# Length scale in k-omega models?

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 May 30, 2014, 13:33 Length scale in k-omega models? #1 Member   Join Date: Jul 2010 Posts: 52 Rep Power: 15 Hi; Does anyone know why the length scale for k-omega models differs by a constant? -In Wilcox for k-omega: length scale = sqrt(k)/omega -In Fluent and other codes : length scale = cmu^(-1./4)*sqrt(k)/omega -In Menter 1994 for k-omega SST: length scale = sqrt(k)/(cmu*omega) Does the definition change between k-omega and k-omega SST? Why? Thanks and good day, Mary

 June 1, 2014, 11:41 #2 Senior Member   N/A Join Date: Mar 2009 Posts: 189 Rep Power: 17 Because of the difference in the definition of the omega variable. The length scale is defined as L = k^3/2 / epsilon When people derive the omega equation from the epsilon equation, there has been differences in the definition of the omega variable. The difference is the inclusion/exclusion of the variable Cmu. However, they adjust the constants to account for this difference, You need to be careful in using the proper constant values associated with each variable depending on the definition. MaryBau, reza2031, PhilippCFD and 1 others like this.

 Tags k-omega, length scale