An implicit implementation of the characteristic boundary condition in a fully coupled pressure-based flow solver

Abstract

The article deals with an implicit formulation of the pressure far field boundary condition, also known as the characteristic boundary condition, in a pressure-based coupled solver. This boundary condition applies to compressible flows over the entire Mach regime, and is derived by invoking the Riemann invariants to implicitly express the flow variables at inlets and outlets in terms of their values inside the domain. A set of inviscid an turbulent flow cases that include pressure far field boundary conditions are tested, namely: low subsonic compressible flow past a NACA0012 airfoil at 10° angle of attack; transonic flow over circular bump; supersonic flow over a series of slender bumps; and DLR-F6 Wing-Body-Nacelle-Pylon Aircraft. Predictions using the prescribed coupled solver are in good agreement with similar results obtained with density-based methods and/or experimental data.