Computational Study of Particle-Eddy Interaction in Sedimentation Tanks
01 Jan 2004-Journal of Environmental Engineering (American Society of Civil Engineers)-Vol. 130, Iss: 1, pp 37-49
TL;DR: In this article, a detailed study of the hydrodynamics of sedimentation tanks is presented using an Eulerian-Lagrangian approach to study the motion of solids in the tank.
Abstract: Sedimentation tanks are used in the process industry to separate the solid particles from the slurry to get the clarified liquid. A detailed study of the hydrodynamics of sedimentation tanks is presented here using an Eulerian-Lagrangian approach to study the motion of solids in the tank. The model, in its present form, is applicable only to nonflocculent discrete (Type I) settling. It is shown that a typical particle-eddy interaction can be characterized by a lower cut-off size below which the particles would be entrained by the eddy; and an upper cut-off size above which the particle would continuously settle through the sedimentation tank in spite of the recirculation. The effect of inlet configuration on the flow field as well as on the settling characteristics has been investigated. The simulations show that both the upper and the lower cut-off sizes for a sedimentation tank are considerably reduced by providing a tulip type of inlet with a conical deflector as compared to a straight inlet.
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TL;DR: This review discusses conventional and current brewery wastewater treatment methods, and the application and potential of microalgae in brewery wastewater Treatment, and discusses the benefits as well as challenges associated withmicroalgae brewery and other industrial wastewater treatments.
Abstract: Concerns about environmental safety have led to strict regulations on the discharge of final brewery effluents into water bodies. Brewery wastewater contains huge amounts of organic compounds that can cause environmental pollution. The microalgae wastewater treatment method is an emerging environmentally friendly biotechnological process. Microalgae grow well in nutrient-rich wastewater by absorbing organic nutrients and converting them into useful biomass. The harvested biomass can be used as animal feed, biofertilizer, and an alternative energy source for biodiesel production. This review discusses conventional and current brewery wastewater treatment methods, and the application and potential of microalgae in brewery wastewater treatment. The study also discusses the benefits as well as challenges associated with microalgae brewery and other industrial wastewater treatments.
99 citations
Cites background from "Computational Study of Particle-Edd..."
...The process also separates materials such as grease and oil from the effluent [13]....
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TL;DR: In this paper, the use of 3D computational fluid dynamics (CFD) is investigated for studying flow, sedimentation, and solids separation in a tank equipped with one inlet pipe and two outlets (outlet pipe, overflow weir).
Abstract: The lack of knowledge about particle behavior in combined sewer detention tanks remains a significant difficulty for the design of these works. In this paper, the use of 3D computational fluid dynamics (CFD) is investigated for studying flow, sedimentation, and solids separation in a tank equipped with one inlet pipe and two outlets (outlet pipe and overflow weir). Twenty-three experiments have been carried out. The Fluent® CFD code is used for simulating the flow field. Sedimentation and solids separation are calculated using the particle tracking facility of the software. Bed shear stress (BSS) and bed turbulent kinetic energy (BTKE) boundary conditions are investigated. The time scale constant of the random walk model has been set to the unexpected value of 0.5-1. The simulated mass percentages and deposit locations are in good agreement with measurements. The sensitivity to the BTKE threshold and particle density is studied. © 2008 Elsevier Ltd. All rights reserved.
82 citations
Cites methods from "Computational Study of Particle-Edd..."
...CFD has been successfully used under various hydraulic conditions: combined sewer overflow (CSO) chambers [2,3], combined sewer detention pipe [4], oil-grit separator [5], hydrodynamic separator [6], rectangular detention tanks [7–11], circular sedimentation tank [12], etc....
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TL;DR: In this article, the authors proposed that ethanol wastewater is one of the most polluted waste products to dispose because of the low pH, high temperature, dark brown color, high ash content and high percentage of dissolved organic and inorganic matter with high biochemical oxygen demand (BOD) and chemical oxygen consumption (COD) values.
Abstract: The alcohol distilleries are growing extensively worldwide due to widespread industrial applications of alcohol such as in chemicals, pharmaceuticals, cosmetics, beverages, food and perfumery industry, etc. The industrial production of ethanol by fermentation results in the discharge of large quantities of high-strength liquid wastes. Distillery wastewater is one of the most polluted waste products to dispose because of the low pH, high temperature, dark brown colour, high ash content and high percentage of dissolved organic and inorganic matter with high biochemical oxygen demand (BOD) and chemical oxygen demand (COD) values. Its characteristics are depending on the feed stock and various aspects of ethanol production process. Spent wash polluted the water bodies into ways; first, the highly coloured nature which can block out sunlight, thus reducing oxygenation of the water by photosynthesis and hence becomes detrimental to aquatic life. Second, it has a high pollution load which would result in eutroph...
