PARALLEL BLADE-VORTEX INTERACTIONS - AN EXPERIMENTAL-STUDY AND COMPARISON WITH COMPUTATIONS

This paper presents results from an experimental study of rotor blade- vortex interaction (BVI) aerodynamics and acoustics, The experiment ut ilized an externally generated vortex interacting with a two-bladed ro tor operating at zero thrust to minimize the influence of the rotor's own wake, The rotor blades were instrumented with a total of 60 absolu te pressure transducers at three spanwise and ten chordwise stations o n both the upper and lower surfaces. Acoustic data were obtained with fixed near-field microphones as well as a movable array of far-field m icrophones. The test was carried out in the acoustically treated test section of the NASA Ames 80- by 120-Foot Wind Tunnel, Several paramete rs which influence BVI, such as vortex-rotor separation distance, vort ex strength, and vortex sense (swirl direction), as well as rotor tip Mach number and advance ratio, were varied, Simultaneous measurements were obtained of blade surface pressure distributions, near-field acou stics, and far-field acoustics during the vortex-blade encounters, A c omparison with computational results from the WOPWOP code shows good c orrelation with experimental data.