
Accession Number : AD0702106
Title : HYPERSONIC AIRFOILS OF MAXIMUM LIFTTODRAG RATIO.
Descriptive Note : Technical rept.,
Corporate Author : TEXAS UNIV AUSTIN APPLIED MECHANICS RESEARCH LAB
Personal Author(s) : Thompson,Roger A. ; Hull,David G.
Report Date : AUG 1969
Pagination or Media Count : 34
Abstract : The problem of determining the slender, hypersonic airfoil shape which produces the maximum lifttodrag ratio for a given profile area, chord, and freestream conditions is considered. For the estimation of the lift and the drag, the pressure distribution on a surface which sees the flow is approximated by the tangentwedge relation. On the other hand, for surfaces which do not see the flow, the PrandtlMeyer relation is used. Finally, base drag is neglected, while the skinfriction coefficient is assumed to be a constant, average value. The method used to determine the optimum upper and lower surfaces is the calculus of variations. Depending on the value of the governing parameter, the optimum airfoil shapes are found to be of three types. For low values of the governing parameter, the optimum shape is a flat plate at an angle of attack followed by slightly concave upper and lower surfaces. The next type of solution has a finite thickness over the entire chord with the upper surface inclined so that the flow is an expansion. Finally, for the last type of solution, the upper surface begins with a portion which sees the flow and is followed by an inclined portion similar to that above. For all of these solutions, the lower surface sees the flow. Results are presented for the optimum nondimensional airfoil shape, its dimensions, and the maximum lifttodrag ratio. To calculate an actual airfoil shape requires an iteration procedure due to the assumption on the skinfriction coefficient. However, simple results can be obtained by assuming an approximate value for the skinfriction coefficient. (Author)
Descriptors : (*AIRFOILS, HYPERSONIC CHARACTERISTICS), SLENDER BODIES, OPTIMIZATION, LIFT, DRAG, PRESSURE, DISTRIBUTION, SKIN FRICTION, FLAT PLATE MODELS, ANGLE OF ATTACK
Subject Categories : Aerodynamics
Aircraft
Fluid Mechanics
Distribution Statement : APPROVED FOR PUBLIC RELEASE