LES初始速度场设置和壁面函数设置

hoversoar

@东岳
上一个过渡性太大的例子算完了。
又做了个过渡性比较好的case，不过表面带坑的圆柱算起来特别久。一个大概要20天，还在跑现在。
prism的ratio取的1.3，然后减小了外面poly的尺寸（这样一来mesh数量会有增大很多），过渡率大概控制再2左右。

hoversoar

@cccrrryyy

原来是ANSYS Meshing，近壁面是规整的四边型，然后五边型过渡，之后就是大量的六边型并掺杂一些不得不用的五边形。

我是用ANSYS meshing生成的全都是棱柱tetra，然后用fluent转化成polymesh就是五边形六边形的样子, 再用fluent with meshing 导出msh文件。

感觉四边型之后全部是三角形最好。不过这个可能不太会影响最终的结果，而且会让cell数量变大。

确实三角形的网格数量会大大增加，所以采用了转化到多边形来减小网格数提高计算效率。之前可能没说清楚，这个算例不是二维的是三维的。之前的polymesh的图是从z轴看过去的样子，所以可能像2D。

李东岳

不过表面带坑的圆柱算起来特别久。一个大概要20天，还在跑现在。

你这个多少网格？

hoversoar

@东岳 poly的话四百多万，tetra一千二百万。
因为坑的地方mesh尺寸很小，CFL数控制下的步长在-5次方量级。

李东岳

@hoversoar 嗯，确实，要解析这么小的坑很麻烦，跟高尔夫球一样。不过你这个挺有意思

hoversoar

@东岳把3D的图贴一下，这样比较直观。

捕获.JPG
如图1的样子，ratio 2-3的话，坑里放不下... 权衡之后取了1.3。
多做了几个density box 逐渐扩大mesh的尺寸，在最靠近边界层的box尺寸取的比较小，来让过渡性处于2左右。

因为计算时长较久，导致试错成本很高，也是一个大问题。

hoversoar

@cccrrryyy

感觉ANSYS Meshing的思路是尽可能缩小五边形所占的比例，从而大量使用六边形？

这个倒是没有研究, 就让他自动转化了。个人觉得可能形状没有太拘泥，如果不是edge的处不能合并三角形的话，尽量会合并成多边形并且满足所设定的size（也就是不会合并到过分大）。

李东岳

@hoversoar

因为计算时长较久，导致试错成本很高，也是一个大问题。

对

你这个网格处理的很精细很厉害

你这个是工程导向还是纯科研？什么上面有这种特别圆的孔？

hoversoar

@东岳谢谢夸奖！
算是基于工程的研究吧.. 桥索上用的

cccrrryyy

@hoversoar 哇，三维的，这网格数量惊人啊。提炼工程问题确实容易这样，需要花很多时间在前处理上，求解器本身其实也不应该特别特别重要。从这个角度讲，感觉可能你需要的是花大量精力在网格上，而不是求解器的那些参数调整。
你之前提到过跟现有文献对比，是哪个文章呀，挺感兴趣的。

羽之下

@cccrrryyy 你好，你贴的这个参考资料好像打不开了，可以更新下链接吗，谢谢，最近也在看壁面函数的内容。

hoversoar

@羽之下还可以打开链接啊。
再贴一次。
壁面函数

hoversoar

@cccrrryyy

从这个角度讲，感觉可能你需要的是花大量精力在网格上，而不是求解器的那些参数调整。

之前几个月自己就一顿乱算，导致连光滑圆柱的结果都很奇怪。所以用那个简单的模型在探讨求解器，设置参数之类的。
对得上了之后，再过来讨论这边这个圆柱的网格。

你之前提到过跟现有文献对比，是哪个文章呀，挺感兴趣的。

非光滑圆柱的话，参考的Experimental study on flow past a circular cylinder with rough surface这篇文献的。

cccrrryyy

@hoversoar 好！谢谢

hoversoar

大家好，又有了新的困惑。
我翻看教程的时候，发现pisofoam和pimplefoam里头LES案例的fvscheme 对流项设置有一些不同，觉得有点困惑。pimplefoam里头有一个B项，pisofoam里头则没有。
pimplefoam/LES/channel395

divSchemes
{
    default         none;
    div(phi,U)      Gauss linear;
    div(phi,k)      Gauss limitedLinear 1;
    div(phi,B)      Gauss limitedLinear 1;
    div(B)          Gauss linear;
    div(phi,nuTilda) Gauss limitedLinear 1;
    div((nuEff*dev2(T(grad(U))))) Gauss linear;
}

pisofoam/LES/motobike:

divSchemes
{
    default         none;
    div(phi,U)      Gauss LUST unlimitedGrad(U);
    div(phi,k)      Gauss limitedLinear 1;
    div(phi,nuTilda) Gauss limitedLinear 1;
    div((nuEff*dev2(T(grad(U))))) Gauss linear;
}

