Numerical Analysis of Resistance and Motions on Trimaran Floating Platform for Tidal Current Power Plant

As an archipelagic country, Indonesia has enormous resources from the sea such as the hydrokinetic energy of the ocean especially in eastern Indonesia. Since the lack of infrastructures and supporting facilities in eastern Indonesia, the study concerning the utilization of the ocean currents showed that the use of the floating platform of ocean current turbines is simpler and cheaper than the gravity type which is submerged in the bottom of the sea. The trimaran floater type has been widely used in shipping technology, moreover according to the trimaran study, it is stated that trimaran technology has advantages in terms of stability, better durability values, and wider deck space. However, the trimaran shapes have not been utilized as a platform for ocean current turbine. The purpose of the study is to conduct the numerical simulation for the trimaran shape as the platform of ocean current turbines. In the computational domain, the trimaran platform is considered fixed by 2 single mooring lines each at the endpoint of the middle float of trimaran, whilst it faces the ocean current at speed of 1.0 – 5.0 m/s. Overset mesh is employed to simulate the behavior of the platforms. The implicit unsteady simulation is set to calculate the 6 degrees of freedom of the ocean current loads and the motions of the platform. The results show relatively good trimaran’s response motion in moored conditions with a maximum of 0.7 degrees of rotation in y-axis. Moreover, the mooring force in the x and z directions shows an increasing trend, reaching its maximum value at a current speed of 4.0 m/s with achieved values of 22.2 kN and-7.4 kN, respectively. However, this is different from pitch motion, where the highest pitch trend is achieved at a current speed of 2 m/s with an average rotation of 0.63. This means that the trimaran’s resistance is proportional to the current speed.