Dynamic behaviour of tension leg platform in short-crested directional seas

The representation of the sea condition has great influence on the behaviour of the Tension Leg Platform, (TLP). A real sea condition is a random directional field that varies both in space and time. The aim of this study is to compare responses of the TLP when the ocean surface is simulated as either unidirectional or directional sea. A stochastic sea surface elevation was assumed and simulated using linear wave superposition method for both unidirectional and directional seas. Joint North Sea Wave Project, (JONSWAP) spectrum was used to simulate wave frequency and quantify the energy density. A numerical code was developed in FORTRAN software for solving non-linear uncoupled dynamic analysis. The nonlinearity considered includes relative velocity square drag force in Morison, large displacement, variable submergence and tension fluctuation in the tendon. It was inferred that unidirectional sea simulation overestimates motion responses when compared to directional sea.