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-   -   Solver is finishing with huge Mach number (http://www.cfd-online.com/Forums/cfx/23733-solver-finishing-huge-mach-number.html)

Fonzie March 12, 2007 13:43

Solver is finishing with huge Mach number
 
Hallo everyone,

my question today is dealing with an issue I have encountered already sveral times and that I have always connected with a bad mesh quality. I am calculating a flow with an inflow of about 36 m/sec, that is far below any transonic effects or something. However for some meshes I am getting the following solver warning and shortly after the residuals will drop to "infinity". +--------------------------------------------------------------------+ | ****** Notice ****** | | The maximum Mach number currently is 4.273E+04. | | If this message persists and you experience robustness problems, | | consider setting the expert parameter 'max continuity loops' to 2. | +--------------------------------------------------------------------+

I have used a mesh generated by ICEMCFD. I have generated a prism layer with 10 layers and the first node 1 mm away from the surface. I have generated these layers "at once" that is without any "split prism"-tactics or something. After that I have transformed the Prisms to Tetras and smoothed the whole stuff so the quality is fine. ICEM tells me that the quality of the mesh is fine, no errors, no possible problems and the element quality is alright, too.

So my question simply is - where is that large Mach number coming from and how can it be explained. Why would the solver calculate such unrealistic high flow velocities?

If anyone had the same problems or just knows what causes that stuff I am grateful for your answer.

Regards Fonzie

Joe March 12, 2007 15:15

Re: Solver is finishing with huge Mach number
 
If you are solving a subsonic compressible flow and your solution is diverging it may generate spurious high Ma warnings.


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