# Impinging Jet Boundary Condition Problem

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 November 22, 2011, 13:16 Impinging Jet Boundary Condition Problem #1 New Member   Matty Join Date: Nov 2011 Posts: 5 Rep Power: 6 Hi all, I have set up a 2D, axisymmetric impinging jet domain similar to that used by Cooper et al (1993) and Craft et al (1993). My aim is to obtain some RANS data for comparison purposes. I have defined the boundary conditions as follows: I have run the simulation using k-e (standard model using non-equilibrium wall functions) and Re stress (quadratic pressure-strain model with non-equilibrium wall functions) In the radial wall jet the turbulent kinetic energy and Re stresses respectively do not go to zero. In the case of the Re stress model, they show a sharp positive spike at the wall. I think this is a problem with the boundary conditions i am using at the wall dont have enough Fluent experience. Is anyone familiar with this problem or could possibly shead some light on my problem? I would be very grateful. Matt

July 6, 2012, 19:50
#2
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Ali nabavi
Join Date: Jul 2012
Posts: 10
Rep Power: 6
Quote:
 Originally Posted by mattyg101 Hi all, I have set up a 2D, axisymmetric impinging jet domain similar to that used by Cooper et al (1993) and Craft et al (1993). My aim is to obtain some RANS data for comparison purposes. I have defined the boundary conditions as follows: I have run the simulation using k-e (standard model using non-equilibrium wall functions) and Re stress (quadratic pressure-strain model with non-equilibrium wall functions) In the radial wall jet the turbulent kinetic energy and Re stresses respectively do not go to zero. In the case of the Re stress model, they show a sharp positive spike at the wall. I think this is a problem with the boundary conditions i am using at the wall dont have enough Fluent experience. Is anyone familiar with this problem or could possibly shead some light on my problem? I would be very grateful. Matt
Hi Matt
Hope ur problem was solved as it was for a long time ago ...
I'm gonna model the impinging jet via fluent and regarding mr cooper data , but I have some problem.
One is about the wall boundary condition which I consider constant flux but I don't know the value another thing is how did you define for ur inlet profile.

 July 7, 2012, 16:34 #3 Member   Casey Join Date: Jun 2009 Posts: 96 Rep Power: 9 I did this a long time ago, and then posted my results on this very forum. Let me see if I can find the link.

 July 7, 2012, 16:39 #4 Member   Casey Join Date: Jun 2009 Posts: 96 Rep Power: 9 here we go, the pdf's are linked towards the bottom of the post. k-omega and k-epsilon turbulence model. Why different?

July 8, 2012, 06:13
#5
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Ali nabavi
Join Date: Jul 2012
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Quote:
 Originally Posted by meangreen here we go, the pdf's are linked towards the bottom of the post. k-omega and k-epsilon turbulence model. Why different?
thanx , but my problem is not the difference between the turbulence model my problem is setupping and optimum case for impinging jet.

tanx so much for your help

 July 9, 2012, 14:11 #6 Member   Casey Join Date: Jun 2009 Posts: 96 Rep Power: 9 I just followed the same simulation guidelines used for the craft paper. You will need to do sensitivity simulations to check the length of the bottom wall and the pipe development to make sure it isn't affecting your solution. Also, you need to look at the mesh size near the bottom wall to be sure your y+ values are in the correct range.

January 29, 2013, 11:35
#7
New Member

Matty
Join Date: Nov 2011
Posts: 5
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Quote:
 Originally Posted by meangreen here we go, the pdf's are linked towards the bottom of the post. k-omega and k-epsilon turbulence model. Why different?
Better late than never: Thank you for the response and i will read those chapters. They might clarify a few things.

I solved/minimised) my boundary problem by using scalable wall functions for the quadratic RSM.

 Tags boundary, condition, fluent, impinging, jet

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