CFD中文网

我认为这个是和几何无关的，衡量网格质量的参数中有一个叫aspect ratio，这个值为1时最好，像那种类似薄片或者细长的网格，这个值会很大，这种网格一般质量很差。

@hhj0219 和y+定义一样。其实就是：流向网格间距除以壁面第一层距离，然后再乘以y+。

我最近也想配一台工作站，导师也不太懂就交给我自己来配了，我之前小打小闹配的第一台机器用的2950x觉得amd挺好的，看到新出的3990x觉得太香了，有没有大佬可以讨论一下具体怎么配置好呀，3990x怎么才能双路并行呀

非常感谢您

但计算过程中会出现CFL数突然增大之后报错的问题Mean and max Courant Numbers = 0.0196702 0.2
deltaT = 1.34917e-09
Time = 1.381229231e-07

diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG: Solving for N2, Initial residual = 0.102714, Final residual = 8.31435e-10, No Iterations 11
DILUPBiCG: Solving for O2, Initial residual = 0.0998228, Final residual = 2.97854e-08, No Iterations 11
DILUPBiCG: Solving for NO, Initial residual = 0.00103043, Final residual = 4.54498e-07, No Iterations 11
DILUPBiCG: Solving for N2+, Initial residual = 0.157236, Final residual = 1.27729e-09, No Iterations 11
DILUPBiCG: Solving for O2+, Initial residual = 0.157241, Final residual = 1.44374e-09, No Iterations 11
DILUPBiCG: Solving for NO+, Initial residual = 0.157279, Final residual = 1.20494e-09, No Iterations 11
DILUPBiCG: Solving for N, Initial residual = 0.00643012, Final residual = 4.19377e-07, No Iterations 11
DILUPBiCG: Solving for O, Initial residual = 0.00193657, Final residual = 2.2919e-07, No Iterations 11
DILUPBiCG: Solving for N+, Initial residual = 0.157174, Final residual = 1.12526e-09, No Iterations 11
DILUPBiCG: Solving for O+, Initial residual = 0.156703, Final residual = 1.23372e-08, No Iterations 11
DILUPBiCG: Solving for e-, Initial residual = 0.0591289, Final residual = 2.85246e-15, No Iterations 5
diagonal: Solving for rhoUx, Initial residual = 0, Final residual = 0, No Iterations 0
diagonal: Solving for rhoUy, Initial residual = 0, Final residual = 0, No Iterations 0
diagonal: Solving for rhoUz, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver: Solving for Ux, Initial residual = 5.41102e-05, Final residual = 5.24963e-09, No Iterations 120
smoothSolver: Solving for Uy, Initial residual = 0.00128686, Final residual = 1.27448e-07, No Iterations 160
smoothSolver: Solving for Uz, Initial residual = 0.000139985, Final residual = 1.28962e-08, No Iterations 70
diagonal: Solving for rhoEv, Initial residual = 0, Final residual = 0, No Iterations 0
diagonal: Solving for rhoE, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver: Solving for hevel, Initial residual = 0.000257938, Final residual = 3.98118e-07, No Iterations 400
smoothSolver: Solving for e, Initial residual = 0.00686842, Final residual = 6.70799e-06, No Iterations 140
Attempt to use rho2ReactionThermo out of temperature range 139 times during this iteration.
 Thigh: 40000 < 640000
Phase no 1.0 ExecutionTime = 4.97 s ClockTime = 5 s Iteration no 112 (0.04 s)

Mean and max Courant Numbers = 0.0196515 0.552368
deltaT = 4.88502e-10
Time = 1.386114254e-07

diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG: Solving for N2, Initial residual = 0.0831271, Final residual = 4.94891e-09, No Iterations 11
DILUPBiCG: Solving for O2, Initial residual = 0.0830444, Final residual = 6.0302e-09, No Iterations 11
DILUPBiCG: Solving for NO, Initial residual = 0.0225179, Final residual = 4.10796e-07, No Iterations 11
DILUPBiCG: Solving for N2+, Initial residual = 0.070932, Final residual = 1.23497e-08, No Iterations 11
DILUPBiCG: Solving for O2+, Initial residual = 0.0707959, Final residual = 1.16027e-08, No Iterations 11
DILUPBiCG: Solving for NO+, Initial residual = 0.0712528, Final residual = 1.38649e-08, No Iterations 11
DILUPBiCG: Solving for N, Initial residual = 0.117227, Final residual = 8.58776e-08, No Iterations 11
DILUPBiCG: Solving for O, Initial residual = 0.209694, Final residual = 8.63459e-07, No Iterations 11
DILUPBiCG: Solving for N+, Initial residual = 0.240723, Final residual = 1.5458e-05, No Iterations 11
DILUPBiCG: Solving for O+, Initial residual = 0.0709349, Final residual = 3.14266e-08, No Iterations 11
DILUPBiCG: Solving for e-, Initial residual = 0.0330941, Final residual = 7.94061e-14, No Iterations 3
diagonal: Solving for rhoUx, Initial residual = 0, Final residual = 0, No Iterations 0
diagonal: Solving for rhoUy, Initial residual = 0, Final residual = 0, No Iterations 0
diagonal: Solving for rhoUz, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver: Solving for Ux, Initial residual = 1.89119e-05, Final residual = 1.65027e-09, No Iterations 70
smoothSolver: Solving for Uy, Initial residual = 0.000264353, Final residual = 2.41377e-08, No Iterations 102
smoothSolver: Solving for Uz, Initial residual = 5.29899e-05, Final residual = 5.01779e-09, No Iterations 70
diagonal: Solving for rhoEv, Initial residual = 0, Final residual = 0, No Iterations 0
diagonal: Solving for rhoE, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver: Solving for hevel, Initial residual = 0.278772, Final residual = 249.287, No Iterations 400
smoothSolver: Solving for e, Initial residual = 0.00510102, Final residual = 1.56626e+32, No Iterations 400
Attempt to use rho2ReactionThermo out of temperature range 3106 times during this iteration.
-2.31822e+10 < Tlow: 200
 Thigh: 40000 < 3.66402e+10
Phase no 1.0 ExecutionTime = 5.02 s ClockTime = 5 s Iteration no 113 (0.05 s)

