fluid PropertiesOn the box, shown below, change the first two input fields to “AIR-SI”, and then click on “OK”. Another box will appear. Accept all defaults on that box by clicking on “OK”.5. Create keypoints:There are several options available for creating the basic geometry. The method that will be employed involves creating “keypoints”, then generating two separate areas, with corners defined by the keypoints.Preprocessor -> -Modeling- Create -> Keypoints -> In Active CS…Fill in the fields as shown below, then click “APPLY”. When you click on “Apply”, the command is issued to create keypoint number 1 at (x,y,z)=(-1,1,0). Note that when the Z field is left blank, in this case, the blank space defaults to zero, which is desired. Since you clicked on “Apply”, instead of “OK”, then the keypoint creation box remains open.Create keypoint number 2 at (x,y,z)=(0,1,0), using the input shown below. After entering the input, again, click on “APPLY”:Create 12 total keypoints in the same manner. The locations for all 12 are shown in the following table. When the final keypoint is created, click on “OK” instead of “APPLY”.“OK” issues the command and also closes the keypoint creation box.Keypoint Number X-Location Y-Location1 -1 12 0 13 1 14 -0.5 05 0 06 0.5 0-0.0017 -0.5-0.0018 0-0.0019 0.510 -1 -111 0 -112 1 -1Before moving on, it is probably a good idea to check the keypoint locations. Along thetop toolbar choose:List -> Keypoint -> Coordinates Only.A box should open up with the keypoint location information. If any keypoint is not inthe correct location, at this point, you can just re-issue the keypoint creation command for that particular keypoint. To do this, choose:Preprocessor -> -Modeling- Create -> Keypoints -> In Active CS…Fill in the correct information for that particular keypoint in the box, and click “OK”. The keypoint will be moved to the correct location. If you have some keypoint incorrectly numbered above number 12, this will not cause a problem. Just be sure you have keypoint numbers 1 thru 12 located correctly.You can close the box listing the keypoint locations, by clicking, in that listing box, on “File-> Close”.6. Create areas:It may be a good idea to save your model at this point, by clicking “SAVE_DB”on the ANSYS Toolbar. Now, if you make a mistake from which you do not know howto recover, just click on “RESUM_DB”, and the model will resume from the point of the last save.We will create two separate areas. One is the left half of the flow field, and the other is the right half. We will do this by defining areas, as outlined below, using the defined keypoints as corners of the areas. The figure below shows the end result, exceptthe figure shows an extremely exaggerated thickness of the flat plate. This is done forclarity. The black dots denote keypoints, and the circled numbers denote the keypoint numbers.In creating the areas, it is probably easiest to use the direct command line entry approach. At the command line, type in, as shown below: a,1,2,5,4,7,8,11,10Hit “Enter”, and the left half of the flow field is generated as an area, defined by the keypoints entered with the “a” command. Now, create the right half, by typing, at the command line: a,2,3,12,11,8,9,6,5After hitting “Enter”, the right side is generated. Note that, although we have created the flow field in two halves, the entire 2 m x 2 m field could have been produced as a single square. Then, the flat plate could have been cut out of that square. However, the method being employed will produce a line of “nodes” protruding vertically from the center of the flat plate, and this will be desirable when the fluid velocity results are compared to the analytical solution. At this time, the horizontal flat plate appears in the graphics window as a single line, because it is so thin. The plot in the graphics window should appear as:7. Specify Mesh Size Controls / Mesh the Model.There are a number of ways to perform this step, but for this exercise, the procedure has been automated, and will involve typing only a single word, below. The actual method employed would involve entering 24 commands at the command line. Because of the possibility of typographical errors, however, for this exercise, this step has been automated, using the “macro” option within ANSYS. A macro has been created. It is a text file named mshfield.mac. It is available for download on the website from which this tutorial was downloaded. The file, mshfield.mac, should be copied to your ANSYS working directory. The commands in the macro are discussed in the Appendix, at the end of these instructions. However, to execute all of the required commands (assuming you have the file “mshfield.mac” stored in your current ANSYS working directory), all that is needed is to type, at the command line:mshfieldThen, hit “Enter”. All of the necessary commands should be executed, and the mesh should appear, as shown in the following figure on the next page. The requiredcommands are listed in the appendix.GUI with Finite Element Mesh in Graphics Window8. Zoom in to see the flat plate (optional)This step is not necessary, but it may be helpful to you to see the flat plate geometry, and the fine mesh near the plate. If you wish to zoom in, first, it may be best to turn off the X-Y-Z Axis “Triad” display, as it is really just in the way. We know that we defined our model so that +x is to the right on the screen, and +y is upward. To turn off the X-Y-Z Axis “Triad” display, on the menu across the very top of the GUI choose:PltCtrls -> Window Controls -> Window OptionsA box appears. Change the [/TRIAD] option to “Not Shown”, and then click “OK”.Then, back to the menu across the very top of the GUI, select:PltCtrls -> Pan, Zoom, Rotate…The “Pan-Zoom-Rotate” box below appears. On that box, select “Box Zoom”Then, in the graphics window, press the left mouse button, and drag to producea box near the center of the flow area. Then, click once with the left mousebutton, and you will see a zoomed view of the region around the plate, withthe fine mesh. At any time, to return to the full model view, on the “Pan-Zoom-Rotate” box, click on “Fit” (near the bottom of the box).Solution:9. Specify boundary conditions.In Step 6, there is a sketch of the geometry, with an exaggerated thickness for the flat plate. You may want to refer to this figure and the figure on page 1, during the boundary condition specification. The boundary condition specification steps are outlined below, in steps 9a thru 9e, where VX denotes X-direction flow velocity, and VY denotes Y-direction flow velocity. Before beginning the specifications, it is probably best to plot the lines, without showing the areas, for better clarity. On the menu along the very top of the GUI, select:Plot -> LinesYou should then see colored lines, which are the boundaries of the areas. Unless you are zoomed in, the flat plate will probably appear as a single horizontal line. Although not necessary, you may also want to turn on “Keypoint Numbering”. To do this, again on the very top menu, choose: PltCtrls -> NumberingZoomed View of PlateThe box below opens. Click on the box to the right of “Keypoint numbers” to toggle from “Off” to “On”. Then, click on “OK”. If you have the lines plotted, then the keypoint numbers should also show.9a) Specification of VX Value and VY=0 on the line connecting keypoints 1 and 10.One way to do this is to choose, and the ANSYS Main Menu:Solution -> Define Loads-> Apply->Fluid/CFD-> Velocity -> On LinesA picking menu appears, as shown (below, left). Click on the far left vertical line (theline which connects keypoints 1 and 10), and it should highlight. In the picking menu, choose “OK”. (Note that if you accidently highlight the wrong line, you can unselect it using the picking menu, and switching from “Pick” to “Unpick”. But here, it’s probably easiest to just hit “Cancel” on the picking menu, then re-open the picking box, using: Solution -> -Loads- Apply -> -Fluid/CFD- Velocity -> On Lines.)After highlighting the appropriate line, and clicking “OK” in the Picking Menu, a box appears (shown below right). Enter “0.072764” (or your assigned value) for VX, and 0.0 for “VY”, then click “OK”. Since this is a 2-D analysis, you don’t need a VZ value.9b) Specification of VX=VY=0.0 along the edges of the flat plate. Here, we could use the picking option to select the correct lines, as we did in Step 9a. But, it would involve zooming in to pick the correct closely-spaced lines. It may be easiest here to initially just select the correct lines, using two successive command line entries, which are:ksel,s,kp,,4,9lslk,s,1Hit “Enter” after each command. Note that there are supposed to be two consecutive commas, as shown, in the “ksel” command. The first command above selects keypoints 4 thru 9, and the second command selects the set of all lines which have their endpoints within the selected set of keypoints. Now, on the menus, choose:Solution -> Define Loads-> Apply -> Fluid/CFD-> Velocity -> On LinesThis time, when the picking menu appears, you don’t need to pick on any lines in the model, just choose “Pick All” at the bottom of the picking menu. Only the lines of interest are currently selected. When the “Velocity Constraints” box opens, just enter VX=0.0 and VY=0.0, then click on “OK”.Now, it is very important that you re-select all entities. On the very top menu, choose: Select -> Everything (or else, equivalently, you can type, at the command line: allsel , then hit “Enter”.Then, on the top menu, choose: Plot -> Lines8c) Specification of atmospheric pressure on five of the six lines that define the outer boundary. These are the lines defined by end keypoints 1-2; 2-3; 3-12; 12-11; and 11-10. Note that the farthest left vertical line, connecting keypoints 1 and 10, is not included in the set. Here, we can return to the picking menu method. Choose:Solution -> Define Loads-> Apply -> Fluid/CFD-> Pressure DOF -> On LinesA picking menu opens. Click on all five of the lines noted above to highlight them. If you make a mistake in picking, it may be best to just click on “Cancel” in the picking menu, then re-start step 8c. Once the correct five lines are highlighted, choose “OK” in the picking menu, and the “Pressure Constraint” box will open, as shown below. Enter “0” for “Pressure value”, and click “OK”. This “0” value indicates atmospheric pressure.10. Specify Number of Solution Iterations:Solution -> FLOTRAN Set Up ->Execution CtrlThe box below appears. Change the first input field value to 500, as shown. No other changes are needed. Click OK.11. Solve the problem:Solution -> Run FLOTRANThe problem will run until the specified 500 iterations are completed. This will take a few minutes. When the solution is completed, a box will appear that reads “Solution is Done!”