Author(s)

A. Goharzadeh, L. Khezzar & A. Molki

Abstract

This paper presents an experimental study of laminar flow past a smoothed hemisphere using the Particle Image Velocimetry technique. The experimental setup consists of a rectangular channel, through which water flows over a 30-mm diameter hemisphere mounted on a horizontal surface. From the measured velocity distribution around the hemisphere a physical insight into the flow is presented. Vertical and horizontal 2D velocity distributions are obtained for a constant Reynolds number of Re=800, corresponding to a regime of laminar flow. Measurements revealed the three dimensional structure of the flow including a horseshoe vortex surrounding the hemisphere and arch-shaped vortices in the downstream region. Both instantaneous and average velocity distribution were studied. The location of the reattachment point, the separation line, and the reverse flow are identified and discussed. Keywords: PIV, horseshoe vortex, hemisphere, dome. 1 Introduction Hemispherical shapes are widely used in many industrial applications such as domed roofs in civil engineering to cover buildings or above-ground steel tanks to store fluids. Domes were used in hydraulic channels as a mechanism to generate and study the shedding of hairpin vortices in their wake [1]. Predicting the three dimensional structure of flow field around a hemisphere is challenging for engineers due to the complexity added by the curved surface. Therefore, in order to ensure proper design of such engineering structures, detailed knowledge of the flow structure around them is necessary. Advances in Fluid Mechanics IX 29

Keywords

PIV, horseshoe vortex, hemisphere, dome.