# 怎样限制流场中最大速度

• 各位前辈好！

我在compressibleInterFoam中引入了空化源项，现在调用自己写的非线性SGS模型计算的时候，流场初始速度10m/s，计算一段时间后，maxU会突然增大，导致流场发散掉，下面是速度暴增的过程

MULES: Solving for alpha.water
Liquid phase volume fraction = 0.997517  Min(alpha.water) = 0.000412402  Max(alpha.water) = 1
Min(alpha.vapor) = -8.20677e-13  Max(alpha.vapor) = 0.999588
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver:  Solving for T, Initial residual = 4.32259e-05, Final residual = 2.38488e-09, No Iterations 2
min(T) 290.144
GAMG:  Solving for p_rgh, Initial residual = 4.54434e-06, Final residual = 7.05483e-10, No Iterations 3
max(U) 13.9186
min(p_rgh) 1843.8
GAMGPCG:  Solving for p_rgh, Initial residual = 3.62757e-07, Final residual = 4.88638e-10, No Iterations 1
max(U) 13.9184
min(p_rgh) 1843.67
ExecutionTime = 275.32 s

Integral of alpha.water = 0.00190802  [0 3 0 0 0 0 0]
fieldAverage fieldAverage1 output:
Calculating averages

Courant Number mean: 0.00487524 max: 0.135574
Time = 0.011952

MULES: Solving for alpha.water
Liquid phase volume fraction = 0.997517  Min(alpha.water) = 0.000413145  Max(alpha.water) = 1
Min(alpha.vapor) = -4.79172e-13  Max(alpha.vapor) = 0.999587
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver:  Solving for T, Initial residual = 4.324e-05, Final residual = 2.42709e-09, No Iterations 2
min(T) 290.146
GAMG:  Solving for p_rgh, Initial residual = 5.42286e-06, Final residual = 7.32723e-10, No Iterations 3
max(U) 26.57
min(p_rgh) 1813.11
GAMGPCG:  Solving for p_rgh, Initial residual = 3.66982e-07, Final residual = 5.21535e-10, No Iterations 1
max(U) 25.4251
min(p_rgh) 1817.97
ExecutionTime = 275.6 s

fieldAverage fieldAverage1 output:
Calculating averages

Courant Number mean: 0.00487537 max: 0.135663
Time = 0.011953

MULES: Solving for alpha.water
Liquid phase volume fraction = 0.997517  Min(alpha.water) = 0.000412369  Max(alpha.water) = 1
Min(alpha.vapor) = -8.14016e-13  Max(alpha.vapor) = 0.999588
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver:  Solving for T, Initial residual = 4.32537e-05, Final residual = 2.41625e-09, No Iterations 2
min(T) 290.148
GAMG:  Solving for p_rgh, Initial residual = 5.31025e-06, Final residual = 6.64697e-10, No Iterations 3
max(U) 20.2828
min(p_rgh) 1797.39
GAMGPCG:  Solving for p_rgh, Initial residual = 3.95326e-07, Final residual = 5.53382e-10, No Iterations 1
max(U) 20.6401
min(p_rgh) 1803.66
ExecutionTime = 275.88 s

fieldAverage fieldAverage1 output:
Calculating averages

Courant Number mean: 0.00487547 max: 0.135752
Time = 0.011954

MULES: Solving for alpha.water
Liquid phase volume fraction = 0.997516  Min(alpha.water) = 0.000412357  Max(alpha.water) = 1
Min(alpha.vapor) = -2.22555e-12  Max(alpha.vapor) = 0.999588
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver:  Solving for T, Initial residual = 4.32478e-05, Final residual = 2.41079e-09, No Iterations 2
min(T) 290.15
GAMG:  Solving for p_rgh, Initial residual = 4.91279e-06, Final residual = 6.3296e-10, No Iterations 3
max(U) 30.2344
min(p_rgh) 1778.9
GAMGPCG:  Solving for p_rgh, Initial residual = 4.09173e-07, Final residual = 3.01626e-10, No Iterations 1
max(U) 29.9168
min(p_rgh) 1779.32
ExecutionTime = 276.17 s

fieldAverage fieldAverage1 output:
Calculating averages

Courant Number mean: 0.00487556 max: 0.135842
Time = 0.011955

MULES: Solving for alpha.water
Liquid phase volume fraction = 0.997516  Min(alpha.water) = 0.000412479  Max(alpha.water) = 1
Min(alpha.vapor) = -4.44089e-16  Max(alpha.vapor) = 0.999588
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver:  Solving for T, Initial residual = 4.32198e-05, Final residual = 2.70013e-09, No Iterations 2
min(T) 290.153
GAMG:  Solving for p_rgh, Initial residual = 1.71158e-05, Final residual = 7.83321e-10, No Iterations 4
max(U) 140.097
min(p_rgh) 1138.55
GAMGPCG:  Solving for p_rgh, Initial residual = 1.088e-06, Final residual = 4.13587e-10, No Iterations 2
max(U) 147.712
min(p_rgh) 1226.71
ExecutionTime = 276.46 s


我仔细检查发现很可能是由于求解U方程时，某个网格上面速度突然变得很大，最终导致流场发散，目前想在U方程中 或者 P方程中限制最大速度不超过某一个值，由于U是矢量，我现在不太清楚怎么限制流场中的U不超过某一个值呢？是分别限制U某一方向的速度 还是 直接限制max(mag(U).value)呢？

麻烦哪位前辈能够指点一下呢？谢谢

• @小考拉 maxU会突然增大只是发散的迹象，不是发散的原因，所以这种问题很难debug CFD中文网 2016 - 2020 | 京ICP备15017992号-2