The present paper proposes the numerical solution of an inverse problem in groundwater flow (Darc... more The present paper proposes the numerical solution of an inverse problem in groundwater flow (Darcy’s equation). This solution was achieved by combining a high-resolution new code HYSFLO-LBM (Hydrodynamic of Subsurface Flow by Lattice Boltzmann Method), based on LBM, to solve the direct problem, and the metaheuristic optimization algorithm CMA-ES ES (Covariance Matrix Adaptation-Evolution Strategy) to solve the optimization step. The integrated optimization algorithm which resulted from this combination, HYSFLO-LBM/CMA-ES, was applied to the hydrogeological experimental site of Beauvais (Northern France), instrumented by a set of sensors distributed over 20 hydrogeological wells. Hydrogeological parameters measured by the sensors are necessary to understand the aquifer functioning and to serve as input data for the identification of the transmissivity field by the HYSFLO-LBM/CMA-ES code. Results demonstrated an excellent concordance between the integrated optimization algorithm and h...
MARINE VI : proceedings of the VI International Conference on Computational Methods in Marine Engineering, 2015
In this work, we propose to implement the v 2 − f turbulence model rarely used in the marine envi... more In this work, we propose to implement the v 2 − f turbulence model rarely used in the marine environment to study the marine bottom boundary layer (MBBL). This model will complete the series of the turbulence models already implemented in the operational model 1DV-MoSeTT (1D Vertical Model of Sediment Transport and Turbulence) developed for the MBBL dynamics analysis. To show the performance of v 2 − f turbulence model first, we give a comparison between this model and q 2 − q 2 model. This comparison is based in various laboratory data proposed in the literature and widely used by the scientific community. Second, and in comparison with in-situ suspended sediment transport measurements, we examine the impact of the v 2 − f and the q 2 − q 2 turbulence models on the quantification of flux sediment at the bottom and on the estimation of the vertical profile of the suspended particle matter (SPM).
A novel e cient implicit direct forcing immersed boundary method for incompressible flows with co... more A novel e cient implicit direct forcing immersed boundary method for incompressible flows with complex boundaries is presented. In the previous work [1], the calculation is performed on the Cartesian grid regardless of the immersed object, with a fictitious force evaluated on the Lagrangian points to mimic the presence of the physical boundaries. However the explicit direct forcing method [1] fails to accurately impose the non-slip boundary condition on the immersed interface. In the present work, the calculation is based on the implicit treatment of the artificial force while in an e↵ective way of system iteration. The accuracy is also improved by solving the Navier-Stokes equation with the rotational incremental pressurecorrection projection method of Guermond and Shen [2]. Numerical simulations performed with the proposed method are in good agreement with those in the literature.
This paper concerns the asymptotic behavior of solutions of the 3D non-newtonian fluid flow with ... more This paper concerns the asymptotic behavior of solutions of the 3D non-newtonian fluid flow with slip condition (Tresca's type) imposed in a part of the boundary domain. Existence of at least one weak solution is proved. We study the limit when the thickness tends to zero and we prove a convergence theorem for velocity and pressure in appropriate functional spaces. The limit of slip condition is obtained. Besides, the uniqueness of the velocity and the pressure limits are also proved.
3D numerical simulation of ship-induced waves and sediment transport in restricted waterways
La Houille Blanche, 2014
In inland waterways, the wave wake is the main factor that erodes the banks and the alluvial bott... more In inland waterways, the wave wake is the main factor that erodes the banks and the alluvial bottom. It may cause sediment resuspension into the water column. A 3D hydrodynamic model based on the Navier-Stokes equations is developed to reproduce these wave wakes and analyze their kinematic characteristics. Then, a 3D model of sediment transport is coupled with the hydrodynamic model to estimate the influence of the wakes and return current to the resuspension of sediments. The coupled model was validated with the experimental data of the Compagnie Nationale du Rhône (CNR, 1997b). The numerical results show that the maximum value of Suspended Particulate Matter (SPM) is proportional to the Froude number (Fr), and also used to estimate the influence of the blocking coefficient (Cb) on sediment transport induced by the passing ship.
The duration of ship-generated waves (wake waves) and accelerated currents can generate significa... more The duration of ship-generated waves (wake waves) and accelerated currents can generate significant influences on the sediment transport. A 3-D numerical model is presented to estimate these effects. The hydrodynamic model is the 3-D Reynolds averaged Navier-Stokes (RANS) equations including the standard-k model while the 3-D convection-diffusion model is for the resuspended sediment transport. This hydro-sedimentary model is firstly validated with the trench experimental results, and then applied to the open channel with a moving ship. The computed results demonstrate that the resuspension generation mainly depends on ship speeds, barge number, and the relative distance away from ship. The acceleration effects of ship on the sediment transport are analyzed as well.
