ANALYTICAL STUDY OF THE NEUTRAL STABILITY OF A MODEL HYPERSONIC BOUNDARY-LAYER

The neutral modes of a hypersonic boundary layer flow over an adiabati c flat plate are considered. A formulation of the governing second-ord er linear equation for the pressure disturbance is developed that lend s itself to the application of the WKB method over the entire boundary layer. This formulation provides analytic eigenvalues and eigenfuncti on relations for the pressure disturbances and is applicable to flows at moderate Mach numbers as well. Solutions are determined for the cas es of the wave speed c = 0 and c = 1, and show good qualitative agreem ent with numerical computations as well as results in the limit M(infi nity) --> infinity.