How to increase mass flow rate in far field

deepak.ar · May 16, 2016, 10:58

Hi, does any one know how to increase mass flow rate in far field. I am simulating jet exhaust flow field, but flow rate from far field is not enough. This results very long jet.

ghorrocks · May 17, 2016, 01:34

Please post an image of what you are modelling and what you see as the problem.

deepak.ar · May 19, 2016, 02:47

Thank you
Here is link to details of the problem.
http://www.cfd-online.com/Forums/cfx...ow-noozle.html

ghorrocks · May 19, 2016, 07:28

You probably have a velocity boundary condition defined on the far field boundaries. So don't you just make it a higher velocity? Isn't that obvious? Or have I missed something?

deepak.ar · May 22, 2016, 03:42

In cfx we can only give pressure and temperature for far field boundary condition.

ghorrocks · May 22, 2016, 07:26

Why not use a velocity boundary condition? If you know the velocity then doesn't this make sense?

deepak.ar · May 22, 2016, 08:43

Velocity in far field disrupts main hot core stream. It creates pressure on hot core stream.
Is it possible to make hot stream to draw more free air from far field?

ghorrocks · May 22, 2016, 22:44

The usual way to model an object in a far field is to use a velocity inlet on the upstream side and the pressure boundary on the outlet side. That allows you to directly specify the free stream velocity on the inlet boundary and allows wakes, exhaust and other things created by the device to simply exit through the outlet.

Would this help?

If not you better explain what you are trying to do and why the normal approach does not work.

May 16, 2016, 10:58	How to increase mass flow rate in far field	#1
deepak.ar New Member Deepak Join Date: Dec 2015 Posts: 8 Rep Power: 10	Hi, does any one know how to increase mass flow rate in far field. I am simulating jet exhaust flow field, but flow rate from far field is not enough. This results very long jet.

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May 17, 2016, 01:34		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Please post an image of what you are modelling and what you see as the problem.

May 19, 2016, 02:47		#3
deepak.ar New Member Deepak Join Date: Dec 2015 Posts: 8 Rep Power: 10	Thank you Here is link to details of the problem. http://www.cfd-online.com/Forums/cfx...ow-noozle.html

May 19, 2016, 07:28		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	You probably have a velocity boundary condition defined on the far field boundaries. So don't you just make it a higher velocity? Isn't that obvious? Or have I missed something?

May 22, 2016, 03:42		#5
deepak.ar New Member Deepak Join Date: Dec 2015 Posts: 8 Rep Power: 10	In cfx we can only give pressure and temperature for far field boundary condition.

May 22, 2016, 07:26		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Why not use a velocity boundary condition? If you know the velocity then doesn't this make sense?

May 22, 2016, 08:43		#7
deepak.ar New Member Deepak Join Date: Dec 2015 Posts: 8 Rep Power: 10	Velocity in far field disrupts main hot core stream. It creates pressure on hot core stream. Is it possible to make hot stream to draw more free air from far field?

May 22, 2016, 22:44		#8
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	The usual way to model an object in a far field is to use a velocity inlet on the upstream side and the pressure boundary on the outlet side. That allows you to directly specify the free stream velocity on the inlet boundary and allows wakes, exhaust and other things created by the device to simply exit through the outlet. Would this help? If not you better explain what you are trying to do and why the normal approach does not work.