multiphaseEulerFoam计算多相反应流发散（类似鼓泡床反应器）

[Number44]

OpenFOAM版本：OpenFOAM v9
求解器 ：multiphaseEulerFoam
模拟对象：圆柱状鼓泡床反应器，多相流，液相反应，无液相进出，气相不反应，底部进气，顶部出气。
算例来源：在tutorials的bubbleColumnEvaporatingReacting算例基础上修改而来，各相初始分布由setFields控制。

问题：即使关掉反应，从数值迭代上看，多相流计算第一个时间步的PIMPLE循环的相分数计算发散，见下日志。存下第一个PIMPLE迭代结果看，气相和液相的基础相莫名其妙地在原本该是0的地方，变成了1，见下图。
确认过setFields正确地初始化了相分布，上半部气相，下半部液相。由于第一次做多相流的算例，无法定位发散的原因是边界设置？constant的多相参数？相分数求解？还是别的问题？求各位大神指点一二，不胜感激。

尝试过的操作：

• 加松弛
• 改矩阵迭代求解器，GAMG换PCG，smoothSolver换PBiCGStab
• 调整气相液相和压力的出口边界类型为zeroGradient
• 关掉反应
• 加压力限制limitPressure
• 将气相从multiComponentMixture改成pureMixture

/*------------------------------------------------------------------------------
算例：
运行meshGen脚本生成网格，allrun脚本运行。
f21a20e8-830b-41ca-8175-7667fab9ab9b-p2.tar.gz

/*------------------------------------------------------------------------------
计算日志，第一个时间步

PIMPLE: Iteration 1
MULES: Solving for alpha.gas
MULES: Solving for alpha.liquid
gas fraction, min, max = 0.4999984327 0.009998944 0.990001056
liquid fraction, min, max = 0.5000016007 0.01 0.990001056
Phase-sum volume fraction, min, max = 1.000000033 1 1.000001067
MULES: Solving for alpha.gas
MULES: Solving for alpha.liquid
gas fraction, min, max = 0.4999968323 0.009997888113 0.9900010559
liquid fraction, min, max = 0.500003201 0.01 0.9900021119
Phase-sum volume fraction, min, max = 1.000000033 1 1.000001067
MULES: Solving for alpha.gas
MULES: Solving for alpha.liquid
gas fraction, min, max = 0.499995232 0.009996832338 0.9900010559
liquid fraction, min, max = 0.5000048013 0.01 0.9900031677
Phase-sum volume fraction, min, max = 1.000000033 1 1.000001067
smoothSolver:  Solving for NH4+.liquid, Initial residual = 1.484075337e-05, Final residual = 1.159761323e-16, No Iterations 2
smoothSolver:  Solving for NO3-.liquid, Initial residual = 0, Final residual = 0, No Iterations 1
smoothSolver:  Solving for O2.liquid, Initial residual = 0.2795617027, Final residual = 6.228131728e-16, No Iterations 2
smoothSolver:  Solving for H+.liquid, Initial residual = 0, Final residual = 0, No Iterations 1
Constructing momentum equations
Tf.gasAndLiquid: min = 299.9947355, mean = 300.0339633, max = 300.0732112
DILUPBiCGStab:  Solving for e.gas, Initial residual = 0.9999999986, Final residual = 7.01286441e-16, No Iterations 1
DILUPBiCGStab:  Solving for e.liquid, Initial residual = 0.1121489206, Final residual = 1.679510257e-16, No Iterations 1
gas min/max T 299.9857036 - 300.0249711
liquid min/max T 299.9714439 - 300.032703
DICPCG:  Solving for p_rgh, Initial residual = 0.9950749712, Final residual = 0.0007476549794, No Iterations 58
DICPCG:  Solving for p_rgh, Initial residual = 0.01716581647, Final residual = 1.54813425e-05, No Iterations 40
DICPCG:  Solving for p_rgh, Initial residual = 0.977211124, Final residual = 0.0007350869486, No Iterations 58
DICPCG:  Solving for p_rgh, Initial residual = 0.01014511789, Final residual = 6.818727967e-12, No Iterations 107
PIMPLE: Iteration 2
MULES: Solving for alpha.gas
MULES: Solving for alpha.liquid
DICPBiCGStab:  Solving for alpha.gas, Initial residual = 5.821421844e-17, Final residual = 8.934357652e-34, No Iterations 1
DICPBiCGStab:  Solving for alpha.liquid, Initial residual = 4.308481516e-17, Final residual = 7.155231175e-34, No Iterations 1
gas fraction, min, max = 0.4310004415 -8.01486001 2.514951181
liquid fraction, min, max = 0.571470277 -0.01414169716 9.01486001
Phase-sum volume fraction, min, max = 1.002470718 0.9165471615 2.502164998
MULES: Solving for alpha.gas
MULES: Solving for alpha.liquid
DICPBiCGStab:  Solving for alpha.gas, Initial residual = 4.38709213e-17, Final residual = 6.868609435e-34, No Iterations 1
DICPBiCGStab:  Solving for alpha.liquid, Initial residual = 4.105585202e-17, Final residual = 6.57320396e-34, No Iterations 1
gas fraction, min, max = 0.3970086899 -84.20635147 74.29030785
liquid fraction, min, max = 0.632777971 -73.29030785 85.20635147
Phase-sum volume fraction, min, max = 1.029786661 0.9005093894 99.99686523
MULES: Solving for alpha.gas
MULES: Solving for alpha.liquid
DICPBiCGStab:  Solving for alpha.gas, Initial residual = 2.799140256e-17, Final residual = 4.373723282e-34, No Iterations 1
DICPBiCGStab:  Solving for alpha.liquid, Initial residual = 3.729944455e-17, Final residual = 5.877805245e-34, No Iterations 1
gas fraction, min, max = -7.192486694 -84273.15366 35913.14461
liquid fraction, min, max = 0.7041286022 -35912.14461 84274.15366
Phase-sum volume fraction, min, max = -6.488358091 -37604.99677 580.9315927
smoothSolver:  Solving for NH4+.liquid, Initial residual = 0.0112574308, Final residual = 4.168831596e-13, No Iterations 13
smoothSolver:  Solving for NO3-.liquid, Initial residual = 0, Final residual = 0, No Iterations 1
smoothSolver:  Solving for O2.liquid, Initial residual = 0.2270999707, Final residual = 5.714438306e-13, No Iterations 12
smoothSolver:  Solving for H+.liquid, Initial residual = 0, Final residual = 0, No Iterations 1
Constructing momentum equations
Tf.gasAndLiquid: min = 299.9711527, mean = 299.9985045, max = 300.0301728

强行存下的第一次PIMPLE循环的结果，下半部应该全都0。