The Effect of Free-Stream Turbulence on Heat Transfer Rates

Abstract

Publisher Summary This chapter investigates the effects of free-stream turbulence on heat transfer rates. The essential characteristic of a turbulent free stream resides in the fact that the oncoming velocity, U ∞ , is quasi-steady, and that locally, at every point in the stream, the velocity fluctuates in magnitude and direction with respect to time. The effect of the free-stream turbulence on heat transfer rates can also be obtained in terms of the boundary-layer concept. First, a blunt body is considered, specifically an infinite cylinder in cross flow. In the flow regime considered, there exists an important relation between the flow field and the temperature field which may be described as unidirectional coupling. Local measurements on a cylinder in the laminar range near the stagnation point, and local measurements on a turbulent boundary layer on a flat plate with a favorable pressure gradient are also examined. The results of the experiments discussed are summarized in the form of several qualitative statements. Some of them are free-stream turbulence affecting heat (and mass) transfer rates both locally and through an effect on the flow configuration, and the combination of pressure gradient and free-stream turbulence may affect the heat transfer rates across laminar boundary layers on plates.