Tag: wave energy

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Drag-induced dissipation in wave-structure interaction

In the interaction of water waves with marine structures, the interplay between wave diffraction and drag-induced dissipation is seldom, if ever, considered. In particular, linear hydrodynamic models, and extensions thereof through the addition of a quadratic force term, do not represent the change in amplitude of the waves diffracted and radiated to the far field, which should result from local energy dissipation in the vicinity of the structure. In this work, a series of wave flume experiments is carried out, whereby waves of increasing amplitude impinge upon a vertical barrier, extending partway through the flume width. As the wave amplitude increases, the effect of drag – which is known to increase quadratically with the flow velocity – is enhanced, thus allowing the examination of the far-field effect of drag-induced dissipation, in terms of wave reflection and transmission. A potential flow model is proposed, with a simple quadratic pressure drop condition through a virtual porous surface, located on the sides of the barrier (where dissipation occurs). Experimental results confirm that drag-induced dissipation has a marked effect on the diffracted flow, i.e. on wave reflection and transmission, which is appropriately captured in the proposed model. Conversely, when diffraction becomes dominant as the barrier width becomes comparable to the incoming wavelength, the diffracted flow must be accounted for in predicting drag-induced forces and dissipation.

Modelling the far-field effect of drag-induced dissipation in wave-structure interaction: A numerical and experimental study
A. Mérigaud, B. Thiria, R. Godoy-Diana, G. Perret
Journal of Fluid Mechanics, 987, A24 (2024).
doi: 10.1017/jfm.2024.298

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Geometrical framework for hydrodynamics and control of wave energy converters

A. Mérigaud, B. Thiria, & R. Godoy-Diana
PRX Energy 2, 023003 (2023)
doi: 10.1103/PRXEnergy.2.023003

Approaches for converting the energy of sea-surface waves into useful power remain on the fringe of renewable energy solutions despite years of research. Among the hundreds of proposed wave-energy converters, no single wave-energy device provides sufficient power to be an attractive practical solution. Therefore, considering an integrated farm of many devices is an intrinsic part of the problem. Models need to consider the dynamics of many devices simultaneously, and the devices’ interaction with each other and the environment introduces additional complexity. In this work, we propose a conceptually simple analysis framework that uses geometry in the complex plane to understand the basic relations underlying wave-energy conversion in a model farm. Under this framework, a single complex variable encapsulates wave reflection, transmission, and absorption by a row of wave-energy converters and provides guidance for achieving maximal power output under impedance-matching conditions.

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BIOMIM @ EWTEC 2021

Two papers from the team were presented at the 11th European Wave and Tidal Energy Conference in Plymouth, UK!

Ocean wave transmission, reflection and absorption by rows of vertical structures along the coastline
A. Mérigaud, B. Thiria & R. Godoy-Diana
In Proceedings of the 11th European Wave and Tidal Energy Conference, 5-9th Sept 2021, Plymouth, UK.
preprint: arXiv:2111.14816

On the interaction of surface water waves and fully-submerged elastic plates
G. Polly, A. Mérigaud, R. Alhage, B. Thiria & R. Godoy-Diana
In Proceedings of the 11th European Wave and Tidal Energy Conference, 5-9th Sept 2021, Plymouth, UK.
preprint: arXiv:2111.03018

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Revisiting the transmission and reflection of water waves over an array of obstacles

With a view to numerical modelling and optimisation of wave energy farms, a simple recursive formulation is employed to solve for the reflection and transmission of plane water waves by a number of rows of vertical obstacles, under the wide-spacing approximation. The proposed recursive formulation relies on the ‘concatenation’ of any two sets of obstacles, for which the reflection–transmission problem is already resolved. Furthermore, the obstacles are allowed to move in any combination of pitch and surge. The proposed recursive model is validated by means of physical experiments in a small-scale wave flume, whereby waves are reflected and transmitted by one, two and three rows of vertical, flexible blades, taking into account dissipation within the fluid along the wave propagation direction. For the special case of identical, regularly spaced rows, under the adopted formalism, distinct theoretical behaviours are highlighted, depending on whether or not individual obstacles absorb (or dissipate) energy as they interact with incoming waves. In a ‘non-dissipative’ case, the well known fact that discrete values of the row-to-row distance 𝐿 completely cancel reflection is retrieved, as well as the existence of ‘band-gap’ intervals, i.e. intervals for 𝐿 where reflection is high, with maximum reflection occurring away from the Bragg condition. In contrast, when the obstacles dissipate or absorb energy as they interact with the fluid, reflection is always non-zero, and, as the number of rows tends to infinity, forms marked Bragg peaks, reaching unity when 𝐿 is a multiple of half a wavelength.

A wide-spacing approximation model for the reflection and transmission of water waves over an array of vertical obstacles
A. Mérigaud, B. Thiria & R. Godoy-Diana
Journal of Fluid Mechanics 923, A2 (2021)
doi: 10.1017/jfm.2021.532

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Interference model for an array of wave-energy-absorbing flexible structures


C. Nové-Josserand, R. Godoy-Diana, & B. Thiria
Physical Review Applied 11, 034054 (2019)
[doi:10.1103/PhysRevApplied.11.034054]

Considerable work has been undertaken for the improvement of wave-energy converters and array design. It has recently been suggested that by extracting wave energy, these farms could also serve to protect shorelines from wave damage. The present work focuses on the local effects of wave-structure interactions within an array of oscillating absorbers to optimize global effects, such as reflection, damping, and energy absorption. We use a model system of flexible blades, subjected to monochromatic waves, and develop a simplified one-dimensional model to predict optimal configurations, depending on various parameters, which include the number of blades, their spacing, and their flexibility. Optimal configurations are found to be close to regular patterns, and the impact of array configurations is shown to be limited regarding wave dissipation, mainly due to a competition between reflection and absorption.

