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D_L February 23, 2010 19:02

turbulent kinetic energy and turbulent dissipation rate
 
Hi all, I am a Star CCM+ user and currently doing a project on wind turbine wakes. In the Star CCM+, I have to assign a value to both turbulent kinetic energy (TKE) and turbulent dissipation rate (TDR) for simulation, but I have no ideas what values should they be.
Could anyone suggest me on how to define these values? If these values are chosen incorrectly, how will it affect the results?

Thank you.

harishg February 24, 2010 18:43

If the values are not chosen to represent the flow conditions approximately, the wind turbine wake predictions will be different. In outflow zerogradient is usually used. At walls you have k=0 and dissipation has to be calculated from asymptotic expressions to avoid singularity. At the inflow you need to know the precise value of k/epsilon/L.

D_L March 2, 2010 18:41

Quote:

Originally Posted by harishg (Post 247265)
If the values are not chosen to represent the flow conditions approximately, the wind turbine wake predictions will be different. In outflow zerogradient is usually used. At walls you have k=0 and dissipation has to be calculated from asymptotic expressions to avoid singularity. At the inflow you need to know the precise value of k/epsilon/L.

Than you for answering. How can I get a precise value of the TKE and TDR at the inflow?
I looked at some technical reports but they did not mention the values of TKE and TDR used in their CFD simulations.

harishg March 3, 2010 21:39

Look for the NREL reports. They did extensive measurements. I am not sure of the exact details of the experiment but you should be able to find some useful information. Another option will be to look into the atmospheric rough boundary layer equations and check in the literature on ways people have used these equations for problem definition.

nvtrieu July 14, 2010 00:55

Hello,

I've been working with Star-CCM+ for several months. I also have the same question with D_L. How do I calculate the value for k,w,epsilon for the boundaries? could any one give me the answer?
Thanks in advance!

Trieu
email: trieuckgt@gmail.com

CCTech_Pune July 17, 2010 02:35

Turbulence Intensity
 
Hi

Please refer to "Development and Validation of WECC Variable Speed Wind Turbine Dynamic Models for Grid Integration Studies". This give good insight.

For length scales, you should consider using a length scale which is based on the size of the object over which flow is moving.

Thanks


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