The Effect of Speed of Advance upon Wave Force acting on a Vertical Circular Cylinder

Abstract

Hydrodynamic forces acting on a vertical circular cylinder moving forward with a constant velocity and making forced oscillations are measured. Wave forces on the moving cylinder in regular waves are also measured. The purpose of this investigation is improving the accuracy in estimation of the motion of an ocean structure in waves, and the reduced velocity and Keulegan-Carpenter number chosen in these experiments are larger than those in exper-iments for the structural vibration induced by the vortex.The measured force is compared with that with no advance velocity.The conclusions obtained are as follows;1) Steady drag coefficient CDY0 of a cylinder forced to sway, nondimensionalized by foward velocity U and swaying velocity X, does not depend on KC number but depend slightly on the advance velocity U.2) Oscillating drag coefficient CDX1 of the cylinder does not depend on U and decrease with the decrease of Kc number at Kc<30.3) Steady drag coefficient CD0 of a cylinder forced to surge does not depend on Kc number but depend slightly on U.4) Oscillating drag coefficient CD1 of the cylinder does not depend on U and decrease with the decrease of Kc number at small Kc number.5) Steady drag coefficient CDW0 of a cylinder in regular waves decreases with the increase of U.6) Oscillating drag coefficient CDW1 is smaller than that with no advance velocity and is slightly smaller than that in steady flow.7) Inertia coefficient CM is almost equal to that with no advance velocity