An Investigation of Turbulence Mechanisms in V/STOL Upwash Flow Fields.
Annual rept. no. 1, Mar 82-Mar 83,
GRUMMAN AEROSPACE CORP BETHPAGE NY RESEARCH AND DEVELOPMENT CENTER
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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 VSTOL 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 VSTOL upwash mechanisms in increasingly more complex flow configurations. In the first years 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.
- Test Facilities, Equipment and Methods
- Fluid Mechanics