【原创】分享我用ansys做的一个cfd问题的例子（GUI方式）及我的疑问，共同讨论

chenyhappy

一平面长方形管道，流体为气体（不可压缩），符合boussinesq假设，壁面无滑移，在一长方形流道内流动，进口速度5m/s,流体初始温度为20度，出口处压力为零， 分下面几种情况模拟,目的是检验流体和壁面温差对对流换热系数的影响：
    1 上下壁面温度均为40度
    2 上下壁面温度均为80度
    3 上壁面温度为 80度，下壁面温度40度
在这3种情况下，求上下壁面节点的对流换热系数结果如下：
  一： 情况3 上下壁面对应位置上节点的对流换热系数一部分相同，另一部分不同
  二：情况1 的节点对流换热系数和情况2对应节点号的节点上的对流换热系数完全相同，但和情况3的对应节点的对流换热系数不太相同
     这是怎莫回事呀？
    大家看看我得分析过程是不是有问题呀？
    对流换热系数和壁面于流体之间的温差到底有无影响？
     
    再有1：如果用紊流模型，如何激活壁面函数法
          2： 如果把载荷和边界条件加在相应边上的节点上（下边的分析是加在 边上）分析后得到的节点对流换热系数与加在边上时也有较大的差别，那莫，那个结果好一些呢？
     请诸位高手看看，并解释一下，谢谢
分析过程（情况1）
设置参数优先选项
Main Menu > Preferences
Turn on FLOTRAN CFD filtering.
OK
设置元素类型
Main Menu > Preprocessor > Element Type > Add/Edit/Delete
Add an element type.
Choose FLOTRAN CFD.
Choose 2D FLOTRAN element (FLUID141).
OK.
Close.
建立模型为一平面长方形
Main Menu> Preprocessor> Modeling> Create> Areas> Rectangle> By Dimensions
Enter the following:
X1 = 0
X2 = 0.1
Enter the following:
Y1 = 0
Y2 = 0.025
OK to create rectangle
Toolbar: SAVE_DB.
划分网格
Utility Menu> Plot> Lines
Choose Lines Set.
Pick lines in flow direction along the inlet(the vertical line at the left).
Apply in the picking menu.
Enter 50 as the No. of element divisions.
Enter -2 as the Spacing ratio (this produces smaller elements near both ends of the line).
Apply.
Pick the top and bottom lines
Apply
Enter 100 as the No. of element divisions.
Enter 3.0 as the Spacing ratio (bias towards outlet).
OK.
（Notice that the upper line is not biased towards the outlet. The line bias needs to be "flipped."）
Choose Flip in the Mesh Tool.
Pick the upper line only.
OK (in the picking menu).
Toolbar: SAVE_DB.
Choose Mapped mesher.
Choose Mesh.
Pick All.
Close the Mesh Tool.
设置CFD分析选项
Main Menu> Solution> FLOTRAN Set Up> Solution Options
TEMP (Adiabatic or thermal) change to "Thermal"（即包括流体的温度分析）
OK
Main Menu> Solution> FLOTRAN Set Up> Exection Ctrl
EXEC Global iterations set to 200 （迭代200次）
OK
Main Menu> Solution> FLOTRAN Set Up> Fluid Properties（流体性质）
OK
input 1.2045 for Density
input 18.201 for Viscosity
input 2.57 for Conductivity
input 1000 for Specific Heat
OK
设置流动环境
Main Menu> Solution> FLOTRAN Set Up> Flow Environment>Ref Conditions
Nominal temperature change from 293 to 20
Stagnation(total) temp change from 293 to 20
Reference (bulk)temp change from 293 to 20
Temp offset from ABS zero change from 0 to 273
OK
定义载荷和边界条件（加在边上，也可加在相应边的结点上，看结果有何差别）
Main Menu> Solution> Loads > Define Loads> Apply> Fluid/CFD> Velocity> On Lines
Pick the inlet line (the vertical line at the left).
OK in the picking menu.
Enter 5.0 for VX. （进口流速）
OK
Main Menu> Solution> Loads> Define Loads> Apply> Thermal> temperature> On Lines（进口流体温度）
Pick the inlet line (the vertical line at the left)
OK in the picking menu.
Select TEMP for DOFs to be constrained
Enter 20 for Load TEMP value.
OK
Main Menu> Solution> Loads> Define Loads> Apply> Fluid/CFD> Velocity> On Lines
Pick the top and bottom line
OK in the picking menu.
Enter 0 for VX
Enter 0 for VY（无滑移边界条件）
OK
Main Menu> Solution> Loads> Define Loads> Apply> Thermal> temperature> On Lines
Pick the top and bottom line
OK in the picking menu.
Select TEMP for DOFs to be constrained
Enter 40 for Load TEMP value（壁面温度）
OK
Main Menu> Solution> Loads> Define Loads> Apply> Fluid/CFD> Pressure DOF> On Lines
Pick the outlet line (the vertical line at the right).
OK in the picking menu.
Enter 0 for pressure value（出口压力）
OK
运行
Main Menu> Solution>Run FLOTRAN
