Flow around a Cone in a Thin Boundary Layer (Variation of the Surface Pressure for an Apex Angle)

Abstract

Surface pressure distributions on a cone in a thin boundary layer have been measured to clarify the relation between the distributions and the flow structure formed around the cone. The apex angle 2α of cone is in the range of 15 to 90°and the height is 50mm. The Reynolds number based on the height is 2.31×104 , and the relative boundary layer thickness is 0.44. The main directions of limited streamlines on the generatrix at θ=0°are predicted from pressure gradient forces in height and circumferential directions, and the front stagnation point which the streamline faced on the cone surface bifurcates downward and circumferentially on the generatrix will be determined as the position where the ratio of the pressure gradients forces is order of 1. Then, the height of the point have a peak value around 2α=45°. The maximum pressure coefficient at θ=0°can be expressed as the cosine law with respect to α . The surface pressure above the position of the maximum pressure at θ=0°can be related to 2α as well as the angle which the curved streamline in upstream region faces on the cone surface. The pressure drag coefficient of the cone mainly depends on the surface pressure distribution at θ=0°varied with 2α .