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Clotilde Nové-Josserand’s PhD defense. Converting wave energy from fluid–elasticity interactions

PhD defense on October 1st, 2018, 2:30pm, at the PMMH meeting room (Sorbonne Université, Barre Cassan, Bât. A 1er Étage, 7 Quai Saint Bernard, 75005 Paris).

Converting wave energy from fluid–elasticity interactions

Understanding the mechanisms involved in wave-structure interactions is of high interest for the development of efficient wave energy harvesters as well as for coastal management. In this thesis, we study the interactions of surface waves with a model array of slender flexible structures, in view of developing an efficient system for both attenuating and harvesting wave energy. The presented results are based around experimental investigations, by means of small scale facilities, in which the spatial arrangement of the flexible objects is the key parameter of Continue reading “Clotilde Nové-Josserand’s PhD defense. Converting wave energy from fluid–elasticity interactions”

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Surface wave energy absorption by a partially submerged bio-inspired canopy

Surface wave energy absorption by a partially submerged bio-inspired canopy
C. Nové-Josserand, F. Castro Hebrero, L.-M. Petit, W. Megill, R. Godoy-Diana & B. Thiria
Bioinspiration & Biomimetics 13 036006 (2018)
[doi:10.1088/1748-3190/aaae8c]
PDF file

Aquatic plants are known to protect coastlines and riverbeds from erosion by damping waves and fluid flow. These flexible structures absorb the fluid-borne energy of an incoming fluid by deforming mechanically. In this paper we focus on the mechanisms involved in these fluid-elasticity interactions, as an efficient energy harvesting system, using an experimental canopy model in a wave tank.We study an array of partially-submerged flexible structures that are subjected to the action of a surface wave field, investigating in particular the role of spacing between the elements of the array on the ability of our system to absorb energy from the flow. The energy absorption potential of the canopy model is examined using global wave height measurements for the wave field and local measurements of the elastic energy based on the kinematics of each element of the canopy. We study different canopy arrays and show in particular that flexibility improves wave damping by around 40%, for which half is potentially harvestable.

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Tuning a wave-energy-driven OWC seawater pump to polychromatic waves

polychromatic_signalsOn the tuning of a wave-energy driven oscillating-water-column seawater pump to polychromatic waves
R. Godoy-Diana & S. P. R. Czitrom.
Ocean Engineering, 34 : 2374-2384 (2007).

Abstract: Performance of wave-energy devices of the oscillating water column (OWC) type is greatly enhanced when a resonant condition with the forcing waves is maintained. The natural frequency of such systems can in general be tuned to resonate with a given wave forcing frequency. In this paper we address the tuning of an OWC sea-water pump to polychromatic waves. We report results of wave tank experiments, which were conducted with a scale model of the pump. Continue reading “Tuning a wave-energy-driven OWC seawater pump to polychromatic waves”

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Hydrodynamics of an oscillating water column seawater pump

sibeo_colorHydrodynamics of an oscillating water column seawater pump. Part I: Theoretical Aspects
S. P. R. Czitrom; R. Godoy; E. Prado; P. Pérez & R. Peralta-Fabi.
Ocean Engineering, 27 : 1181-1198 (2000).

Abstract: A wave-driven seawater pump, composed of a resonant and an exhaust duct joined by a variable-volume air compression chamber, is studied. The time dependent form of Bernoulli’s equation, adapted to incorporate losses due to friction, vortex formation at the mouths and radiation damping, describes the pump behaviour. A dimensional analysis of the pump equations shows that a proposed scale-model will perform similar to a full-scale seawater pump. Continue reading “Hydrodynamics of an oscillating water column seawater pump”

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Hydrodynamics of an oscillating water column seawater pump (Part II)

sibeoHydrodynamics of an oscillating water column seawater pump. Part II: Tuning to Monochromatic Waves
S. P. R. Czitrom; R. Godoy; E. Prado; A. Olvera & C. Stern.
Ocean Engineering, 27 : 1199-1219 (2000).

Abstract: Flume experiments with a scale-model of a wave driven seawater pump in monochromatic waves are described. A tuning mechanism optimises the pump performance by keeping it at resonance with the waves. The pumping process itself was found to de-tune the system because of the reduced gravity restoring force due to spilling in the compression chamber. A perturbation analysis of the pump equations shows that performance of the system can be increased by optimising the shape of the pump intake to minimise losses due to vortex formation. Continue reading “Hydrodynamics of an oscillating water column seawater pump (Part II)”

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Vortex suppresion in an oscillating flow

conical_diffuserVortex suppresion in an oscillating flow
C. Stern; S. Czitrom; E. Prado & R. Godoy.
Revista Mexicana de Fisica, 46 : 409-410 (2000).

Abstract: The motivation for this work was the reduction of losses due to vortex formation at the entrance of a wave driven seawater pump. Measurements in a wave tank using a prototype had shown a 10% ¡ncrease in the pumping efficiency when a trumpet like shape was added to the intake. This lead us to search for an inlake that would reduce or completely suppress vortex formation. In this experiment a piston produces an oscil1ating flow inside a partly submerged duct. At the end of the duct four different shapes were tested. Continue reading “Vortex suppresion in an oscillating flow”