Flow visualization during multiple-axis motions using a wind-driven manipulator

Abstract

This article explores the problem of capturing vortex flow interactions that occur during coupled-axis maneuvers at finite rates. A wind-driven dynamic manipulator (WDM) has been developed to perform simultaneous motions repetitively about two degrees of freedom under open-loop or feedback control in a low-speed wind tunnel. The concept of the WDM is examined and support interference is shown to be small compared to that in conventional approaches to maneuver simulation. Vortex flow interactions occurring near the vertical fins of a 1/32-scale fighter configuration during pitch, yaw, and coupled pitch-yaw motions are explored using quantitative laser sheet videography. Large asymmetry and complex interactions are observed in the flowfield. Vortices generated by the forebody, wing leading edge, wingtip, and vertical fins are seen to interact during the coupled pitch-yaw maneuver. Maneuvers are limited to reduced frequencies below 0.036, based on wingspan. Vortex locations are seen to be accurately reproducible and to be independent of rate as expected in this regime. Even at such low rates, several transient interaction phenomena are observed, involving vortices and control surfaces. Quantification of such phenomena is demonstrated.