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-   -   inflow BC for LES (http://www.cfd-online.com/Forums/fluent/35444-inflow-bc-les.html)

 Hu January 12, 2005 03:57

inflow BC for LES

I am using LES to simulate the boundary layer flows in a wind tunnel. The boundary layer is quite thick, about 0.6m and the turbulence intensity is about 30% near the ground and it is about 5% at the top of the boundary layer. The profile of turbulence intensity (Urms/Umean) is not uniform but it can be approximated by a polynominal function to the 4th order.

The problem I've encountered is, how to input the turbulence intensity profile into FLUENT 6.1.22 when LES is used? There is a slot for input of the turbulence intensity in the pannel of "velocity inlet" in Fluent but it can only accept a fixed value.

Could anyone tell me how to do this? Or is there any paper I can consult for using LES in Fluent?

 zxaar January 12, 2005 04:34

Re: inflow BC for LES

in fluent doc section "10.7.3 Boundary Conditions for the LES Model" the way they have defined fluctuations , it seems the value of intensity is constant (i am not very much sure about this). But if the value of I is constant than fluent will not allow you to read it from profile.

 Hu January 12, 2005 05:35

Re: inflow BC for LES

Thanks.

I've also noticed that and I understand the "scale of turbulence" generated by Fluent is to randomly perturb the mean value by adding a r.m.s value times a random number of Gaussian distribution with a zero mean and standard deviation of 1. If there is no direct way to control the intensity profile in Fluent, can UDF or other methods do this job?

Has anyone used LES to simulate a similar problem by Fluent? Please advise. Many thanks.

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