# Simulation of cavitation flow:problem of heat transfer

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 October 4, 2012, 01:46 Simulation of cavitation flow:problem of heat transfer #1 New Member   Lee Join Date: Oct 2012 Posts: 26 Rep Power: 6 Sponsored Links 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|

 October 4, 2012, 07:42 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,736 Rep Power: 106 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?

 October 5, 2012, 00:45 #3 New Member   Lee Join Date: Oct 2012 Posts: 26 Rep Power: 6 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?

 October 5, 2012, 06:17 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,736 Rep Power: 106 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

 October 5, 2012, 08:44 #5 New Member   Lee Join Date: Oct 2012 Posts: 26 Rep Power: 6 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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