Computations of steady and unsteady low-speed turbulent separated flows

Abstract

Numerical computations are presented for two-dimensional steady and unsteady separated flows. The first case is a low-speed, converging-diverging duct with a rapid expansion, creating a large separated flow region. The second case is the Massachusetts Institute of Technology flapping foil experiment, where a stationary hydrofoil is subject to gust loading. Numerical solutions are obtained by solving the incompressible Navier-Stokes equations. These equations are solved in a time accurate manner using the method of artificial compressibility. The Johnson and King turbulence model is employed for modeling the turbulent flow. Modifications to the model are suggested that take into account the normal stress production of energy and the strong adverse pressure gradient associated with separating flows. The performance of the Johnson and King model and its modifications are studied for both steady and unsteady flow conditions