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Fish and other sea borne creatures have invoked interest in the minds of many professionals to study how they propel themselves in water and whether similar principles can be applied to the design of underwater vehicles. Adopting these principles for propulsion had been a challenge some decades ago, but with the current technological progress in robotics, design analysis, advanced computing, precision manufacturing, 3D printing, sensors, actuation, image processing etc have rekindled an interest in this field, especially in the Indian context. Moreover, with the thrust on development of unmanned autonomous systems, especially for the naval warfare, there is a case for looking at an efficient way to propel such vehicles that can stay underwater for a longer duration, move and navigate faster than those traditionally shaped and propelled by screw propellers or pump jets. This paper looks at some of the basics of fish locomotion; technology trends; examples of the current developments; benefits of emerging technologies, investigate performance of some basic shapes of caudal fin of fish with the help of modern analytical tools such as Computational Fluid Dynamics and the way ahead.

Propulsors are an integral part of marine robots (MR), and their characteristics determine control algorithms of MR. The paper analyzes the features of marine robot propulsors, assesses the relevance of their use for various tasks. The propulsors with open and ducted propellers and bow thruster were investigated. The analysis of propulsors efficiency has been presented in the paper at different operating modes, including in the flow inclination. It has been showed that modern methods of propulsor design and optimization allow to greatly improve the propulsor in comparison with the ordinary propulsors of MR. For example application of optimized propulsors may get 1.5 times higher thrust on the bollard pool mode. Additional increasing of thrust and efficiency may be realized by means of energy saving devices. A few types of energy saving devices for the bow thruster have been matched. There presented stator blades rows, coaxial propellers and rim driver. For instance an application of rim driver leads to the thrust increase of about 17% in the case study. The issues of engine and propulsor interaction and noise of propulsors have been investigated separately. The propulsor – engine interaction has been investigated for two modes of engine performance: in case of a constant capacity or a constant torque on the shaft when changed is the number of revolutions. It has been demonstrated the deviation of propulsor mode from the planned one may lead to mismatch of propulsor and engine. It may results in serious thrust reduction. It is concluded that it is necessary to design propulsors of MR by modern methodology and advisable to develop the collection of propellers with different power for use on MR.

This study investigates the performance of podded propulsors in various operating conditions: open water and different ice conditions. The model used in this study is an icebreaker driven by twin-podded propulsors. Preliminary results from ice tank tests are presented. These include steering moment generated by the propulsors, thrust and torque of the propellers and the forces exerted on the hull at the location of the connection of the propulsors for different levels of ice and pack ice conditions, as well as in open water. © 2011 National Research Council of Canada.

This paper presents results and analyses of an experimental study into the effects of static and dynamic azimuthing conditions on the propulsive characteristics of a puller podded unit in open water. The model propulsor was instrumented to measure thrust and torque of the propeller, three orthogonal forces and moments on the unit, rotational speed of the propeller, azimuthing angle and azimuthing rate. The model was first tested over a range of advance coefficients at various static azimuthing angles in the range of-180° to 180°. These tests were followed by tests in which the azimuthing angle was varied dynamically at certain azimuthing rate and propeller rotational speed. A comparative study of the performance coefficients at static and dynamic azimuthing conditions in the range of-180° to 180° is presented. The performance coefficients of the propeller and the pod unit showed a strong dependence on the propeller loading and azimuthing angle. The coefficients in static azimuthing conditions fit well with a 10th order polynomial fit of the data obtained in the dynamic azimuthing condition in the corresponding azimuthing angles and advance coefficient. An uncertainty analysis of the measurements is also presented. © 2012-IOS Press and the authors. All rights reserved.

The following is a report detailing the procedure, analysis, and results of seven sets of tests conducted on podded propellers. The tests were conducted on either a single pod or dual pods running along side one another. Two sets of tests were conducted on a propeller of 270mm while the remainder were on a prop of 200mm. Two of the cases were numerical.Not much is known about the performance characteristics of podded propellers to this date. This is reason behind the current study. With the data already collected along with future tests planned researchers will gain valuable knowledge about podded propellers and will be able to engineer future pods more efficiently and effectively.

Ever since their first appearances, azimuthing podded propulsors have become increasingly popular. In a parallel development, there has been an increasing interest in arctic shipping. Hence, the number of vessels with azimuthing podded propulsors being capable of navigating in arctic conditions is increasing. The aim of this study is to help the understanding of ice effects on this type of propulsors. The knowledge generated could then be used in updating the regulations governing the design of vessels for arctic navigation, including the podded propulsion systems, by the International Association of Classification Societies. The paper describes the preliminary experimental results obtained in this study so far. The setup designed and built at NRC-IOT, Canada, has the capabiligy of measuring the loads on a podded propeller system operating in ice. It is able to measure loads on the entire model, propeller shaft bearing loads and clade loads. The results suggested that the bearings undergo cyclic loading conditions during the encounters with ice., 1st International Conference on Technological Advances in Podded Propulsion, 14th-16th April 2004, University of Newcastle, UK

Performance tests of the longitudinal and lateral propulsion devices for use on the Naval Postgraduate School (NPS) Autonomous Underwater Vehicle (AUV) II are presented. The propulsion requirements for the AUV are discussed and a brief review of the theoretical performance of propulsors is presented. The test procedures used to determine the operating range characteristics of the candidate propulsion devices are described and the results are compared with those obtained theoretically as well as with the parameters of large marine propulsion systems. The results of simulations of longitudinal motion using a non-linear model of the AUV are documented, providing an initial estimate of vehicle accelerationdeceleration performance. http://archive.org/details/performanceofsma1094534859 Lieutenant Commander, United States Navy Approved for public release; distribution is unlimited.