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...Physical treatment is used to decrease suspended/settable solids from wastewater which may be removed inexpensively via sedimentation by using the force of gravity to separate suspended material, oil, and grease from the wastewater (Jayanti and Narayanan 2004)....
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TL;DR: The results suggest that more observations inside the inlet zone are needed to achieve better model calibration and correct application of the turbulence model, which can be crucial to optimizing the geometry of inlet structure and sludge hopper as well as changing return solids concentration for the operation.
Abstract: The secondary sedimentation tank (SST) is a sensitive and complicated process in an activated sludge process. Due to the importance of its performance, computational fluid dynamics (CFD) methods have been employed to study the underflow hydrodynamics and solids distribution. Unlike most of the previous numerical studies, in the present investigation, the performance of three different types of turbulence models, standard k-e, RNG k-e and Realizable k-e, are evaluated. Firstly, two-dimensional axisymmetric CFD models of two circular SSTs are validated with the field observations. Next, comprehensive comparisons are presented of the model predictions of the key physical quantities, such as the concentration of effluent suspended solids (ESS), and returned activated sludge (RAS), sludge blanket height (SBH), turbulent properties and flow and concentration patterns. A surprising result shows that the prediction of the ESS concentration is not sensitive to the change of turbulence models; while remarkable prediction difference can be observed in the inlet zone and near-field of sludge hopper and SBH. The results suggest that more observations inside the inlet zone are needed to achieve better model calibration and correct application of the turbulence model, which can be crucial to optimizing the geometry of inlet structure and sludge hopper as well as changing return solids concentration for the operation.
46 citations
TL;DR: In this paper, the authors studied the flow dynamics in a secondary sedimentation tank with the three-dimensional two-fluid model and showed the significant effects of the baffle height and baffle location on the distribution of solid concentrations.
Abstract: Secondary sedimentation tanks, which are used widely in wastewater treatment, require optimization to improve wastewater treatment efficiency. The flow dynamics is an important parameter for the design of reactors. However, very little literature deals with the flow in secondary sedimentation tanks. Therefore, the flow dynamics in a secondary sedimentation tank is studied in this paper. The solid–liquid two-phase turbulent flow in the tank is modeled with the three-dimensional two-fluid model. Using computational fluid dynamics (CFD), the velocity profile and distribution of solid concentration are given. The use of different baffles in the same tank is also simulated. With the inclusion of the baffle, the distribution of the solid concentration differs greatly. The significant effects of the baffle height and baffle location on the distribution of solid concentrations are also discussed. These results provide useful information for the design of secondary sedimentation tanks.
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01 Jan 2006
TL;DR: In this article, Navier and Stokes this article proposed a solution to the problem of finding a solution for the problem in a three-dimensional (3-dimensional) boundary layer.
Abstract: Important Nomenclature Kinematics of Fluid Motion Introduction to Continuum Motion Fluid Particles Inertial Coordinate Frames Motion of a Continuum The Time Derivatives Velocity and Acceleration Steady and Nonsteady Flow Trajectories of Fluid Particles and Streamlines Material Volume and Surface Relation between Elemental Volumes Kinematic Formulas of Euler and Reynolds Control Volume and Surface Kinematics of Deformation Kinematics of Vorticity and Circulation References Problems The Conservation Laws and the Kinetics of Flow Fluid Density and the Conservation of Mass Principle of Mass Conservation Mass Conservation Using a Control Volume Kinetics of Fluid Flow Conservation of Linear and Angular Momentum Equations of Linear and Angular Momentum Momentum Conservation Using a Control Volume Conservation of Energy Energy Conservation Using a Control Volume General Conservation Principle The Closure Problem Stokes' Law of Friction Interpretation of Pressure The Dissipation Function Constitutive Equation for Non-Newtonian Fluids Thermodynamic Aspects of Pressure and Viscosity Equations of Motion in Lagrangian Coordinates References Problems The Navier--Stokes Equations Formulation of the Problem Viscous Compressible Flow Equations Viscous Incompressible Flow Equations Equations of Inviscid Flow (Euler's Equations) Initial and Boundary Conditions Mathematical Nature of the Equations Vorticity and Circulation Some Results Based on the Equations of Motion Nondimensional Parameters in Fluid Motion Coordinate Transformation Streamlines and Stream Surfaces Navier--Stokes Equations in Stream Function Form References Problems Flow of Inviscid Fluids Introduction Part