Experimental study of flow around a pole standing in a scour

Department of Mechanical Engineering, The National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan

Corresponding author: tsutsui@nda.ac.jp

Published online: 6 May 2015

Abstract

The characteristics of fluid flow and fluid force of the pole standing in scour were investigated with several different scour depths conditions by using a wind tunnel. The scour was modeled into a mortar, with an inverted circular cone. The diameter of the pole was 40 mm and the scour depth was changed from H / D (= depth / diameter of the pole) 0.25 to 1.75. The free stream velocity was 16 m / s, making the Reynolds number 4.2 × 10⁴. Flow visualization was carried out using a surface oil-film method and smoke-wire method. The surface pressure distributions on the pole and the scour were measured and the drag coefficient acting on the pole was determined by integrating the surface pressure distribution on the pole. The characteristics of the flow around the pole and the drag acting on the pole standing on the scour were clarified. The results show that as the scour depth become deep, the flow around the pole is extremely characteristic and the drag coefficient has a maximum value at Z / D = 0.25 and a minimum value at about the midpoint between the ground level and the bottom of the scour.