Determination of Parameters for Boundary Layer Development in Rough Plates

Abstract

Research on the development of boundary layer and its parameters such as nominal boundary layer thickness, the displacement thickness, the momentum thickness and the energy thickness has been carried out for various objects. In this paper, the velocity distribution and the boundary layer development has been studied for flat plates with four different roughness’ (125μm, 290μm, 345μm, 375μm) by using emery paper. Experimental observations undertaken in a low speed wind tunnel at National Institute of Technology, Rourkela for such surfaces are taken into consideration. The effect of roughness, on these plates has been studied here. The plates have been inclined at four different angles (0°, 2°, 4°, 6°) with respect to the leading edge in order to create a negative pressure and the variation in boundary layer is observed. Due to no-slip condition, the velocity of fluid near the wall is assumed to be zero. The speed of fluid increases from zero at the boundary of the plate to the free stream velocity of the fluid in the direction normal to the boundary. The locale of fluid within which the gradient of velocity occurs is called the boundary layer. Boundary layer is illustrated by four fundamental parameters to describe its size and state, namely boundary layer thickness, displacement thickness, momentum thickness and the energy thickness. In this paper, the variation of these four different parameters of boundary layer has been studied. The parameters are observed to depend upon the main stream velocity (V), the distance from the leading edge (χ), the roughness coefficient (γ) and the angle of inclination of the flat plates (Φ).