This is a modern 16-foot Hover Facility where the rotor blades can be subjected to digitally-controlled higher-harmonic excitation using hydraulic actuators on the pitch links. We have completed a detailed test case on a two-bladed Bell 212 tail rotor running at 600rpm, with 4-per-rev (40Hz)) pitch excitation. The blade surface pressure distributions, wake geometry and the time-varying inflow velocity field, were measured and correlated with predictions from several analytical methods. To measure velocity, we used a laser velocimeter, obtaining data rates as high as 6000 per second with sufficient accuracy to interpret data from a single blade passage at 600rpm. The effects of the 1-degree, 4-per-rev pitch oscillation were successfully measured. The wake was visualized using a laser sheet. The pressure effects of the pitch excitation were measured using Kulite sensors.
Lal, M.K., Liou, S-G., Pierce, A-G. and Komerath, N.M., "Correlations of Unsteady Pressure and Inflow Velocity Fields of a Pitching Rotor Blade". Journal of Aircraft, Vol. 32, No.3, May-June 1995, p. 520 -528.
Liou, S-G., Komerath, N.M., Lal, M.K., "Measurements Around a Rotor Blade Excited in Pitch. Part 1: Dynamic Inflow". Journal of the American Helicopter Society, Vol. 39, No. 2, April 1994, p. 3-12.
Lal, M.K., Liou, S-G., Pierce, G.A., and Komerath, N.M., "Measurements Around a Rotor Blade Excited in Pitch. Part 2: Blade Surface Pressure". Journal of the American Helicopter Society, Vol. 39, No.2, p.13-20, April 1994.
Lal, M.K., Liou, S.G., Pierce, G.A., Komerath, N.M., "Measurements of Unsteady Pressure on a Pitching Rotor Blade". Proceedings of the 49th Annual Forum of the American Helicopter Society, St. Louis, MO, May 1993.
Lal, M.K., Liou, S-G., Komerath, N.M., and Pierce, A-G., "Correlations of Pressure and Velocity Data with predictions for Unsteady Inflow to a Vibrating Rotor Blade". AIAA Paper 93-3082, 24th Fluid Dynamics Conference, Orlando, FL, July 1993.
Liou, S-G., Komerath, N.M., "Measurements of the Inflow to a Vibrating Rotor Blade". AIAA 92-0634, 30th Aerospace Sciences Meeting, Reno, NV, January 1992.