Natural convection from a vertical plane surface

Abstract

Theoretical studies of turbulent natural convection phenomena have for some time been hindered by a lack of any reliable experimental data. The primary objective of this investigation was the provision of such data... Mean velocity and temperature profiles have been measured. These are in general agreement with the only previous results which were obtained in 1921, but show substantial disagreements when compared with theoretical predictions. Distribution of frequency and amplitude in the turbulent temperature fluctuations have also been measured. In addition to the investigation of the turbulent boundary layer, a considerable number of experiments have been carried out on laminar and transitional boundary layers. The work on the laminar boundary layer was prompted by the discovery of the effect of a vertical temperature gradient outside the boundary layer. New similarity solutions to the laminar boundary layer equation have been derived for a wide range of conditions. These solutions suggest that the presence of a temerature gradient outside the boundary layer can cause instability, throughout the whole laminar region. Experimental measurements of local heat transfer rates and temperature profiles tend to confirm the theoretical results. Measurements in a transitional boundary layer show the variation of the local heat-transfer coefficient, together with the development of the mean temperature profiles and the temperature fluctuations. In the derivation of the theoretical results, a new method for the numerical solution of coupled, non-linear differential equations on a digital computer, as been developed. A comparison is made between this method and the more commonly used method of Bunge-Kutta. a.