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Old   July 12, 2007, 08:17
Default Jet Impingement (results improvement) ...
  #1
Sri
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Hello Fluent users

I am working on high reynolds number "2D axisymmetrical jet impingement on a free surface. The physical domain is explained by H/D=2 and thus from previous literature I expect to obtain a local maxima where turbulent boundary layer developed.

My Modeling approach:- I ran many simulation with several turbulence model with a range of y+ value from .7 to 31.

Simulations details:

1) k-epsilon, Enhanced Wall Treatment, y+=1: Good agreement in HTC at stagnation region but lack local maxima

2) k-w, SST, y+=1: Good agreement in HTC at stagnation region but lack local maxima.

3) k-w, y+=1, Standard model: The results are quiet overpredicted at the stagnation region and no maxima appear at turbulent boundary region.

At higher y+, the results were highly overpredicted at the region of interest, with the same initial conditions.

I think I am missing something in my modeling approach which restrict me in emulating the physical phenomenon in its true structure. Kindly suggest me some ways which could help in improving the results quality in the turbulent bounary region.

Regards Sri
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Old   July 12, 2007, 10:09
Default Re: Jet Impingement (results improvement) ...
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Joe
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Is your implicit isotropic turbulence assumption valid for this case?
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Old   July 13, 2007, 03:08
Default Re: Jet Impingement (results improvement) ...
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Sri
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Hello Joe

Thanks for your time in considering my post

I would be really thankful, if you can please ellaborate on "Implicit Isotropic turbulence assumption."

Please let me know, what settings are you referring to.

Regards Sri
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Old   July 13, 2007, 09:13
Default Re: Jet Impingement (results improvement) ...
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Joe
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Read section 12.2.3 Boussinesq Approach vs. Reynolds Stress Transport Models ... in the users guide.
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Old   July 13, 2007, 09:51
Default Re: Jet Impingement (results improvement) ...
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Sri
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Hi

Boussinesq Approach:- But I am not using Boussinesq approximation and also there has been quiet of validation data set using axisymmetric 2D case file.

So I am unable to get your point.

Regards Sri
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Old   July 15, 2007, 10:31
Default Re: Jet Impingement (results improvement) ...
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Josh
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I have not calculated any imoinging jets, but a comment could be - You are using standard 2 equations turbulence models which assume isotropic turbulence. Is that valid for your case?
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Old   July 16, 2007, 06:33
Default Re: Jet Impingement (Divergence with RSM) ...
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Sri
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hello

Thanks for your kind input.

As mentioned in your reply, I have switched to RSM 5 stress equation model for my model. Unfortunately, whenever I run my simulations, the system diverge.

The y+ of the mesh is in the range of 8-10 at the impinging plate and inlet reynolds no is 23,000.

Any suggestions please to prevent divergence.

Regards Sri
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