Numerical Dissipation

sam

Is it true that the dissipative effect due to two k-epsilon type models is more (may be by far) than that due to discretization of convective (or diffusive fluxes). I am trying to develope a fudamental understanding for the cause of such dissipation. And what is the relation between such dissipation and dampening of unsteadiness in certain problems that employ thse turbulence models. I noticed that using a steady state simulation for a problem that is known to be hihjly turbulent (vortex shedding for flow past cylinder at the sub-critical reynolds) is possible while that as laminar (same Re) is not. I appreciate your inputs