Non-linear behaviour of an idealised submerged WEC with Coulomb damping

Research output: Chapter in Book/Conference paperConference paper

Abstract

Abstract—Wave energy converters (WECs) with Coulomb-type damping are relatively common as this behaviour is typical of hydraulic power take-off (PTO) systems. This study investigates motion response of a mass-spring system under combined linear and Coulomb damping, as a simplified representation of a WEC with a Coulomb damping force in the PTO. Motivation for this work stems from observed heave motions, of a submerged model-scale WEC with Coulomb PTO damping, which in some cases exhibited large offsets/drifts from the mean position. For submerged devices any restoring force must be engineered, as the
hydrostatic restoring force is zero. Given a choice of restoring force and Coulomb coefficients, we are interested in how to make the optimum choice to minimise displacements in large waves. In this paper a simple model is used to investigate this question. In the range of parameters considered, the extreme
displacements are minimised by adopting negligible Coulomb damping force (relative to the exciting forces) and a weak detuned spring coefficient. The low-frequency drifting behaviour is seen to be important for both mean and extreme behaviour of the oscillator.
Original languageEnglish
Title of host publicationProceedings of the 12th European Wave and Tidal Energy Conference (EWTEC)
Place of PublicationCork, Ireland
PublisherTechnical Committee of the European Wave and Tidal Energy Conference
Pages1088-1-1088-9
Publication statusPublished - 2017
Event12th European Wave and Tidal Energy Conference - Cork, Ireland, United Kingdom
Duration: 27 Aug 20171 Sep 2017
http://www.ewtec.org/ewtec-2017/

Conference

Conference12th European Wave and Tidal Energy Conference
CountryUnited Kingdom
CityCork, Ireland
Period27/08/171/09/17
Internet address

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Damping
Takeoff
Hydraulics

Cite this

Orszaghova, J., Wolgamot, H., Draper, S., & Rafiee, A. (2017). Non-linear behaviour of an idealised submerged WEC with Coulomb damping. In Proceedings of the 12th European Wave and Tidal Energy Conference (EWTEC) (pp. 1088-1-1088-9). Cork, Ireland: Technical Committee of the European Wave and Tidal Energy Conference.
Orszaghova, Jana ; Wolgamot, Hugh ; Draper, Scott ; Rafiee, Ashkan. / Non-linear behaviour of an idealised submerged WEC with Coulomb damping. Proceedings of the 12th European Wave and Tidal Energy Conference (EWTEC) . Cork, Ireland : Technical Committee of the European Wave and Tidal Energy Conference, 2017. pp. 1088-1-1088-9
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title = "Non-linear behaviour of an idealised submerged WEC with Coulomb damping",
abstract = "Abstract—Wave energy converters (WECs) with Coulomb-type damping are relatively common as this behaviour is typical of hydraulic power take-off (PTO) systems. This study investigates motion response of a mass-spring system under combined linear and Coulomb damping, as a simplified representation of a WEC with a Coulomb damping force in the PTO. Motivation for this work stems from observed heave motions, of a submerged model-scale WEC with Coulomb PTO damping, which in some cases exhibited large offsets/drifts from the mean position. For submerged devices any restoring force must be engineered, as thehydrostatic restoring force is zero. Given a choice of restoring force and Coulomb coefficients, we are interested in how to make the optimum choice to minimise displacements in large waves. In this paper a simple model is used to investigate this question. In the range of parameters considered, the extremedisplacements are minimised by adopting negligible Coulomb damping force (relative to the exciting forces) and a weak detuned spring coefficient. The low-frequency drifting behaviour is seen to be important for both mean and extreme behaviour of the oscillator.",
keywords = "Coulomb damping, Submerged device, Non-linearity, Wave energy, Extreme response",
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Orszaghova, J, Wolgamot, H, Draper, S & Rafiee, A 2017, Non-linear behaviour of an idealised submerged WEC with Coulomb damping. in Proceedings of the 12th European Wave and Tidal Energy Conference (EWTEC) . Technical Committee of the European Wave and Tidal Energy Conference, Cork, Ireland, pp. 1088-1-1088-9, 12th European Wave and Tidal Energy Conference, Cork, Ireland, United Kingdom, 27/08/17.

Non-linear behaviour of an idealised submerged WEC with Coulomb damping. / Orszaghova, Jana; Wolgamot, Hugh; Draper, Scott; Rafiee, Ashkan.

Proceedings of the 12th European Wave and Tidal Energy Conference (EWTEC) . Cork, Ireland : Technical Committee of the European Wave and Tidal Energy Conference, 2017. p. 1088-1-1088-9.

Research output: Chapter in Book/Conference paperConference paper

TY - GEN

T1 - Non-linear behaviour of an idealised submerged WEC with Coulomb damping

AU - Orszaghova, Jana

AU - Wolgamot, Hugh

AU - Draper, Scott

AU - Rafiee, Ashkan

PY - 2017

Y1 - 2017

N2 - Abstract—Wave energy converters (WECs) with Coulomb-type damping are relatively common as this behaviour is typical of hydraulic power take-off (PTO) systems. This study investigates motion response of a mass-spring system under combined linear and Coulomb damping, as a simplified representation of a WEC with a Coulomb damping force in the PTO. Motivation for this work stems from observed heave motions, of a submerged model-scale WEC with Coulomb PTO damping, which in some cases exhibited large offsets/drifts from the mean position. For submerged devices any restoring force must be engineered, as thehydrostatic restoring force is zero. Given a choice of restoring force and Coulomb coefficients, we are interested in how to make the optimum choice to minimise displacements in large waves. In this paper a simple model is used to investigate this question. In the range of parameters considered, the extremedisplacements are minimised by adopting negligible Coulomb damping force (relative to the exciting forces) and a weak detuned spring coefficient. The low-frequency drifting behaviour is seen to be important for both mean and extreme behaviour of the oscillator.

AB - Abstract—Wave energy converters (WECs) with Coulomb-type damping are relatively common as this behaviour is typical of hydraulic power take-off (PTO) systems. This study investigates motion response of a mass-spring system under combined linear and Coulomb damping, as a simplified representation of a WEC with a Coulomb damping force in the PTO. Motivation for this work stems from observed heave motions, of a submerged model-scale WEC with Coulomb PTO damping, which in some cases exhibited large offsets/drifts from the mean position. For submerged devices any restoring force must be engineered, as thehydrostatic restoring force is zero. Given a choice of restoring force and Coulomb coefficients, we are interested in how to make the optimum choice to minimise displacements in large waves. In this paper a simple model is used to investigate this question. In the range of parameters considered, the extremedisplacements are minimised by adopting negligible Coulomb damping force (relative to the exciting forces) and a weak detuned spring coefficient. The low-frequency drifting behaviour is seen to be important for both mean and extreme behaviour of the oscillator.

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KW - Submerged device

KW - Non-linearity

KW - Wave energy

KW - Extreme response

M3 - Conference paper

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BT - Proceedings of the 12th European Wave and Tidal Energy Conference (EWTEC)

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Orszaghova J, Wolgamot H, Draper S, Rafiee A. Non-linear behaviour of an idealised submerged WEC with Coulomb damping. In Proceedings of the 12th European Wave and Tidal Energy Conference (EWTEC) . Cork, Ireland: Technical Committee of the European Wave and Tidal Energy Conference. 2017. p. 1088-1-1088-9