Mean velocity and pressure and velocity spectral measurements within a separated flow around a prolate spheroid at incidence

Hot-wire velocity measurements were made on the lee-side of a 6:1 prolate spheroid, ReL = 4.2xl0, at 10° and 20° angles of attack, and at x/L = 0.600 and 0.772. The dominant feature of each of these flowfields is the presence of a shed vortex due to cross-flow separation. This is a source of considerable noise and vibration. At a = 10° the most turbulent fluid is confined to the near wall region. At a = 20° the most turbulent fluid appears away from the wall at locations where the flow is separating. Velocity spectra for regions with weaker 3-D effects exhibit features that are observed for equilibrium flows. Spectra in strong vortical flow regions show unusual and apparently non-equilibrium behavior. This behavior has some qualitative similarities with surface pressure fluctuation spectra. Nomenclature______________ L Model length, 1.37 m. p Pressure fluctuation at the model surface qe Dynamic pressure at boundary layer edge Graduate Assistant, Student Member AIAA f Jack E. Cowling Professor, Fellow AIAA * Former Graduate Assistant 5 Member AIAA, now at David Taylor Model Basin CD/NSWC, Bethesda, MD 1 Associate Professor, Senior Member AIAA Copyright © 1998 By M. Goody, R. Simpson, M. Engel, C. Chesnakas, and W. Devenport. Published by the American Institute of Aeronautics and Astronautics with permission. ReL TKE Distance from model surface along a line perpendicular to the model axis Reynolds number, U_L / v Turbulent kinetic energy, denned as, TKE = V2p(u+ V*+ w) Friction velocity, (%/p) u, v, w Fluctuating velocity components in the directions of U, V, and W, respectively Velocity component in a plane parallel to the surface, in the axial direction Total velocity at edge of shear layer Wind tunnel free-stream velocity Mean velocity component normal to the local model surface Mean velocity component in a plane parallel to the local model surface and perpendicular to the axial direction (positive in -$ direction) Axial distance from the nose of the model ru/v Angle of attack of model relative to incoming flow Boundary layer thickness Boundary layer streamwise displacement thickness, defined as U