A Study on the Interaction between a Grid-generated Turbulence and a Circular Cylinder. Influence of the Main Stream Turbulence on the Wake-Induced Velocity Field and the Pressure Fluctuations on the Cylinder Surface.

Abstract

The interaction between the grid-generated turbulent flow and a 2 dimensional circular cylinder is investigated experimentally. Particular attention has been devoted to the effect of the main stream turbulence (intensity and scale of the turbulence) on the wake-induced velocity field in the upstream region and the pressure fluctuation on the cylinder surface. The velocity in the upstream region and the pressure on the cylinder surface have been measured simultaneously with the velocity in the near wake, using the I-type hot wire probes and the pressure transducer. The velocity signals measured in the upstream region and the pressure signals on the cylinder surface are analyzed by the phase average technique on the basis of the reference band-passed velocity signals in the near wake. It is found that in the case that the intensity of main stream turbulence is large and the rate of the scale of turbulence to the cylinder diameter is small, the upstream region where the periodic velocity fluctuations appear becomes large. In this case, the fluctuation of the lift force is also large.