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-   -   about combustion in fluent (http://www.cfd-online.com/Forums/fluent/28515-about-combustion-fluent.html)

Mark May 9, 2001 22:06

about combustion in fluent
 
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 relaxtion:pressure: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

K. Tsai May 10, 2001 14:36

Re: about combustion in fluent
 
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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