Holographic Investigation of Slender Body Vortex Wakes.

Abstract : The three dimensional vortex flow field behind slender missile configurations at high angle of attack was investigated using laser holography. Holographic interferograms of the flow about two ogive cylinder models were recorded for low speed flows, M less than .1, at angles of attack from 20 to 50 degrees. Helium injected into the flow above the model was entrained into the entire vortex structure, and the three dimensional position of the core could not be determined from the interferograms. Dual exposure holograms of the flow field seeded with 40-100 micron glass microballoons were recorded using a pulsed ruby laser. Pairs of particles could not be easily identified in the reconstructed image and the three dimensional velocity field could not be measured. Surface pressures were measured and integrated to provide load distributions, normal and side force coefficients. Roll angle was varied with angle of attack and tunnel conditions constant. Conditions of maximum vortex asymmetry were determined from the measured pressure distributions. (Author)