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August 23, 2016, 05:33 |
CFX High speed wall function-ERROR
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#1 |
New Member
Fabio
Join Date: Jun 2016
Posts: 11
Rep Power: 10 |
I'm performing a parallel run with CFX of a supersonic flow inside a tank, using the RNG-K-epsilon turbolent model with the activation of the high- speed Wall Heat Transfer Model..
It's my first time facing with this fluid dynamic problems so I would like to have a discussion about this. This is the output of ANSYS: Parallel run: Received message from slave ----------------------------------------- Slave partition : 3 Slave routine : get_TWFTFC Master location : End of Continuity Loop Message label : 009100015 Message follows below - : +--------------------------------------------------------------------+ | ****** Notice ****** | | The non-dimensional near wall temperature (T+) has been clipped | | for calculation of Wall Heat Transfer Coefficient. | | | | Boundary Condition : Walls | | T+ clip value = 1.0000E-10 | | | | If this situation persists and you are using the High Speed Model, | | consider enabling Mach number based blending between low speed and | | high speed wall functions. You can do so by specifying a Mach | | number threshold as follows: | | | | EXPERT PARAMETERS: | | highspeed wf mach threshold = 0.1 # default=0.0 (off) | | END What should I do in this case? Modify the wall function mach threshould as suggested by the programme, using the text command line? Thanks for your comprehension! |
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August 23, 2016, 06:05 |
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#2 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,830
Rep Power: 144 |
It is more likely that your simulation has resulting in a non-physical solution and is possibly diverging. I would check the result you have to see if something weird is happening. Do not change the mach threshold until you are absolutely sure that your model is correct and that you need to do it.
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August 23, 2016, 06:26 |
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#3 | |
New Member
Fabio
Join Date: Jun 2016
Posts: 11
Rep Power: 10 |
Quote:
The same model starting from 100 Pa as initial pressure works well. Instead, tuning the initial pressure to 5 Pa, the software gives me that error. I should check if the continuity regime is still valid, shoudn't it? Regards |
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August 23, 2016, 06:50 |
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#4 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,830
Rep Power: 144 |
Yes, you should check that.
If you save a backup file in the iteration before it crashes you should be able to see where the simulation is going weird. It would be even better if you add the residuals to the results file because then you can see where the residuals are worst, which is likely to be the location of the problem. |
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April 29, 2021, 09:24 |
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#5 |
New Member
Tamil Nadu
Join Date: Apr 2021
Posts: 6
Rep Power: 5 |
Hi,
I am working on heat addition to compressible flow. Basically, I have a straight rectangular channel with a pressure inlet and pressure outlet. My lower wall is set with a heat flux(thermal boundary condition) of 5000W/m2. I chose the k-epsilon model. But I cannot see this heat addition effect on the flow. Can someone suggest to me any other way to do this? |
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April 29, 2021, 12:53 |
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#6 |
Senior Member
Join Date: Jun 2009
Posts: 1,860
Rep Power: 33 |
Assuming you are running steady-state, what value will you get for the following expression?
massFlowInt(Total Enthalpy)@Outlet - massFlowInt(Total Enthalpy)@Inlet It better be areaInt(Heat Flux)@Lower Wall Otherwise, you have not converged the solution well enough.
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