Rotorwash Prediction Using an Applied Computational Fluid Dynamics Tool

This paper describes the application of a Computational Fluid Dynamics (CFD) methodology to compute rotor flowfields in the vicinity of the ground. The method approximates the solution to the incompressible, laminar Navier-Stokes equations utilizing stretched Cartesian grids. The rotor is modeled as sources in the momentum equations. The two-dimensional airfoil characteristics of the rotor blades and the local velocity of the flow are the basis for the computation of the momentum sources. Fuselages are simply modeled by “blanking-out” cells within the surface boundary. As a result of the simplifications of the rotor and fuselage modeling, the method is grid point efficient since it is not burdened with resolving shed tip vortices and body surface flow. The CFD methodology has been successfully applied to various helicopter configurations in the vicinity of the ground and demonstrates the ability to predict the flow conditions directly beneath the aircraft as well as in the farfield.