Use of a Numerical Model in the Conceptual Design of a New Blade Vortex Interaction Facility. Department of Aerospace Engineering internal report no. 9509

This report describes and presents results from a numerical model developed to aid the preliminary design of a new wind tunnel based blade-vortex interaction (BVI) facility. The proposed facility will simulate tail rotor BVI by interacting a transverse vortex, produced by a single-bladed rotor situated in the wind tunnel contraction, with a blade mounted vertically in the tunnel working section. In the model a three dimensional source panel method is used to calculate the constrained flow through the low speed wind tunnel and a free wake vortex model represents the wake generated by the upstream rotor. Convection of the wake is then determined by superposition of the undisturbed tunnel velocity and the induced velocity components from the wake itself. Results, obtained via a parametric analysis, illustrate the geometry of the wake and tip vortex and their relation to basic design parameters. In particular, two possible operational strategies for the upstream rotor are examined with reference to development of the experimental facility. It is concluded that, while a short duration finite rotor traverse may be the optimum vortex generation strategy, a continuous running rotor may be the most cost effective option