Wall modeling for large eddy simulation of turbulent boundary layers
October 24, 2014
Parviz Moin, Professor
Center for Turbulence Research, Mechanical Engineering
A pacing item for large eddy simulation of high Reynolds number turbulent boundary layers is the modeling of turbulence near the wall. Local large eddies near a wall are minute in size compared to the overall flow dimensions, but are known to be the major contributors to the overall turbulence energy production and stresses. Accordingly, numerical resolution of the near wall flow structures is prohibitively expensive: the required number of grid points scales as Re13/7. In practical large eddy simulations, one attempts to use a reduced order model to represent the near wall region instead of resolving it. In this talk I will describe our recent developments in wall modeling for high Reynolds number turbulent boundary layers. First, a generalization of the traditional wall modeling approach based on using the Reynolds averaged Navier Stokes equations in the wall layer coupled to LES away from the wall will be presented. I will then describe a novel approach in which a slip velocity boundary condition is derived from the constitutive LES equations using a differential filter. This approach is very promising, and in contrast to RANS based approaches is free of any a priori specified coefficients. Applications ranging from canonical transitional and turbulent boundary layers flows to complex multi-element airfoil systems will be presented.