Vortex breakdown location over 65° delta wings empiricism and experiment

Abstract

Abstract Thirty-eight data sets from static tests of various 65° delta wings in many water and wind tunnels are compared with four empirical vortex breakdown location prediction methods and the results of two Navier-Stokes computations to assess their range of validity in pitch. Vortex breakdown is the sudden expansion and subsequent chaotic evolution of the otherwise orderly, spiraling, leading-edge vortex flow over the upper surface. Large fluctuations occur in vortex breakdown location at static test conditions making accurate experimental determination difficult. The prediction methods do not account for the seemingly minor geometric details that vary between the models such as thickness, leading-edge bevel angle and radius, trailing-edge bevel angle, sting mounting, instrument housings, etc. These geometric variations significantly affect the position of vortex breakdown and degrade the accuracy of the predictions. The large changes in the flow produced by small geometric changes indicate that an efficient flow control strategy may be possible. Many of the data sets are not corrected for tunnel wall effects, which may account for some of the differences. Data presented herein are as published by the original authors, without additional corrections.