Accession Number : ADA309863

Title :   Investigation of the Physics of Screech in Supersonic Jets and Turbulent Boundary Layers at High Reynolds Number and Control of Separation Through Oscillatory Blowing.

Descriptive Note : Final rept. 1 Mar 93-1 Mar 96,

Corporate Author : ILLINOIS INST OF TECH CHICAGO FLUID DYNAMICS RESEARCH CENTER

Personal Author(s) : Nagib, Hassan ; Wark, Candace ; Naguib, Ahmed ; Wygnanski, Israel ; Hites, Michael

PDF Url : ADA309863

Report Date : 15 MAR 1996

Pagination or Media Count : 79

Abstract : Using a flapped NACA 0015 airfoil, measurements of static pressure and lift, with and without oscillatory forcing from the leading edge and flap, demonstrated effective separation control and lift enhancement over the range 0.1<M<0.4. Measurements showed that the lift increment was sensitive to the dimensionless forcing frequency. Additionally, a suction pressure coefficient of nearly -5.0 was produced on a previously stalled airfoil at M=0.4, indicating a region of supercritical flow on the airfoil, and suggesting that oscillatory blowing is a viable separation-control technique under compressible flow conditions. Using both the NDF test-section floor boundary layer and a suspended axisymmetric body, a range of momentum thickness Reynolds numbers of 7000<Re<50000 was investigated with a hot-wire anemometer. Streamwise mean and rms velocity and spectra in these boundary layers showed good agreement with established scaling observations. An increasing separation of scales and the appearance of a second low-frequency spectral peak were observed indicating a clear discrimination between inner and outer scales at high Reynolds number. Although some dependence on both axial and momentum thickness Reynolds number was observed, there appeared to be a linear relationship between friction velocity and free-stream velocity over this wide range of Reynolds numbers.

Descriptors :   *TURBULENT BOUNDARY LAYER, *FLAPS(CONTROL SURFACES), *SUPERSONIC FLOW, *AERODYNAMIC LIFT, OPTIMIZATION, TURBULENT FLOW, SWEPT WINGS, COMPRESSIBLE FLOW, STALLING, SHEAR STRESSES, WIND TUNNEL TESTS, SUPERCRITICAL FLOW, LEADING EDGES, MACH NUMBER, FREE STREAM, VISCOUS FLOW, FLOW SEPARATION, STATIC PRESSURE, PRESSURE DISTRIBUTION, REYNOLDS NUMBER, INCOMPRESSIBLE FLOW, SKIN FRICTION, MOMENTUM, HOT WIRE ANEMOMETERS, BOUNDARY LAYER CONTROL, BOUNDARY LAYER FLOW, LIFTING SURFACES.

Subject Categories : Aerodynamics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE