Flow over Rectangular Cylinders Immersed in a Turbulent Boundary Layer : Part 1, Correlation between Pressure Drag and Boundary-Layer Characteristics

Abstract

Measurement of the pressure distribution on the two-dimensional rectangular cylinders are correlated with the characteristics of a smooth-wall turbulent boundary layer in which the cylinders are immersed. The contribution of the shear stress on the horizontal upper surface of the cylinders to the total drag is estimated to be a few per cent at most over the entire range of the width-to-height ratios tested. For flows with zero pressure gradient, correlations are obtained for the variation of pressure drag with the height of the cylinder h, which are analogous in form to the law of the wall for the boundary-layer velocity profile. The coefficients of the law of the wall for the drag are functions of simply the width-to-height ratio of the cylinder. This law of the wall is valid up to h/σ = 1.37, where σ is the thickness of the boundary layer at the location of the cylinders. The contribution of the base pressure to the pressure drag coefficient is found to be sensitive to the width-to-height ratio of the cylinders, while that of the pressure on the upstream face is almost constant over the entire range of the width-to-height ratios treated in this investigation.