. You may close this box.Postprocessing:12. Plot the x-direction velocity distribution.First, read in the results by selecting:General Postproc -> Read Results-> Last SetThen, to plot, choose:General Postproc -> Plot Results ->Contour Plot-> Nodal SoluThe box below opens:Highlight “DOF solution” and “X-Component of Fluid Velocity” and click “OK”. In the graphics window, a plot, as shown below, should appear. Note that the velocity values corresponding to the colors are shown in the legend to the right.You may want to zoom in closer to the flat plate to get a better view of the velocity distribution near the flat plate. See Step 8 for instructions on zooming in to get a closer look. It is also possible to save plots in the graphics window to graphics files, in formats such as “TIFF”, “JPEG”, or “BITMAP”, and subsequently insert them into a word processing document. This option is not covered in this exercise. If you want to try this, though, you can select, from the top menu: PltCtrls -> Hard Copy -> To File. A box opens up with the plot file creation options.13. List VX at Nodes.13a. Select nodes along the plate center (x=0.0 meters).For comparison with the analytical solution, you will need a listing of specific x-direction velocities at specific locations in the flow field. ANSYS has calculated VX, VY, and the pressure at each “node”. Because of our method of creating the model by automatic “meshing” of the areas, at this time, we do not know specific node numbers at specific locations. But, we can get a listing of node numbers, including the locations of each node, and also a listing of velocities by node numbers. To keep the amount of information to a workable level, it is probably best to include in these lists only a subset of nodes. To get such a list, we can first select only the nodes at x=0 (at the center of the plate – recall the plate ends are at x=-0.5 m and x=+0.5 m). This is a case where it isprobably easiest to just use the direct command line entry option, rather than operate through the menus. On the command line, type:nsel,s,loc,x,0Hit “enter”.Then, reduce the selected set even further by reselecting, from the currently selected set, only those nodes above the plate, up to y=0.15 m. To do this, type, at the command line:nsel,r,loc,y,0,0.15Hit “enter”.13b. List the locations of the selected nodes.On the very top menu, choose List -> Nodes. In the box that appears, on the “Output listing will contain” option, choose “Coordinates Only”. Then for the “Sort first by” option, select “Y coordinate” as shown below:Then, just click on “OK” at the bottom. A listing box appears:You can get a hard copy of the information in this box by clicking, in this listing box:File -> Print.You can also save this information to a file using the option:File -> Save As.If desired, you may close the node listing box to get it out of the way. To do this, in that listing box, choose: File -> Close.13c. List x-direction velocity (VX) at each of these nodes.First, for convenience, sort the nodes so that the results listing will list the velocities of the selected nodes in ascending order of y-location. Choose:General Postproc -> List Results -> -Sorted Listing-> Sort NodesIn the box that opens, shown below, select “Ascending Order”, for “ORDER”, and highlight “Geometry” and “Y”, as shown, and hit “OK”. This produces another listing box of node locations, which you may close.Then, to get the list of nodal velocities, select:General Postproc -> List Results -> Nodal SolutionIn the box that appears, select “DOF Solution” and “X Component of Fluid Velocity”, as shown, then click “OK”.The listing, as shown below, should appear. You will probably want to either print these velocities out, or save them to a file, as you did the node locations. The locations of the same nodes have already been listed, in Step 13b, above. Since you now have velocities (VX) at various y-locations, all at the center of the plate (x=0), the results for these nodes can be checked with the analytical solution.Re-select all nodes in the model for additional plotting, or listing, as desired. To do this, simply type, at the command line: “allsel” and hit enter:Or else, on the very top menu, choose: Select -> EverythingSubsequent lists and plots will include all nodes. Steps 12 and 13 can be repeated to get listings of velocities and pressures of nodes at other locations. Of course, Y-direction velocities (VY) are also available. In addition, there are options for velocity vector plots, and also animations of the steady-state flow, available on the ANSYS