Effects of Free-Stream Turbulence and Pressure Gradient on Flat-Plate Boundary-Layer Velocity Profiles and on Heat Transfer

Abstract

Experimental data indicating some effects of free-stream turbulence intensity on time-average boundary-layer velocity profiles and on heat transfer from a constant-temperature flat plate with a favorable pressure gradient are presented for local Reynolds numbers ranging from 4 × 104 to 4 × 105 and for free-stream turbulence intensities from 0.4 to 8.3 percent. It is concluded that, for the range of variables covered by the experiments: (a) The effect of free-stream turbulence intensity on heat transfer through the laminar boundary layer with a zero pressure gradient is negligible; (b) for a given Reynolds number, the local Nusselt number increases with increasing free-stream turbulence intensity when a pressure gradient is present, the boundary-layer profiles for these conditions changing with a variation in free-stream turbulence intensity; and (c) no increase in Nusselt number with increase in free-stream turbulence intensity occurs for turbulent boundary layers with a favorable pressure gradient.