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.

## 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 |
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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: | Users 810 not found. |

Deposited On: | 24 Jun 2010 09:17 |

Refereed?: | Yes |

Published?: | Published |

Last Modified: | 25 Jun 2017 02:07 |

Identification Number: | |

URI: | http://eprints.lancs.ac.uk/id/eprint/33754 |

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