Main Menu> General Postproc> Read Results> Last set
Main Menu> General Postproc> Plot Results> Vector Plot> Predefined
Choose DOF solution.
Choose Velocity V. （观察流场分布）
OK.
Main Menu> General Postproc> Plot Results> Contour Plot> Nodal Solu
Choose Other quantities.
Choose Film coeff HELM（列出节点对流换热系数）
OK.
结束
分析过程（情况2）
设置参数优先选项
Main Menu > Preferences
Turn on FLOTRAN CFD filtering.
OK
设置元素类型
Main Menu > Preprocessor > Element Type > Add/Edit/Delete
Add an element type.
Choose FLOTRAN CFD.
Choose 2D FLOTRAN element (FLUID141).
OK.
Close.
建立模型为一平面长方形
Main Menu> Preprocessor> Modeling> Create> Areas> Rectangle> By Dimensions
Enter the following:
X1 = 0
X2 = 0.1
Enter the following:
Y1 = 0
Y2 = 0.025
OK to create rectangle
Toolbar: SAVE_DB.
划分网格
Utility Menu> Plot> Lines
Choose Lines Set.
Pick lines in flow direction along the inlet(the vertical line at the left).
Apply in the picking menu.
Enter 50 as the No. of element divisions.
Enter -2 as the Spacing ratio (this produces smaller elements near both ends of the line).
Apply.
Pick the top and bottom lines
Apply
Enter 100 as the No. of element divisions.
Enter 3.0 as the Spacing ratio (bias towards outlet).
OK.
（Notice that the upper line is not biased towards the outlet. The line bias needs to be
"flipped."）
Choose Flip in the Mesh Tool.
Pick the upper line only.
OK (in the picking menu).
Toolbar: SAVE_DB.
Choose Mapped mesher.
Choose Mesh.
Pick All.
Close the Mesh Tool.
设置CFD分析选项
Main Menu> Solution> FLOTRAN Set Up> Solution Options
TEMP (Adiabatic or thermal) change to "Thermal"（即包括流体的温度分析）
OK
Main Menu> Solution> FLOTRAN Set Up> Exection Ctrl
EXEC Global iterations set to 200 （迭代200次）
OK
Main Menu> Solution> FLOTRAN Set Up> Fluid Properties（流体性质）
OK
input 1.2045 for Density
input 18.201 for Viscosity
input 2.57 for Conductivity
input 1000 for Specific Heat
OK
设置流动环境
Main Menu> Solution> FLOTRAN Set Up> Flow Environment>Ref Conditions
Nominal temperature change from 293 to 20
Stagnation(total) temp change from 293 to 20
Reference (bulk)temp change from 293 to 20
Temp offset from ABS zero change from 0 to 273
OK
定义载荷和边界条件（加在边上，也可加在相应边的结点上，看结果有何差别）
Main Menu> Solution> Loads > Define Loads> Apply> Fluid/CFD> Velocity> On Lines
Pick the inlet line (the vertical line at the left).
OK in the picking menu.
Enter 5.0 for VX. （进口流速）
OK
Main Menu> Solution> Loads> Define Loads> Apply> Thermal> temperature> On Lines（进口流体温度）
Pick the inlet line (the vertical line at the left)
OK in the picking menu.
Select TEMP for DOFs to be constrained
Enter 20 for Load TEMP value.
OK
Main Menu> Solution> Loads> Define Loads> Apply> Fluid/CFD> Velocity> On Lines
Pick the top and bottom line
OK in the picking menu.
Enter 0 for VX
Enter 0 for VY（无滑移边界条件）
OK
Main Menu> Solution> Loads> Define Loads> Apply> Thermal> temperature> On Lines
Pick the top and bottom line
OK in the picking menu.
Select TEMP for DOFs to be constrained
Enter 80 for Load TEMP value（壁面温度）
OK
Main Menu> Solution> Loads> Define Loads> Apply> Fluid/CFD> Pressure DOF> On Lines
Pick the outlet line (the vertical line at the right).
OK in the picking menu.
Enter 0 for pressure value（出口压力）
OK
运行
Main Menu> Solution>Run FLOTRAN
Main Menu> General Postproc> Read Results> Last set
Main Menu> General Postproc> Plot Results> Vector Plot> Predefined
Choose DOF solution.
Choose Velocity V. （观察流场分布）
OK.
Main Menu> General Postproc> Plot Results> Contour Plot> Nodal Solu
