This paper presents the results of wave and current forces acting on a surface piercing, vertical truncated rectangular cylinder. The combined wave-current effect has been produced by towing the cylinder in regular waves, along and opposite to the wave direction. Drag and Inertia coefficients are evaluated and are presented, as a function of KC number, for two aspect ratios of cylinders, equal to 1/2 and 2/1. The results show that drag and inertia coefficients are strongly affected by (i) variation in the aspect ratio of the cylinder and (ii) variation in the current speed. The comparison between measured forces and computed forces using Morison's equation shows good agreement.


The increasing exploration and exploitation of ocean mineral resources has required the use of various offshore cylindrical structures. The research into hydrodynamic loading on ocean structures has concentrated mostly on circular cross-section members and relatively limited work has been carried out on wave loading on other crosssections such as rectangular sections. Designs with these sections may be economically more viable than the conventional one with circular members. The square or rectangular sections may find applications in many coastal and offshore structures as caissons, columns & pontoons in semi-submersibles and tension-leg platforms. The present investigation demonstrates the behaviour of rectangular cylinders subject to wave"and current loading and also supplies the hydrodynamic coefficients for the design of these sections. (a) Regular waves Sharp edged cylindrical bodies, such as square sections, rectangular sections and flat plates develop wider wake and shed vortices in oscillatory flow even at very low KC values. As a result of this they experience larger drag coefficients than the circular cylinders. Keulegan and Carpenter (1958) investigated the loading on circular cylinder and flat plates. The square cylinder showed the highest value of CM compared with other sections.

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