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Old   May 9, 2001, 22:06
Default about combustion in fluent
  #1
Mark
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Hi,

When I use couple solver,finate rate model,massinlet boundary(subsonic)and pressure-outboundary(supersonic)to simulate all the flow in rocket moter(including nozzle), I get the result of cold flow,then I patch temperature to spark.I find the temperature is very high.After handrands of interation,there is error message: divergence detected-temporarily reducing courant number 0.5 and try again...

divergence detected-temporarily reducing courant number 0.05 and try again...

divergence detected-temporarily reducing courant number 0.005 and try again...

divergence detected-temporarily reducing courant number 0.0005 and try again...

divergence detected-temporarily reducing courant number 5e-5 and try again...

error:internal error at line 688 in file"rp-mstage.c" divergence detected in AMG solver error object )

When I use segregated solver,finate rate model,massinlet boundary(subsonic)and outflow(subsonic)to simulate some part f the flow in rocket moter(not including nozzle,just the flow of chamber in rocket motor ),I get the result of cold flow,then I patch temperature to spark.And I also set under relaxtionressure:0.8,monument:0.25,and other scalars:0.5.After handrands of interation,there is message about reversed flow.After handrands of interation,there is error message: divergence detected-temporarily reducing courant number 0.5 and try again...

divergence detected-temporarily reducing courant number 0.05 and try again...

divergence detected-temporarily reducing courant number 0.005 and try again...

divergence detected-temporarily reducing courant number 0.0005 and try again...

divergence detected-temporarily reducing courant number 5e-5 and try again...

error:internal error at line 719 in file"amgif.c" divergence detected in AMG solver error object )

If I just simulate the flow in chamber,I don't how to define the boundary at the end of chamber.I used the outflow boundary,but reversed flow come into being.If I define pessure-out boundary,I don't know how to define the value of pressure and temperature.

Would you give me some advice?Any ansnwer will be welcome.

Thank you.

Mark 2001.5.10
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Old   May 10, 2001, 14:36
Default Re: about combustion in fluent
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K. Tsai
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Try using the double precision version with a smaller courant number (e.g. <= 1.0 ) and see how it goes. Also make sure that your boundary conditions are correct, especially temerature. Initialize the data field with some reasonable values should also help.
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