The Seventh Asian Congress of Fluid Dynamics Dec 8-12, 1997, Madras, India Velocity Field Measurements in 3d Rotor Flows

This research aims to measure four-dimensional, spatio-temporal velocity fields in unsteady periodic flows, such as those around rotorcraft. Periodic planar velocity fields at several slices of the flowfield are used to compute the component normal to the planes. The flow being incompressible, satisfying the continuity equation is sufficient. The velocity field reconstruction technique is validated against the Bödewadt-Nydahl solution for viscous rotating flow above a wall. The technique is shown to be robust to 15% band-limited white noise in boundary and other planes. The high Reynolds-number velocity field between a 2-bladed rotor and a wing in a large wind tunnel is captured using Spatial Correlation Velocimetry at video rate using pulsed laser sheet images in 27 planes across the rotor wake. The planar velocity data correlates well with previous flow imaging and single-point laser velocimetry results.