Turbulence measurements in a heated, concave boundary layer under high-free-stream turbulence conditions
- ISITEM, Nantes (France). Lab. de Thermocinetique
- Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Mechanical Engineering
Turbulence measurements for both momentum and heat transfer are taken in a low-velocity, turbulent boundary layer growing naturally over a concave wall. The experiments are conducted with negligible streamwise acceleration and a nominal free-stream turbulence intensity of {approximately} 8%. Comparisons are made with data taken in an earlier study in the same test facility but with a 0.6% free-stream turbulence intensity. Results show that elevated free-stream turbulence intensity enhances turbulence transport quantities like {ovr uv} and {ovr vt} in most of the boundary layer. In contrast to the low-turbulence cases, high levels of transport of momentum are measured outside the boundary layer. Stable, Goertlerlike vortices, present in the flow under low-turbulence conditions, do not form when the free-stream turbulence intensity is elevated. Turbulent Prandtl numbers, Pr{sub t}, within the log region of the boundary layer over the concave wall increase with streamwise distance to values as high as 1.2. Profiles of Pr{sub t} suggest that the increase in momentum transport with increased free-stream turbulence intensity precedes the increase in heat transport. Distributions of near-wall mixing length for momentum remain unchanged on the concave wall when free-stream turbulence intensity is elevated. Both for this level of free-stream turbulence and for the lower level, mixing length distributions increase linearly with distance from the wall, following the standard slope. However, when free-stream turbulence intensity is elevated, this linear region extends farther into the boundary layer, indicating the emerging importance of larger eddies in the wake of the boundary layer with the high-turbulence free stream. Because these eddies are damped by the wall, the influence of the wall grows with eddy size.
- OSTI ID:
- 194227
- Report Number(s):
- CONF-940626-; ISSN 0889-504X; TRN: IM9611%%68
- Journal Information:
- Journal of Turbomachinery, Vol. 118, Issue 1; Conference: 39. international gas turbine and aeroengine congress and exposition, The Hague (Netherlands), 13-16 Jun 1994; Other Information: PBD: Jan 1996
- Country of Publication:
- United States
- Language:
- English
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