Hydrodynamic forces acting on cylinders oscillating at small amplitudes

Abstract

The hydrodynamic forces resulting from small-amplitude harmonic oscillations of arbitrarily shaped cylinders are considered both experimentally and theoretically. The fluid is assumed to be initially at rest. The theoretical model assumes a laminar, nonseparating flow, where the in-line force has two components, one due to normal pressure stresses and one due to skin friction. In the limit of zero amplitude oscillations, comparisons between theory and experiment demonstrate that the nonseparating theoretical model captures the essential behavior of real fluid hydrodynamics. This is valid for a variety of shapes including sharp-edged bodies such as squares. Through model testing, it is possible to estimate an “effective eddy viscosity” which can then be used in conjunction with the theoretical laminar flow model to give empirical drag coefficients.