Oscillating Foil Propulsion

Lai, Peter Shung Kin (1990) Oscillating Foil Propulsion. PhD thesis, University of Glasgow.

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Abstract

In this thesis, an investigation on the use of oscillating foil propulsion for marine vehicle as an alternate effective propulsion system is presented. Three different oscillating foil propellers, namely: two-dimensional oscillating foil propeller; flexible fin propeller, and rotary foil propeller, have been studied. The thesis is made up of four parts: one related to each type of propeller and one on the application of oscillating foil propellers along with general conclusions. Two-Dimensional Oscillating Foil Propeller A review on the hydrodynamic forces and moments acting on a two-dimensional oscillating foil is presented. The equations for estimating the force system have been extended to cover different phase lags between heave and pitch and to calculate the force system at a particular instant of time within an oscillating cycle. The sensitivity of the propulsive thrust coefficient and the hydromechanical efficiency has been investigated for a range of different parameters. The operating condition for optimum performance is identified. Flexible Fin Propeller The theoretical model of the flexible fin propeller, which has been set up by combining linearised unsteady foil theory and large deflection beam theory, is described. Non-dimensional parameters are established to study the performance of this type of propeller. A flexible fin propeller model and its test rig was designed and built. The model was tested in the Hydrodynamics Laboratory at the Department of Naval Architecture and Ocean Engineering, the University of Glasgow. The performance of the propeller was examined at both forward and zero speeds. Results have been compared with theoretical predictions. Conclusions on the performance of the flexible fin propeller are drawn based on the theoretical predictions and experimental results. The stress acting on the flexible bar has been computed and discussed. The selection of material has been discussed and promising materials identified. The feasibility of using flexible fin propellers for wave propulsion to absorb wave energy and convert it into propulsive thrust has been studied. A one-fifth scale model of a three quarter ton racing yacht with a flexible fin propeller model mounted at the stem was tested. At a low Froude number, there is a significant reduction in the motion response and in the required thrust around the resonance zone, where the encounter wave length is equal to the ship length. Rotary Foil Propeller A three bladed propeller model with high-aspect ratio blades was tested in forward and reverse directions and zero speed conditions. The experimental results on the performance of the model at forward speed have been compared to that predicted by Bose [1987] using multiple stream tube theory and discussed. Application of Oscillating Foil Propeller and General Conclusions The practical application of three oscillating foil propellers and economic studies of their operation have been studied and discussed. Three ship examples with the same Froude number but different in sizes and a high speed craft have been used in these studies. Three types of oscillating foil propeller are designed for each ship example. The required stem hull form and the driving mechanism have been discussed. The application of the flexible fin propeller in wave propulsion has been demonstrated. The natural frequency of a full scale flexible fin propeller was calculated and found to be much higher than the optimum driving frequencies in the operating condition. The net present value method has been applied in the economic studies where breakeven conditions, different interest rates, fluctuation of oil price, and different additional maintenance costs have been considered. The main conclusions of this research have been drawn up and are presented. Recommendation on the design of these propeller are also made.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Naval engineering
Date of Award: 1990
Depositing User: Enlighten Team
Unique ID: glathesis:1990-78049
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 15:42
Last Modified: 30 Jan 2020 15:42
URI: http://theses.gla.ac.uk/id/eprint/78049

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