The in-line forces on small square cylinder caused by both waves (regular and irregular) and currents based on the extend Morison Equation and model test were analyzed and results are detailed in this paper. The hydrodynamic coefficient Cd and Cm related to KC number and the effect of direction of wave incidence, which may be useful for the practical engineering application, are are also given.
The square cylinder is widely used for pile structures in harbour engineering. The cross section of the hull and legs of semisubmersibles and of tension leg platforms of the new generation are also square or rectangular. But so far the existing research on small cylinders has been concentrated on the care of a circular cylinder, with very few studies are related to the square cylinder(Bearman 1980, 1984, Deroich 1992). Consequently the research on wave current forces acting on square cylinders is very useful to real engineering applications. On the other hand, there are sharp edges on a square cylinder, the flow behaviour around which is quite characteristic to the form. The research on flow behaviour around a square cylinder is helpful to us to learn more about the mechanism of flow around small cylinder, which is quite important for the theoretical development.
So far, the most practical method to be used for in-line hydrodynamic force evaluation in engineering applications is the Morison Equation. The results by this analysis are: firstly the linear wave theory, which is very simple to use, may give better results than Stokes second order theory, secondly the least square method (LSM) is the best method for analysis in the time domain and the modified cross spectral method is a good method for analysis in the frequency domain.
