Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - A time-varying parameter model of a body oscillating in pitch.
AU - McCabe, A. P.
AU - Aggidis, George A.
AU - Stallard, T. J.
PY - 2006/12
Y1 - 2006/12
N2 - 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.
AB - 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.
KW - Time-varying parameter model
KW - Time-domain model
KW - Potential-flow hydrodynamics
U2 - 10.1016/j.apor.2007.05.001
DO - 10.1016/j.apor.2007.05.001
M3 - Journal article
VL - 28
SP - 359
EP - 370
JO - Applied Ocean Research
JF - Applied Ocean Research
IS - 6
ER -