Experimental Study of Wave Force Distribution on a Monopile Structure

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

Abstract

As the demand for offshore wind energy continues to grow, the strive to understand the wave forces acting on the substructure of the wind turbines continues. In regard to wind turbine
design, it is vital to consider not only the total wave force, but also the local wave forces. Local forces are particularly important for the design of secondary structures as e.g. mooring platforms. Typically, however, experimental studies mainly concern total forces or idealized local forces. We present here a rather simple way to measure local forces along a model monopile. The study is conducted in a wave flume of 28 m in length, in which waves are generated by a piston-type wave maker at a water depth of 0.515 m and shoal onto a bed of slope 1:25. A model monopile is installed and subjected to forcing from a series of both regular and irregular waves. In the experimental set-up, the model monopile is fixed at the bottom and the top and consists of seven independent cylindrical sections. The cylindrical sections are connected by force transducers which measure local shear, and so the associated local forces may be determined. The measured local forces are compared to the force distribution given by Morisons equation combined with linear theory and Wheeler stretching, which is a force estimate commonly used in the industry. This study shows that the total force is rather well captured by Morison’s equation. The force distribution estimated from Morison’s equation, however, shows larger discrepancies from the measured forces. This encourages for further measurements. In this study, we show that it is possible to measure force distribution on a model monopile in a simple and cost-effective manner. The aim is here to demonstrate the method and we will later present a larger body of work associated with the outcome of the measurements.
Original languageEnglish
Title of host publicationASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering
Number of pages8
Volume7B: Ocean Engineering
PublisherAmerican Society of Mechanical Engineers
Publication date2018
Article numberOMAE2018-77509
ISBN (Electronic)978-0-7918-5127-2
DOIs
Publication statusPublished - 2018
Event37th International Conference on Ocean, Offshore and Artic Engineering (OMAE2018) - Madrid, Spain
Duration: 17 Jun 201822 Jun 2018

Conference

Conference37th International Conference on Ocean, Offshore and Artic Engineering (OMAE2018)
CountrySpain
CityMadrid
Period17/06/201822/06/2018

Cite this

Vested, M. H., Carstensen, S., & Christensen, E. D. (2018). Experimental Study of Wave Force Distribution on a Monopile Structure. In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering (Vol. 7B: Ocean Engineering). [OMAE2018-77509] American Society of Mechanical Engineers. https://doi.org/10.1115/OMAE2018-77509
Vested, Malene Hovgaard ; Carstensen, Stefan ; Christensen, Erik Damgaard. / Experimental Study of Wave Force Distribution on a Monopile Structure. ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. Vol. 7B: Ocean Engineering American Society of Mechanical Engineers, 2018.
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abstract = "As the demand for offshore wind energy continues to grow, the strive to understand the wave forces acting on the substructure of the wind turbines continues. In regard to wind turbinedesign, it is vital to consider not only the total wave force, but also the local wave forces. Local forces are particularly important for the design of secondary structures as e.g. mooring platforms. Typically, however, experimental studies mainly concern total forces or idealized local forces. We present here a rather simple way to measure local forces along a model monopile. The study is conducted in a wave flume of 28 m in length, in which waves are generated by a piston-type wave maker at a water depth of 0.515 m and shoal onto a bed of slope 1:25. A model monopile is installed and subjected to forcing from a series of both regular and irregular waves. In the experimental set-up, the model monopile is fixed at the bottom and the top and consists of seven independent cylindrical sections. The cylindrical sections are connected by force transducers which measure local shear, and so the associated local forces may be determined. The measured local forces are compared to the force distribution given by Morisons equation combined with linear theory and Wheeler stretching, which is a force estimate commonly used in the industry. This study shows that the total force is rather well captured by Morison’s equation. The force distribution estimated from Morison’s equation, however, shows larger discrepancies from the measured forces. This encourages for further measurements. In this study, we show that it is possible to measure force distribution on a model monopile in a simple and cost-effective manner. The aim is here to demonstrate the method and we will later present a larger body of work associated with the outcome of the measurements.",
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Vested, MH, Carstensen, S & Christensen, ED 2018, Experimental Study of Wave Force Distribution on a Monopile Structure. in ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. vol. 7B: Ocean Engineering, OMAE2018-77509, American Society of Mechanical Engineers, 37th International Conference on Ocean, Offshore and Artic Engineering (OMAE2018), Madrid, Spain, 17/06/2018. https://doi.org/10.1115/OMAE2018-77509

Experimental Study of Wave Force Distribution on a Monopile Structure. / Vested, Malene Hovgaard; Carstensen, Stefan; Christensen, Erik Damgaard.

ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. Vol. 7B: Ocean Engineering American Society of Mechanical Engineers, 2018. OMAE2018-77509.

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

TY - GEN

T1 - Experimental Study of Wave Force Distribution on a Monopile Structure

AU - Vested, Malene Hovgaard

AU - Carstensen, Stefan

AU - Christensen, Erik Damgaard

PY - 2018

Y1 - 2018

N2 - As the demand for offshore wind energy continues to grow, the strive to understand the wave forces acting on the substructure of the wind turbines continues. In regard to wind turbinedesign, it is vital to consider not only the total wave force, but also the local wave forces. Local forces are particularly important for the design of secondary structures as e.g. mooring platforms. Typically, however, experimental studies mainly concern total forces or idealized local forces. We present here a rather simple way to measure local forces along a model monopile. The study is conducted in a wave flume of 28 m in length, in which waves are generated by a piston-type wave maker at a water depth of 0.515 m and shoal onto a bed of slope 1:25. A model monopile is installed and subjected to forcing from a series of both regular and irregular waves. In the experimental set-up, the model monopile is fixed at the bottom and the top and consists of seven independent cylindrical sections. The cylindrical sections are connected by force transducers which measure local shear, and so the associated local forces may be determined. The measured local forces are compared to the force distribution given by Morisons equation combined with linear theory and Wheeler stretching, which is a force estimate commonly used in the industry. This study shows that the total force is rather well captured by Morison’s equation. The force distribution estimated from Morison’s equation, however, shows larger discrepancies from the measured forces. This encourages for further measurements. In this study, we show that it is possible to measure force distribution on a model monopile in a simple and cost-effective manner. The aim is here to demonstrate the method and we will later present a larger body of work associated with the outcome of the measurements.

AB - As the demand for offshore wind energy continues to grow, the strive to understand the wave forces acting on the substructure of the wind turbines continues. In regard to wind turbinedesign, it is vital to consider not only the total wave force, but also the local wave forces. Local forces are particularly important for the design of secondary structures as e.g. mooring platforms. Typically, however, experimental studies mainly concern total forces or idealized local forces. We present here a rather simple way to measure local forces along a model monopile. The study is conducted in a wave flume of 28 m in length, in which waves are generated by a piston-type wave maker at a water depth of 0.515 m and shoal onto a bed of slope 1:25. A model monopile is installed and subjected to forcing from a series of both regular and irregular waves. In the experimental set-up, the model monopile is fixed at the bottom and the top and consists of seven independent cylindrical sections. The cylindrical sections are connected by force transducers which measure local shear, and so the associated local forces may be determined. The measured local forces are compared to the force distribution given by Morisons equation combined with linear theory and Wheeler stretching, which is a force estimate commonly used in the industry. This study shows that the total force is rather well captured by Morison’s equation. The force distribution estimated from Morison’s equation, however, shows larger discrepancies from the measured forces. This encourages for further measurements. In this study, we show that it is possible to measure force distribution on a model monopile in a simple and cost-effective manner. The aim is here to demonstrate the method and we will later present a larger body of work associated with the outcome of the measurements.

U2 - 10.1115/OMAE2018-77509

DO - 10.1115/OMAE2018-77509

M3 - Article in proceedings

VL - 7B: Ocean Engineering

BT - ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering

PB - American Society of Mechanical Engineers

ER -

Vested MH, Carstensen S, Christensen ED. Experimental Study of Wave Force Distribution on a Monopile Structure. In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. Vol. 7B: Ocean Engineering. American Society of Mechanical Engineers. 2018. OMAE2018-77509 https://doi.org/10.1115/OMAE2018-77509