前言
遇到的问题是：使用Gambit生成网格之后，欲生成OpenFOAM可用的cyclic边界条件，直接应用fluentMeshToFoam转换是不行的，还需要使用createPatch。
参考CFD Online的一个回答：
https://www.cfd-online.com/Forums/openfoam-meshing/107664-usage-createpatchdict.html
二维周期边界
本文代码和case均基于OpenFOAM v8.0，分以下几个步骤介绍：
- 基础网格生成
- 网格转换
- 创建cyclic边界
1. 基础网格生成
使用Gambit划分如下二维计算域的网格，并给各个边界命名。
需要注意的是，生成网格之前必须用Gambit的link功能将配对的边界链接起来，以保证配对的两个边界上的网格保持一致。生成网格之后导出为 tri.msh 网格文件，边界条件的类型设为 wall 即可。
2. 网格转换
应用fluentMeshToFoam将 tri.msh 转换为OpenFOAM的网格文件，所得 case/constant/polyMesh/boundary 文件如下
/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 8
\\/ M anipulation |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class polyBoundaryMesh;
location "constant/polyMesh";
object boundary;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
5
(
upperWall
{
type wall;
inGroups List<word> 1(wall);
nFaces 160;
startFace 85726;
}
rightWall
{
type wall;
inGroups List<word> 1(wall);
nFaces 160;
startFace 85886;
}
leftWall
{
type wall;
inGroups List<word> 1(wall);
nFaces 160;
startFace 86046;
}
lowerWall
{
type wall;
inGroups List<word> 1(wall);
nFaces 160;
startFace 86206;
}
frontAndBackPlanes
{
type empty;
inGroups List<word> 1(empty);
nFaces 114728;
startFace 86366;
}
)
// ************************************************************************* //
生成cyclic边界之前还需要做点准备工作，那就是修改上述boundary文件为
/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 8
\\/ M anipulation |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class polyBoundaryMesh;
location "constant/polyMesh";
object boundary;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
5
(
upperWall
{
type cyclic;
inGroups List<word> 1(cyclic);
nFaces 160;
startFace 85726;
matchTolerance 0.0001;
neighbourPatch lowerWall;
}
rightWall
{
type cyclic;
inGroups List<word> 1(cyclic);
nFaces 160;
startFace 85886;
matchTolerance 0.0001;
neighbourPatch leftWall;
}
leftWall
{
type cyclic;
inGroups List<word> 1(cyclic);
nFaces 160;
startFace 86046;
matchTolerance 0.0001;
neighbourPatch rightWall;
}
lowerWall
{
type cyclic;
inGroups List<word> 1(cyclic);
nFaces 160;
startFace 86206;
matchTolerance 0.0001;
neighbourPatch upperWall;
}
frontAndBackPlanes
{
type empty;
inGroups List<word> 1(empty);
nFaces 114728;
startFace 86366;
}
)
// ************************************************************************* //
主要是将 wall 边界类型改为 cyclic边界类型，并用neighbourPatch指定各个cyclic边界之间的配对关系，用matchTolerance指定配对的精度。
3. 创建cyclic边界
在 case/system 文件夹中新建控制文件 createPatchDict ，文件内容如下
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object createPatchDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
// This application/dictionary controls:
// - optional: create new patches from boundary faces (either given as
// a set of patches or as a faceSet)
// - always: order faces on coupled patches such that they are opposite. This
// is done for all coupled faces, not just for any patches created.
// - optional: synchronise points on coupled patches.
// 1. Create cyclic:
// - specify where the faces should come from
// - specify the type of cyclic. If a rotational specify the rotationAxis
// and centre to make matching easier
// - always create both halves in one invocation with correct 'neighbourPatch'
// setting.
// - optionally pointSync true to guarantee points to line up.
// 2. Correct incorrect cyclic:
// This will usually fail upon loading:
// "face 0 area does not match neighbour 2 by 0.0100005%"
// " -- possible face ordering problem."
// - in polyMesh/boundary file:
// - loosen matchTolerance of all cyclics to get case to load
// - or change patch type from 'cyclic' to 'patch'
// and regenerate cyclic as above
// Do a synchronisation of coupled points after creation of any patches.
// Note: this does not work with points that are on multiple coupled patches
// with transformations (i.e. cyclics).
pointSync false;
// Patches to create.
