Viiflow—A New Inverse Viscous-Inviscid Interaction Method

Abstract

Viscous–inviscid interaction is the fastest method in computational fluid dynamics available for airfoil design and analysis that is able to capture viscous effects on the flow. Despite advances in (Reynolds-averaged) Navier–Stokes equations solvers and models, it is arguably the first choice for preliminary and even detailed design. A new method of coupling the boundary-layer equations to the inviscid flow is presented. The boundary-layer equations are solved with given displacement thickness, and a Newton method couples the viscous and inviscid regimes. This leads to a significant decrease in computational effort as compared to a joint solution of the boundary-layer equations with the coupling problem. The software Viiflow uses this mechanism, and examples that couple the integral boundary-layer equations with a panel method are presented: assessing accuracy using wind-tunnel measurements, using the software for a fluid–structure interaction problem, and a runtime performance comparison demonstrating a significant improvement as compared to the popular viscous–inviscid interaction airfoil analysis software XFOIL for higher numbers of panels.