A unified view of energetic efficiency in active drag reduction, thrust generation and self-propulsion through a loss coefficient with some applications

Arakeri, Jaywant H and Shukla, Ratnesh K (2013) A unified view of energetic efficiency in active drag reduction, thrust generation and self-propulsion through a loss coefficient with some applications. In: Journal of Fluids and Structures, 41 . pp. 22-32.

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Abstract

An analysis of the energy budget for the general case of a body translating in a stationary fluid under the action of an external force is used to define a power loss coefficient. This universal definition of power loss coefficient gives a measure of the energy lost in the wake of the translating body and, in general, is applicable to a variety of flow configurations including active drag reduction, self-propulsion and thrust generation. The utility of the power loss coefficient is demonstrated on a model bluff body flow problem concerning a two-dimensional elliptical cylinder in a uniform cross-flow. The upper and lower boundaries of the elliptic cylinder undergo continuous motion due to a prescribed reflectionally symmetric constant tangential surface velocity. It is shown that a decrease in drag resulting from an increase in the strength of tangential surface velocity leads to an initial reduction and eventual rise in the power loss coefficient. A maximum in energetic efficiency is attained for a drag reducing tangential surface velocity which minimizes the power loss coefficient. The effect of the tangential surface velocity on drag reduction and self-propulsion of both bluff and streamlined bodies is explored through a variation in the thickness ratio (ratio of the minor and major axes) of the elliptical cylinders.

Item Type:	Journal Article
Publication:	Journal of Fluids and Structures
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	Bluff Body Flows; Drag Reduction; Self-Propulsion
Department/Centre:	Division of Mechanical Sciences > Mechanical Engineering
Date Deposited:	25 Oct 2013 06:35
Last Modified:	25 Oct 2013 06:35
URI:	http://eprints.iisc.ac.in/id/eprint/47545

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