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Hurther D.,CNRS Laboratory of Geophysical and Industrial Flows | Thorne P.D.,National Oceanography Center
Journal of Geophysical Research: Oceans | Year: 2011

The present study focuses on the fine-scale flow and sand transport processes above onshore migrating ripples below skewed surface gravity waves in the shoaling zone. A set of acoustic instruments was deployed in the shoaling region of the large-scale wave channel at Canal d'Investigacío i Experimatacío Marítima, Universitat Polticnica de Catalunya, Barcelona, Spain, in order to provide high-resolution velocity and sediment concentration profiles with an acoustic concentration and velocity profiler (ACVP). Measurements are analyzed relative to the positions of the measured nonmoving sand bed and the interface separating the suspension from the near-bed load layer. This interface is detected here by the application of a novel acoustic bed echo detection method. Furthermore, the use of the dual-frequency inversion proposed in the work of Hurther et al. (2011) allows for the calculation of the sediment concentration profile across both the suspension and near-bed load layers. The sand bed was covered by quasi-two-dimensional suborbital ripples migrating onshore. As proposed by O'Donoghue et al. (2006), the occurrence of quasi-two-dimensional ripples is attributed to the fine-size sand of D50 = 250 m used in the present study under full-scale forcing conditions. In order to determine the effect of shoaled wave skewness on the ripple vortex entrainment and sediment transport, the instantaneous and mean measurements of the flow, sediment concentration, and sediment flux along the ripple profile are discussed in terms of (1) the occurrence of ripple vortex entrainment on either side of the ripple crest; (2) the wave velocity phase lagging driven by the ripple vortex entrainment process and the turbulent bed friction effects in the wave boundary layer; (3) phase lagging between velocity and maximum concentration and sediment flux events; (4) the structure of bed friction and ripple-driven turbulence across the suspension and the near-bed load layers; and (5) the streaming components. The results on these aspects strongly support that the wave velocity skewness effect under shoaling waves is fairly similar to the one obtained in skewed oscillatory water tunnel flows. Furthermore, it is found that the onshore-oriented net bed load sediment transport is at the origin of the onshore ripple migration. This flux is roughly twice as much as the opposite offshore-oriented net suspension flux dominated by the ripple vortex entrainment processes. Copyright 2011 by the American Geophysical Union. Source


Goncalves E.,CNRS Laboratory of Geophysical and Industrial Flows
Computers and Fluids | Year: 2013

A compressible, multiphase, one-fluid inviscid solver has been developed to investigate the behavior of various cavitation models. A new source term for the mass transfer between phases is proposed. A range of models from three to five equations is compared. Numerical simulations are performed on rarefaction problems and compared with reference solutions. © 2012 Elsevier Ltd. Source


Thorne P.D.,National Oceanography Center | Hurther D.,CNRS Laboratory of Geophysical and Industrial Flows
Continental Shelf Research | Year: 2014

For over two decades, coastal marine scientists studying boundary layer sediment transport processes have been using, and developing, the application of sound for high temporal-spatial resolution measurements of suspended particle size and concentration profiles. To extract the suspended sediment parameters from the acoustic data requires an understanding of the interaction of sound with a suspension of sediments and an inversion methodology. This understanding is distributed around journals in a number of scientific fields and there is no single article that succinctly draws together the different components. In the present work the aim is to provide an overview on the acoustic approach to measuring suspended sediment parameters and assess its application in the study of non-cohesive inorganic suspended sediment transport processes. © 2013. Source


Goncalves E.,CNRS Laboratory of Geophysical and Industrial Flows
International Journal of Heat and Mass Transfer | Year: 2014

A compressible, two-phase, one-fluid solver has been developed to investigate the behaviour of cavitation models including thermodynamic effects. The code is composed by three conservation laws for mixture variables (mass, momentum and total energy) and a supplementary transport equation for the void ratio. Two formulations for the mass transfer between phases are studied. Numerical simulations are firstly performed on rarefaction cavitating problems in which the working fluid is hot water and freon R-114. A realistic turbulent Venturi case with freon R-114 is performed and comparisons are done between 3- and 4-equation models. A warming effect is highlighted downstream the cavitation pocket in the region of pressure recuperation. © 2014 Elsevier Ltd. All rights reserved. Source


Goncalvs E.,CNRS Laboratory of Geophysical and Industrial Flows
European Journal of Mechanics, B/Fluids | Year: 2011

The simulation of cavitating flows is a challenging problem both in terms of modelling the physics and developing robust numerical methodologies. Such flows are characterized by important variations of the local Mach number, compressibility effects on turbulence and involve thermodynamic phase transition. To simulate these flows by applying homogeneous models and Reynolds averaged codes, the turbulence modelling plays a major role in the capture of unsteady behaviours. This paper presents a one-fluid compressible Reynolds-Averaged NavierStokes (RANS) solver with a simple equation of state (EOS) for the mixture. A special focus is devoted to the turbulence model influence. Unsteady numerical results are given for Venturi geometries and comparisons are made with experimental data. © 2010 Elsevier Masson SAS. All rights reserved. Source

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