Awakening of renewable energy in the latter half of the twentieth century has identified wave energy as a potential source of clean energy due to its high intensity of energy flux compared with other renewable sources of energy. Subsequent research found out that Oscillating Water Column (OWC) concept is an easier and simple technology to harness energy from the Ocean waves. This had lead to a rapid progress in research pertaining to tuning of the system for optimum efficiency. The Double Chamber Oscillating Water Column (DCOWC) concept is a modified form of OWC. The present study is an extension of previous studies for understanding its hydrodynamics with respect to its two geometric parameters; bottom opening and front duct width. The experimental works carried out on a scaled down model for identifying the effective combination between them is explained. The hydrodynamic principles governing the maximum harness of wave energy is detailed here. The discussions related to wave energy absorption, wave energy conversion, phase angle difference between pressure excitation and air pressure and wave amplification which govern the efficiency of the DCOWC are included for a better understanding on the effect between geometry and wave characteristics. It is expected that the findings of this study enhance knowledge on the hydrodynamic aspects of the concept of a DCOWC.
Assistant Professor, Civil Engineering Department, Govt.Engineering College Wayanad, Kerala, India-670644
Professor, Ocean Engineering Department, Indian Institute of Technology Madras, Chennai, India-600036
This paper presents a study to examine the characteristics of the rudder inflow (propeller slipstream) using FLUENT v.6 visualization technique. The rotating propeller of 5 blades and semi-spade rudder were set in a uniform flow condition. The rudder distorts the angle-of-attack (AoA) or incident angle to the leading edge of the rudder blade. Time-averaged pressure and velocity field are proposed to analyze the AoA and show similar AoA values of 0°–7° at the region on rudder. However, it increases to 20° by those effects as the inflow comes to the rudder. From the AoA analysis the similar flow pattern is found to be about 7° in terms of the rudder angle. Cautious access is additionally necessary to introduce a reasonable safety against those inflow phenomena that would significantly influence the durability of the rudder.
Marine Technology Centre, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia
This paper discusses the numerical prediction of the semi-submersible’s heave motion. In the previous study, it is observed that the heave motion response predicted by diffraction potential theory is over-estimated in the region where the heave motion is dominated by damping. In this research, viscous damping is included in the calculation to increase the heave damping magnitude in motion equation. The wave force and added mass of semi-submersible is predicted by diffraction potential theory, only the total damping is corrected by sum-up the linear damping from diffraction potential theory with the proposed viscous damping. The heave motion response obtained from the proposed numerical method also compared to the data from the experiment. From the comparison, it can conclude that involved of viscous damping in the calculation will corrected a part of heave motion response tendency and reduce the large over-predicted error of heave motion response at the damping dominate.
Department of Aeronautics, Automotive and Ocean Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Malaysia
Ocean and Aerospace Engineering Research Institute, Indonesia
This paper is aimed to design a prototype of screw turbine for power generation. Using principles of velocity vector, the governing equations have been identified for an ideal case of force acting on blade. The paper also describes the conception of a screw turbine rotor for remote area electricity production. The research is done by calculating based on theoretical way and compared with experimental results. Output power can be generated by this small size of turbine is 0.236 watt theoretically and 0.098 watt experimentally. Various losses in the system are discussed, which is also demonstrated that the experimental power outputs and theoretical predictions has a discrepancy. However, it has a great potential to be used for remote area to generated power by using low head water source as this research is developed.
Mechanical Engineering Department, Bengkulu University, Indonesia
