Correlation of time-dependent force coefficients for cylinders in oscillatory flow

Attention is given to the inertial pressure concept, a semiempirical technique for determining the forces acting on immersed bodies in unsteady flow situations. It is noted that force expressions obtained using this concept contain empirically determined time-varying coefficients that perform roles similar to those of the constant mass and drag coefficients associated with Morison's (1950) equation. The feasibility of correlating these time-varying coefficients and employing the results to determine the in-line forces on circular cylinders in one-dimensional oscillatory flows is investigated. The possibility for correlation is deonstrated both qualitatively and quantitatively. In addition, a simple representation of the time-dependent coefficients, referred to as the 'universal' curve, is presented. It is shown that forces predicted using the 'universal' curve are more consistent with measured data than the forces predicted by Morison's equation in the drag-inertia regime.