Measurements to Understand the Flow Mechanisms Contributing to Tandem Rotor Outwash
US Army Aviation Development Directorate Moffett Field United States
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Downwash and outwash characteristics of a model-scale tandem-rotor system in the presence of the ground were analyzed by identifying and understanding the physical mechanisms contributing to the observed flow field behavior. A building block approach was followed in simplifying the problem, separating the effects of the fuselage, effects of one rotor on the other, etc. Flow field velocities were acquired in a vertical plane at four aircraft azimuths of a small-scale tandem rotor system using the particle image velocimetry PIV technique for radial distances up to 4 times the rotor diameter. Results were compared against full-scale CH-47D measurements.