CFD中文网

lcx

颗粒数1e10，那应该是属于密相了。催化反应+颗粒密相OpenFOAM里应该没有现成的求解器。

lcx

前一段时间搭建了流化床求解器（燃烧、密相颗粒流动求解器，下称newSolver），目前需要对这个求解器进行冷态颗粒流动的验证（常温，关闭化学反应、燃烧和传热）。通过验证发现颗粒轴向速度和实验吻合较好，但是气相压降差距很大，而使用MPPICFoam计算相同的case可以得到准确的压降（稳定时newSolver比MPPICFoam压降高两倍多）。

为了找到问题所在，于是关闭颗粒计算纯气体流动的速度和压降，发现newSolver和MPPICFoam计算得到的气相速度相同但是压降有一定差距。因此猜测是气相压力方程计算的问题。

由于newSolver是基于coalChemistryFoam流体方程加入alpha的修改的，纯气体流动情况下alpha=1。为了排除我修改方程所导致的错误，因此用coalChemistryFoam（关闭化学反应、燃烧和传热）计算纯气体流动看能否得到准确的结果。结果发现压降仍然有差距。

难道coalChemisryFoam变密度的求解器无法计算常密度的情况吗？coalChemistryFoam是反应所导致的密度变化，关闭化学反应按理说密度应该是不变的，为何计算结果与实际差距大？常温纯气体流动压降都不准，加上化学反应燃烧后压降会准吗？

MPPICFoam压力方程

fvScalarMatrix pEqn
        (
            fvm::laplacian(alphacf*rAUcf, p)
         ==
            fvc::ddt(alphac) + fvc::div(alphacf*phiHbyA)
        );

coalChemistryFoam压力方程

fvScalarMatrix pEqn
        (
            fvm::ddt(psi, p)
          + fvc::div(phiHbyA)
          - fvm::laplacian(rhorAUf, p)
         ==
            coalParcels.Srho()
          + fvOptions(psi, p, rho.name())
        );

纯气体流动验证的几何模型和网格如下图所示
图片1.png

请各位大佬指教！

lcx

@lcx 在在coalChemistryFoam中加入MPPIC应力模型中说：

在1基础上关闭MPPIC颗粒应力仅考虑颗粒所受曳力和重力得到较为合理的结果。颗粒没有出现过度堆积的情况。(gif见下楼)

结果如下

lcx

各位前辈好，
目前在openfoam v2212版本上搭建流化床热态模拟的求解器。主要是通过在coalChemistryFoam中加入体积分数α和MPPIC颗粒应力来考虑密相颗粒。

参考了CFD Online上的一个讨论：https://www.cfd-online.com/Forums/openfoam-programming-development/158458-colliding-coal-cloud-coalcollidingchemistryfoam.html 和Chalmers OpenFOAM的课程资料:https://zhuanlan.zhihu.com/p/342917899

体积分数的添加可以参考Chalmers课程资料，没什么变化。MPPIC颗粒应力的添加在新版本v2212出现一些变化。查看MPPICFoam求解器发现MPPICFoam求解过程中直接定义了

#ifdef MPPIC
    #include "basicKinematicCloud.H"
#define basicKinematicTypeCloud basicKinematicCloud

而不是旧版本v2006及以前的

#ifdef MPPIC
    #include "basicKinematicMPPICCloud.H"
    #define basicKinematicTypeCloud basicKinematicMPPICCloud

通过gdb调试新版本MPPICFoam求解器确实发现新版本的MPPIC颗粒应力计算整合到了KinematicCloud和KinematicParcel中，因此新版本中调用MPPIC颗粒应力不需要在云、颗粒模板上添加MPPICCloud和MPPICParcel，直接在constant/Cloud1Properties中直接添加packing、damping、isotropyModel关键字就可以实现MPPIC颗粒应力。

目前求解器的搭建已经基本完成。但是通过MPPICFoam下Goldschmidt案例进行热态求解器颗粒运动求解的验证，发现了一些奇异的现象。

1. 采用MPPICFoam标准算例Goldschmidt验证热态求解器（关闭燃烧、化学反应）的颗粒碰撞，考虑颗粒所受曳力、重力和颗粒应力影响。颗粒在底部出现过度堆积现象(求解过程中固相体积分数甚至已达到6以上)，之后体积分数大导致所受曳力增大，颗粒被推起、抛飞。

Log文件部分内容如下

Courant Number mean: 0.0555298 max: 0.12225
Time = 0.4736


Solving3-D cloud coalCloud1
Cloud: coalCloud1
    Current number of parcels       = 24750
    Current mass in system          = 0.511442
    Linear momentum                 = (-0.00018024 0.000454129 -0.644986)
   |Linear momentum|                = 0.644987
    Linear kinetic energy           = 0.450077
    Average particle per parcel     = 1
    Injector model1:
      - parcels added               = 24750
      - mass introduced             = 0.511478
    Surface film:
      - parcels absorbed            = 0
      - mass absorbed               = 0
      - parcels ejected             = 0
    Parcel fate: system (number, mass)
      - escape                      = 9046, 0.186929
    Parcel fate: patch (top|bottom|walls|frontAndBack) (number, mass)
      - escape                      = 0, 0
      - stick                       = 0, 0
    Min cell volume fraction        = 0
    Max cell volume fraction        = 6.86133
    Min dense number of parcels     = 1258
    Temperature min/max             = 291.614, 292.984
    Mass transfer phase change      = 3.60952e-05
    Mass transfer devolatilisation  = 0
    Mass transfer surface reaction  = 0

diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
PIMPLE: iteration 1
smoothSolver:  Solving for Ux, Initial residual = 0.0338563, Final residual = 7.04861e-06, No Iterations 1
smoothSolver:  Solving for Uy, Initial residual = 0.132381, Final residual = 9.38479e-08, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.00769001, Final residual = 2.67996e-06, No Iterations 1
smoothSolver:  Solving for O2, Initial residual = 0.00121389, Final residual = 1.11529e-06, No Iterations 1
smoothSolver:  Solving for CH4, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver:  Solving for H2, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver:  Solving for CO2, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver:  Solving for H2O, Initial residual = 0.00121249, Final residual = 1.11141e-06, No Iterations 1
smoothSolver:  Solving for h, Initial residual = 0.0505897, Final residual = 9.40878e-08, No Iterations 2
DICPCG:  Solving for G, Initial residual = 0.0108795, Final residual = 9.04101e-06, No Iterations 32
T gas min/max   = 291.971, 293.866
GAMG:  Solving for p, Initial residual = 0.639901, Final residual = 0.00540426, No Iterations 3
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 5.44867e-05, global = -1.29277e-06, cumulative = -7.83327e-05
GAMG:  Solving for p, Initial residual = 0.0144207, Final residual = 7.37421e-07, No Iterations 14
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 7.70534e-09, global = 2.93038e-10, cumulative = -7.83324e-05
ExecutionTime = 1760.01 s  ClockTime = 1774 s

1. 在1基础上关闭MPPIC颗粒应力仅考虑颗粒所受曳力和重力得到较为合理的结果。颗粒没有出现过度堆积的情况。(gif见下楼)

按理说颗粒应力的作用是阻止颗粒体积分数过大，但是就目前的结果看添加了颗粒应力，颗粒反而更加聚集，体积分数更大。是我MPPIC代码理解错误颗粒应力耦合有问题吗？希望得到各位前辈的指点！

CFD中文网

lcx

帖子