Choose Other quantities.
Choose Film coeff HELM（列出节点对流换热系数）
OK.
结束
分析过程（情况3）
设置参数优先选项
Main Menu > Preferences
Turn on FLOTRAN CFD filtering.
OK
设置元素类型
Main Menu > Preprocessor > Element Type > Add/Edit/Delete
Add an element type.
Choose FLOTRAN CFD.
Choose 2D FLOTRAN element (FLUID141).
OK.
Close.
建立模型为一平面长方形
Main Menu> Preprocessor> Modeling> Create> Areas> Rectangle> By Dimensions
Enter the following:
X1 = 0
X2 = 0.1
Enter the following:
Y1 = 0
Y2 = 0.025
OK to create rectangle
Toolbar: SAVE_DB.
划分网格
Utility Menu> Plot> Lines
Choose Lines Set.
Pick lines in flow direction along the inlet(the vertical line at the left).
Apply in the picking menu.
Enter 50 as the No. of element divisions.
Enter -2 as the Spacing ratio (this produces smaller elements near both ends of the line).
Apply.
Pick the top and bottom lines
Apply
Enter 100 as the No. of element divisions.
Enter 3.0 as the Spacing ratio (bias towards outlet).
OK.
（Notice that the upper line is not biased towards the outlet. The line bias needs to be
"flipped."）
Choose Flip in the Mesh Tool.
Pick the upper line only.
OK (in the picking menu).
Toolbar: SAVE_DB.
Choose Mapped mesher.
Choose Mesh.
Pick All.
Close the Mesh Tool.
设置CFD分析选项
Main Menu> Solution> FLOTRAN Set Up> Solution Options
TEMP (Adiabatic or thermal) change to "Thermal"（即包括流体的温度分析）
OK
Main Menu> Solution> FLOTRAN Set Up> Exection Ctrl
EXEC Global iterations set to 200 （迭代200次）
OK
Main Menu> Solution> FLOTRAN Set Up> Fluid Properties（流体性质）
OK
input 1.2045 for Density
input 18.201 for Viscosity
input 2.57 for Conductivity
input 1000 for Specific Heat
OK
设置流动环境
Main Menu> Solution> FLOTRAN Set Up> Flow Environment>Ref Conditions
Nominal temperature change from 293 to 20
Stagnation(total) temp change from 293 to 20
Reference (bulk)temp change from 293 to 20
Temp offset from ABS zero change from 0 to 273
OK
定义载荷和边界条件（加在边上，也可加在相应边的结点上，看结果有何差别）
Main Menu> Solution> Loads > Define Loads> Apply> Fluid/CFD> Velocity> On Lines
Pick the inlet line (the vertical line at the left).
OK in the picking menu.
Enter 5.0 for VX. （进口流速）
OK
Main Menu> Solution> Loads> Define Loads> Apply> Thermal> temperature> On Lines（进口流体温度）
Pick the inlet line (the vertical line at the left)
OK in the picking menu.
Select TEMP for DOFs to be constrained
Enter 20 for Load TEMP value.
OK
Main Menu> Solution> Loads> Define Loads> Apply> Fluid/CFD> Velocity> On Lines
Pick the top and bottom line
OK in the picking menu.
Enter 0 for VX
Enter 0 for VY（无滑移边界条件）
OK
Main Menu> Solution> Loads> Define Loads> Apply> Thermal> temperature> On Lines
Pick the top line
OK in the picking menu.
Select TEMP for DOFs to be constrained
Enter 80 for Load TEMP value（壁面温度）
Apply
Pick the bottom line
OK in the picking menu.
Select TEMP for DOFs to be constrained
Enter 40 for Load TEMP value（壁面温度）
OK
Main Menu> Solution> Loads> Define Loads> Apply> Fluid/CFD> Pressure DOF> On Lines
Pick the outlet line (the vertical line at the right).
OK in the picking menu.
Enter 0 for pressure value（出口压力）
OK
运行
Main Menu> Solution>Run FLOTRAN
Main Menu> General Postproc> Read Results> Last set
Main Menu> General Postproc> Plot Results> Vector Plot> Predefined
Choose DOF solution.
Choose Velocity V. （观察流场分布）
OK.
Main Menu> General Postproc> Plot Results> Contour Plot> Nodal Solu
Choose Other quantities.
Choose Film coeff HELM（列出节点对流换热系数）
OK.
结束

shaoyun1987

这个用命令流稍微改一点就可以了

shaoyun1987

没有选择对流换热系数输出就可以了？貌似这样的操作有点问题。