An Experimental Study of the Effects of Nonuniform Wall Temperature on Heat Transfer in Laminar and Turbulent Axisymmetric Flow Along a Cylinder

Abstract

Measurements of both the hydrodynamic and thermal characteristics of flow over an axial cylinder at subsonic speeds are reported. It was found that the boundary layer along an axial cylinder tends to become asymmetrical as it approaches the transition point. This asymmetry vanishes again in turbulent flow. For both laminar and turbulent flow, the average boundary-layer growth could be predicted by the standard flat-plate relationships, and simple methods were deduced for determining the effective hydrodynamic length of the boundary layers. Local and total heat-transfer measurements were made with both laminar and turbulent flow for various unheated starting lengths followed by linearly increasing wall temperatures. For laminar flow, agreement with theory was obtained, this agreement being improved by the Seban and Bond cylindrical curvature correction. The turbulent-flow results indicated preference for the theory of Seban. Isothermal equations represent turbulent heat transfer within approximately 20 per cent when the wall-temperature variations are not too abrupt.