Accession Number : ADA114942

Title :   Viscous-Inviscid Interactions over Transonic Tangentially Blown Airfoils.

Descriptive Note : Final rept. 16 Feb 81-15 Feb 82,


Personal Author(s) : Malmuth,N D ; Murphy,W D ; Cole,J D

PDF Url : ADA114942

Report Date : Apr 1982

Pagination or Media Count : 74

Abstract : A viscous interaction model has been developed for the treatment of tangentially blown transonic airfoils. The coupling procedure employs a small disturbance approximation for the nearly inviscid outer flow and interacts this region with the boundary layer, wall jets, and propulsive wake. Keller's box scheme is utilized to treat these viscous zones. On the basis of parametric studies for laminar flow, the skin friction drag appears to increase nearly linearly with the blowing coefficient CJ for a fixed Mach number-incidence combination, giving a substantial scrubbing drag penalty for overblowing beyond the CJ necessary to achieve attached flow. Increases in wave drag over the same range of CJ are much smaller. Associated supercirculation gains with overblowing are inefficient from the standpoint of L/D due to the large values of scrubbing drag. The role of surface skin friction in modifying the viscous cambering of the airfoil in the laminar case is compared to a turbulent modification of the coupling model. Whereas the laminar results show a lift increase associated with the cambering action of the wall jets, the turbulent solutions indicate a decambering effect resulting in decreased lift. Also evident with the turbulent results are increased skin friction and wave drag. A explanation of these trends in terms of the Karman momentum equation is given. (Author)

Descriptors :   *Airfoils, *Viscous flow, *Inviscid flow, Transonic airfoils, Interactions, Boundary layer, Coupling(Interaction), Models, Laminar flow, Parametric analysis, Drag, Skin friction, Turbulence, Viscosity, Blowers, Coefficients

Subject Categories : Aircraft
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE