Hydrodynamic Drag on Bottom-Mounted Smooth and Rough Cylinders in Periodic Flow

Abstract

The in-line and transverse forces acting on smooth and sand-roughened circular cylinders placed on a plane boundary (with no gap) in a sinusoidally oscillating flow in a U-shaped vertical water tunnel have been measured. The drag and inertia coefficients for the in-line force have been determined through the use of the Morison's equation and the Fourier analysis. The transverse force has been analyzed in terms of its maximum and minimum values, root-mean-square values, and the time it remains above a fraction of its maximum. The results have been presented as a function of the Keulegan-Carpenter number and the frequency parameter β=D²/ѵT.