[10] #0 Foam::error::printStack(Foam::Ostream&)[9] #0 Foam::error::printStack(Foam::Ostream&) at ??:?
at ??:?
[9] #1 Foam::sigFpe::sigHandler(int)[10] #1 Foam::sigFpe::sigHandler(int) at ??:?
[9] #2 ? at ??:?
[10] #2 ? in "/lib/x86_64-linux-gnu/libc.so.6"
[9] #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&) at ??:?
[9] #4 Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::sqrt<Foam::fvPatchField, Foam::volMesh>(Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > const&) in "/home/sy/OpenFOAM/sy-v1706/platforms/linux64GccDPInt32Opt/bin/hy2Foam"
[9] #5 at ??:?
[10] #4 ?Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::sqrt<Foam::fvPatchField, Foam::volMesh>(Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > const&) in "/home/sy/OpenFOAM/sy-v1706/platforms/linux64GccDPInt32Opt/bin/hy2Foam"
[9] #6 in "/home/sy/OpenFOAM/sy-v1706/platforms/linux64GccDPInt32Opt/bin/hy2Foam"
[10] #5 ?? in "/home/sy/OpenFOAM/sy-v1706/platforms/linux64GccDPInt32Opt/bin/hy2Foam"
[9] #7 __libc_start_main in "/home/sy/OpenFOAM/sy-v1706/platforms/linux64GccDPInt32Opt/bin/hy2Foam"
[10] #6 in "/lib/x86_64-linux-gnu/libc.so.6"
[9] #8 ?? in "/home/sy/OpenFOAM/sy-v1706/platforms/linux64GccDPInt32Opt/bin/hy2Foam"
[10] #7 __libc_start_main in "/home/sy/OpenFOAM/sy-v1706/platforms/linux64GccDPInt32Opt/bin/hy2Foam"
[DESKTOP-N36BFE3:23240] *** Process received signal ***
[DESKTOP-N36BFE3:23240] Signal: Floating point exception (8)
[DESKTOP-N36BFE3:23240] Signal code: (-6)
[DESKTOP-N36BFE3:23240] Failing at address: 0x3e800005ac8
[DESKTOP-N36BFE3:23240] [ 0] /lib/x86_64-linux-gnu/libc.so.6(+0x43090)[0x7f49b1370090]
[DESKTOP-N36BFE3:23240] [ 1] /lib/x86_64-linux-gnu/libc.so.6(gsignal+0xcb)[0x7f49b137000b]
[DESKTOP-N36BFE3:23240] [ 2] in "/lib/x86_64-linux-gnu/libc./lib/x86_64-linux-gnu/libc.so.6(+0x43090)[0x7f49b1370090]
[DESKTOP-N36BFE3:23240] [ 3] so.6"
[10] #8 /home/sy/OpenFOAM/OpenFOAM-v1706/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so(_ZN4Foam4sqrtERNS_5FieldIdEERKNS_5UListIdEE+0x3a)[0x7f49b1f24b7a]
[DESKTOP-N36BFE3:23240] [ 4] hy2Foam(ZN4Foam4sqrtINS_12fvPatchFieldENS_7volMeshEEENS_3tmpINS_14GeometricFieldIdT_T0_EEEERKS8+0x174)[0x55dafcc83f74]
[DESKTOP-N36BFE3:23240] [ 5] hy2Foam(+0x3fed5)[0x55dafcc10ed5]
[DESKTOP-N36BFE3:23240] [ 6] hy2Foam(+0x3464c)[0x55dafcc0564c]
[DESKTOP-N36BFE3:23240] [ 7] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf3)[0x7f49b1351083]
[DESKTOP-N36BFE3:23240] [ 8] hy2Foam(+0x35f1e)[0x55dafcc06f1e]
[DESKTOP-N36BFE3:23240] *** End of error message ***
? in "/home/sy/OpenFOAM/sy-v1706/platforms/linux64GccDPInt32Opt/bin/hy2Foam"
[DESKTOP-N36BFE3:23241] *** Process received signal ***
[DESKTOP-N36BFE3:23241] Signal: Floating point exception (8)
[DESKTOP-N36BFE3:23241] Signal code: (-6)
[DESKTOP-N36BFE3:23241] Failing at address: 0x3e800005ac9
[DESKTOP-N36BFE3:23241] [ 0] /lib/x86_64-linux-gnu/libc.so.6(+0x43090)[0x7fb8d8d28090]
[DESKTOP-N36BFE3:23241] [ 1] /lib/x86_64-linux-gnu/libc.so.6(gsignal+0xcb)[0x7fb8d8d2800b]
[DESKTOP-N36BFE3:23241] [ 2] /lib/x86_64-linux-gnu/libc.so.6(+0x43090)[0x7fb8d8d28090]
[DESKTOP-N36BFE3:23241] [ 3] /home/sy/OpenFOAM/OpenFOAM-v1706/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so(_ZN4Foam4sqrtERNS_5FieldIdEERKNS_5UListIdEE+0x3a)[0x7fb8d98dcb7a]
[DESKTOP-N36BFE3:23241] [ 4] hy2Foam(ZN4Foam4sqrtINS_12fvPatchFieldENS_7volMeshEEENS_3tmpINS_14GeometricFieldIdT_T0_EEEERKS8+0x174)[0x55f634616f74]
[DESKTOP-N36BFE3:23241] [ 5] hy2Foam(+0x3fed5)[0x55f6345a3ed5]
[DESKTOP-N36BFE3:23241] [ 6] hy2Foam(+0x3464c)[0x55f63459864c]
[DESKTOP-N36BFE3:23241] [ 7] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf3)[0x7fb8d8d09083]
[DESKTOP-N36BFE3:23241] [ 8] hy2Foam(+0x35f1e)[0x55f634599f1e]
[DESKTOP-N36BFE3:23241] *** End of error message *** Primary job terminated normally, but 1 process returned
a non-zero exit code. Per user-direction, the job has been aborted. mpirun noticed that process rank 9 with PID 0 on node DESKTOP-N36BFE3 exited on signal 8 (Floating point exception).

