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Restoration or Rehabilitation of the Faleme River Affected by Mining Activities: What Methods?

Journal of Water Resource and Protection 2024年第4期16卷 233-263页

作者： Mor Diop Ibrahima Mall Elhadji Mamadou Sonko Tidiane Diop Birane Niane cheikh mbow Environmental Sciences Institute (ISE) Cheikh Anta Diop university of Dakar Dakar Senegal Higher School of Mines Geology and Environment Amadou Mahtar Mbow University of Diamniadio (UAM) Dakar Senegal Department of Chemical Cheikh Anta Diop university of Dakar Dakar Senegal Departmentof Engineering Sciences Iba Der Thiam University of Thi&#232s Thi&#232s Senegal

The Faleme River, a West Africa long transboundary stream (625 km) and abundant flow (>1100 million m3) is affected by severe erosion because of mining activities that takes place throughout the riverbed. To preserve this important watercourse and ensure the sustainability of its services, selecting and implementing appropriates restorations techniques is vital. In this context, the purpose of this paper was to present an overview of the actions and techniques that can be implemented for the restoration/rehabilitation of the Faleme. The methodological approach includes field investigation, water sampling, literature review with cases studies and SWOT analysis of the four methods presented: river dredging, constructed wetlands, floating treatment wetlands and chemical precipitation (coagulation and flocculation). The study confirmed the pollution of the river by suspended solids (TSS > 1100 mg/L) and heavy metals such as iron, zinc, aluminium, and arsenic. For the restoration methods, it was illustrated through description of their mode of operation and through some case studies presented, that all the four methods have proven their effectiveness in treating rivers but have differences in their costs, their sustainability (detrimental to living organisms or causing a second pollution) and social acceptance. They also have weaknesses and issues that must be addressed to ensure success of rehabilitation. For the case of the Faleme river, after analysis, floating treatment wetlands are highly recommended for their low cost, good removal efficiency if the vulnerability of the raft and buoyancy to strong waves and flow is under control.

关键词： Faleme River River Restoration Constructed Wetlands Dredging Floating Treatment Wetlands Coagulation-Flocculation

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Numerical Study of the Effect of Thermosiphon on the Vertical Dispersion of Pollutants

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Journal of Mechanics Engineering and Automation 2016年第6期6卷 295-300页

作者： Zeinebou Yahya cheikh mbow Department of Physics Faculty of Sciences and Arts Qassim University Buraidah 51452 Kingdom of Saudi Arabia Department of Physics Faculty of Science and Technology Cheikh Anta Diop of Dakar University Dakar 61641 Sengal

The dispersion of pollutants in urban environments is a major problem. Because of this fact our study comes to propose prevention and security system against the dispersion of releases and fumes from industrial smokestacks. The system is modeled by a plume-thermosiphon interaction flow resulting from a vertical cylinder open at both ends with a generating source of the plume centered at the opening of the cylinder. The cylindrical wall heats under the effect of the thermal radiation emitted by the generator source, which causes a flow of thermosiphon around the flow of the thermal plume. In order to determine the radiosity of radiation leaving the wall we have been used the Simpson quadrature and the Gaussian elimination method with a dominant pivot. Numerical simulations have been executed for different positions of the thermosiphon compared to the plume source, and for a number of Rayleigh fixed Ra = 10＋7, and a radius of the hot source corresponds to R＊ = 0.46. The results oftbe numerical model that we have been developed, help first identify the behavior of pollutants from the dynamic and thermal point of view and then explore the different locations of the thermosiphon compared to the source of the plume which causes a major influence on the dispersion of pollutants.

关键词： Interaction numerical modelling pollutants thermosiphon.

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Numerical Simulation of the Natural Convection in a Tunnel Whose Floor Has a Variable Sinusoid with a Roof Opening

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Open Journal of Fluid Dynamics 2019年第4期9卷 326-333页

作者： Oumar Drame cheikh mbow Florin Bode Fluid Mechanics Laboratory and Applications Department of Physics Faculty of Science and Technology Cheikh Anta Diop University of Dakar Dakar Senegal Department of Mechanical Engineering Technical University of Cluj-Napoca Cluj-Napoca Romania

