Accession Number : ADA137775

Title :   An Investigation of Turbulence Mechanisms in V/STOL Upwash Flow Fields.

Descriptive Note : Annual rept. no. 1, Mar 82-Mar 83,


Personal Author(s) : Gilbert,B

PDF Url : ADA137775

Report Date : May 1983

Pagination or Media Count : 36

Abstract : The results of the first year of an experimential investigation of the abnormally high turbulence level and mixing layer growth rate characteristics found in the upwash regions of V/STOL flows in ground effect are presented. The overall objectives of this program were to examine the origin of the increased fluctuations, to systematically characterize the development and structure of the upwash, and to determine the parameters that influence these characteristics. The approach adopted was to investigate the fundamental turbulent V/STOL upwash mechanisms in increasingly more complex flow configurations. In the first year's effort, a two-dimensional upwash was formed by the collision of opposed two-dimensional wall jets. Extensive measurements were made in the two-dimensional wall jet to establish the starting conditions of the upwash. Evaluation of these measurements have shown classical wall jet behavior, and by the time the wall jet reaches the collision zone, both the mean and turbulence profiles are fully developed. A unique set of velocity profiles was obtained at six locations in the upwash. By using an X-probe anemometer, two components of the velocity were found simultaneously. This baseline set of two component velocity profiles has never been reported before. While the turbulence levels and mixing layer growth rates were larger than those found in a free two-dimensional jet, these values were less than those reported by previous investigators.

Descriptors :   *Turbulent flow, *Ground effect, Vertical takeoff aircraft, Short takeoff aircraft, Interactions, Flow fields, Velocity, Experimental design, Anemometers, Jet flow, Cross flow, Measurement, Walls, Jet mixing flow, Rates, Layers, Two dimensional flow

Subject Categories : Test Facilities, Equipment and Methods
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE