Noise reduction and control is an important problem in the performance of underwater acoustic systems and in the habitability of the passenger ship for crew and passenger. Furthermore, sound generated by a propeller is critical in underwater detection and it is often related to the survivability of the vessel. This paper presents a numerical study on noises of the underwater propeller for different performance conditions. The non-cavitating and blade sheet cavitation noise generated by an underwater propeller is analyzed numerically in this study. The flow field is analyzed with finite volume method (FVM), and then the time-dependent flow field data are used as the input for Ffowcs Williams–Hawkings (FW-H) formulation to predict the far-field acoustics. Noise characteristics are presented according to noise sources and conditions. The developed flow solver is applied to the model propeller in uniform inflow. Computed results are shown to be in good agreement with other numerical results. The overall results suggest that the present approach is a practicable tool for predicting cavitation and non-cavitation noise of propellers in far field.
Sharif University of Technology, Center of Excellence in Hydrodynamic and Dynamic of Marine Vehicles, Tehran, Iran
Traditional ship in Indonesia which usually built from wood has small capacity compared to modern steel ship. Compared to modern ship building, mostly the production is to assemble block by block with machines and big cranes. However, traditional ship is one hundred per cent made from the work of man. Workers are not properly trained in a formal engineering school but only learnt the skill from senior workers. Hence, all modern concepts such as the need for safety and a proper ship production flow are not a great concern for them. In this paper, safety issue in traditional ship production process is being observed conducting direct survey to traditional shipbuilding company in Bintan, Indonesia. It is hoped that the outcome is to bring safety awareness to the traditional ship builders.
Department of Aeronautical, Automotive and Ocean Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Malaysia
Ocean and Aerospace Engineering Research Institute, Indonesia
Mechanical Engineering, Universitas Riau, Indonesia
Due to the advantages of high head, no leakage, multistage canned motor pump is widely used in the national economic construction department. At present, in the premise of guarantee reliability, saving energy efficient become an important development direction of canned motor pump. In order to research and improve the performance of the pump, this paper designed and used symmetric multistage canned motor pump DBP15-50x8 as the research object. Three-dimensional model of the main flow passage components is built and the mesh is generated respectively by using Pro/E and ICEM software, and we calculated the whole internal flow field of the pump that was selected by using ANSYS CFX software, achieving the pressure and velocity distribution rule in the pump and the internal details of flow in impeller and other main flow components. It is found that there is pre-whirl flow in the front of inlet in the first stage impeller under the conditions of 0.5 Q and Q flux, obtained the unstableness in inlet when this pump works under the low flux conditions. The post-processing showed the internal flow of bearing section and volute is chaotic, etc. The results provide theoretical basis for the design optimization of multistage canned motor pump.
Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, China
In present study, video images technique is used to investigate the transformation of the directional wave spreading in shallow water. The technique is based on time series of the pixel brightness on video images. The Bayesian Directional Method is conducted in estimating the directional wave spectrum for evaluating the change of the directional wave spreading in the surf zone area. Video image data recorded at Hasaki beach in Japan are used in the analysis. Estimation of principle direction and spreading parameter in the surf zone regions indicated that principle directions at peak frequency are not strongly affected by wave breaking process. In contrast, the broadenings of directional spreading were observed when the waves start breaking on the sand bar and toward the shore area.
Department of Ocean Engineering, Faculty of Marine Technology, Institut Teknologi Sepuluh Nopember (ITS), Keputih Sukolilo, Surabaya, Indonesia
Department of Urban and Environmental Engineering, Faculty of Engineering, Kyushu University, Fukuoka, Kyushu, Japan
Department of Urban and Environmental Eng., Faculty of Engineering, Kyushu University, Fukuoka, Kyushu, Japan
Marine Environmental Information Group, Port & Airport Research Institute (PARI), Tokyo, Japan