MODEL FOR ROTOR TIP VORTEX-AIRFRAME INTERACTION .2. COMPARISON WITH EXPERIMENT

The interaction between a vortex and a solid boundary involves the development of a variety of length and time scales, some of which are due to very strong viscous effects. Prediction of these phenomena from first principles would remove a major obstacle in the computation of flows around rotorcraft. In Part 1 of this work,2 analytical and computational tools to advance the tip vortex in time and compute the surface pressure are presented for a vortex tube approaching an infinite circular cylinder. In this paper, quantitative comparisons are made with experimental results for a rotor tip vortex approaching a cylindrical airframe with a hemispherical leading edge. Unsteady velocity, surface pressure, and vortex trajectory data are used to define the initial conditions and perform the comparisons. The results are in substantial agreement before the impact of the vortex on the airframe.