Indonesia has abundant of renewable sources of energy, among others: geothermal, solar, water, wind and marine therefore the promotion of the utilization of the renewable and sustainable energy is urgent. Since 2006 Indonesian Hydrodynamic Laboratory (IHL) BPPT has conducted research and developed a technology converts the ocean energy resources into electricity, the kinetic energy of marine current and the potential energy of wave. The prototype of marine current turbine, 2 kW and 10 kW respectively, had been installed in Larantuka Strait in 2010 and 2011 (http://www.youtube.com/user/erw4ndi). Since mostly the maximum speed of the marine current of many straits in Indonesia are in order 1.0 - 2.0 m/s, we developed the turbine prototype that can convert not only the kinetic energy of marine current but also the potential energy of the wave, called as wave-current rotor turbine, in 2013. The current usually mixes with wave height with order 0.4 - 0.8 m. A 2 kW prototype was installed under Suramadu (Surabaya - Madura) Bridge close to pier no. 56. The prototype showed a good performance especially in converting the kinetic energy of marine current. The research was continued in 2014-2016 under Ministry of Research and Technology (INSINAS RISTEK) budget scheme. Some innovations have been done to improve the performance of turbines.

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This paper is the second report that describes the capability of projected light distribution method to measure the diffraction waves generated by a ship operating in regular incident waves. In this method the waves are projected onto a screen as light distribution images and the images are recorded using a CCD Camera. In order to obtain diffraction waves, experiments were divided into two steps. Firstly, incident waves were measured. Secondly, the combination between incident waves with diffraction waves around a ship model was measured. The diffraction waves can then be obtained by subtracting incident wave images from combined one. The Kochin function was obtained using the same method as explained in the previous paper6). The results are evaluated by making some transverse cuts on the image data in the y-direction (transverse cut). The obtained Kochin functions are compared with the longitudinal cut results based on Ohkusu method, and also with theoretical results based on slender body theory. Using the results of Kochin Function, the wave pattern are recalculated and they are compared with the results of measurement using super sonic wave height meters.

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In hydrodynamic ship-model experiments, motion tracking of ship model trajectory is employed to predict the maneuverability of the ship when operating in its actual environment. There are some systems for motion tracking, such as inertial measurement unit, radar, laser, and infrared sensors. The system has proven reliable, however, the disadvantage is that they are all relatively expensive. This paper proposes a low-cost digital optic-based motion tracking system using consumer-grade video camera. In order to examine the accuracy of the system, some experiments to apply the method were carried out in maneuvering offshore engineering basin at the Indonesian Hydrodynamics Laboratory, The National Agency for Research and Innovation. To cover a broader area of the trajectory, a wide-angle camera lens was utilized, consequently, the image recorded by the camera experienced a barrel distortion. As a reference for the measurements, gridlines spaced 2 meters apart were drawn on the floor of the basin. Using the grid pattern, the distortion was corrected by finding the relationship between the grid pattern in the object space and in the distorted image. A fourth-order polynomial regression was applied to solve the problem. The results showed that the method was effective for correcting distorted images with a relative standard error of 0.42%.

Landing Craft Utility (LCU) is one type of ship whose role is to transport combat equipment vehicles and amphibious troops to make landings on the beach. On the ship, bilge keels were installed. However, the installation of bilge keels on the surface of the ship’s hull will add resistance to the ship’s speed. To find out the effect of placing bilge keels on the additional ship speed resistance, a towing test experiment was carried out in the towing tank using the LCU ship model. Two bilge keels were manufactured in 4 (four) different positions, called A, B, C, and D positions. From the results of the study, it is known that the average value of the addition to the total resistance is; at A position there is an increase in ship speed resistance of 3.22%, at B position by 3.36%, at C position by 2.67%, and at D position by 1.83% of the total resistance in bare hull conditions. The results of this study indicate that the placement of bilge keels with the same shape and dimensions can add to different total resistances.

In 2020, the Agency for the Assessment and Application of Technology – Indonesia (BPPT) is designing wave glider systems for Tsunami Early Warning System. The wave glider systems consist of two components, the floater at the water surface and the wave glider submerged 2 meters or more below the water surface. Wave glider contains several foils that can flap up and down due to the heave and pitch motion of the floater so that the system affords the force to move forward. This paper describes the numerical analysis of the resistance of floater and the selection of the pivot position of the foil where it flaps. The speed of the floater is set from 0.3 m/s up to 1 m/s. NACA-0012 is selected as the first choice of the foil. It flaps in pure pitch motion and coupled pitch and heave motion in the different pivot positions. The flapping frequency is set to 0.1 Hz since the peak period of the wave about 10 seconds. The surge forces due to the flapping motion are then analysed to determine the best position of the pivot. The numerical simulation shows that the pivot position at 2.5% - 5% of chord length from the leading edge of NACA-0012 generates the optimum surge force.

This paper is the third report that describes the application of the Least Square Method to analyze the Kochin function of the radiation waves and diffraction waves obtained by the Projected Light Distribution Method. The previous papers used only one line transverse cut data instead of two-dimensional data provided by Projected Light Distribution Method. The results are compared with the longitudinal cut method proposed by Ohkusu and with the previous result as reported in the first and second reports. The detail description about the effects of the integration region is also described.