- **OpenFOAM**
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- - **problem with Min/max rho**
(*https://www.cfd-online.com/Forums/openfoam/87748-problem-min-max-rho.html*)

problem with Min/max rhoHi,
I have problems of an increasing density. Even after the third time step (deltat=1) Min/max rho = 0,38 / 2,82. The fluid is air. So I would expect something around 0,6 I think the boundary conditions are set wrong. But I have made a setup identic to an other case where the density doesn't increase. Does someone have a clue which boundary conditions are prone to increase density? Best Regards, tH3f0rC3 |

Time = 0
Solving for fluid region air DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 0.075451081, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 1, Final residual = 0.016409508, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 1, Final residual = 0.085782023, No Iterations 1 DILUPBiCG: Solving for h, Initial residual = 0.99999999, Final residual = 0.01679794, No Iterations 2 Min/max T:573 973.15 GAMG: Solving for p_rgh, Initial residual = 1, Final residual = 0.0092815957, No Iterations 15 time step continuity errors : sum local = 0.008788245, global = -0.00098784668, cumulative = -0.00098784668 Min/max rho:0.35717528 0.68357341 DILUPBiCG: Solving for epsilon, Initial residual = 0.16612435, Final residual = 0.01454185, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 0.017992387, No Iterations 2 maxResidual: 1 convergence criterion: 1e-05 Solving for solid region stahl DICPCG: Solving for T, Initial residual = 0.99999768, Final residual = 0.068942702, No Iterations 3 Min/max T:573.14686 573.15 maxResidual: 0.99999768 convergence criterion: 0 Solving for solid region nickel DICPCG: Solving for T, Initial residual = 0.99994028, Final residual = 0.090359384, No Iterations 3 Min/max T:573.14825 573.15 maxResidual: 0.99994028 convergence criterion: 0 ExecutionTime = 38.64 s ClockTime = 39 s Time = 1 Solving for fluid region air DILUPBiCG: Solving for Ux, Initial residual = 0.53667496, Final residual = 0.0085865982, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.35251486, Final residual = 0.0051391246, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.52233136, Final residual = 0.0087582447, No Iterations 2 DILUPBiCG: Solving for h, Initial residual = 0.21057797, Final residual = 0.012716529, No Iterations 1 Min/max T:462.59027 973.15 GAMG: Solving for p_rgh, Initial residual = 0.70446497, Final residual = 0.0050321126, No Iterations 11 time step continuity errors : sum local = 0.55674613, global = 0.024030378, cumulative = 0.023042532 Min/max rho:0.35717528 1.0058956 DILUPBiCG: Solving for epsilon, Initial residual = 0.46625579, Final residual = 0.0099261637, No Iterations 2 DILUPBiCG: Solving for k, Initial residual = 0.43643392, Final residual = 0.0066078085, No Iterations 2 maxResidual: 0.70446497 convergence criterion: 1e-05 Solving for solid region stahl DICPCG: Solving for T, Initial residual = 0.25011936, Final residual = 0.012310353, No Iterations 3 Min/max T:573.14525 573.15 maxResidual: 0.25011936 convergence criterion: 0 Solving for solid region nickel DICPCG: Solving for T, Initial residual = 0.25023018, Final residual = 0.016446415, No Iterations 3 Min/max T:573.14708 573.15 maxResidual: 0.25023018 convergence criterion: 0 ExecutionTime = 64.08 s ClockTime = 65 s Time = 2 Solving for fluid region air DILUPBiCG: Solving for Ux, Initial residual = 0.13403801, Final residual = 0.013230832, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.16595325, Final residual = 0.0020208299, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.25960355, Final residual = 0.025016317, No Iterations 1 DILUPBiCG: Solving for h, Initial residual = 0.16627559, Final residual = 0.010752132, No Iterations 1 Min/max T:534.64735 973.15 GAMG: Solving for p_rgh, Initial residual = 0.89506057, Final residual = 0.0080816829, No Iterations 13 time step continuity errors : sum local = 0.45956801, global = 0.0087655559, cumulative = 0.031808087 Min/max rho:0.35717528 1.7719564 DILUPBiCG: Solving for epsilon, Initial residual = 0.21378091, Final residual = 0.0026405132, No Iterations 2 DILUPBiCG: Solving for k, Initial residual = 0.22492817, Final residual = 0.0028870615, No Iterations 2 maxResidual: 0.89506057 convergence criterion: 1e-05 Solving for solid region stahl DICPCG: Solving for T, Initial residual = 0.27108477, Final residual = 0.014070673, No Iterations 3 Min/max T:573.13955 573.15 maxResidual: 0.27108477 convergence criterion: 0 Solving for solid region nickel DICPCG: Solving for T, Initial residual = 0.2830701, Final residual = 0.020013987, No Iterations 3 Min/max T:573.14254 573.15 maxResidual: 0.2830701 convergence criterion: 0 ExecutionTime = 89.86 s ClockTime = 92 s Time = 3 Solving for fluid region air DILUPBiCG: Solving for Ux, Initial residual = 0.23944968, Final residual = 0.0038426078, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.21150255, Final residual = 0.0020588047, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.32799999, Final residual = 0.0046439848, No Iterations 2 DILUPBiCG: Solving for h, Initial residual = 0.10107597, Final residual = 0.0078826869, No Iterations 1 Min/max T:386.21599 973.15 GAMG: Solving for p_rgh, Initial residual = 0.49927178, Final residual = 0.0044080049, No Iterations 7 time step continuity errors : sum local = 