The Heat Transfer and Fluid Dynamics of Concave Surface Curvature
Abstract
This project investigated the mechanisms responsible for the known increases in shear stress and convective heat transfer when a turbulent boundary layer flows over a concave wall compared to a similar flow over a flat wall. The effects of grid-generated Free-Stream Turbulence (FST level< or = 7.5% ) were also examined for flat and concave-wall TBL's. The work was conducted in a large scale boundary layer using low-speed water flow. Momentum thickness Re was = 1400. Surface heat transfer rate was measured with a constant temperature metal surface and by use of a liquid crystal surface. Temperature profiles were obtained by miniature thermocouple probe down to y+ = 3 and all three velocity components by a 3-D, laser velocimeter down to y+ = 7. Heat transfer and wall shear stress were both found to be augmented by curvature and free-stream turbulence applied separately, but the combined effect of curvature and FST is not simply the sum of the individual effects. In the case of wall stress, the effects of curvature are much larger than FST effects once the flow develops downstream. The nature of the interaction is being investigated using a working hypothesis based on the ideas of active (Reynolds stress producing) and inactive can stimulate only a limited increase (order 25%) in wall friction coefficient. However, for the moderate levels of FST used in this study, no such saturation process exists to limit the increase in surface heat transfer rate.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 21, 1988
- Accession Number
- ADA207811
Entities
People
- J. P. Johnston
- P. Bradshaw
- R. J. Moffat
Organizations
- Stanford University