Accession Number : ADA190433

Title :   The Sensitivity of Boundary Layer Instability Growth Rates to Compliant Wall Properties.

Descriptive Note : Master's thesis,

Corporate Author : PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB

Personal Author(s) : Joslin, R D ; Morris, Philip J

PDF Url : ADA190433

Report Date : Dec 1987

Pagination or Media Count : 102

Abstract : A spatial stability analysis is performed for the boundary layer over a non-isotropic compliant surface. A spectral approximation is used to obtain a solution of the equations governing the normal velocity component of a small disturbance. The streamwise wavenumber becomes the eigenvalue in the nonlinear eigenvalue problem formed. The resulting solution spectrum contains values which indicate the growth rates of the Tollmien-Schlichting and flow-induced surface instabilities. It is shown that the Tollmien-Schlichting instability is most sensitive to changes in the surface properties. It is shown that varying the surface properties can reduce the growth rate fo the Tollmien Schlichting instability but has little effect on the flow-induced surface instability. The surface properties are optimized using a minimization algorithm. It is found that appropriate surface properties lead to a decrease in the growth rates of the flow instability. The simple mechanical model for the compliant surface is an elastic plate over spring-rigid supports. The functional relationship between the flexural rigidity, thickness, and modulus of elasticity of the plate provides a means to vary the properties and determine the effect on the instabilities. It is found that by keeping the flexural rigidity essentially constant and simultaneously increasing the plate thickness and decreasing the modulus of elasticity a decrease in the growth rate of the Tollmien-Schlichting instability is obtained. Alternatively, by keeping the plate thickness and modulus of elasticity essentially constant and decreasing the flexural rigidity a decrease in the growth rate of the Tollmien-Schlichting instability results.

Descriptors :   *BOUNDARY LAYER, *COMPLIANT WALLS, *STABILITY, ALGORITHMS, ANISOTROPY, EIGENVALUES, ELASTIC PROPERTIES, EQUATIONS, FLEXURAL PROPERTIES, FLOW, GROWTH(GENERAL), MECHANICAL COMPONENTS, MODELS, MODULUS OF ELASTICITY, NONLINEAR ANALYSIS, PLATES, PROBLEM SOLVING, RATES, RIGIDITY, SENSITIVITY, SOLUTIONS(GENERAL), SPATIAL DISTRIBUTION, SPECTRA, SURFACE PROPERTIES, SURFACES, THICKNESS, BOUNDARY LAYER TRANSITION

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE