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-   -   MACH=25 HAVE YOU TRIED ? (https://www.cfd-online.com/Forums/fluent/28108-mach-25-have-you-tried.html)

Tomawak December 19, 2000 03:44

MACH=25 HAVE YOU TRIED ?
 
Hi, ANYBODY TRIED MACH=25 ? ANY SUGGESTION HOW TO SET UP A CASE TO MAKE IT CONVERGE ? BC, OPERATING PRESSURE ETC.. THANK YOU.

Patxi Gil December 19, 2000 15:53

Re: MACH=25 HAVE YOU TRIED ?
 
I have tested Fluent for hypersonic flow (Ma=7 to 25) for 2D-axysimmetric cases and Fluent works good. It match really good the experimental result (I didn't try it with 3d cases)

The settings that I used in my project was:

BC

+Pressure_far_field for the outside

+Axis

+Wall for the surface of rocket

Procedure to get a converge solution

1. Initial run with cold combustion

2. Once that we have a good convergence in cold combustion, then we activate the dissociating equations

3. If we consider catalytic effects, these ones have to be considered as a third stage. That is, run the point 2 without catalytic effects and once that we have a converged solution - set the catalytic BC

It is important to start with a good mesh (otherwise you won't get converged results), although it will needed a couple of refine mesh to get accuracy results. Here you have to play with time-accurancy

Solver: Couple Implicit

Important: don't increase the Clk number more than 1 Start with a low Clk number (0.01 or 0.1) and increase it very little by little - otherwise the process will not converge

PATXI


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