Viscous Force Acting on Bluff Bodies Started from Rest

Abstract

Viscous force acting on bluff bodies which is started from rest are investigated experimentally. A rectangular prism deeply submerged in uniform flows with different accelerations in circulating water channel, and the force acting on it are measured by load-cell. The experimental results show that the drag coefficient which is obtained by subtracting the potential inertia force form the measured hydrodynamic force depends only on the relative displacement of the body from rest. The lift force and the moment acting on the body which has angle of attack to the flow are also confirmed to depend on the relative displacement. Experimental results for a circular cylinder, a flat plate and a ship model moving laterally show the same tendency.