EXPERIMENTAL STUDIES OF BOUNDARY LAYER TRANSITION ON A SPINNING AND NON-SPINNING AXISYMMETRIC BODY

An experimental investigation of natural and forced boundary layer transition on a secant ogive nose axisymmetric body was conducted for Reynolds numbers between 315,000 through 1,030,000. Two different modes of instability, a viscosity conditioned Tollmien-Schlichting instability as well as a crossflow or inflectional instability were observed and documented. The boundary layer displacement thickness, momentum thickness and shape factors were determined in order to provide a complete data base for testing current transition theories. Wind tunnel freestream turbulence and sound pressure levels were measured to provide an estimate of the freestream disturbance environment. Velocity profiles and pressure distributions were documented and combined with flow visualization data to yield a more complete understanding of the transition processes. A considerable part of this investigation was directed toward the development of the wind tunnel equipment, instrumentation, and computer software necessary to obtain meaningful experimental data.