Étude de la réouverture de la lagune du Havre aux Basques. II. Modélisation numérique du processus de mélange des eaux

1995 ◽  
Vol 22 (1) ◽  
pp. 72-79
Author(s):  
A. Khelifa ◽  
Y. Ouellet ◽  
J.-L. Robert
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Transport Model ◽  
Numerical Study ◽  
Time Discretization ◽  
Element Formulation ◽  
Modélisation Numérique ◽  
Advection Diffusion ◽  
Space Discretization ◽  
Triangular Elements

This paper, the second of a series, presents the results of a numerical study of the advection–diffusion water mixing process between the Havre aux Basques lagoon and the Gulf of St. Lawrence, after the proposed reopening of the lagoon. In this study, the reopening scheme of the inlet, which has been closed in 1957, is analyzed by using a horizontal two-dimensional numerical model. The transport model is based on the Douglas–Wang finite element formulation for a space discretization. The approximation is quadratic, using six-node triangular elements. The semi-implicit Crank–Nicholson scheme is used for a time discretization. The results show that after reopening the lagoon, mixing may take between 5 and 22 days for a diffusion coefficient considered constant throughout the region and varying from 5 to 500 m2/s. Key words: lagoon, Havre aux Basques, advection–diffusion, mixing, numerical model, finite element, Douglas–Wang.

Étude sédimentologique de sites de dépôt de matériaux de dragage dans le fleuve Saint-Laurent. I. Modélisation numérique tridimensionnelle du panache de dispersion des sédiments retenus dans la colonne d'eau

1994 ◽  
Vol 21 (6) ◽  
pp. 1025-1036
Author(s):  
Ali Khelifa ◽  
Yvon Ouellet
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Water Discharge ◽  
Three Dimensional ◽  
Element Formulation ◽  
Modélisation Numérique ◽  
Advection Diffusion Equation ◽  
Advection Diffusion ◽  
La Madeleine ◽  
St Lawrence River

Within the sedimentological study of disposal sites of dredged materials along the St. Lawrence River between Sorel and Saint-Pierre-les-Becquets, a three-dimensional numerical model (SED3D) has been developed to reproduce the dispersion of sediments maintained in the water column during an open-water discharge operation. This model is based on the extension of the Douglas–Wang finite element formulation to discretize the steady three-dimensional advection–diffusion equation. The space discretization is quadratic using 20 nodes hexahedron elements (H20). Results of SED3D model applied to Cap-de-la-Madeleine disposal site show that suspended sediments settle in a domain less than 200 m of the disposal point by 50 m and so they can not reach the seaway. The qualitative validity of these results was demonstrated by the analysis of some sediment samples taken in the St. Lawrence River at Cap-de-la-Madeleine. Key words: dredging, sediments, St. Lawrence River, advection–diffusion, numerical model, Douglas–Wang, finite element.

Étude de la réouverture de la lagune du Havre aux Basques. I. Modélisation numérique des conditions d'écoulement

1995 ◽  
Vol 22 (1) ◽  
pp. 55-71
Author(s):  
Y. Ouellet ◽  
A. Khelifa ◽  
J.-F. Bellemare
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Element Model ◽  
Two Dimensional ◽  
Flow Conditions ◽  
Modélisation Numérique ◽  
Tidal Flows ◽  
Dimensional Finite Element ◽  
The Stability ◽  
La Madeleine

A numerical study based on a two-dimensional finite element model has been conducted to analyze flow conditions associated with different possible designs for the reopening of Havre aux Basques lagoon, located in Îles de la Madeleine, in the middle of the Gulf of St. Lawrence. More specifically, the study has been done to better define the depth and geometry of the future channel as well as its orientation with regard to tidal flows within the inlet and the lagoon. Results obtained from the model have been compared and analyzed to put forward some recommendations about choice of a design insuring the stability of the inlet with tidal flows. Key words: numerical model, finite element, lagoon, reopening, Havre aux Basques, Îles de la Madeleine.

Numerical Study of Hydrodynamic Forces on a Submarine Piggyback Pipeline Under Wave Action

2012 ◽  
Author(s):  
Xiaofei Cheng ◽  
Yongxue Wang ◽  
Bing Ren ◽  
Guoyu Wang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Numerical Model ◽  
Stokes Equations ◽  
Numerical Study ◽  
Hydrodynamic Forces ◽  
Wave Action ◽  
Numerical Results ◽  
Physical Model Test ◽  
Element Method

In the paper, a 2D numerical model is established to simulate the hydrodynamic forces on a submarine piggyback pipeline under regular wave action. The two-dimensional Reynolds-averaged Navier-Stokes equations with a κ-ω turbulence model closure are solved by using a three-step Taylor-Galerkin finite element method (FEM). A Computational Lagrangian-Eulerian Advection Remap Volume of Fluid (CLEAR-VOF) method is employed to simulate free surface problems, which is inherently compatible with unstructured meshes and finite element method. The numerical results of in-line force and lift (transverse) force on the piggyback pipeline for e/D = G/D = 0.25 and KC = 25.1 are compared with physical model test results, which are conducted in a marine environmental flume in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, China. It is indicated that the numerical results coincide with the experimental results and that the numerical model can be used to predict the hydrodynamic forces on the piggyback pipeline under wave action. Based on the numerical model, the surface pressure distribution and the motion of vortices around the piggyback pipeline for e/D = G/D = 0.25, KC = 25.1 are investigated, and a characteristic vortex pattern around the piggyback pipeline denoted “anti-phase-synchronized” pattern is recognized.

