# wall functions.-E value, epsilon calculation

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 April 5, 2009, 05:40 wall functions.-E value, epsilon calculation #1 New Member   Join Date: Mar 2009 Posts: 20 Rep Power: 9 Hi all! I am reading through the wall functions code for OF and comparing it with fluent and I noticed some strange things: 1- For the value E instead of using 9.781 as fluent 9 is used. 2- When OF calculates the epsilon for the wall function uses the following formula: epsilon_[faceCelli] +=Cmu75*pow(k_[faceCelli], 1.5)/(kappa_.value()*RASModel::y_[patchi][facei]); In Fluent the same formula is used but what is bothering me is the faceCelli term. In fluent epsilon_ is calculated at the point (epsilonp), however, in OF the term epsilon_[faceCelli] seems to refer to the value at the wall. Thank you in advance, Xabi

 September 10, 2009, 13:57 #2 Member   Sven Schweikert Join Date: Jun 2009 Posts: 38 Rep Power: 9 Hey Xabi I'm also interested how OF is dealing with the wall functions. So far I'm not really deep in it but about the E thing I found out that they overwriting the E=9 to E=9.8 in the respective turbulence Model with this autoCreateEpsilon (-Nut etc.) function. Cheers, Sven

 September 11, 2009, 18:54 #3 Member   Sven Winkler Join Date: May 2009 Posts: 70 Rep Power: 9 Hey Xabi, I am also interested in OpenFOAM deals with wall functions. In which file did you find the equation epsilon_[faceCelli] +=Cmu75*pow(k_[faceCelli], 1.5)/(kappa_.value()*RASModel::y_[patchi][facei]); you mention in 2.? Thanks a lot!

 February 25, 2014, 12:24 #4 Member   Manan Join Date: Oct 2013 Location: Göteborg Posts: 37 Rep Power: 5 Hi On this note of the epsilonWallFunction, does anybody know the source of the formulation mentioned above by Sven? I wish to know the reasoning behind why epsilon @ the first node near wall is recalculated this way. If anyone can direct me to the scientific article, which forms the basis of the epsilonWallFunction, I would be grateful. Thanks.

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