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A time-varying parameter model of a body oscillating in pitch.

McCabe, A. P. and Aggidis, George A. and Stallard, T. J. (2006) A time-varying parameter model of a body oscillating in pitch. Applied Ocean Research, 28 (6). pp. 359-370.

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Abstract

Among the assumptions upon which linear time-invariant models of floating bodies are based is that the body motions are so small that any change in the body’s angular position can be disregarded. However, it is often a major design requirement of a wave energy conversion device that the response amplitude is large, thereby invalidating one of the assumptions of the linear model. In particular, the immersed geometry of a body undergoes considerable variation when it is moved in pitch. With regard to this we investigate the difference in performance between a quasi-linear model in which the change of immersed surface is modelled by time-varying parameters and a basic linear model in which the immersed surface is time-invariant. The time-varying parameter model is realized by interpolation between the appropriate parameter values of a set of linear time-invariant (LTI) models derived for the different immersed surfaces that occur at discrete body displacements. It is shown that the responses predicted using the time-varying parameter model are closer to those measured experimentally than those of a standard frequency-domain model. Particular improvement occurs when the responses are large, such as at or near the resonance frequency. A problem which may limit the general use of the model is also discussed.

Item Type: Article
Journal or Publication Title: Applied Ocean Research
Uncontrolled Keywords: Time-varying parameter model ; Time-domain model ; Potential-flow hydrodynamics
Subjects: T Technology > TC Hydraulic engineering. Ocean engineering
Departments: Faculty of Science and Technology > Engineering
ID Code: 33754
Deposited By: Mrs Yaling Zhang
Deposited On: 24 Jun 2010 09:17
Refereed?: Yes
Published?: Published
Last Modified: 24 Jan 2014 05:18
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/33754

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