patches
(
{
// Name of new patch
name lowerWall;
// Type of new patch
patchInfo
{
type cyclic;
neighbourPatch upperWall;
transform translational;
separationVector (0 1 0);
}
constructFrom patches;
patches (lowerWall);
set f0;
}
{
// Name of new patch
name upperWall;
// Type of new patch
patchInfo
{
type cyclic;
neighbourPatch lowerWall;
transform translational;
separationVector (0 1 0);
}
constructFrom patches;
patches (upperWall);
set f0;
}
{
// Name of new patch
name rightWall;
// Type of new patch
patchInfo
{
type cyclic;
neighbourPatch leftWall;
transform translational;
separationVector (1 0 0);
}
constructFrom patches;
patches (rightWall);
set f0;
}
{
// Name of new patch
name leftWall;
// Type of new patch
patchInfo
{
type cyclic;
neighbourPatch rightWall;
transform translational;
separationVector (1 0 0);
}
constructFrom patches;
patches (leftWall);
set f0;
}
);
// ************************************************************************* //
最后运行createPatch，即可生成带正确 cyclic 边界的网格文件。
/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 8
\\/ M anipulation |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class polyBoundaryMesh;
location "0.002/polyMesh";
object boundary;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
5
(
upperWall
{
type cyclic;
inGroups List<word> 1(cyclic);
nFaces 160;
startFace 85726;
matchTolerance 0.0001;
neighbourPatch lowerWall;
transformType translational;
separation (0 1 0);
}
rightWall
{
type cyclic;
inGroups List<word> 1(cyclic);
nFaces 160;
startFace 85886;
matchTolerance 0.0001;
neighbourPatch leftWall;
transformType translational;
separation (1 0 0);
}
leftWall
{
type cyclic;
inGroups List<word> 1(cyclic);
nFaces 160;
startFace 86046;
matchTolerance 0.0001;
neighbourPatch rightWall;
transformType translational;
separation (-1 -0 -0);
}
lowerWall
{
type cyclic;
inGroups List<word> 1(cyclic);
nFaces 160;
startFace 86206;
matchTolerance 0.0001;
neighbourPatch upperWall;
transformType translational;
separation (-0 -1 -0);
}
frontAndBackPlanes
{
type empty;
inGroups List<word> 1(empty);
nFaces 114728;
startFace 86366;
}
)
// ************************************************************************* //
三维周期边界
1. Gambit网格划分
采用link功能建立对应面的映射关系，注意选中 Reverse orientation 和 Periodic，
生成网格的时候，Gambit会保证对应面上的网格一致性。
生成网格之后检查一下各个对应面的网格是否一致：
2. 网格转换
注意：必须使用 Fluent3DMeshToFoam转换网格，否则在生成cyclic边界时会遇到问题
网格转换完成之后，将周期边界的类型都先调整为 patch
/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 7
\\/ M anipulation |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class polyBoundaryMesh;
location "constant/polyMesh";
object boundary;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
6
(
upper
{
type patch;
inGroups List<word> 1(patch);
nFaces 3596;
startFace 938740;
}
lower
{
type patch;
inGroups List<word> 1(patch);
nFaces 3596;
startFace 942336;
}
back
{
type patch;
inGroups List<word> 1(patch);
nFaces 3618;
startFace 945932;
}
front
{
type patch;
inGroups List<word> 1(patch);
nFaces 3618;
startFace 949550;
}
right
{
type patch;
inGroups List<word> 1(patch);
nFaces 3606;
startFace 953168;
}
left
{
type patch;
inGroups List<word> 1(patch);
nFaces 3606;
startFace 956774;
}
)
// ************************************************************************* //
3. 生成周期边界
编写 system/createPatchDict 文件如下
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object createPatchDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
pointSync false;
// Patches to create.
patches
(
{
// Name of new patch
name lowerWall;
// Type of new patch
patchInfo
{
type cyclic;
neighbourPatch upperWall;
transform translational;
separationVector (0 6.283185308 0);
matchTolerance 1E-5;
}
constructFrom patches;
patches (lower);
set f0;
}
{
// Name of new patch
name upperWall;
// Type of new patch
patchInfo
{
type cyclic;
neighbourPatch lowerWall;
transform translational;
separationVector (0 -6.283185308 0);
matchTolerance 1E-5;
}
constructFrom patches;
patches (upper);
set f0;
}
{
// Name of new patch
name rightWall;
// Type of new patch
patchInfo
{
type cyclic;
neighbourPatch leftWall;
transform translational;
separationVector (-6.283185308 0 0);
matchTolerance 1E-5;
}
constructFrom patches;
patches (right);
set f0;
}
{
// Name of new patch
name leftWall;
// Type of new patch
patchInfo
{
type cyclic;
neighbourPatch rightWall;
transform translational;
separationVector (6.283185308 0 0);
matchTolerance 1E-5;
}
constructFrom patches;
patches (left);
set f0;
}
{
// Name of new patch
name frontWall;
// Type of new patch
patchInfo
{
type cyclic;
neighbourPatch backWall;
transform translational;
separationVector (0 0 -6.283185308);
matchTolerance 1E-5;
}
constructFrom patches;
patches (front);
set f0;
}
{
// Name of new patch
name backWall;
// Type of new patch
patchInfo
{
type cyclic;
neighbourPatch frontWall;
transform translational;
separationVector (0 0 6.283185308);
matchTolerance 1E-5;
}
constructFrom patches;
patches (back);
set f0;
}
);
// ************************************************************************* //
这里需要注意以下几点：
(1) name of new patch 最好与源面的名字不同，例如示例中的 backWall (new) 和 back (source)
(2) separationVector 在相对的两个面上是一正一负，可以先自己根据面的法向量给定一个向量，如果计算的时候求解器提示如下 warning
Specified separationVector (0 1 0) differs from computed separation vector 1((0 6.2831853 0))
可以根据提示调整 separationVector。
编写好上述文件之后，执行 createPatch，生成周期边界条件。
Enjoy!
Contact me
E-mail: 18810577380@163.com
3633
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