In the dynamic subgrid sgs les model, the test filter is added, so if we have get the velocity u, I want to ask how to get the u' in the test filter? and if the grids are unstructured, how to average?

Thanks!

Avaraging over an element (in my case a tetrahedron) is enough. as for the u` - check Larey sgs model. I don't have papers with me now, but i think i can mail you a photo of a page later, if you like.

Thanks for your page!