Free Stream Turbulence. A Unified Investigation of its Effects on Skin Friction and Heat Transfer.
Abstract
Existing prediction formulas for the effect of freestream turbulence (PST) on skin friction and heat transfer, based on measurements in low-intensity grid turbulence, fail at high intensities typical of the upstream stages of gas turbines. However, the previous evidence for this came from tests with various unconventional turbulence generators. In the present work measurements were made on the downstream-moving surface of a conveyor belt. This increased the effective value of Tu, the ratio of r.m.s. free-stream intensity to the veiocity difference across the boundary layer. Thus conventional grids could be used to generate high Tu. Heat transfer was measured by a quasi-transient technique. A fixed heating lamp shone on the belt near its upstream end. and the streamwise decrease of surface temperature was measured using a chordwise strip of liquid crystals. Conductive heat transfer into the belt was calculable. so convective heat transfer into the airstream could be deduced. Skin-friction results collapse fairly well using Hancock & Bradshaw's combination of intensity and length scale but lie well above their low-Tu correlation. (AN)
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1995
- Accession Number
- ADA299575
Entities
People
- Donald M. Bott
- Peter Bradshaw
Organizations
- Stanford University