Accession Number : ADA292819

Title :   Investigating the use of Smart Acoustically Active Surfaces for Flow Separation Control in Turbomachinery.

Descriptive Note : Final rept. 1 Sep 91-31 Aug 94,

Corporate Author : MISSISSIPPI UNIV UNIVERSITY DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Sinha, Sumon K.

PDF Url : ADA292819

Report Date : 21 FEB 1995

Pagination or Media Count : 60

Abstract : In order to develop a mechanically simple and robust actuator for active flow separation control on axial compressor blades, three different types of acoustic transducers were tested in a wind tunnel. Flow separation on a cylinder in cross flow was used. The first transducer had an internally mounted acoustic speaker blowing through a slot. It could control flow separation only for low Reynolds number laminar flows. A flush mounted high-frequency circular piezo-electric transducer was tried next. It was marginally effective only around the laminar-turbulent transition regime. Since it could not focus the perturbations over a small area, the Acoustosurf was developed next. It consisted of an array of flush mounted narrow strip shaped acoustic transducers capable of detecting surface pressure fluctuations prior to separation. When the appropriate strips were excited at the predominant fluctuation frequency, separation was delayed for transitional and tripped flows. It is believed that the Acoustosurf produces a synergistic interaction between roughness, surface compliance and acoustic radiation to redirect the kinetic energy of the flow by exploiting flow instabilities. Negligible power is therefore needed to operate the Acoustosurf. This has attracted the attention of several aircraft manufacturers. (AN)

Descriptors :   *UNSTEADY FLOW, *FLOW SEPARATION, *AXIAL FLOW COMPRESSORS, ACOUSTIC WAVES, SURFACE ROUGHNESS, TURBULENT FLOW, KINETIC ENERGY, WIND TUNNEL TESTS, PERTURBATIONS, ACTUATORS, ACOUSTIC SCATTERING, BOUNDARY LAYER TRANSITION, LAMINAR FLOW, SOUND PRESSURE, INSTABILITY, REYNOLDS NUMBER, SYNERGISM, ELECTROACOUSTIC TRANSDUCERS, TURBOMACHINERY, CROSS FLOW, PIEZOELECTRIC TRANSDUCERS, AXIAL FLOW COMPRESSOR BLADES.

Subject Categories : Fluid Mechanics
      Hydraulic and Pneumatic Equipment
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE