Accession Number : ADA194191

Title :   Noise Generation and Boundary Layer Effects in Vortex-Airfoil Interaction and Methods of Digital Hologram Analysis for these Flow Fields.

Descriptive Note : Interim rept. no. 2, 28 Nov 87-28 Mar 88,

Corporate Author : MAX-PLANCK-INST FUER STROEMUNGSFORSCHUNG GOETTINGEN (GERMANY F R)

Personal Author(s) : Meier, G E

PDF Url : ADA194191

Report Date : 31 Mar 1988

Pagination or Media Count : 10

Abstract : For the generation of impulsive sound waves caused by parallel interaction of a vortex and an airfoil in a plane flow field, two different mechanisms are responsible by experimental evidence. The first one originates from the area of the stagnation point of the airfoil: a temporal increase of pressure and density - in consequence of the incoming vortex - relaxes by sound wave emission, when the vortex vanishes behind the airfoils nose. This is called a compressibility wave. The second one is reasoned by a supersonic flow regime, which appears, when the stationary airfoil flow is augmented by the flow field of the vortex: at the shoulder of the airfoil we get an unsteady return to subsonics by a shock wave. This moves upstream after the vortex has passed and is named transonic wave. Evidently both mechanisms only occur, if the flow field at the airfoil is augmented by the vortex, i.e. the vortex has a special spin orientation with respect to the airfoil. Keywords: Sound generation mechanism; Vortex airfoil interaction; Image processing; Image analysis; Vortex generation system.

Descriptors :   *AIRFOILS, *HOLOGRAMS, *INTERACTIONS, *VORTICES, *AERODYNAMIC NOISE, *FLOW VISUALIZATION, AUGMENTATION, COMPRESSIVE PROPERTIES, DIGITAL SYSTEMS, EMISSION, FLOW, FLOW FIELDS, GENERATORS, IMAGE PROCESSING, IMPULSE NOISE, NOISE GENERATORS, NOSES, ORIENTATION(DIRECTION), PARALLEL ORIENTATION, SHOCK WAVES, SOUND WAVES, SPINNING(MOTION), STAGNATION POINT, STATIONARY, SUPERSONIC FLOW, VORTEX GENERATORS

Subject Categories : Fluid Mechanics
      Acoustics
      Holography

Distribution Statement : APPROVED FOR PUBLIC RELEASE