10:30
Computational Fluid Dynamics I
Chair: Da liu
10:30
30 mins
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EVALUATION OF THAI LONG-TAIL BOAT PROPELLER PERFORMANCE AND ITS IMPROVEMENT
Prachakon Kaewkhiaw, Jun Ando
Abstract: Long-Tail Boat is a type of boat native in Thailand. It is often used to transport passengers and tourists especially in Chao Phraya River in Bangkok. It is classified in kind high speed boat because operating velocity is much high. The propeller is conducted to inclined shaft propeller condition with 12º from horizontal axis because it has shallow water draft.
The propulsion systems of Long-Tail Boat propeller have never been studied theoretically. Therefore, the evaluation of propeller performance of standard propeller of Long-Tail Boat by model test and optimization of propeller blade shapes are considered to the objective of this study.
The improving propulsive efficiency is a eternal goal for naval architects. It is good established helping for reduction of the CO_2 emissions which impacted to environment. Therefore, propeller performance has great influence on propulsive performances of the boat. Then, propeller improvement is significant for energy saving.
This paper is presented numerical calculation of propeller performance in standard propeller of Thai Long-Tail Boat by RANS code Fluent and a simple surface panel method “SQCM”. After that, blade shapes of the Long-Tail Boat propeller are optimized by using real-coded genetic algorithm. The calculated results of propeller performances with original and improved propellers by both methods are compared with experimental data of high speed circulating water channel at Kyushu University.
The agreement between the experiment and numerical results are good in original and improved propeller. Moreover, the propeller performances of original and improved propellers in actual inclined shaft condition are calculated by using Fluent. The calculated propeller efficiency of improved propeller is increased in inclined shaft condition.
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11:00
30 mins
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ON THE PHYSICAL MECHANISMS FOR THE NUMERICAL MODELLING OF FLOWS AROUND AIR LUBRICATED SHIPS
Gem Rotte, Oleksandr Zverkhovskyi, Maarten Kerkvliet, Tom van Terwisga
Abstract: Air lubrication techniques are very promising in reducing ship drag. It has been demonstrated that air cavity applications can realise propulsive power reduction percentages of 10-20% due to the reduction of the frictional resistance [1, 2]. However, a complete understanding of the two-phase flow physics involved with air cavity flows is still missing. Multiphase CFD methods can help to get a better understanding of these physics. The largest challenge in predicting the air cavity characteristics lies in the correct modelling of their closure (reattachment) region [3, 4]. In this region the separated air-water flow transforms into a more dispersed flow. The transformation is partly caused by instabilities in the two-phase flow. This article aims to link the physical modelling of the relevant phenomena to their numerical modelling. The link to the numerical modelling is addressed with an emphasis on different RaNS and hybrid RaNS-LES turbulence models. The article is based on the available literature in the public domain and knowledge gained in research projects carried out at Delft University of Technology and Maritime Research Institute Netherlands (MARIN).
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11:30
30 mins
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HYDRODYNAMIC PERFORMANCES ON THE EFFICIENCY GLIDING OF THE UNDERWATER GLIDER
Yongcheng Li, Zheng Ma
Abstract: ABSTRACT
The underwater glider is a new kind of autonomous underwater vehicle.It has many advantages such as a long endurance, and a long operational range with its unique device.The research of the autonomous underwater gliders ,which represents the developing direction of the AUV ,is now at the forefront of the international marine technology.In order to fully improve the gliding efficiency of AUG,we have adopted the new conceptual design of high efficiency gliding.In this article, the turtle hydrofoil propulsion method was adopted to the traditional autonomous underwater glider (AUG) for improving its propulsion efficiency and maneuverability. Using CFD methods, a set of numerical simulations considering different torsion angles along with different installation positions of hydrofoil were carried out, and the gliding efficiency of AUG was evaluated, accordingly. The simulation results show that, upon suitable torsion angles, despite greater drag, the horizontal gliding speed as well as the gliding efficiency of AUG has been improved considerably. Besides, the forward movement of the hydrofoil along the body axis may reduce the energy consumption of AUG. The obtained results could provide theoretical guidance for future AUG design.
Keywords:Autonomous Underwater Glider; Turtle hydrofoil;Efficiency gliding;CFD
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