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-   -   Impinging Jet Boundary Condition Problem (http://www.cfd-online.com/Forums/fluent/94680-impinging-jet-boundary-condition-problem.html)

mattyg101 November 22, 2011 13:16

Impinging Jet Boundary Condition Problem
 
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:

http://i.imgur.com/5jxkL.jpg

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

Ali.nabavi July 6, 2012 20:50

Quote:

Originally Posted by mattyg101 (Post 333128)
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:

http://i.imgur.com/5jxkL.jpg

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.

meangreen July 7, 2012 17:34

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.

meangreen July 7, 2012 17:39

here we go, the pdf's are linked towards the bottom of the post.

http://www.cfd-online.com/Forums/mai...different.html

Ali.nabavi July 8, 2012 07:13

Quote:

Originally Posted by meangreen (Post 370263)
here we go, the pdf's are linked towards the bottom of the post.

http://www.cfd-online.com/Forums/mai...different.html

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

meangreen July 9, 2012 15:11

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.

mattyg101 January 29, 2013 11:35

Quote:

Originally Posted by meangreen (Post 370263)
here we go, the pdf's are linked towards the bottom of the post.

http://www.cfd-online.com/Forums/mai...different.html

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.


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