Body force term comparison in lattice Boltzmann method for shallow water equations
AIP Conference Proceedings, 2013
ABSTRACT We present the Lattice Boltzmann method for modelling shallow water equations with a foc... more ABSTRACT We present the Lattice Boltzmann method for modelling shallow water equations with a focus on external forces. Three different approximations for modelling the body force terms are used and compared in a 1D steady flow simulation over a bump. The accuracy, the mass conservation and the CPU time are discussed in this study.
Afin de simuler la morphodynamique de plages à barres et leur évolution depuis la zone de shoalin... more Afin de simuler la morphodynamique de plages à barres et leur évolution depuis la zone de shoaling jusqu'à la zone de swash, un modèle hydrodynamique en éléments finis (Reflux2dv), couplé à un modèle sédimentaire et d'évolution du fond, est présenté. Ce modèle est basé sur les équations de Boussinesq étendues et utilise des schémas numériques à Variation Totale Décroissante (TVD). La pertinence du modèle à simuler l'évolution des profils bathymétriques au cours de la formation puis la migration d'une barre est testée sur un cas test expérimental issu de Dette et al. 2002. Une application de ce couplage est effectuée sur le cas réel de la plage de Rousty (delta du Rhône).
Numerical modeling and parameters identification of overland and channel flows in watersheds
AIP Conference Proceedings, 2012
ABSTRACT We present a 2D numerical model based on the finite element method FEM to simulate the s... more ABSTRACT We present a 2D numerical model based on the finite element method FEM to simulate the surface flow of Watershed model. The kinematic wave approximation describing surface water flow under constant rainfall rate with infiltration is considered. Slopes and roughness are varying in space, while rainfall intensity varies in time. Thus, sensitivity to mesh size and time-step studies are carried out to ensure accuracy of results, and comparisons of simulation results with analytical solutions are done to assess the accuracy of the herein used numerical scheme and to validate the model. In this study, an identification procedure is also proposed to estimate the local roughness parameter, by using optimization tools based on CMA - ES (Covariance Matrix Adaptation Evolution Strategy) algorithm. The model was applied to the realistic case of Hirson's watershed (France).
Coupled 1D-river and 2D-overland flow model to simulate the rainfall-runoff process in watersheds
La Houille Blanche, 2014
A modeling system integrating river and watershed, capable of simulating overland flow and surfac... more A modeling system integrating river and watershed, capable of simulating overland flow and surface runoff in natural streams, is proposed. This model is based on the coupling of two models: a 2D-model for the flow in the plain and a 1D- model for the river flow. It constitutes a possible alternative to conceptual models with lockers, which are based on a coarse partition of watershed tanks communicating with each other by transfer laws. The 2D model is based here on the kinematic wave approximation constructed from 2D equations of Barré Saint-Venant. To better determine the state of flow, an optimization procedure is then implemented to identify the boundary conditions upstream (unknown incoming flow) for the real watershed Hirson (France). In the present work, we tested algorithms without gradient calculation (Simplex), algorithms with gradient calculation (SQP: Sequential Quadratic Programming, BFG: Broyden-Fletcher-Goldfarb-Shanno) and probabilistic CMAES type algorithms (Covariance Matrix Adaptation Evolution Strategy). The numerical solutions were compared with success, first with analytical solutions and then with numerical solutions found in the international literature. The results show that the CMAES algorithm is more relevant for identifying unknown flows in the case of a real watershed.
Dans ce travail on s'intéresse à une modélisation numérique qui permet de décrire la prise en com... more Dans ce travail on s'intéresse à une modélisation numérique qui permet de décrire la prise en compte de la houle dans un écoulement généré par les courants de marée. Notre contribution à cette étude a été réalisée à partir de deux modèles : le modèle MECCA, et le modèle SWAN. L'interaction houle-courant a été incluse. Les résultats entrepris dans ce travail montrent l'effet de la superposition de la houle et du courant sur le cisaillement au fond par rapport au courant seul. Autrement dit, près du fond, l'effet de la houle augmente la turbulence, de ce fait, le cisaillement et le frottement augmentent en entraînant une réduction de la vitesse près du fond.
