Accession Number:

ADA125436

Title:

Preliminary Rotor Wake Measurements with a Laser Velocimeter.

Descriptive Note:

Technical memo.,

Corporate Author:

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CENTER

Report Date:

1983-03-01

Pagination or Media Count:

92.0

Abstract:

An experimental investigation using a laser velocimeter LV was conducted in the Langley 4- by 7-Meter Tunnel to determine rotor wake characteristics. The purpose of the project was to define the effect of various fuselage widths and rotor-fuselage spacings on time-averaged and detailed time-dependent rotor wake velocity characteristics. Definition of time-dependent velocity characteristics was attempted with the LV by associating a rotor azimuth position with each velocity measurement. The results were discouraging in that no apparent time-dependent velocity characteristics could be discerned from the LV measurements. Since the LV is a relatively new instrument in the rotor wake measurement field, the cause of this lack of periodicity is as important a result as the basic research objectives. An attempt was made to identify the problem by simulated acquisition of LV-type data for a predicted rotor wake velocity time history. Power spectral density and autocorrelation function estimation techniques were used to further substantiate the conclusion that the primary cause of the lack of time-dependent velocity characteristics was the nonstationary flow condition generated by the periodic turbulence level that currently exists in the open-throat configuration of the wind tunnel.

Subject Categories:

  • Helicopters
  • Lasers and Masers
  • Test Facilities, Equipment and Methods

Distribution Statement:

APPROVED FOR PUBLIC RELEASE