Low-re k-epsilon : launder sharma. Exact form in fluent?

unred486 · February 25, 2016, 01:20

Hello all,

I am attempting to verify a results from nasa using fluent. Attempts with standard k-epsilon, SA, SST were fruitless up until now. It seems to me that all the models I have used use a wall function which may not be applicable for my case. (Or I think wall function is the problem because I have literally transformed k epsilon transport eq in fluent to the exact same form used in the nasa program using udf) But anyways, so right now I am attempting to just run a low re ke model (launder sharma) which does not use any wall function. I want to modify this lowreke transport too to match the nasa model( not sure how yet). But I just cannot find what transport equation is embedded in fluent.

Does anyone know what the exact form of the lowreke( launder sharma) is in fluent?

Also, if anyone knows how to turn off a wall function in the standard ke, please let me know.

Thanks!

HJ

AshwaniAssam · February 25, 2016, 02:56

Hi,

You can try to make your mesh such that y-plus is less than 2. And try to use the either standard or Enhanced wall treatment (mostly it will be better).

If you see fluent manual you will find that there is a switch to non-wall function implementation when y plus value falls below certain range.

http://aerojet.engr.ucdavis.edu/flue...ug/node512.htm

Please share you experience, on how did you handled this problem.

February 25, 2016, 01:20	Low-re k-epsilon : launder sharma. Exact form in fluent?	#1
unred486 New Member codenamenone Join Date: Jun 2015 Posts: 11 Rep Power: 11	Hello all, I am attempting to verify a results from nasa using fluent. Attempts with standard k-epsilon, SA, SST were fruitless up until now. It seems to me that all the models I have used use a wall function which may not be applicable for my case. (Or I think wall function is the problem because I have literally transformed k epsilon transport eq in fluent to the exact same form used in the nasa program using udf) But anyways, so right now I am attempting to just run a low re ke model (launder sharma) which does not use any wall function. I want to modify this lowreke transport too to match the nasa model( not sure how yet). But I just cannot find what transport equation is embedded in fluent. Does anyone know what the exact form of the lowreke( launder sharma) is in fluent? Also, if anyone knows how to turn off a wall function in the standard ke, please let me know. Thanks! HJ

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February 25, 2016, 02:56		#2
AshwaniAssam Senior Member Ashwani Join Date: Sep 2013 Location: Hyderabad Posts: 154 Rep Power: 13	Hi, You can try to make your mesh such that y-plus is less than 2. And try to use the either standard or Enhanced wall treatment (mostly it will be better). If you see fluent manual you will find that there is a switch to non-wall function implementation when y plus value falls below certain range. http://aerojet.engr.ucdavis.edu/flue...ug/node512.htm Please share you experience, on how did you handled this problem.