Post-processor.14. Exit ANSYS, Saving All Data. On the ANSYS Toolbar, choose:Quit ->Save Everything -> OKTo recall the model and solution at a later date, assuming you have deleted no files, simply re-launch ANSYS, specify the same working directory as before, re-issue the same jobname as used in Step 2 of these instructions, and then click on “RESUME_DB” on the ANSYS Toolbar shown above.To see the resumed model in the graphics window, you may then need to click on “Plot” on the very top menu, then, choose either “Elements”, “Nodes”, or “Areas”, depending on which entities you wish to plot.Appendix – Discussion of Step 7 (This appendix is included for discussion only, and may be skipped.)The commands on the following page are designed to produce a fine mesh near the plate, but a more coarse mesh away from the plate. In Step 7 of these instructions, all of these commands were issued automatically, by simply typing “mshfield”. This only worked because a file named “mshfield.mac” was copied to your ANSYS working directory. This is not a standard ANSYS command. It is a user-created macro containing a string of commands.Regarding the mesh, a fine mesh was desired near the flat plate, where the velocity gradients are highest. This is necessary to accurately calculate the flow velocity near the plate. However, away from the high velocity gradient region, a fine mesh is not necessary. For solution accuracy, there is no problem with simply creating a very fine mesh in all regions of the model. However, producing a fine mesh in regions where it is not necessary results in longer solution time and higher computer memory and hard drive storage requirements, without significantly increasing the solution accuracy. Therefore, it is useful to control the mesh. A discussion of the method used follows: •We first select the two horizontal lines, which define the plate top and bottom, and we specify that there are to be 100 element divisions along each of these lines. This is accomplished with the first five commands.•Then, the vertical line along the center of the flow field, above the flat plate, is selected, and 30 element divisions are specified, with a spacing ratio of 0.01. This means that the ratio of the longest division to the shortest is 100. This is done with commands 6 thru 8.•Next, the vertical line along the center of the flow field, below the flat plate, is selected, and again, 30 element divisions are specified, with a spacing ratio of 100. This is handled with commands 9 thru 11. Note: It may be confusing that in one case we entered a spacing ratio of “0.01”, and in the other case, we entered a spacing ratio of “100”. In both cases, this means that the ratio of the longest division to the shortest is 100. The line “directions” (which are determined and stored internally in ANSY) were automatically determined when the areas were generated. Because of these directions, in the first case, the spacing ratio of “0.01” will produce the smallest element divisions at the ends of the lines nearer the plate. In the next case, a spacing ratio of “100” is needed to produce the smaller divisions nearer the plate. It is possible to check the directions of all lines, but it is not necessary in this exercise, because the required commands have already been determined for you.•Next, the two vertical lines at the ends of the flow fields are selected, and the number of element divisions specified for each is 20. The spacing ratio is uniform, so no spacing ratio is entered. This is handled with commands 12 thru16.•Next, the four horizontal lines, at the top and bottom of the flow fields, are selected, and the number of element divisions specified for each is 10. Again, the spacing ratio is uniform, so no spacing ratio is entered. This is handled with commands 17 thru 21.•Everything is re-selected with the “allsel” command, command number 22.•The element shape is set to triangular, with the “mshape” command. Triangular elements are sometimes better than quadrilateral elements for irregularly shaped areas, such as we have.•The two areas are meshed, using the “amesh” command.The mesh that should result was shown in Step 7 of these instructions.Rather than use the macro “mshfield.mac”, in Step 7, the commands below could have been issued in the order shown below, at the ANSYS command line. The user would not have typep the numbers in parentheses, but would have just typed the commands. These numbers were included for reference only. The user could have typed the commands, exactly as shown, including all commas, and hit “Enter” after each command was typed. The macro “mshfield.mac” is simply an ASCII text file containing the string of commands below (without the numbers).Commands:(1) ksel,s,kp,,4,6(2)lslk,s,1(3) ksel,s,kp,,7,9(4) lslk,a,1(5) lesize,all,,,200(6) ksel,s,kp,,2,5,3(7) lslk,s,1(8) lesize,all,,,30,0.01(9) ksel,s,kp,,8,11,3(10) lslk,s,1(11) lesize,all,,,30,100(12) ksel,s,kp,,1,10(13) lslk,s,1(14) ksel,s,kp,,3,12(15) lslk,a,1(16) lesize,all,,,20(17) ksel,s,kp,,1,3(18) lslk,s,1(19) ksel,s,kp,,10,12(20) lslk,a,1(21) lesize,all,,,10(22) allsel(23) mshape,1,2d(24) amesh,all。