@suzuhaz 大师求助帮忙看一下简单的一个模型块的划分0_1532943202163_05.zip

@alex 看到你的网格了，感谢分享，感觉划分的非常不错，好厉害！学习了！

@BINFeng 好的，谢谢老师

看了一下你的模型，之所以你在相贯线处网格画不好，这主要问题在于你的几何模型——相贯线与底面相切，出现了三角区域。从而导致网格在该三角区域网格质量奇差无比。如下图所示

该问题导致出现了如下问题：

解决的办法是将底面拉伸一段距离，避免出现相贯线与底面相切即可，如下图所示
0_1536142189833_4ccfa31a-f8b8-4435-87b6-c322423cd7e1-image.png
如此，便可愉快的进行分块和关联
0_1536142304777_9fb3a5ee-3695-47f4-971f-61fe9c119d23-image.png
接着对其进行O型块划分
0_1536142342178_11fb8b28-9d22-441a-978f-e0f2d4ed1c7c-image.png
最终网格效果图如下
0_1536142436479_986e33bd-8587-4ee0-a010-5f914675e718-image.png

@尚善若水 喔喔好的，谢谢了

@CT 很遗憾，没有。我现在转去了别的方向，也不再使用该求解器了。如果只是希望做DSMC模拟而不是必须使用OpenFOAM的话，可以尝试其它开源软件，如Sparta等。

@李东岳 哦哦，没问题了。:142:

放点图有利于讨论..

@zhangxc0223
Hi
因为并没有做deterministic的模拟，所以code也基本没看过。。
stochastic collision 在计算collision probablity的时候是有限制的，具体你可以看一下O‘roucke的论文。具体是怎么定义的，怎么得到一个non-dimensional collision probablity的，还有如何决定这两个parcel发生了碰撞。

虽然碰撞在这个instantaneously 随机的，但是在统计学上，比如你有1M次碰撞的话，总的碰撞的结果就是相似的。
这也就是为什么stochastic碰撞会比deterministic相对来说’便宜'的原因，通过统计学的方法达到相似的碰撞结果，但是不需要追踪所有的parcel。

lagnrangian maxCo 存在的意义，个人认为，在一定程度上可以理解为再一次离散了每个euler time step，所以maxCo一定程度上决定了每个lagrangian time step的大小，和Euler 的Co 定义是相似的。

碰撞是不会被错过的，因为deterministic理论上来说是追踪所有的parcel，所以下一步这个parcel会在哪，走的路径应该也是计算的，所以不会存在错过的，stochastic collision 会计算两个parcel的碰撞概率，当概率很高的时候，也是不会错过的，而且就算是这次错过了，在茫茫parcel海中，总会碰到的。。统计学上是不会错过的

以上仅为个人理解

画周期网格不行吗，取出1/10画好就行了啊

如果我没记错的话，流体中文网上的ICEM版块里有人画过4119桨的结构网格，也传了文件在上面，你可以去上面找一下看还在不在。（耐心往后翻一下）

测试编辑

我不是很理解。不过如果你不想写laplacian，你可以写div(grad())

@Samuel-Tu 会的