A SNOWPLOW MODEL OF HYPERSONIC UNSTEADY FLOWS,
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1967
- Accession Number
- AD0647267
Entities
People
- A. F. Charwat
- J. Aroesty
- J. D. Cole
- S. Y. Chen
Organizations
- RAND Corporation