Three-dimensional Viscous Coupling & Flow Separation Enhancements to an Inviscid Surface Vorticity Flow Solver

As part of NASA 2018-20 SBIR-funded activities, Viscous modeling and coupled-solver enhancements have been applied to an existing commercial surface vorticity inviscid flow solver, FlightStream®. These models are physics-based and higher-fidelity than available empirical methods, but at the same time are computationally efficient and suitable for early design phase trade studies. These enhancements enable the prediction of viscous boundary layer, flow separation and stall characteristics in early design aerodynamics of unconventional UAM and DEP aircraft. A coupling has been created between the new boundary layer models and the flow solver to displace the inviscid boundaries using the boundary layer data and iteratively solve for the combined aerodynamic loads. Models have been added to simulate the effects of artificial boundary layer transition trips and surface roughness effects. Spatial-tree algorithms have been implemented to maintain O(NlogN) computational performance in line with the core inviscid flow solver. Validation studies have been performed using computational Navier-Stokes flow solutions and experimental results, demonstrating the validity of the proposed methods.