Wind tunnel measurements of the surface pressure distribution on a spinning Magnus rotor

Abstract

The aerodynamic pressure distribution acting on the surface of a spinning four-vaned, cylindrical Magnus rotor in cross flow was experimentally obtained during a series of subsonic wind tunnel tests. A pressure tap located in the non-spinning inner portion of the wind tunnel model detected the surface pressures through a series of vent holes in the spinning outer portion of the model. The pressures were measured by means of a sliding seal arrangement. For the test condition used, K=100 fps and Rd =277,000, the autorotating (steady state) tip speed ratio of this Magnus rotor was 0.46, corresponding to a spin rate of 2050 rpm. Surface pressure distribution over the entire circumference of the spinning Magnus rotor are presented at 1 ms intervals. Resultant lift and drag coefficients computed by integrating the measured pressure distribution data reveal the cyclic nature of the lift and drag with time and their relative phase relations. Comparison of measured pressure distribution profiles with corresponding smoke flow data indicates the unsteady, periodic separated flowfield and illustrates the powerful tool provided by the pressure distribution toward interpreting and analyzing aerodynamic phenomena on spinning configurations having irregular external shapes.