A Study on the Fluctuating Force acting on a Cylinder Placed in the Downstream of a Moving Cylinder

Abstract

Experiments of the fluctuating force acting on a cylinder placed in the downstream of a moving cylinder with constant velocity in a uniform airstream have been carried out. At first, the case where both cylinders are stationary is treated. Our experimental results and knowledge of the flow pattern around the cylinders enable us to form an idea that the separation point shifts downstream because of the turbulence arising from the upper cylinder. Owing to this interference, the lift and drag acting on the cylinder placed in the downstream are changed. When the upper cylinder moves with constant velocity in the direction normal to the airstream, the variation of fluctuating force with time differs for various values of the velocity of the cylinder, distance between both cylinders and diameter ratio of the cylinders. Causes for these variations are explained from the results of the flow measurements around the stationary cylinders.