Accession Number : ADA188812

Title :   On the Nature of Oblique Instability Waves in Boundary Layer Transition.

Descriptive Note : Doctoral thesis,

Corporate Author : CALIFORNIA INST OF TECH PASADENA GRADUATE AERONAUTICAL LABS

Personal Author(s) : Robey, Harry F , III

PDF Url : ADA188812

Report Date : 23 May 1986

Pagination or Media Count : 141

Abstract : An experimental study of boundary layer transition is conducted using the active surface heating technique. This technique is extended to provide a means for controllably and repeatedly introducing three dimensional disturbances into a laminar boundary layer. These generated harmonics are not sufficient to explain the transition from small linear oscillations to the large amplitude, broad band, three dimensional oscillations characteristic of a fully turbulent boundary layer. The effect of three dimensionality on boundary layer transition is then investigated through an analytical and experimental study of single oblique instability waves. Through a series of experiments, it is shown that certain conditions exist for which oblique waves are observed to be more unstable than any two dimensional wave. It is shown that oblique waves exhibit a non stationary period doubling behavior that is not seen in two-dimensional disturbances. A vortex pairing mechanism is proposed to explain the behavior, and is shown to occur in a manner consistent with the Biot-Savart law for the induced velocity field.

Descriptors :   *BOUNDARY LAYER TRANSITION, AMPLITUDE, BROADBAND, HARMONICS, HEATING, LAMINAR BOUNDARY LAYER, OSCILLATION, STABILITY, SURFACE TEMPERATURE, THESES, THREE DIMENSIONAL, TURBULENT BOUNDARY LAYER, TWO DIMENSIONAL, VELOCITY, WAVES, VORTICES, EXCITATION, NONLINEAR SYSTEMS, WATER TUNNELS, HYDRODYNAMICS, BOUNDARY LAYER CONTROL

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE