TURBULENT BOUNDARY LAYER AND HEAT TRANSFER CHARACTE RISTICS OVER A ROUGH FLAT PLATE IN PRESSURE GRADIENTS

Abstract

In the present work, the turbulent convective transfer characteristics over a rough flat plate in heat both zero and adverse pressure gradient flows were investigated. Experimental and theoretical investigations were performed. A test set-up was designed and constructed for this investigation. A flat plate of 320 mm length and 120 mm width, made of brass was taken as the heating surface. The heating surface as placed at a distance of 1130 mm fron the beginning of the test section. The heating plate was heated by means of electric heaters. The heating condition was adjusted to supply uniforn heat flux to the plate. The roughness elenents were taken as rectangular brass ridges. The ridges height must be sufficiently snall compared with the local boundary layer thickness for the ridges to lie in the logarithmic part of the undisturbed velocity profile. The ridges were equally spaced along the heating surface to obtain unifornly distributed roughness arrays. The equivalent sandgrain roughness was calculated. For the equilibrium adverse pressure gradient flo, the freestream velocity was varied as U a x-0.215,