Sylvain Delacroix - Academia.edu (original) (raw)
Papers by Sylvain Delacroix
L'une des principales missions de l'Ifremer consiste a etudier les ressources sous-marine... more L'une des principales missions de l'Ifremer consiste a etudier les ressources sous-marines et les fonds marins via une flotte oceanographique importante, employee a travers le globe. Pour ce faire, les navires sont equipes d'equipements acoustiques de type SONAR afin d'obtenir les informations recherchees dans la colonne d'eau. Dans certaines conditions de navigation, la houle et les mouvements du navire generent un entrainement d'air consequent sous la surface. Des nuages de bulles sont ainsi formes et entraines sous la carene par l'ecoulement. L'interaction entre ces bulles et les ondes acoustiques peuvent entrainer des pertes de donnees, et par consequent une diminution importante de la productivite du navire. Les outils permettant l'etude du phenomene sont actuellement limites. Les modeles numeriques ne sont pas suffisamment performants, pour simuler conjointement les mecanismes d'entrainement d'air a l'etrave puis l'ecoulement...
An experimental study of a 1/20th scale undulating membrane tidal energy converter (UMTEC) based ... more An experimental study of a 1/20th scale undulating membrane tidal energy converter (UMTEC) based on EEL Energy’s device is presented to assess the impact of the membrane's aspect ratio on its behaviour. The aim of this work is to study 3D effects on the machine to optimise the energy extraction. Five aspect ratios from 0.26 to 0.57 are tested at constant length, keeping other geometric parameters constant too. The mechanical energy of the membrane is conveyed above the free surface by a vertical cogwheel/chain assembly to be converted by an electric generator. After describing the experimental set-up, results are presented according to the reduced flow speed. Undulation dynamics and power conversion are analysed. This study highlights the effects of an undulation mode change on the undulation amplitude and frequency, independently from the aspect ratio. In addition, it shows that the UMTEC performances increase with the aspect ratio up to 0.5. Over this aspect ratio value, the e...
Applied Ocean Research, 2020
Most of the research done on tidal energy focuses on marine current turbines. Therefore, tidal tu... more Most of the research done on tidal energy focuses on marine current turbines. Therefore, tidal turbine's wake is well-documented. The tidal energy converter studied here is based on the fluid-structure interactions that occur between a flexible membrane and an axial flow, resulting in an undulating motion that can be used to harvest energy. This device's performance had been studied but it is the first time its wake is experimentally characterized from two-dimensional Particle Image Velocimetry (PIV) measurements. PIV is synchronized with a motion tracking system that gives information on trajectory and power conversion. Wake measurement gives access to velocity deficit, turbulence intensity and vorticity. Three configurations are tested in order to identify the influence of the main adjustment parameters. Pre-stress increases the membrane vertical speed, leading to a more important vertical expansion of the wake. The power extraction slows down the membrane's motion, thus limiting the wake's length and intensity. The flume tank measurements suggest that the best location for a downstream device in a tidal farm would be in the same horizontal position, at 5 membrane's length. In the open sea, the membrane interaction effects should not predominant. Highlights ► Undulating membrane first wake characterization from PIV measurements, ► Phase-averaged velocity deficit and vorticity are measured and presented, ► Vorticity dissipation rate result can be used to calibrate numerical model.
Comptes Rendus Mécanique, 2016
Ocean Engineering, 2016
Bubble sweep-down on oceanographic vessels generates acoustic perturbations. We propose in this w... more Bubble sweep-down on oceanographic vessels generates acoustic perturbations. We propose in this work to characterize the sub-surface bubbles occurrence conditions from acoustic data analysis acquired during surveys in relatively shallow water with the IFREMER research vessels Thalassa and Pourquoi Pas?. The methodology of data analysis used in this work allows us to characterize the sailing conditions influence on bubble sweep-down occurrence. The correlation between sailing conditions and acoustic perturbations tends to demonstrate that the presence of bubbles under the hull is clearly related to the wind speed and natural aeration, and that surface bubbles are advected differently in the water column by the two vessels Highlights ► Characterization of sub-surface bubbles occurrence conditions from acoustic data analysis. ►Correlation between sailing conditions and acoustic perturbations. ► Bubbles distribution comparisons demonstrate the effect of bubble sweep-down.
Volume 1A: Offshore Technology, 2014
L'une des principales missions de l'Ifremer consiste a etudier les ressources sous-marine... more L'une des principales missions de l'Ifremer consiste a etudier les ressources sous-marines et les fonds marins via une flotte oceanographique importante, employee a travers le globe. Pour ce faire, les navires sont equipes d'equipements acoustiques de type SONAR afin d'obtenir les informations recherchees dans la colonne d'eau. Dans certaines conditions de navigation, la houle et les mouvements du navire generent un entrainement d'air consequent sous la surface. Des nuages de bulles sont ainsi formes et entraines sous la carene par l'ecoulement. L'interaction entre ces bulles et les ondes acoustiques peuvent entrainer des pertes de donnees, et par consequent une diminution importante de la productivite du navire. Les outils permettant l'etude du phenomene sont actuellement limites. Les modeles numeriques ne sont pas suffisamment performants, pour simuler conjointement les mecanismes d'entrainement d'air a l'etrave puis l'ecoulement...
An experimental study of a 1/20th scale undulating membrane tidal energy converter (UMTEC) based ... more An experimental study of a 1/20th scale undulating membrane tidal energy converter (UMTEC) based on EEL Energy’s device is presented to assess the impact of the membrane's aspect ratio on its behaviour. The aim of this work is to study 3D effects on the machine to optimise the energy extraction. Five aspect ratios from 0.26 to 0.57 are tested at constant length, keeping other geometric parameters constant too. The mechanical energy of the membrane is conveyed above the free surface by a vertical cogwheel/chain assembly to be converted by an electric generator. After describing the experimental set-up, results are presented according to the reduced flow speed. Undulation dynamics and power conversion are analysed. This study highlights the effects of an undulation mode change on the undulation amplitude and frequency, independently from the aspect ratio. In addition, it shows that the UMTEC performances increase with the aspect ratio up to 0.5. Over this aspect ratio value, the e...
Applied Ocean Research, 2020
Most of the research done on tidal energy focuses on marine current turbines. Therefore, tidal tu... more Most of the research done on tidal energy focuses on marine current turbines. Therefore, tidal turbine's wake is well-documented. The tidal energy converter studied here is based on the fluid-structure interactions that occur between a flexible membrane and an axial flow, resulting in an undulating motion that can be used to harvest energy. This device's performance had been studied but it is the first time its wake is experimentally characterized from two-dimensional Particle Image Velocimetry (PIV) measurements. PIV is synchronized with a motion tracking system that gives information on trajectory and power conversion. Wake measurement gives access to velocity deficit, turbulence intensity and vorticity. Three configurations are tested in order to identify the influence of the main adjustment parameters. Pre-stress increases the membrane vertical speed, leading to a more important vertical expansion of the wake. The power extraction slows down the membrane's motion, thus limiting the wake's length and intensity. The flume tank measurements suggest that the best location for a downstream device in a tidal farm would be in the same horizontal position, at 5 membrane's length. In the open sea, the membrane interaction effects should not predominant. Highlights ► Undulating membrane first wake characterization from PIV measurements, ► Phase-averaged velocity deficit and vorticity are measured and presented, ► Vorticity dissipation rate result can be used to calibrate numerical model.
Comptes Rendus Mécanique, 2016
Ocean Engineering, 2016
Bubble sweep-down on oceanographic vessels generates acoustic perturbations. We propose in this w... more Bubble sweep-down on oceanographic vessels generates acoustic perturbations. We propose in this work to characterize the sub-surface bubbles occurrence conditions from acoustic data analysis acquired during surveys in relatively shallow water with the IFREMER research vessels Thalassa and Pourquoi Pas?. The methodology of data analysis used in this work allows us to characterize the sailing conditions influence on bubble sweep-down occurrence. The correlation between sailing conditions and acoustic perturbations tends to demonstrate that the presence of bubbles under the hull is clearly related to the wind speed and natural aeration, and that surface bubbles are advected differently in the water column by the two vessels Highlights ► Characterization of sub-surface bubbles occurrence conditions from acoustic data analysis. ►Correlation between sailing conditions and acoustic perturbations. ► Bubbles distribution comparisons demonstrate the effect of bubble sweep-down.
Volume 1A: Offshore Technology, 2014