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Spalart Allmaras Y-Plus Recommendation

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Old   June 3, 2017, 20:08
Default Spalart Allmaras Y-Plus Recommendation
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Abhimanyu
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Hey guys,

I am performing URANS wing simulations for naca 4415 profile ,Re 3 million, using FLUENT for alpha range from 0 - 90 deg (not dynamic pitching). Now, in order to achieve y-plus 1 and cell aspect ratio of less than 10k for fluent to work properly, the cell count has gone insanely high for a structured grid.

I am trying to make a hybrid mesh with hex cells in a near-field region surrounded by tets outside to reduce the cell count and maintain the aspect ratio in the required range.

Another thing I wanted to explore was increasing the y-plus value to 5 or something beyond 30, say 50, to get rid of the aspect ratio issue, but I wanted to know if that is recommended for SA model. How accurate are the wall functions in FLUENT for SA?

Also, is there an alternative way to approach this problem so that I have a good quality mesh with the required y-plus of 1?

Separation point is an important parameter I am looking at, hence accuracy of model is necessary.

Any guidance is appreciated.

Regards
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Old   June 5, 2017, 12:41
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Old   June 6, 2017, 09:42
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Quang Le Dang
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Quote:
Originally Posted by abhi.jam22 View Post
Hey guys,

I am performing URANS wing simulations for naca 4415 profile ,Re 3 million, using FLUENT for alpha range from 0 - 90 deg (not dynamic pitching). Now, in order to achieve y-plus 1 and cell aspect ratio of less than 10k for fluent to work properly, the cell count has gone insanely high for a structured grid.

I am trying to make a hybrid mesh with hex cells in a near-field region surrounded by tets outside to reduce the cell count and maintain the aspect ratio in the required range.

Another thing I wanted to explore was increasing the y-plus value to 5 or something beyond 30, say 50, to get rid of the aspect ratio issue, but I wanted to know if that is recommended for SA model. How accurate are the wall functions in FLUENT for SA?

Also, is there an alternative way to approach this problem so that I have a good quality mesh with the required y-plus of 1?

Separation point is an important parameter I am looking at, hence accuracy of model is necessary.

Any guidance is appreciated.

Regards
First of all, your model is 2D or 3D? And mesh size you have for wallYplus 1?
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Old   June 6, 2017, 10:43
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I am performing wing simulations for constant chord (1m) and different aspect ratios of 8,12,16, hence 3D. For y-plus 1, my first cell height is 8.5e-6 m. Total mesh count is around 70 million.
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spalart allmaras, spalart allmaras model, turbulence, unsteady, wing

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