Accurate and flexible formulation of a dual-solver hybrid CFD framework

Abstract

Various hybrid computational fluid dynamics (CFD) methods have recently been developed which couple Navier-Stokes solvers to vortex-based solvers for cost-effective rotorcraft aeromechanical analysis. Previous hybrid methods have had implementation issues which result in in-accurate and/or inflexible frameworks. Methodological approaches to CFD/free-wake coupling that address these issues and are unique among other hybrid CFD methods are introduced, including rotor tracking, blade deformation treatment, unsteady free-wake boundary pressure, boundary characteristic treatment, boundary value interpolation, and single gridded blade (SGB) simulation. These improvements are implemented into the OVERFLOW-CHARM hybrid CFD framework and their impact is demonstrated using three example scenarios: vortex advection, wing-integrated propulsion, and a rotor in hover. The new methods quantifiably improve the quality of the hybrid CFD solutions in these cases and enhance the generality of the framework to problems related to future vertical lift.