Optical Tomography With a Least Square Finite Element Formulation of the Collimated Irradiation in Frequency Domain

2010 ◽  
Author(s):  
Olivier Balima ◽  
Joan Boulanger ◽  
Andre´ Charette ◽  
Daniel Marceau
Keyword(s):  
Finite Element ◽  
Optical Properties ◽  
Frequency Domain ◽  
Complex Geometry ◽  
Numerical Study ◽  
Optical Tomography ◽  
Least Square ◽  
Finite Element Formulation ◽  
Element Formulation ◽  
Scattering Media

This paper presents a numerical study of optical tomography in frequency domain for the reconstruction of optical properties of scattering and absorbing media with collimated irradiation light sources. The forward model is a least square finite element formulation of the collimated irradiation problem where the intensity is separated into its collimated and scattered parts. This model does not use any empirical stabilization and moreover the collimated source direction is taken into account. The inversion uses a gradient type minimization method where the gradient is computed through an adjoint formulation. Scaling is used to avoid numerical round errors, as the output readings at detectors are very low. Numerical reconstructions of optical properties of absorbing and scattering media with simulated data (noised and noise-free) are achieved in a complex geometry with satisfactory results. The results show that complex geometries are well handled with the proposed method.

Thermohydrodynamic Analysis for a Hydrodynamic Journal Bearing Groove

2005 ◽  
Vol 219 (4) ◽  
pp. 263-274 ◽  
Author(s):  
L Jeddi ◽  
M El Khlifi ◽  
D Bonneau
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Journal Bearing ◽  
Numerical Procedure ◽  
Navier Stokes ◽  
Element Formulation ◽  
Lubricant Flow ◽  
Hydrodynamic Journal Bearing ◽  
Feeding Pressure ◽  
Energy Equations

A numerical procedure is developed for the analysis of thermohydrodynamic behaviour of the hydrodynamic (HD) flow in the groove of a journal bearing. The Navier-Stokes and energy equations are written in terms of the primitive variables u, v, p, and T and solved simultaneously using the incremental load method and the finite element formulation. The numerical model is applied to the analysis of the velocities, the pressure, and the temperature patterns that characterize the lubricant flow in the HD groove. The effects of the runner velocity and the feeding pressure are investigated.

scholarly journals A fully discrete finite element scheme for the Kelvin-Voigt model

Filomat ◽  
2019 ◽  
Vol 33 (18) ◽  
pp. 5813-5827 ◽  
Author(s):  
Xiaoli Lu ◽  
Lei Zhang ◽  
Pengzhan Huang
Keyword(s):  
Finite Element ◽  
Time Discretization ◽  
Finite Element Approximation ◽  
Element Approximation ◽  
Step Method ◽  
Fully Discrete ◽  
Space Discretization ◽  
Voigt Model ◽  
Discrete Finite Element ◽  
Present Algorithm

In this paper, we study convergence of a fully discrete scheme for the two-dimensional nonstationary Kelvin-Voigt model. This scheme is based on a finite element approximation for space discretization and the Crank-Nicolson-type scheme for time discretization, which is a two step method. Moreover, we obtain error estimates of velocity and pressure. At last, the applicability and effectiveness of the present algorithm are illustrated by numerical experiments.

scholarly journals Numerical Study of a Francis Turbine over Wide Operating Range: Some Practical Aspects of Verification

2020 ◽  
Vol 12 (10) ◽  
pp. 4301
Author(s):  
Chirag Trivedi ◽  
Igor Iliev ◽  
Ole Gunnar Dahlhaug
Keyword(s):  
Numerical Model ◽  
Transport Model ◽  
Numerical Study ◽  
Operating Conditions ◽  
Francis Turbine ◽  
Step Size ◽  
Time Step ◽  
Angular Rotation ◽  
Time Step Size ◽  
Automatic Optimization

Hydropower plays an essential role in maintaining energy flexibility. Modern designs focus on sustainability and robustness using different numerical tools. Automatic optimization of the turbines is widely used, including low, mini and micro head turbines. The numerical techniques are not always foolproof in the absence of experimental data, and hence accurate verification is a key component of automatic optimization processes. This work aims to investigate the newly designed Francis runner for flexible operation. Unsteady simulations at 80 operating points of the turbine were conducted. The numerical model consisted of 16 million nodes of hexahedral mesh. A SAS-SST (scale adaptive simulation-shear stress transport) model was enabled for resolving/modeling the turbulent flow. The selected time-step size was equivalent to one-degree angular rotation of the runner. Global parameters, such as efficiency, torque, head and flow rate were considered for proper verification and validation. (1) A complete hill diagram of the turbine was prepared and verified with the reference case. (2) The relative error in hydraulic efficiency was computed and the over trend was studied. This allowed us to investigate the consistency of the numerical model under extreme operating conditions, far away from the best efficiency point. (3) Unsteady fluctuations of runner output torque were studied to identify unstable regions and magnitude of torque oscillations.

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