Meaning of flow functional in Vreman SGS model
 

Hi,
Recently I read paper about SGS model proposed by Vreman in 2004 (POF)
In this paper, he divided various types of fluids into 10 groups. In this progress, he used "flow functional" J. He used J as 0, subgrid dissipation, magnitude of strain rate tensor, and so on. I want to know about the exact meaning of flow functional J. Is there anyone who can explain in detail?

I never studied the paper, however it is based on the static version of the eddy viscosity model

http://www.vremanresearch.nl/Vreman-...bgridmodel.pdf