L/Δ factor for LES mesh
 

Hi guys, im going to run an LES case for buoyancy driven natural ventilation case. Guys i have been told by my supervisor that to check if the mesh i have selected is fine enough for LES i need to first run a RANS simulation on that mesh density. Once that is done i have to check if L/Δ > 20. If this condition is met then the mesh is ok for LES as well.
Now L = integral turbulence length scale = [k^(2/3)]/ε
and Δ = filter width (grid size)
and that L/Δ= (k/ kSGS) this is what i need to calculate.
Let me define:
KRES= resolved kinetic energy

KSGS= subgrid-scale kinetic energy

K = total turbulence energy = KRES + KSGS

Guys i hope u can tell me a way of how i can calculate this L/Δ factor as i have got the RANS results. Thank you :)