k-w model, interlengthscale
 

Hello to all, I am working with a two phase flow(water-air)in a horizontal pipe and i have to define the values for the turbulence model. I have read in a paper that appropriate is the k-w model. in that paper the author gives very spezific values. How can i determine these values(except of automatic, which is default).Is the geometry important? in addition, this interlength scale is not totally clear to me...could anybody help??

Best regards