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-   -   good Cold Flow Results but problem with Hot Flow (http://www.cfd-online.com/Forums/cfx/22698-good-cold-flow-results-but-problem-hot-flow.html)

Rams June 12, 2006 10:17

good Cold Flow Results but problem with Hot Flow
 
Hello Friends,..

i have got good results in agreement with the experimental values for cold flow analyis,... but when am starting combustion on the same geometry,... am getting negative pressures at the throat of the inlet and oulet nozzles of the combustion chamber,... this negetive pressures is not dying down but going on increasing,...

am doing non-premixed combustion using mixture fraction/pdf model,...

am unable to locate where the problem lies,.. is it in the pre-pdf or any where else,...

My inlet boundry conditions for hotflow are

Pressure inlet : 60bar at inlet nozzle

Pressure oulet : 0bar (i.e atmospheric pressure ) at outlet nozzle

Wall Temperature : 500K

Operating pressure is 0 pa

Please help me in solving my problem,..

Thanks regards,..

Rams

Rajit June 12, 2006 23:31

Re: good Cold Flow Results but problem with Hot Fl
 
I presume it is a pretty weak constraint on the sytem With pressure condition at the inlet and at the outlet.

Are you sure the results have converged for this case.

Try to calculate the velocity at the inlet and change the inlet condition to the same.

Regards Rajit

Rams June 13, 2006 03:30

Re: good Cold Flow Results but problem with Hot Fl
 
Hello Sir,...

My results are not converged but after around some 1000 or 1500 iterations the when i check the pressure,.. there is negative pressure at the throat of the inlet and outlet nozzle,............... if am continuing iterations the whole pressuree in the combustion chamber is becoming negative,................

I'll try what eveer suggestions u have made,..

thanks,...

regards,

Rams


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