A 3-D version of the MECCA model (Model of Estuarine and Coastal Circulation Assessment) is used ... more A 3-D version of the MECCA model (Model of Estuarine and Coastal Circulation Assessment) is used to simulate the dynamics of the Eastern part of the English Channel. This area is characterized by a strong tidal turbulent regime and a frontal zone identified near the French coast by a low-salinity band. The model uses the upwind scheme to approximate the
Dans ce travail, nous nous proposons d'appliquer le modèle k-à un écoulement combinant houle et c... more Dans ce travail, nous nous proposons d'appliquer le modèle k-à un écoulement combinant houle et courant afin de proposer une nouvelle paramétrisation des contraintes de cisaillement (maximale et moyenne) de cet écoulement. La précision d'une telle paramétrisation est nécessaire pour une bonne estimation des échanges à l'interface fluide-sédiment qui conditionne le transport sédimentaire (charriage et suspension). Une comparaison des performances des modèles classiques de turbulence : k-et k-appliqués à un écoulement purement oscillatoire sera également donnée. Mots-clés : Houle-courant-turbulence-modèle k-modèle k-contrainte de cisaillementinterface fluide-sédiment.
Cette étude s'intéresse à la remise en suspension de sédiments occasionnée par le passage de bate... more Cette étude s'intéresse à la remise en suspension de sédiments occasionnée par le passage de bateaux. En complément à des mesures in situ, une modélisation 1DV (1D Vertical) est proposée pour estimer les paramètres qui se sont révélés mal déterminés. Le modèle résout la structure verticale de la vitesse horizontale (u), de la concentration en MES (matières en suspension) (c), de l'Energie Cinétique Turbulente (k) et sa longueur de mélange (L). La turbulence est modélisée par un modèle à deux équations de type (k-kL), et le forçage est effectué à la surface libre par les passages de bateaux. Les résultats montrent que l'hypothèse d'un écoulement cisaillé à la surface est satisfaisante pour simuler les pics de MES générés par les bateaux.
A one-dimensional model of the vertical exchange of suspended sediment in a tidal boundary layer ... more A one-dimensional model of the vertical exchange of suspended sediment in a tidal boundary layer is proposed. The model includes two linearized momentum equations for the horizontal velocity components and a series of advection–diffusion equations for concentrations of suspended sediment of specific size. Turbulence generated at the sea-bed is computed with the aid of a two-equation closure describing the time–space
In this paper, we present a 2D coupled fluid-structure interaction procedure to assess the stabil... more In this paper, we present a 2D coupled fluid-structure interaction procedure to assess the stability of a cracked gravity dam against increasing water level. In this procedure the structure is assumed to be a discontinuous deformable solid containing pre-existing cracks. Thus, the Discontinuous Deformation Analysis DDA method is used to study the solid discontinuous medium, and the continuum finite element flow model to calculate the hydrostatic forces corresponding to the water level. The contact constraints between discrete blocks are imposed through an implicit augmented Lagrangian format. Numerical results show the potential of the proposed coupled model to quantify the direct influence of the nature and location of the internal cracks on the overall stability of common gravity dams. RÉSUMÉ. Dans ce travail, une procédure de couplage fluide-structure 2D est mise en oeuvre pour étudier la stabilité d'un barrage poids fissuré et soumis à la pression hydrostatique due à l'augmentation brusque du niveau d'eau. Cette modélisation tient compte de la nature et de la position de la fissure interne du barrage. Le module solide est basé sur la méthode de l'analyse des déformations discontinues (DDA). Les forces mises en jeu dans ce module proviennent d'un module fluide qui fournit la pression hydrostatique. Les simulations ont mis
3-D Numerical Simulation of Convoy-Generated Waves in a Restricted Waterway
Journal of Hydrodynamics, 2012
ABSTRACT We consider waves generated by the passing of convoys in a restricted waterway. The magn... more ABSTRACT We consider waves generated by the passing of convoys in a restricted waterway. The magnitude of these waves depends mainly on the geometrical and kinematical parameters of the convoy, such as the speed and the hull geometry. The objective of this study is to predict the relationship between these geometrical and kinematical parameters and the amplitude of ship-generated waves as well as the water plane drawdown. Numerical simulations are conducted by solving the 3-D Navier-Stokes equations along with the standard k – ɛ model for turbulent processes. The results are compared first with the empirical model and second with experimental measurements performed by the French company Compagnie National du Rhône (CNR).
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