EXPERIMENTAL STUDIES OF THE NOISE PRODUCED IN A SUPERSONIC NOZZLE BY UPSTREAM ACOUSTIC AND THERMAL DISTURBANCES

A novel noise source mechanism whereby sound is produced by time-dependent entropy non-uniformities in a flow with a mean velocity gradient is investigated experimentally. A steady accelerating flow was produced in a rectangular supersonic nozzle with an entrance Mach number of 0.2 - and an exit Mach number of 1.38. A rotary valve bleed flow system and an electrical wire resistance heater upstream of the nozzle introduced mass flow and temperature fluctuations into the nozzle flow at frequencies up to 500 Hz. Sound measurements were made at six positions along the nozzle and outside the nozzle assembly, which was enclosed in an anechoic chamber. All data acquisition and processing was done with a computer-controlled data acquisition system. By synchronization of the bleed flow and heater, a pure temperature disturbance without an associated pressure disturbance caused by heating was produced. Excellent agreement was found between the nozzle sound measurements and one-dimensional small disturbance theory. External field measurements yield jet noise levels and spectra agreeing with other reported studies, spatial variations of the sound field due to a pure pressure fluctuation at the nozzle exit, and cross-correlation data between the external sound field and the pressure fluctuations at the nozzle exit.

• Corporate Authors:

  California Institute of Technology

  Jet Propulsion Laboratory
  Pasadena, CA  United States 

  Office of the Secretary of Transportation

  Office of Noise Abatement, 1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Auerbach, J M
• Publication Date: 1976-6

Media Info

• Pagination: 259 p.

Subject/Index Terms

• TRT Terms: Aircraft noise; Data collection; Information entropy; Jet engines; Noise; Power spectra; Supersonic flow; Turbojet engines
• Uncontrolled Terms: Supersonic nozzles
• Old TRIS Terms: Jet engine noise
• Subject Areas: Environment; Vehicles and Equipment;

Filing Info

• Accession Number: 00153993
• Record Type: Publication
• Source Agency: National Technical Information Service
• Report/Paper Numbers: DOT/TST-76-105
• Contract Numbers: DOT-OS-20197
• Files: NTIS, USDOT
• Created Date: Jun 17 2002 12:00AM