Reactive Turbulent Flow in Low-Dimensional, Disordered Media

We analyze the reactions $A+A \to \emptyset$ and $A + B \to \emptyset$ occurring in a model of turbulent flow in two dimensions. We find the reactant concentrations at long times, using a field-theoretic renormalization group analysis. We find a variety of interesting behavior, including, in the presence of potential disorder, decay rates faster than that for well-mixed reactions.Comment: 6 pages, 4 figures. To appear in Phys. Rev.

THE CHERLOC PROJECT: AN EXPERIMENTAL CASE STUDY OF MARINE STRUCTURES COMBINING ENGINEERING AND BIODIVERSITY

A topical issue for coastal structures is the development of innovative solutions combining functional requirement and ecological improvement. The CHERLOC collaborative project seeks to meet engineering design needs for coastal structures while preserving the ecological habitat of coastal areas and develop biodiversity on marine infrastructures. The aim of the project is to perform in-situ coastal protection experiments designed via a cross-disciplinary engineering, biodiversity and societal approach. Two pilot sites were set up in the Normandy region Ouistreham and Cherbourg. The Cherbourg site involved the installation of new artificial concrete block armour along a damaged trunk section of the existing Eastern port breakwater. These blocks are more specifically a new block armour known as "Double-Cube (DC)" and a new generation of toe blocks called ACCROBERM™ II, which are designed to replace "classic" toe rocks and limit direct and indirect environmental impacts. The design aimed to achieve a limited footprint on the seabed and an enhanced cavity. This paper gives an overview of the design conditions of the experiment, details the construction aspects of the pilot site, and points out the first lessons learned and the outcomes regarding stability and biodiversity surveys after more than one (1) year of the experiment

THE CHERLOC PROJECT: AN EXPERIMENTAL CASE STUDY OF MARINE STRUCTURES COMBINING ENGINEERING AND BIODIVERSITY

International audienceA topical issue for coastal structures is the development of innovative solutions combining functional requirement and ecological improvement. The CHERLOC collaborative project seeks to meet engineering design needs for coastal structures while preserving the ecological habitat of coastal areas and develop biodiversity on marine infrastructures. The aim of the project is to perform in-situ coastal protection experiments designed via a cross-disciplinary engineering, biodiversity and societal approach. Two pilot sites were set up in the Normandy region Ouistreham and Cherbourg. The Cherbourg site involved the installation of new artificial concrete block armour along a damaged trunk section of the existing Eastern port breakwater. These blocks are more specifically a new block armour known as "Double-Cube (DC)" and a new generation of toe blocks called ACCROBERM™ II, which are designed to replace "classic" toe rocks and limit direct and indirect environmental impacts. The design aimed to achieve a limited footprint on the seabed and an enhanced cavity. This paper gives an overview of the design conditions of the experiment, details the construction aspects of the pilot site, and points out the first lessons learned and the outcomes regarding stability and biodiversity surveys after more than one (1) year of the experiment

THE CHERLOC PROJECT: AN EXPERIMENTAL CASE STUDY OF MARINE STRUCTURES COMBINING ENGINEERING AND BIODIVERSITY

A topical issue for coastal structures is the development of innovative solutions combining functional requirement and ecological improvement. The CHERLOC collaborative project seeks to meet engineering design needs for coastal structures while preserving the ecological habitat of coastal areas and develop biodiversity on marine infrastructures. The aim of the project is to perform in-situ coastal protection experiments designed via a cross-disciplinary engineering, biodiversity and societal approach. Two pilot sites were set up in the Normandy region Ouistreham and Cherbourg. The Cherbourg site involved the installation of new artificial concrete block armour along a damaged trunk section of the existing Eastern port breakwater. These blocks are more specifically a new block armour known as "Double-Cube (DC)" and a new generation of toe blocks called ACCROBERM™ II, which are designed to replace "classic" toe rocks and limit direct and indirect environmental impacts. The design aimed to achieve a limited footprint on the seabed and an enhanced cavity. This paper gives an overview of the design conditions of the experiment, details the construction aspects of the pilot site, and points out the first lessons learned and the outcomes regarding stability and biodiversity surveys after more than one (1) year of the experiment

Three-dimensional structure and decay properties of vortices in shallow fluid layers

Recently, several laboratory experiments on vortex dynamics and quasi-two-dimensional turbulence have been performed in thin (stratified) fluid layers. Commonly, it is tacitly assumed that vertical motions, giving rise to a three-dimensional character of the flow, are inhibited by the limited vertical dimension. However, shallow water flows, which are vertically bounded by a no-slip bottom and a free surface, necessarily possess a three-dimensional structure due to the shear in the vertical direction. This shear may lead to significant secondary circulations. In this paper, the three-dimensional (3D) structure and the decay properties of vortices in shallow layers of fluid, both homogeneous and stratified, have been studied in detail by 3D direct numerical simulations. The quasi-two-dimensionality of these flows is an important issue if one is interested in a comparison of experiments of this type with purely two-dimensional theoretical models. The influence of several flow parameters, like the depth of the fluid and the Reynolds number, has been investigated. In general, it can be concluded that the flow loses its two-dimensional character for larger fluid depth and larger Reynolds number. Furthermore, it is possible to construct a regime diagram that allows the assessment of the parameter regime, where the flow can be considered as quasi-two-dimensional. It is found that the presence of secondary circulations within a planar vortex flow results in a deformation of the radial profile of axial vorticity. In the limiting case of quasi-two-dimensional flow, the vorticity profiles can be scaled according to a simple diffusion model. In a two-layer stratified system, the decay is reduced and three-dimensional motions are significantly inhibited compared to the corresponding flows in a homogeneous layer