There is a lot of studies on the hydrodynamic forces acting on two dimensional circular cylinder. However, the ocean structures are usually made of finite-length cylinders. The hydrodynamic coefficients of finite-length cylinder, therefore, play important role for the design of ocean structure. In this paper, the hydrodynamic forces acting on finite-length circular cylinder oscillating in a uniform flow were studied investigated experimentally. Forced in-line and transverse oscillation tests under towing condition were carried out on the vertical finite-length circular cylinders of various length to diameter ratio. And the in-line force and transverse force were measured at various positions of cylinder. The experiments in uniform flow and oscillating flow were also made for comparison. From these measured forces, the end effects on the drag coefficient, added mass coefficient, lift coefficient and Strouhal number were investigated in various conditions.
Most of the floating marine structures are consisted of the columns and bracings shaped with the circular cylinders of finite-length. The flow pattern around the circular cylinders in the real ocean where current, waves and the motion of the structures coexist, may become so different from that of the case of a cylinder in the uniform flow or in the oscillating flow. Koterayama(1984) made the same kind of experiment and obtained the drag, added mass and lift force coefficient while making an another experiment of towing the two dimensional circular cylinder in waves. Iwagaki(1983) considered that the essential difference between the case in the coexistence of waves and current and that in the existence of waves only comes from the asymmetry of the wave particle velocity against the circular cylinder. He investigated the mechanism of the hydrodynamic force comparing the drag and mass coefficient with the wake pattern of the circular cylinder through the flow visualization techniques.