National Strategic Reference Framework  NSRF  2007-2013

Operational Program "Education and Lifelong Learning" Research Funding Program "ARISTEIA"


Research project  BIO-PROPSHIP, c.n. 444

Augmenting ship propulsion in rough sea by biomimetic-wing system

Ελληνικά

Latest news

1 June 2015: New publications.

14 May 2014: English version of project's website.

10 July 2013: Project's new website.

Bιομιμητικό σύστημα

Objectives

Biomimetic propulsors is the subject of intensive investigation, since they are ideally suited for converting environmental (atmospheric or sea wave) energy to useful thrust, succeeding efficiencies over 100%. Recent research and development results concerning biomimetic foils and wings, supported also by extensive experimental evidence and theoretical analysis, have shown that such systems, operating under conditions of optimal wake formation, could achieve such high levels of propulsive efficiency; see, e.g., Triantafyllou et al (2000, 2004), Taylor et al (2010). [Reference list can be found in the webpage: http://arion.naval.ntua.gr/~flappropship]. On the other hand, the complexity of kinematics of flapping wings necessitates the development of more sophisticated power transmission mechanisms and control devices, as compared to the standard marine propeller systems, preventing at present its application as the main or sole propulsion system of ships.

A main difference between a biomimetic propulsor and a conventional propeller is that the former absorbs its energy by two independent motions, the heaving and the pitching motion, while for the propeller there is only rotational power feeding. In real sea conditions, the ship undergoes a moderate or higher-amplitude oscillatory motion due to waves, and the vertical ship motion could be exploited for providing one of the modes of combined/complex oscillatory motion of a biomimetic propulsion system. At the same time, due to waves, wind and other reasons, ship propulsion energy demand in rough sea is usually increased well above the corresponding value in calm water for the same speed, especially in the case of bow/quartering seas.

The objectives of the proposed project are: to theoretically investigate, design and experimentally test an innovative biomimetic-wing system for augmenting ship propulsion efficiency, in operating conditions corresponding to realistic sea states. To this end, new and existing computational models will be produced and integrated, supporting the development of appropriate control methods for optimizing real-time performance. For testing and evaluation of the validity of the present methods, and demonstration of the whole idea, a prototype model will be constructed and tested, independently and attached to the ship hull(s) in towing tank. Theoretical predictions will be compared against experimental measurements and computing tools will be developed and validated, supporting the overall design procedure and, especially, the control of the examined system. The latter augments the overall propulsive efficiency of the ship by extracting energy from the waves, damping at the same time partially the vertical ship motion (see Rozhdestvensky& Ryzhov 2003), and after theoretical model development combined with experimental study and validation, it could offer a new technological design contributing to greening of sea transport and safer operation of ships.

In order to better understand the performance features and deliver the required design tools, one of the main objectives of the proposed project is the development of new numerical methods and integration with existing and established computational codes for the calculation of the unsteady propulsive characteristics of a biomimetic wing system placed under the hull of a ship, which is advancing in waves. A definitive sketch of the examined system is presented in Fig.1. In this connection, it is important to realize that the vertical (heave-like) oscillatory motion of the flapping propulsion system is partially induced by the waves, in conjunction with the seakeeping response of the ship, while the rotational one (pitch-like motion) is provided by the motor driving the flapping system through the use of suitable control device and automation. We plan to examine both monobloc biomimetic wings (like that on a fish tail) or a more complex arrangements, like the fish dorsal fins. In the last case, the motion of port and starboard parts of the wing(s) could be set asynchronous. In addition to thrust force production, the control of pitching phase of the two wing parts could generate useful antirolling moment for ship stabilization.