查了下LES对应的B，RAS用的R，是雷诺应力张量的求解。那既然default都是none，按照user guide是要对每一项进行定义的，为什么pisofoam里头缺失了这一项呢？
ps我看到我之前的case也都没写这一项，估计是直接复制了摩托车的代码。不知道这项是不是必须的？

cccrrryyy

@hoversoar 说实话FOAM的tutorial里面的设置不太可靠，只能拿来做个参考。

我看了pimpleFoam的这个算例，不太清楚具体是哪里用到了B，去掉的话可以算么？按道理说它用的是WALE模型，是个代数模型，不需要用方程去求解B才对。pisoFoam用的是SpalartAllmaras模型，不涉及到求解B，但要求解nuTilda。不太清楚为什么需要div(phi,k)，可能这个去掉也可以算。

这些设置我觉得主要是根据湍流模型的不同带来的，如果去掉某一个不能算我感觉重点可能在速度方程的turbulence->divDevReff(U)这一项里面，这个得去代码里面找了，不同版本好像还有点区别。

hoversoar

@cccrrryyy 感谢解答。

我看了pimpleFoam的这个算例，不太清楚具体是哪里用到了B，去掉的话可以算么？按道理说它用的是WALE模型，是个代数模型，不需要用方程去求解B才对。pisoFoam用的是SpalartAllmaras模型，不涉及到求解B，但要求解nuTilda。不太清楚为什么需要div(phi,k)，可能这个去掉也可以算。

pimpleFoam没有B项也是可以算的，我这期间就是没发现还有个这个就一直在算..所以才会疑惑。

李东岳

@hoversoar 怎么样，带坑的算了么。这种小尺度坑，感觉网格会特别多

hoversoar

@东岳完全失败中...

hoversoar

尝试把湍流模型从kEqn换成了dynamicKEqn，结果报了错。没看懂，有大佬能帮我解释一下吗..

