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.
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.
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.
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.
Currently, the exploration of ocean renewable energy sources was mostly carried out to obtain optimal results and low cost. The waves that arrive on the beach consist of both potential energy where the water surface moves up and down and hydrokinetic energy where the volume of water comes and goes into the beach sand. They had the potential to be converted to electricity. This paper explained the study of the hydrodynamic aspects of turbines that convert hydrokinetic and potential coastal wave energy. The vertical axis darrieus turbine was modified to catch both energies. It could convert energies from hydrokinetics and the potential of waves simultaneously, whereas a vertical axis turbine with 6 horizontal blades and 3 vertical blades in a shaft. Testing was done at the testing Tank, Hydrodynamic Technology Research Center, National Research and Innovation Agency. The hydrodynamic tests were with 3 turbine variations, wave variations, and current velocity. The test results, vertical axis turbines with horizontal blades could receive wave energy, due to the orbital motion of water particles and vertical blades were very effective in receiving current energy so that turbines with 2 types of vertical and horizontal blades could convert wave and current energy.
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%.
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