ansysfluent中文版流体计算工程案例详解

ansysfluent中文版流体计算工程案例详解以汽车空气动力学为例，我们可以利用ANSYS Fluent来模拟车辆行驶过程中的风阻和气动性能。

首先，我们需要建立车辆的几何模型，并进行网格划分。

网格划分的精度和密度直接影响到计算结果的准确性。

在划分网格时，我们需要考虑到车辆外形的复杂性以及细节特征，如轮胎、后视镜等。

建立几何模型和划分网格后，我们可以导入该模型并设置初始条件。

初始条件包括初始流速、压力和温度等。

接下来，我们需要设置流体物性，如空气的密度、粘度和热导率等。

在进行计算之前，我们还需要设置边界条件。

车辆表面通常设定为无滑移壁面，即在边界处满足流速为零的条件。

此外，我们还需要设置出口条件来模拟车辆行驶过程中的空气流动。

出口条件可以设定为自由出流或常数质量流率出流。

此外，我们还可以设置车辆的速度和方向等边界条件。

设置完边界条件后，我们可以开始求解流体力学方程。

ANSYS Fluent使用的是控制方程的有限差分形式来近似求解。

利用迭代算法，可以逐步优化流场的精度和稳定性，直至达到收敛条件。

在求解过程中，我们可以通过图形输出和数据记录等方式来观察和分析结果。

图形输出可以显示出流场、压力分布、速度分布和湍流特性等。

数据记录可以提供流场参数的详细信息，如压力、温度、速度和质量流率等。

通过以上步骤，我们可以获得汽车在不同速度下的风阻系数、力矩和气动特性等重要参数。

这些结果可以为汽车的空气动力学设计和优化提供依据。

综上所述，ANSYS Fluent可以应用于各种流体力学计算工程。

通过几何建模、网格划分、边界条件设置、流体力学方程和求解等步骤，我们可以对流动过程进行模拟和分析，并获得各种流场参数。

这些参数对于优化设计、性能评估和产品改进等方面具有重要意义。

ANSYS流体第4章flotran流体分析典型工程实例

ANSYS流体第4章flotran流体分析典型工程实例ANSYS程序中的FLOTRAN CFD流体分析是一个用于分析二维及三维流体流淌场的先进工具。

本章重点通过实例讲解介绍FLOTRAN CFD流体分析在工程上的一些典型应用。

本章要点如何解决流体力学问题FLOTRAN流体分析典型工程实例本章案例三维U型管道速度场的数值模拟实际生活中射流现象的数值模拟4.1 如何解决流体力学问题在流体力学的研究中，常用的方法有理论研究方法、数值计算方法与实验研究方法。

