Simulation of cavitation flow:problem of heat transfer
While I solve the cavitation flow of LNG with k-omiga turbulence model, the RMS of H-Energy in the result kept being 1.0e+01 after only five steps(the curve of heat transfer is obviously wrong),and the rate of convergence were both zero.The details were as follows:
OUTER LOOP ITERATION = 5 CPU SECONDS = 2.227E+03 ---------------------------------------------------------------------- | Equation | Rate | RMS Res | Max Res | Linear Solution | +----------------------+------+---------+---------+------------------+ | U-Mom-Bulk | 0.97 | 1.4E-04 | 1.3E-02 | 1.2E-01 ok| | V-Mom-Bulk | 0.96 | 1.3E-04 | 1.9E-02 | 1.1E-01 ok| | W-Mom-Bulk | 0.97 | 1.9E-04 | 2.7E-02 | 1.5E-01 ok| | P-Vol | 0.87 | 1.2E-05 | 7.4E-04 | 5.2 9.1E-02 OK| +----------------------+------+---------+---------+------------------+ | Mass-LNG | 0.93 | 2.5E-04 | 6.8E-02 | 6.1 2.2E-02 OK| +----------------------+------+---------+---------+------------------+ | H-Energy-LNG |99.99 | NaN | 0.0E+00 | 0.0E+00 OK | | H-Energy-lngs |99.99 | NaN | 0.0E+00 | 5.9 0.0E+00 OK | +----------------------+------+---------+---------+------------------+ | K-TurbKE-Bulk | 0.96 | 2.8E-04 | 4.4E-02 | 6.0 3.1E-02 OK| | O-TurbFreq-Bulk | 0.95 | 1.2E-04 | 4.1E-02 | 7.7 1.9E-02 OK| +----------------------+------+---------+---------+------------------ OUTER LOOP ITERATION = 6 CPU SECONDS = 2.735E+03 ---------------------------------------------------------------------- | Equation | Rate | RMS Res | Max Res | Linear Solution | +----------------------+------+---------+---------+------------------+ | U-Mom-Bulk | 1.22 | 1.7E-04 | 1.4E-02 | 2.8E-01 ok| | V-Mom-Bulk | 1.24 | 1.7E-04 | 2.1E-02 | 2.8E-01 ok| | W-Mom-Bulk | 0.97 | 1.9E-04 | 2.4E-02 | 1.1E+00 ok| | P-Vol | 8.43 | 1.0E-04 | 3.8E-03 | 5.2 9.6E-02 OK| +----------------------+------+---------+---------+------------------+ +--------------------------------------------------------------------+ | ****** Notice ****** | | A wall has been placed at portion(s) of an OUTLET | | boundary condition (at 0.3% of the faces, 0.6% of the area) | | to prevent fluid from flowing into the domain. | | The boundary condition name is: Blade Outlet. | | The fluid name is: LNG. | | If this situation persists, consider switching | | to an Opening type boundary condition instead. | +--------------------------------------------------------------------+ | Mass-LNG | 8.05 | 2.0E-03 | 2.6E-01 | 6.1 5.1E-03 OK| +----------------------+------+---------+---------+------------------+ | H-Energy-LNG | 0.00 | NaN | 0.0E+00 | 0.0E+00 OK | | H-Energy-lngs | 0.00 | NaN | 0.0E+00 | 5.9 0.0E+00 OK | +----------------------+------+---------+---------+------------------+ | K-TurbKE-Bulk | 1.15 | 3.3E-04 | 4.5E-02 | 6.0 4.6E-02 OK| | O-TurbFreq-Bulk | 2.35 | 2.8E-04 | 7.3E-02 | 7.7 2.9E-02 OK| |
This looks like a complex model with cavitation, heat transfer and multiple phases. Have you started with a simple model and introduced the physics one bit at a time?
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In fact,I have solved many cases about cavitation at different conditions. Sometimes the result I got looks very well.But for the case with different geometrics (nozzle angle),it won't work.Maybe if I change the reference state of the materials I used,it will work and I can get a result that looks reasonable .But this strategy doesn't fit any case .Do youknow the reason ? Will the reference point affect so much ? How could I avoid this wrong results with what proper settings?
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Do you think explaining what you are modelling might help? And while you are at it maybe what is different about this one compared to the ones which worked well? I think that might help :)
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I have compared the result with those worked well .The unique difference is that I set the simulation with different reference point .If with a actual reference point , ref-enthalpy and ref-entropy ,only some cases could work well .If with automatic ref-point ,there will be more cases that will work will .If with none, the effect will get better . However there are still some cases that can't work will. That is the problem I want to know.In different cases ,everything is same except that the geometric has different nozzle angle. Thank you for your help!
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