Laboratoire dHydraulique Saint Venant

Chatou, France

Laboratoire dHydraulique Saint Venant

Chatou, France
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Ray R.K.,Indian Institute of Technology Guwahati | Ray R.K.,Laboratoire dHydraulique Saint Venant
Journal of Scientific Computing | Year: 2011

In the present work, a numerical study is made using a recently developed Higher Order Compact (HOC) finite difference scheme to test its capacity in capturing the very complex flow phenomenon of unsteady flow past a rotating and translating circular cylinder. The streamfunction-vorticity formulation of the Navier-stokes equations in cylindrical polar coordinate are considered as the governing equations. In the present investigation, flow is computed for a fixed Reynolds number (Re) 200 and rotational parameter values 0.5, 1.0, 2.07 and 3.25 are considered. Firstly, the flow patterns for different α values and for long time range are computed and qualitative comparisons are made with existing experimental and numerical results. Then, as a further check on the consistency of the experimental and present numerical results, quantitative comparisons are made for the velocity profiles at several locations. All these qualitative and quantitative comparisons show excellent agreements with existing experimental and numerical results. © 2010 Springer Science+Business Media, LLC.


Yates M.L.,Bureau de Recherches Géologiques et Minières | Yates M.L.,Laboratoire dHydraulique Saint Venant | Le Cozannet G.,Bureau de Recherches Géologiques et Minières
Natural Hazards and Earth System Sciences | Year: 2012

The coastal zone is a complex environment in which a variety of forcing factors interact causing shoreline evolution. Coastal managers seek to predict coastal evolution and to identify regions vulnerable to erosion. Here, a Bayesian network is developed to identify the primary factors influencing decadal-scale shoreline evolution of European coasts and to reproduce the observed evolution trends. Sensitivity tests demonstrate the robustness of the model, showing higher predictive capabilities for stable coasts than for eroding coasts. Finally, the study highlights the need to update and expand large-scale coastal data sets, particularly by including local scale processes and anthropogenic impacts. © 2012 Author(s).


Demangeon F.,Laboratoire dHydraulique Saint Venant | Goeury C.,Électricité de France | Zaoui F.,Électricité de France | Goutal N.,Laboratoire dHydraulique Saint Venant | And 3 more authors.
Houille Blanche | Year: 2016

The information on sensitivity provided by derivatives is indispensable in many fields of science. In numerical analysis, computing the accurate value of the derivatives of a function can be a challenge. The classical Finite Differences (FD) method is a simple solution to implement when estimating the value of a derivative. However, it remains highly sensitive numerically and costly in calculation time. Conversely, the Algorithmic Differentiation Method (AD) is a powerful tool for calculating the derivatives of a function described by a computer program. Whatever the complexity of the algorithms implemented in the expression of a function, AD calculates its derivative accurately and reduces development efforts. This article presents the contribution of AD in comparison to FD in the problem of calibrating an industrial class 1D shallow water model. Model calibration is performed by a deterministic mathematical optimiser requiring accurate calculation of the sensitivity of the water surface profile in relation to the friction on a river bed. Two comparative real test cases are presented. They permit validating the better performance expected from AD as a tool used to obtain optimal calibration. © Société Hydrotechnique de France, 2016.


Ray R.K.,Laboratoire dHydraulique Saint Venant
World Academy of Science, Engineering and Technology | Year: 2010

An unstructured finite volume numerical model is presented here for simulating shallow-water flows with wetting and drying fronts. The model is based on the Green's theorem in combination with Chorin's projection method. A 2nd-order upwind scheme coupled with a Least Square technique is used to handle convection terms. An Wetting and drying treatment is used in the present model to ensures the total mass conservation. To test it's capacity and reliability, the present model is used to solve the Parabolic Bowl problem. We compare our numerical solutions with the corresponding analytical and existing standard numerical results. Excellent agreements are found in all the cases.


Ray R.K.,Laboratoire dHydraulique Saint Venant | Nguyen K.D.,Laboratoire dHydraulique Saint Venant
World Academy of Science, Engineering and Technology | Year: 2010

An unstructured finite volume numerical model is presented here for simulating shallow-water flows with wetting and drying fronts. The model is based on the Green's theorem in combination with Chorin's projection method. A 2 nd-order upwind scheme coupled with a Least Square technique is used to handle convection terms. An Wetting and drying treatment is used in the present model to ensures the total mass conservation. To test it's capacity and reliability, the present model is used to solve the Parabolic Bowl problem. We compare our numerical solutions with the corresponding analytical and existing standard numerical results. Excellent agreements are found in all the cases.


Violeau D.,Laboratoire dHydraulique Saint Venant | Leroy A.,Laboratoire dHydraulique Saint Venant
Journal of Computational Physics | Year: 2015

A classical incompressible algorithm for Smoothed Particle Hydrodynamics (ISPH) is analyzed in terms of critical time step for numerical stability. For this purpose, a theoretical linear stability analysis is conducted for unbounded homogeneous flows, leading to an analytical formula for the maximum CFL (Courant-Friedrichs-Lewy) number as a function of the Fourier number. This gives the maximum time step as a function of the fluid viscosity, the flow velocity scale and the SPH discretization size (kernel standard deviation). Importantly, the maximum CFL number at large Reynolds number appears twice smaller than with the traditional Weakly Compressible (WCSPH) approach. As a consequence, the optimal time step for ISPH is only five times larger than with WCSPH. The theory agrees very well with numerical data for two usual kernels in a 2-D periodic flow. On the other hand, numerical experiments in a plane Poiseuille flow show that the theory overestimates the maximum allowed time step for small Reynolds numbers. © 2015 Elsevier Inc.


Violeau D.,Laboratoire dHydraulique Saint Venant | Leroy A.,Laboratoire dHydraulique Saint Venant
Journal of Computational Physics | Year: 2014

In the SPH method for viscous fluids, the time step is subject to empirical stability criteria. We proceed to a stability analysis of the Weakly Compressible SPH equations using the von Neumann approach in arbitrary space dimension for unbounded flow. Considering the continuous SPH interpolant based on integrals, we obtain a theoretical stability criterion for the time step, depending on the kernel standard deviation, the speed of sound and the viscosity. The stability domain appears to be almost independent of the kernel choice for a given space discretisation. Numerical tests show that the theory is very accurate, despite the approximations made. We then extend the theory in order to study the influence of the method used to compute the density, of the gradient and divergence SPH operators, of background pressure, of the model used for viscous forces and of a constant velocity gradient. The influence of time integration scheme is also studied, and proved to be prominent. All of the above theoretical developments give excellent agreement against numerical results. It is found that velocity gradients almost do not affect stability, provided some background pressure is used. Finally, the case of bounded flows is briefly addressed from numerical tests in three cases: a laminar Poiseuille flow in a pipe, a lid-driven cavity and the collapse of a water column on a wedge. © 2013 Elsevier Inc.

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