Evaluation of Outflow Boundary Conditions in DNS of Turbulent Jet Flows

Choice of an outflow boundary condition (BC) for a turbulent free-jet flow simulation in a finite domain is non trivial, where neighbouring boundaries and their BCs may also have an influence. In this work, three different outflow BCs, Neumann BC with back-flow limiter, convective BC and Chapman BC (which is based on Orlanski scheme), were considered. A planar turbulent jet at Re= 4000 was simulated using direct numerical simulation (DNS), where an entrainment BC is applied on the lateral sides of the jet. The outflow BC proposed by Orlanski in an explicit form, which was later re-formulated by Chapman, was found to be a good choice in the present problem, where entrainment effects are also present.