[10] #0  Foam::error::printStack(Foam::Ostream&)[12] #0  Foam::error::printStack(Foam::Ostream&)[13] #0  [7] #0  Foam::error::printStack(Foam::Ostream&)Foam::error::printStack(Foam::Ostream&)[3] #0  [11] #0  Foam::error::printStack(Foam::Ostream&)Foam::error::printStack(Foam::Ostream&) at ??:?
[12] #1  Foam::sigFpe::sigHandler(int) at ??:?
 at ??:?
[11] #1  Foam::sigFpe::sigHandler(int)[10] #1  Foam::sigFpe::sigHandler(int) at ??:?
[3] #1  Foam::sigFpe::sigHandler(int) at ??:?
[13] #1  Foam::sigFpe::sigHandler(int) at ??:?
[7] #1  Foam::sigFpe::sigHandler(int) at ??:?
[12] #2  ? at ??:?
[3] #2  ? at ??:?
[11] #2  ? at ??:?
[10] #2  ? at ??:?
[7] #2  ? in "/lib/x86_64-linux-gnu/libc.so.6"
[12] #3  Foam::sqrt(Foam::Field<double>&, Foam::UList<double> const&) at ??:?
[13] #2  ? in "/lib/x86_64-linux-gnu/libc.so.6"
 in "/lib/x86_64-linux-gnu/libc.so.6"
[3] #3  Foam::sqrt(Foam::Field<double>&, Foam::UList<double> const&) in "/lib/x86_64-linux-gnu/libc.so.6"
[10] #3  Foam::sqrt(Foam::Field<double>&, Foam::UList<double> const&)[7] #3  Foam::sqrt(Foam::Field<double>&, Foam::UList<double> const&) in "/lib/x86_64-linux-gnu/libc.so.6"
[11] #3  Foam::sqrt(Foam::Field<double>&, Foam::UList<double> const&) in "/lib/x86_64-linux-gnu/libc.so.6"
[13] #3  Foam::sqrt(Foam::Field<double>&, Foam::UList<double> const&) at ??:?
[12] #4  Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::sqrt<Foam::fvPatchField, Foam::volMesh>(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
[3] #4  Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::sqrt<Foam::fvPatchField, Foam::volMesh>(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
[10] #4  Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::sqrt<Foam::fvPatchField, Foam::volMesh>(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
[7] #4  Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::sqrt<Foam::fvPatchField, Foam::volMesh>(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
[11] #4  Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::sqrt<Foam::fvPatchField, Foam::volMesh>(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
[12] #5  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::Ck(Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) const at ??:?
[13] #4  Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::sqrt<Foam::fvPatchField, Foam::volMesh>(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
[3] #5  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::Ck(Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) const at ??:?
[10] #5  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::Ck(Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) const at ??:?
[11] #5  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::Ck(Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) const at ??:?
[7] #5  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::Ck(Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) const at ??:?
[12] #6  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::correctNut(Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
[10] #6  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::correctNut(Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
[13] #5  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::Ck(Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) const at ??:?
[12] #7  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::correctNut() at ??:?
[3] #6  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::correctNut(Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
[11] #6  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::correctNut(Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
[7] #6  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::correctNut(Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
[13] #6  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::correctNut(Foam::GeometricField<Foam::SymmTensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
[12] #8   at ??:?
[10] #7  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::correctNut() at ??:?
[11] #7  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::correctNut() at ??:?
[3] #7  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::correctNut() at ??:?
[7] #7  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::correctNut()? at ??:?
[13] #7  Foam::LESModels::dynamicKEqn<Foam::IncompressibleTurbulenceModel<Foam::transportModel> >::correctNut() at ??:?
[11] #8   at ??:?
[12] #9  __libc_start_main at ??:?
[10] #8   at ??:?
[13] #8   at ??:?
[7] #8   at ??:?
[3] #8  ?? in "/lib/x86_64-linux-gnu/libc.so.6"
[12] #10  ?? at ??:?
[11] #9  __libc_start_main at ??:?
[13] #9  __libc_start_main?? in "/lib/x86_64-linux-gnu/libc.so.6"
[13] #10   in "/lib/x86_64-linux-gnu/libc.so.6"
[11] #10   at ??:?
[10] #9  __libc_start_main at ??:?
[3] #9  __libc_start_main at ??:?
[7] #9  __libc_start_main?? in "/lib/x86_64-linux-gnu/libc.so.6"
[10] #10   at ??:?
[DL-BoxII:41641] *** Process received signal ***
[DL-BoxII:41641] Signal: Floating point exception (8)
[DL-BoxII:41641] Signal code:  (-6)
[DL-BoxII:41641] Failing at address: 0x3ea0000a2a9
[DL-BoxII:41641] [ 0] /lib/x86_64-linux-gnu/libc.so.6(+0x354b0)[0x2ad9e28f14b0]
[DL-BoxII:41641] [ 1] /lib/x86_64-linux-gnu/libc.so.6(gsignal+0x38)[0x2ad9e28f1428]
[DL-BoxII:41641] [ 2]  in "/lib/x86_64-linux-gnu/libc.so.6"
[3] #10  /lib/x86_64-linux-gnu/libc.so.6(+0x354b0)[0x2ad9e28f14b0]
[DL-BoxII:41641] [ 3] /opt/openfoam5/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so(_ZN4Foam4sqrtERNS_5FieldIdEERKNS_5UListIdEE+0x28)[0x2ad9e1941728]
[DL-BoxII:41641] [ 4] /opt/openfoam5/platforms/linux64GccDPInt32Opt/lib/libincompressibleTurbulenceModels.so(_ZN4Foam4sqrtINS_12fvPatchFieldENS_7volMeshEEENS_3tmpINS_14GeometricFieldIdT_T0_EEEERKS7_+0x190)[0x2ad9ddd760f0]
[DL-BoxII:41641] [ 5] /opt/openfoam5/platforms/linux64GccDPInt32Opt/lib/libincompressibleTurbulenceModels.so(_ZNK4Foam9LESModels11dynamicKEqnINS_29IncompressibleTurbulenceModelINS_14transportModelEEEE2CkERKNS_14GeometricFieldINS_10SymmTensorIdEENS_12fvPatchFieldENS_7volMeshEEERKNS6_IdS9_SA_EE+0x2a5)[0x2ad9ddd87f15]
[DL-BoxII:41641] [ 6] /opt/openfoam5/platforms/linux64GccDPInt32Opt/lib/libincompressibleTurbulenceModels.so(_ZN4Foam9LESModels11dynamicKEqnINS_29IncompressibleTurbulenceModelINS_14transportModelEEEE10correctNutERKNS_14GeometricFieldINS_10SymmTensorIdEENS_12fvPatchFieldENS_7volMeshEEERKNS6_IdS9_SA_EE+0x79)[0x2ad9ddd88859]
[DL-BoxII:41641] [ 7] /opt/openfoam5/platforms/linux64GccDPInt32Opt/lib/libincompressibleTurbulenceModels.so(_ZN4Foam9LESModels11dynamicKEqnINS_29IncompressibleTurbulenceModelINS_14transportModelEEEE10correctNutEv+0x1f4)[0x2ad9ddd89874]
[DL-BoxII:41641] [ 8] pimpleFoam[0x4254ad]
[DL-BoxII:41641] [ 9] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x2ad9e28dc830]
[DL-BoxII:41641] [10] pimpleFoam[0x428729]
[DL-BoxII:41641] *** End of error message ***
 at ??:?

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LES初始速度场设置和壁面函数设置