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-   -   RANS - time averaging? (http://www.cfd-online.com/Forums/star-ccm/86808-rans-time-averaging.html)

Connor April 2, 2011 15:18

RANS - time averaging?
 
Hi,


using the Reynolds-Averaged-Navier-Stokes (RANS), the air flow is averaged over a certain time t. What is the value of t for non-transient simulations?


Maybe this quotation of the CCM+ user guide helps to understand my question:

"To obtain the Reynolds-Averaged Navier-Stokes (RANS) equations, the
Navier-Stokes equations for the instantaneous velocity and pressure fields
are decomposed into a mean value and a fluctuating component. The
averaging process may be thought of as time averaging for steady-state
situations and ensemble averaging for repeatable transient situations. The
resulting equations for the mean quantities are essentially identical to the
original equations, except that an additional term now appears in the
momentum transport equation." (S. 2109 Version 5.02)

Thanks!
Connor


Maddin April 5, 2011 04:52

I think you understand the text incorrect - think about the "may be thought".
That's a text for non-geeks :D


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