理论研究方法的特点是：能够清晰、普遍地揭示出流淌的内在规律，但该方法目前只局限于少数比较简单的理论模型。

研究更复杂更符合实际的流淌通常使用数值计算方法，它的特点就是能够解决理论研究方法无法解决的复杂流淌问题，如常见的航空工程、气象预报、水利工程、环境污染预报、星云演化过程等。

实验研究方法的特点就是结果可靠，但其局限性在于相似准侧不能全部满足、尺寸限制、边界影响等。

数值计算方法与实验研究方法相比，它所需的费用与时间都比较少，同时有较高的精度，但它要求对问题的物理特性有足够的熟悉（通过实验方法熟悉），并能建立较精确的描述方程组（通过理论分析）。

关于流体力学的数值模拟常使用的步骤如下。

（1）建立力学模型通过流淌分析，使用合理的假设与简化，建立力学模型。

假设与简化：连续介质与不连续介质；理想流体与粘性流体；不可压缩流体与可压缩流体；定常流淌与非定常流淌。

（2）建立数学模型根据力学模型，建立描述力学模型的数学方程组，并利用无量钢化、量纲分析、引进新的物理参数、经验或者半经验公式等方法对基本方程组进行简化，得到相应流淌的求解方程组，再根据具体的流淌条件确定流淌的初始条件与边界条件。

描写流体运动的两种方法：拉格朗日方法与欧拉方法。

ansys FLOTRAN

目录第一章FLOTRAN 计算流体动力学(CFD)分析概述一、FLOTRAN CFD 分析的概念二、FLOTRAN 分析的种类1、层流分析2、紊流分析3、热分析4、可压缩流分析5、非牛顿流分析6、多组份传输分析FLOTRAN CFD 分析的概念ANSYS程序中的FLOTRAN CFD分析功能是一个用于分析二维及三维流体流动场的先进的工具，使用ANSYS中用于FLOTRAN CFD分析的FLUID 141和FLUID 142 单元，可解决如下问题：作用于气动翼(叶)型上的升力和阻力超音速喷管中的流场弯管中流体的复杂的三维流动同时，FLOTRAN还具有如下功能：计算发动机排气系统中气体的压力及温度分布研究管路系统中热的层化及分离使用混合流研究来估计热冲击的可能性用自然对流分析来估计电子封装芯片的热性能对含有多种流体的(由固体隔开)热交换器进行研究FLOTRAN 分析的种类FLOTRAN可执行如下分析：层流或紊流传热或绝热可压缩或不可压缩牛顿流或非牛顿流多组份传输这些分析类型并不相互排斥，例如，一个层流分析可以是传热的或者是绝热的，一个紊流分析可以是可压缩的或者是不可压缩的。

层流分析层流中的速度场都是平滑而有序的，高粘性流体（如石油等）的低速流动就通常是层流。

紊流分析紊流分析用于处理那些由于流速足够高和粘性足够低从而引起紊流波动的流体流动情况，ANSYS中的二方程紊流模型可计及在平均流动下的紊流速度波动的影响。

如果流体的密度在流动过程中保持不变或者当流体压缩时只消耗很少的能量，该流体就可认为是不可压缩的，不可压缩流的温度方程将忽略流体动能的变化和粘性耗散。

热分析流体分析中通常还会求解流场中的温度分布情况。

如果流体性质不随温度而变，就可不解温度方程。

在共轭传热问题中，要在同时包含流体区域和非流体区域（即固体区域）的整个区域上求解温度方程。

在自然对流传热问题中，流体由于温度分布的不均匀性而导致流体密度分布的不均匀性，从而引起流体的流动，与强迫对流问题不同的是，自然对流通常都没有外部的流动源。