Unsteady Flows Past a Circular Cylinder Started Impulsively in the Reynolds Number Range, 500 < Re< 10⁴ : 2nd Report, The Pressure Distribution on the Surface of the Cylinder

Abstract

The velocity fields around a circular cylinder which was started impulsively in a water tank were measured by flow visualization techniques. The pressure on the surface of the cylinder was estimated by the line integral of the Temples equation using the measured velocities on a closed circuit which is selected to avoid the cumbersome estimation of viscous terms. The estimated distributions of the pressure coefficient C_pθ at Re=1 200, which are in disagreement with those of the numerical analysis for Re= 1 000 by Bar-Lev, are in agreement with those of the numerical analysis for Re=500 by Collins. The variation of the local values of the pressure coefficient C_pθ (θ=90° and 180°, θ: azimuthal angle measured from the frontal stagnation point of the cylinder) with elapsed time was found to be similar as that of C_pθ obtained by both the conventional numerical analysis and the experimental study, though their quantitative agreement is insufficient.