CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > CFX

good Cold Flow Results but problem with Hot Flow

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 12, 2006, 11:17
Default good Cold Flow Results but problem with Hot Flow
  #1
Rams
Guest
 
Posts: n/a
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
  Reply With Quote

Old   June 13, 2006, 00:31
Default Re: good Cold Flow Results but problem with Hot Fl
  #2
Rajit
Guest
 
Posts: n/a
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
  Reply With Quote

Old   June 13, 2006, 04:30
Default Re: good Cold Flow Results but problem with Hot Fl
  #3
Rams
Guest
 
Posts: n/a
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
  Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Flow not moving - Supersonic/Initial Pressure problem? shankara.2 FLUENT 0 June 9, 2009 21:49
LES of highly heated pipe flow - incorrect results MichalH FLUENT 3 June 3, 2009 06:00
transient compressible flow problem (urgent plz) jehanzeb FLUENT 5 August 3, 2004 09:04
Inviscid Drag at subsonic, subcritical Mach # Axel Rohde Main CFD Forum 1 November 19, 2001 13:19
computation about flow around a yawed cone Tylor Xie Main CFD Forum 0 June 9, 1999 08:33


All times are GMT -4. The time now is 02:03.