Characteristics of Fluid Flow and Heat Transfer in Combined-Convection Boundary Layer along a Vertical Plate.

Abstract

Fluid flow and heat transfer characteristics in a turbulent combined-convection boundary layer in air along a vertical heated plate have been investigated with normal hot and cold wires. The measured heat transfer rates and turbulent quantities show that the turbulent transition moves downstream with a slight increase in freestream velocity. Then, the heat transfer rate rapidly decreases to about 40% of that obtained in the turbulent natural-convection boundary layer, and velocity and temperature fluctuations become smaller in amplitude and change from random to harmonic at a specific frequency. Thus, the characteristics of the turbulent combined-convection boundary layer differ in several respects from those observed in both natural and forced convection. Based on the experimental results, the regimes of boundary layer flows are classified as a function of local Reynolds and Grashof numbers.