HYDRODYNAMIC FORCE EXERTING ON A SQURE PILLAR IN STEADY FREE SURFACE SHEAR FLOWS

Hydrodynamic force exerting on a squre pillar placed in steady free surface shear flows were investigated experimentally. The angle of attack α of a suare pillar and the ratio of channel width B/d (blockage-ratio) to pillar width were changed in the range of 0deg;-45deg; and 3-30, respectively. It is found that the drag coefficient Cd of a squre pillar decreases with B/d in the range of B/d=3-14, and the values of Cd at a given α becomes constant when B/d≥14 when provided that the Reynolds number based on pillar size, namely Red≥2.0×104. The values of Cd at a given α in a shear flow are different from those in uniform flow. Diagrams to describe the relationships between Cd and α as well as Cd and B/d are presented.