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-   -   urgent help needed with 2d compressible flow (http://www.cfd-online.com/Forums/fluent/45093-urgent-help-needed-2d-compressible-flow.html)

James June 19, 2007 13:14

urgent help needed with 2d compressible flow
 
Hello everyone,

I am simulating a 2d compressible flow of methane/air and i am having problems....i do the cold flow first incompressible and then change to compressible and it works fine and residuals are behaving fine. When i switch to the hot flow using the species transport and the eddy dissipation/finite rate chemistry model, my flame is not good and i also get my velocity field completely reversed and my flame eventually begins to propagate in the flame holder. My residuals are also fluctuating meanwhile my flow is steady.

I tried the same case hot but incompressible ideal gas and it works fine. I also have a 3d case and it works fine with the compressible flow as well.

So my question is why is the compressible 2d hot case not working? Is it due to the pressure at the outlet.....in the 3d case, one has the option is setting radial equilibrium pressure distribution at the outlet but i do not see this option in the 2d case?

If you have any way around this problem, i will be grateful for yor input.

James


thandavan June 19, 2007 23:15

Re: urgent help needed with 2d compressible flow
 
Hi,

Good initial guess will solve your problem. For example you can use the fluent manual to calculate the k and epsilon values and also initializing the velocity field will help over come this issue.

Thandavan

James June 20, 2007 04:22

Re: urgent help needed with 2d compressible flow
 
Hi,

Thanks for responding to my post. I realized that i had done the wrong specification for the velocity field. When i changed that, i worked fine.

James



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