Accession Number : ADA130923

Title :   Scanning Laser Doppler Anemometer and Its Application in Turbulent Separated Flow.

Descriptive Note : Technical rept. Mar 80-Jun 83,

Corporate Author : SOUTHERN METHODIST UNIV DALLAS TX DEPT OF CIVIL AND MECHANICAL ENGINEERING

Personal Author(s) : Chehroudi,Behrouz ; Simpson,Roger L

PDF Url : ADA130923

Report Date : Jul 1983

Pagination or Media Count : 147

Abstract : A rapidly scanning directionally-sensitive fringe-type Laser Doppler Anemometer (SLDA) which scans the measurement volume perpendicular to the optical axis of the transmitting optics is described. Scan frequencies up to 60 Hz over scan distances of 40 cm. have been used, although scan frequencies up to 150 Hz are possible. The maximum scanning velocity of the measurement volume that can be used is directly proportional to the shift frequency of the Bragg cell since each signal producing particle must cross a minimum number of fringes to produce a valid signal. Signal averaging bias is lower with a scanning LDA than with pointwise measurements. Results obtained for a separating turbulent boundary layer show that very good mean and rms velocity profiles of the fraction of time that the flow moves downstream can be obtained in less than one minute of data acquisition. Space-time correlations show that the degree of coherence between outer region and near wall region increases as flow goes into separated zone. (Author)

Descriptors :   *Anemometers, *Scanning, *Turbulent flow, *Flow separation, Wind velocity, Fluid mechanics, Experimental data, Wind tunnels, Turbulent boundary layer, Coherence, Doppler systems, Lasers, Optics, Transmitting, Data acquisition, Data processing, Instrumentation

Subject Categories : Test Facilities, Equipment and Methods
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE