Accession Number : AD0647267

Title :   A SNOWPLOW MODEL OF HYPERSONIC UNSTEADY FLOWS,

Corporate Author : RAND CORP SANTA MONICA CALIF

Personal Author(s) : Aroesty,J. ; Chen,S. Y. ; Charwat,A. F. ; Cole,J. D.

Report Date : FEB 1967

Pagination or Media Count : 20

Abstract : The pressure on a slender linearly accelerating airfoil or body of revolution traveling at high speed is estimated by using snowplow theory in a plane transverse to the direction of motion. The theory is valid for rapid accelerations and provides a quantitative estimate of the effect of acceleration on the air forces. The significant parameter measuring the effect is shown to be a Froude number, Fr = (body length) (acceleration)/(speed) squared. The results from this analysis show that only in extreme cases does linear acceleration or deceleration exert an important effect on air forces. For example, a 50-ft body accelerating 1000 g at Mach 4 has approximately 10 per cent larger wave resistance than in steady flight. The theory is extended to unsteady forces acting on two-dimensional oscillating airfoils. A pressure formula which is valid for linear and nonlinear oscillations is obtained, and comparisons are made with the exact, linearized gasdynamic theory for a hypersonic slender wedge. These comparisons indicate that Newtonian theory is qualitatively correct but quantitatively not very accurate for the calculation of unsteady stability derivatives. (Author)

Descriptors :   (*HYPERSONIC FLOW, STABILITY), (*AIRFOILS, PRESSURE), ACCELERATION, SLENDER BODIES, THEORY, OSCILLATION, WEDGES, MATHEMATICAL MODELS

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE