Off-wall boundary conditions for bounded turbulent flow simulations

Copyright © ETC 2013 - 14th European Turbulence Conference.All rights reserved. We investigated the possibility of modeling off-wall boundary conditions for bounded turbulent flows. Such boundary conditions circumvent the need to resolve the buffer layer near the wall by providing conditions directly above it for the overlying flow. Our objective is to model the effect of the buffer layer on the overlying flow as an off-wall, Dirichlet boundary condition for the flow variables. We selected the plane at y+ ≈ 100 as our off-wall boundary, since this plane can be interpreted as a notional interface between the buffer and logarithmic regions. We tested different boundary conditions on channel flow with increasing levels of abstraction/modeling, starting from exact, time-resolved conditions from a previous DNS, all the way to a reduced-order model obtained from minimal flow units of a transitional boundary layer.