How to get shock self oscillation in Sajben transonic diffuser?

slaon · April 2, 2014, 22:45

Hi, all:

I'm doing a transient flow in the Sajben diffuser including self-excited oscillation, following the work of
Hsieh, T., Bogar, T. J., and Coakley, T. J. (1987) "Numerical Simulation and Comparison with Experiment for Self-Excited Oscillations in a Diffuser Flow," AIAA Journal, Vol. 25, No. 7, pp. 936-943.

The steady state flow is list in NASA's verification page. The geometry looks like this.

First, I get the steady state flow. It agrees well with the mean experiment results, as shown in NASA's verification page.

Then, I start a transient calculation. The time increment is set to 1e-6 s. However, it still keeps steady state. I changed the turbulence models (standard k-e, RNG k-e, standard k-w, SST k-w). Still steay flow.

Anybody know how to get a self oscillating flow in the Sajben diffuser?

Thanks for many suggestions.

Best wishes,
Cheng, Yao.

slaon · May 22, 2014, 00:39

I solved the problem by using CFL=100 in a 2nd order implicit time scheme. :-)

April 2, 2014, 22:45	How to get shock self oscillation in Sajben transonic diffuser?	#1
slaon New Member Yao, Cheng Join Date: Nov 2011 Location: Harbin Posts: 7 Rep Power: 15	Hi, all: I'm doing a transient flow in the Sajben diffuser including self-excited oscillation, following the work of Hsieh, T., Bogar, T. J., and Coakley, T. J. (1987) "Numerical Simulation and Comparison with Experiment for Self-Excited Oscillations in a Diffuser Flow," AIAA Journal, Vol. 25, No. 7, pp. 936-943. The steady state flow is list in NASA's verification page. The geometry looks like this. First, I get the steady state flow. It agrees well with the mean experiment results, as shown in NASA's verification page. Then, I start a transient calculation. The time increment is set to 1e-6 s. However, it still keeps steady state. I changed the turbulence models (standard k-e, RNG k-e, standard k-w, SST k-w). Still steay flow. Anybody know how to get a self oscillating flow in the Sajben diffuser? Thanks for many suggestions. Best wishes, Cheng, Yao.

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May 22, 2014, 00:39		#2
slaon New Member Yao, Cheng Join Date: Nov 2011 Location: Harbin Posts: 7 Rep Power: 15	I solved the problem by using CFL=100 in a 2nd order implicit time scheme. :-)