An Investigation of Turbulence Mechanisms in V/STOL Upwash Flow Fields.
Abstract
This report presents results of an experimental investigation of the abnormally high turbulent mixing layer growth rate characteristics found in the upwash regions of V/STOL flows in ground effect. The fundamental turbulent V/STOL upwash mechanisms were investigated in increasingly more complex flow configurations. Most of this study uses the two-dimensional upwash formed by the collision of opposed two-dimensional wall jets. Initial parameters used to characterize the upwash formation were identified as the maximum wall jet velocity and wall jet half velocity width. Upwash measurements were taken in flows formed from equal wall jets with the same maximum velocities and equal wall jets with the same half widths. While mixing layer growth rates were larger than those found in a free two-dimensional jet, these values were less than those previously reported. An explanation based on non-similarity conditions in the flow is offered. Abnormally high turbulence levels reported by other investigators were not found. The increased growth rate seem to be a direct effect of the head-on collision process. There is an indication that in the far field the upwash growth characteristics are approaching those found in free jets which has profound implications to the turbulence modelers.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 15, 1985
- Accession Number
- ADA166286
Entities
People
- Barry Gilbert
Organizations
- Grumman