Accession Number : ADA328847

Title :   Laminar Turbulent Transition in a Hypersonic Boundary Layer. Receptivity and Instability Pre-History.

Descriptive Note : Final rept.,

Corporate Author : MOSCOW INST OF PHYSICS AND TECHNOLOGY DOLGOPRUDNYI (RUSSIA)

Personal Author(s) : Fedorov, Alexander V.

PDF Url : ADA328847

Report Date : JUL 1997

Pagination or Media Count : 72

Abstract : This report results from a contract tasking Moscow Inst. of Physics and Technology as follows: The contractor will perform research in accordance with contractor's proposal entitled, 'Laminar-Turbulent Transition in an Hypersonic Boundary Layer.' This report addresses the initial phase of hypersonic boundary-layer transition comprising excitation of unstable normal modes and their downstream evolution from receptivity regions to the instability growth onset (instability pre-history problem). It is shown that this phase is more complicated than in subsonic and moderate supersonic cases due to the following features of the disturbance field: (1) the first and second modes are synchronized with acoustic waves near the body nose region; (2) further downstream the first mode is synchronized with entropy/vorticity waves; (3) near the instability growth onset the first mode is synchronized with the second mode. Disturbance behavior in the synchronism regions (2) and (3) are studied using the multiple-mode method, which accounts for interaction between modes of discrete and continuous spectrum due to nonparallel effects of the mean flow. It is shown that vorticity/entropy waves are partially swallowed by the boundary layer and effectively generate the first mode due to Synchronism (2). This mechanism can compete with the leading edge receptivity to the freestream acoustic waves in cases of 'quiet' freestream conditions and conical body configurations. The inter-mode exchange rule coupling input and output characteristics of the first and second modes crossing the branch point vicinity was established. Combination of the receptivity estimates related to Synchronism (2) and the inter-mode exchange rule related to Synchronism; (3) allows the evaluation of instability initial amplitudes required for the PSE calculations of the transition onset point.

Descriptors :   *TURBULENT BOUNDARY LAYER, *BOUNDARY LAYER TRANSITION, *HYPERSONIC CHARACTERISTICS, *LAMINAR BOUNDARY LAYER, ACOUSTIC WAVES, TURBULENCE, VORTICES, COMPUTATIONAL FLUID DYNAMICS, RUSSIA, FLOW NOISE, SUPERSONIC CHARACTERISTICS, AEROTHERMODYNAMICS, FREE STREAM, ENTROPY, BOUNDARY LAYER FLOW, HYPERSONIC FLOW.

Subject Categories : Aerodynamics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE