Morison Inertia Coefficients in Orbital Flow

Abstract

Inertia coefficients for use in Morison's equation in conditions of orbital flow are significantly lower than those appropriate to planar oscillatory flow. Circulation around the cylinder resulting from asymmetrical shedding of vorticity generates a lift which opposes the conventional inertia force. The magnitude of the lift and the effect of Reynolds number are discussed on theoretical grounds and with reference to force and velocity measurements in orbital flow. Consideration of the lift leads to the formulation of a modified Morison equation, which is appropriate to all circumstances of wave loading on a cylinder when the incident velocity vector is not collinear with the incident acceleration vector.