0.34430616, global = -0.030489443, cumulative = 0.0013186441 Min/max rho:0.35717528 2.6131937 DILUPBiCG: Solving for epsilon, Initial residual = 0.1490834, Final residual = 0.0017493873, No Iterations 2 DILUPBiCG: Solving for k, Initial residual = 0.16570862, Final residual = 0.0019370394, No Iterations 2 maxResidual: 0.49927178 convergence criterion: 1e-05 Solving for solid region stahl DICPCG: Solving for T, Initial residual = 0.16418744, Final residual = 0.0058820311, No Iterations 3 Min/max T:573.13867 573.15 maxResidual: 0.16418744 convergence criterion: 0 Solving for solid region nickel DICPCG: Solving for T, Initial residual = 0.19501926, Final residual = 0.007847645, No Iterations 3 Min/max T:573.14225 573.15483 maxResidual: 0.19501926 convergence criterion: 0 ExecutionTime = 113.36 s ClockTime = 116 s Time = 4 Solving for fluid region air DILUPBiCG: Solving for Ux, Initial residual = 0.22595321, Final residual = 0.0030393622, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.15238153, Final residual = 0.0013200909, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.22923122, Final residual = 0.002846462, No Iterations 2 DILUPBiCG: Solving for h, Initial residual = 0.062614351, Final residual = 0.0006806479, No Iterations 2 Min/max T:279.0118 973.15 GAMG: Solving for p_rgh, Initial residual = 0.53300073, Final residual = 0.003828913, No Iterations 13 time step continuity errors : sum local = 0.26512713, global = -0.013485795, cumulative = -0.012167151 Min/max rho:0.35717528 2.7375473 DILUPBiCG: Solving for epsilon, Initial residual = 0.1074059, Final residual = 0.0012632828, No Iterations 2 DILUPBiCG: Solving for k, Initial residual = 0.10654469, Final residual = 0.0013340781, No Iterations 2 maxResidual: 0.53300073 convergence criterion: 1e-05 Solving for solid region stahl DICPCG: Solving for T, Initial residual = 0.13716868, Final residual = 0.0042027179, No Iterations 3 Min/max T:573.1365 573.15153 maxResidual: 0.13716868 convergence criterion: 0 Solving for solid region nickel DICPCG: Solving for T, Initial residual = 0.22413245, Final residual = 0.012011063, No Iterations 3 Min/max T:573.13721 573.16733 maxResidual: 0.22413245 convergence criterion: 0 ExecutionTime = 140.03 s ClockTime = 143 s Time = 5 Solving for fluid region air DILUPBiCG: Solving for Ux, Initial residual = 0.13262467, Final residual = 0.0018728448, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.082841106, Final residual = 0.00090359221, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.13754567, Final residual = 0.0017803001, No Iterations 2 DILUPBiCG: Solving for h, Initial residual = 0.041531078, Final residual = 0.00048567902, No Iterations 2 Min/max T:103.60674 973.15 GAMG: Solving for p_rgh, Initial residual = 0.53253605, Final residual = 0.0047493003, No Iterations 11 time step continuity errors : sum local = 0.2933433, global = -0.018351634, cumulative = -0.030518785 Min/max rho:0.1 3.3626218 DILUPBiCG: Solving for epsilon, Initial residual = 0.088507022, Final residual = 0.0010018227, No Iterations 2 DILUPBiCG: Solving for k, Initial residual = 0.075575277, Final residual = 0.00099140799, No Iterations 2 maxResidual: 0.53253605 convergence criterion: 1e-05 Solving for solid region stahl DICPCG: Solving for T, Initial residual = 0.14197114, Final residual = 0.0055143839, No Iterations 3 Min/max T:573.13286 573.15009 maxResidual: 0.14197114 convergence criterion: 0 Solving for solid region nickel DICPCG: Solving for T, Initial residual = 0.18726851, Final residual = 0.0087153376, No Iterations 3 Min/max T:573.12588 573.16692 maxResidual: 0.18726851 convergence criterion: 0 ExecutionTime = 165.79 s ClockTime = 169 s _______________________________________ This is the error message. Maybe someone of you knows why the temperature goes down wo fast and why the density goes to 0.1 and to 3.36. Maybe there is a typical error which has this for result. Best Regards, tH3f0rC3 |

Develop your caseHi tH3f0rC3,
Would you mind expliciting your case more precisely please? What are you studying, what is the solver you're using, maybe even share the OF case. Minh |

I'm using the chtMultiRegionSimpleFoam-Solver.
heat transfer from hot air to two solids is solved in this case. The flow is turbulent. I will post the case files on Monday. Best Regards, tH3f0rC3 |

1 Attachment(s)
The whole case is too large.
I uploaded the 0-files. There must be the mistake. Maybe it has to do something with the velocity at the Outlet! I don't really know the velocity at the outlet. So how do I have to set up the boundary condition for unknown velocity at the outlet? Remember, the temperature and the density are solved strange. I have a new log-file of a test run of the case: Code:
`/*---------------------------------------------------------------------------*\` tH3f0rC3 |

Hi,
is there someone who can help me with that? Best Regards, tH3f0rC3 |

hi.although it has past 2 years.do you remember how you solved the problem?
I have similar trouble with velocity. |

Hi,
I'm sorry, I don't have the files anymore. And I don't know how I solved the problem anymore. However, I hope you will solve the problem. |

Quote:
Hi, i have run into the same problem but through OFv6. Did you find a solution to your problem? If you still remember, it would be nice if you could share it. Thanks owais |

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