A two-dimensional numerical study of natural convection in a tunnel whose plane is sinusoidal with an opening on the horizontal ceiling is presented. In this work, we study the thermoconvective instabilities of air in a tunnel closed at both ends and heated by the floor. The study was carried out for different cases of geometry by varying the thickness of the sinusoid and the height of the tunnel. In order to create a transverse movement of the air, we heated the floor to the temperature Tf and kept the horizontal ceiling at the temperature Tg?such that Tg? Tf. This work has a lot of scope of application ranging from geothermal flow to the civil engineering like ventilation in the case of tunnels and thermal comfort of buildings. The Navier Stokes equations that model this problem have been solved using the numerical method with simplifying assumptions such as the Boussinesq hypothesis. And finally an interpretation of the results of the simulations has been made taking into account the variation of the form factors such as the amplitude of the sinusoid for Rayleigh number 2 x 104 ≤Ra?≤7 x 106?and Prendtl number Pr = 0.71.

关键词： Convection CFD Tunnel Sunisoide Thermoconvective

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The Magnetic Field as Trigger for Disturbances of a Flow of a Newtonian Fluid through a Cylindrical Pipe with a Horizontal Axis

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Modern Mechanical Engineering 2022年第4期12卷 83-97页

作者： Ibrahima Kama Mamadou Lamine Sow cheikh mbow Department of Physics University Cheikh Anta Diop (UCAD) Dakar Senegal

A Fourrier Petrov Galerkin spectral method is described for high accuracy computation of linearized dynamics for flow in a circular pipe. The code used here is based on solenoidal velocity variables. It is written in FORTRAN. Systematic studies are presented on the dependence of eigenvalues and other quantities on the axial and azimuthal wave number;the reynolds’ number Re and a new none-dimensional number Ne. The flow will be considered stable if all the real parts of the eigenvalues are negative and unstable if only one of them is positive.

关键词： Newtonian Fluids Magnetic Field Linear Stability Petrov-Galerkin Generalized Eigenvalue Problem

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Solution of 1D Poisson Equation with Neumann-Dirichlet and Dirichlet-Neumann Boundary Conditions, Using the Finite Difference Method

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Journal of Electromagnetic Analysis and Applications 2014年第10期6卷 309-318页

作者： Serigne Bira Gueye Kharouna Talla cheikh mbow Département de Physique Faculté des Sciences et Techniques Université Cheikh Anta Diop Dakar-Fann Sénégal

An innovative, extremely fast and accurate method is presented for Neumann-Dirichlet and Dirichlet-Neumann boundary problems for the Poisson equation, and the diffusion and wave equation in quasi-stationary regime;using the finite difference method, in one dimensional case. Two novels matrices are determined allowing a direct and exact formulation of the solution of the Poisson equation. Verification is also done considering an interesting potential problem and the sensibility is determined. This new method has an algorithm complexity of O(N), its truncation error goes like O(h2), and it is more precise and faster than the Thomas algorithm.

关键词： 1D Poisson Equation Finite Difference Method Neumann-Dirichlet Dirichlet-Neumann Boundary Problem Tridiagonal Matrix Inversion Thomas Algorithm

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Generalization of the Exact Solution of 1D Poisson Equation with Robin Boundary Conditions, Using the Finite Difference Method

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Journal of Electromagnetic Analysis and Applications 2014年第12期6卷 372-381页

作者： Serigne Bira Gueye Kharouna Talla cheikh mbow Département de Physique Faculté des Sciences et Techniques Université Cheikh Anta Diop Dakar-Fann Sénégal

A new and innovative method for solving the 1D Poisson Equation is presented, using the finite differences method, with Robin Boundary conditions. The exact formula of the inverse of the discretization matrix is determined. This is the first time that this famous matrix is inverted explicitly, without using the right hand side. Thus, the solution is determined in a direct, very accurate (O(h2)), and very fast (O(N)) manner. This new approach treats all cases of boundary conditions: Dirichlet, Neumann, and mixed. Therefore, it can serve as a reference for solving the Poisson equation in one dimension.

