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[SU2] Axissymmetric nozzle flow, initialization, force calculation etc.

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Old   April 10, 2019, 10:40
Red face [SU2] Axissymmetric nozzle flow, initialization, force calculation etc.
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Hi Community,


I'm dealing with with internal flow analysis of solid propellant rocket motor nozzle. I have walls, pressure inlet and outlet (which is large domain like far-field).


I have few problems about initialization and force calculation.



First of all, For convergence I have to initialize my case with chamber total conditions which is similar to pressure inlet conditions. Therefore, I set my reference quantities such as reference_temp, reference_press as inlet quantities. Then I successfully obtain the results in contour plot which I expect indeed.



However, I need also thrust value which is obtained by wall forces (just forget about inlet). When SU2 write the CL and CD values on terminal, they are all meaningless. Because SU2 uses the reference quantities (which is my inlet total conditions) to calculate Force. I have checked the source code (CEulerSolver::Pressure_Forces). I am sure about the force calculation is CL or CD = (P-Pref)/(0.5*Rho_ref*Vref^2*Sref).


In order to solve this problem. First I solve the case with reference quantities as inlet conditions and converged it. Then I used restart file and changing the reference quantities which satisfy (0.5*Rho_ref*Vref^2*Sref) = 1 , run again. Force results are still meaningless. By the way, I need also some explanation for axissymmetric force factor etc. which can also be a problem.



I hope, I can explain the situation. Any help will be appreciated.


Best regards.
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Old   April 11, 2019, 03:04
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If it is not well understood, I can further explain the used domain with some visuals.
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Old   May 4, 2019, 16:19
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Hi Ali,
You can use the values in the "forces_breakdown.dat" file, there are force coefficients (the denominator for the normalization is also in the file) listed by surface in there, so it should be straightforward to convert those to force along some direction.
Cheers,
Pedro
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