关键词： Robin Boundary Poisson Equation Matrix Inversion

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Linear and Nonlinear Stokes Waves Theory: Numerical Hydrodynamic and Energy Studies

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Open Journal of Fluid Dynamics 2023年第1期13卷 61-79页

作者： Alpha Malick Ndiaye Fadel Diop Samba Dia cheikh mbow Laboratoire de Mécanique des Fluides et Transferts Département de Physique Faculté des Sciences et Techniques Université Cheikh Anta Diop (UCAD) Dakar Sénégal

The increase of wave energy in electricity production is an objective shared by many countries to meet growing demand and global warming. To analyze devices capable of converting the energy of sea waves into electrical energy, it is important to master the various theories of gravity waves and generation. We will in our work consider a numerical waves tank for an amplitude A=0.5, a wavelength λ=0.25 , an average height He=10 and a Froude number fixed at 1 × 105. Numerical wave channel analysis is used to reproduce the natural phenomenon of wave propagation in an experimental model. Wave makers are usually used to generate waves in the channel. In theory, the influence of an incident wave can be considered, as in the case of our study. In this study, the evolution of the hydrodynamic parameters and the energy transported in one wavelength can be determined by calculation. A change of variable will be done in this work to facilitate the writing of the boundary conditions at the free surface and at the bottom. The nonlinear Stokes theory will be studied in this case in order to provide hydrodynamic solutions through the Navier-Stokes equations to finally deduce the energetic results. To do this, the finite difference method will be used for the hydrodynamic results such as the velocity potential and the free surface elevation and the trapezium method of Newton for the energetic results. Thus, we will determine the energetic potential according to the decrease in the slope of the tank. To do this, we will take as values of beta representing the inverse of the slope of the tank, β=100, β=105, β=110 and β=105. .

关键词： Waves Tank Energy Waves Gravity Waves Navier-Stokes Numerical Nonlinear Stokes Theory

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Efficient BTCS + CTCS Finite Difference Scheme for General Linear Second Order PDE

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Journal of Electromagnetic Analysis and Applications 2021年第10期13卷 135-143页

作者： Gueye Serigne Bira mbow cheikh Diagana Mouhamed Fadel Département de Physique Faculté des Sciences et Techniques Université Cheikh Anta Diop Dakar-Fann Sénégal

This work deals with a second order linear general equation with partial derivatives for a two-variable function. It covers a wide range of applications. This equation is solved with a finite difference hybrid method:... 详细信息

关键词： Finite Difference BCTS + CTCS Usmani’s Algorithm Tridiagonal Matrix Telegraph Equation

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Study of a Parabolic Trough Adequate for the CERER Site （Dakar-Senegal）

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Journal of Energy and Power Engineering 2016年第5期10卷 275-282页

作者： Awa Mar Serigne Thiao cheikh mbow Issakha Youm CERER (Center of Studies and Research on Renewable Energies) Dakar BP. 476 Senegal Laboratory of Solar Energy Materials and Systems Department of Physics Faculty of Sciences and Technology UniversityCheikh anta Diop of Dakar Senegal Laboratory of Fluid Mechanical and Hydraulic Department of Physics Faculty of Sciences and Technology University CheikhAnta Diop of Dakar Senegal

This study presents the modeling of a parabolic trough solar collector. The main objective is to show the influences of the parabolic trough sensor effective efficiency （concentrator optical efflciencies of transmission, reflection, geometrical and the receiver absorption coefficient）, of its length, of the mass flow rate on temperatures distributions of the heat fluid and the receiver and on thermal global efficiency （solar conversion efficiency into energy usable）. The atmospheric parameters are those of Senegal in April. A prototype existing in the CERER （Center of Studies and Research on Renewable Energies）（Dakar-Senegal） is given as example of application.

关键词： Parabolic trough solar collector receptor efficiency temperature fluid.

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Effects of the Reynolds and Weissenberg’s Numbers on the Stability of Linear Pipe Flow of Viscous Fluid

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Modern Mechanical Engineering 2018年第4期8卷 264-277页

作者： Ibrahima Kama Mamadou Lamine Sow Kodjo Kpode cheikh mbow Department of Physics University Cheikh Anta DIOP-UCAD Dakar Senegal Department of Physics University of Kara Kara Togo

A Fourier-Chebyshev Petrov-Galerkin spectral method is described for high accuracy computation of linearized dynamics for flow in a circular pipe. The code used here is based on solenoidal velocity variables and is written in FORTRAN. Systematic studies are presented of the dependence of eigenval-ues and other quantities on the axial and azimuthal wave numbers;the Reyn-olds’ number of up to 107 and the Weissenberg’s number that is considered lower here. The flow will be considered stable if all the real parts of the ei-genvalues obtained are negative and unstable if only one of these values is positive.

关键词： Viscoelastic Fluids Oldroyd-B Model Linear Stability Petrov-Galerkin Generalized Eigenvalue Problem

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