I: Inviscid Incompressible Flow The Bernoulli Constant Method of Conformal Mapping in Inviscid Flows Sources, Sinks, and Doublets in Three Dimensions Part II: Inviscid Compressible Flow Basic Thermodynamics Subsonic and Supersonic Flow Critical and Stagnation Quantities Isentropic Ideal Gas Relations Unsteady Inviscid Compressible Flow in One-dimension Steady Plane Flow of Inviscid Gases Theory of Shock Waves References Problems Laminar Viscous Flow Part I: Exact Solutions Introduction Exact Solutions Exact Solutions for Slow Motion Part II: Boundary Layers Introduction Formulation of the Boundary Layer Problem Boundary Layer on 2-D Curved Surfaces Separation of the 2-D Steady Boundary Layers Transformed Boundary Layer Equations Momentum Integral Equation Free Boundary Layers Numerical Solution of the Boundary Layer Equation Three-Dimensional Boundary Layers Momentum Integral Equations in Three Dimensions Separation and Attachment in Three Dimensions Boundary Layers on Bodies of Revolution and Yawed Cylinders Three-Dimensional Stagnation Point Flow Boundary Layer On Rotating Blades Numerical Solution of 3-D Boundary Layer Equations Unsteady Boundary Layers Second-Order Boundary Layer Theory Inverse Problems in Boundary Layers Formulation of the Compressible Boundary Layer Problem Part III: Navier--Stokes Formulation Incompressible Flow Compressible Flow Hyperbolic Equations and Conservation Laws Numerical Transformation and Grid Generation Numerical Algorithms for Viscous Compressible Flows Thin-Layer Navier--Stokes Equations (TLNS) References Problems Turbulent Flow Part I: Stability Theory and the Statistical Description of Turbulence Introduction Stability of Laminar Flows Formulation for Plane-Parallel Laminar Flows Temporal Stability at In nite Reynolds Number Numerical Algorithm for the Orr--Sommerfeld Equation Transition to Turbulence Statistical Methods in Turbulent Continuum Mechanics Statistical Concepts Internal Structure in Physical Space Internal Structure in the Wave-Number Space Theory of Universal Equilibrium Part II: Development of Averaged Equations Introduction Averaged Equations for Incompressible Flow Averaged Equations for Compressible Flow Turbulent Boundary Layer Equations Part III: Basic Empirical and Boundary Layer Results in Turbulence The Closure Problem Prandtl's Mixing-Length Hypothesis Wall-Bound Turbulent Flows Analysis of Turbulent Boundary Layer Velocity Pro les Momentum Integral Methods in Boundary Layers Differential Equation Methods in 2-D Boundary Layers Part IV: Turbulence Modeling Generalization of Boussinesq's Hypothesis Zero-Equation Modeling in Shear Layers One-Equation Modeling Two-Equation (K-Ae) Modeling Reynolds' Stress Equation Modeling Application to 2-D Thin Shear Layers Algebraic Reynolds' Stress Closure Development of A Nonlinear Constitutive Equation Current Approaches to Nonlinear Modeling Heuristic Modeling Modeling for Compressible Flow Three-Dimensional Boundary Layers Illustrative Analysis of Instability Basic Formulation of Large Eddy Simulation References Problems Mathematical Exposition 1: Base Vectors and Various Representations Introduction Representations in Rectangular Cartesian Systems Scalars, Vectors, and Tensors Differential Operations On Tensors Multiplication of A Tensor and A Vector Scalar Multiplication of Two Tensors A Collection of Usable Formulas Taylor Expansion in Vector Form Principal Axes of a Tensor Transformation of T to the Principal Axes Quadratic Form and the Eigenvalue Problem Representation in Curvilinear Coordinates Christoffel Symbols in Three Dimensions Some Derivative Relations Scalar and Double Dot Products of Two Tensors Mathematical Exposition 2: Theorems of Gauss, Green, and Stokes Gauss' Theorem Green's Theorem Stokes' Theorem Mathematical Exposition 3: Geometry of Space and Plane Curves Basic Theory of Curves Mathematical Exposition 4: Formulas for Coordinate Transformation Introduction Transformation Law for Scalars Transformation Laws for Vectors Transformation Laws for Tensors Transformation Laws for the Christoffel Symbols Some Formulas in Cartesian and Curvilinear Coordinates Mathematical Exposition 5: Potential Theory Introduction Formulas of Green Potential Theory General Representation of a Vector An Application of Green's First Formula Mathematical Exposition 6: Singularities of the First-Order ODEs Introduction Singularities and Their Classi cation Mathematical Exposition 7: Geometry of Surfaces Basic De nitions Formulas of Gauss Formulas of Weingarten Equations of Gauss Normal and Geodesic Curvatures Grid Generation in Surfaces Mathematical Exposition 8: Finite Difference Approximation Applied to PDEs Introduction Calculus of Finite Differences Iterative Root Finding Numerical Integration Finite Difference Approximations of Partial Derivatives Finite Difference Approximation of Parabolic PDEs Finite Difference Approximation of Elliptic Equations Mathematical Exposition 9: Frame Invariancy Introduction Orthogonal Tensor Arbitrary Rectangular Frames of Reference Check for Frame Invariancy Use of Q References for the Mathematical Expositions Index
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TL;DR: In this paper, the process of determining appropriate constitutive equations for multidimensional time averaged two-phase flow equations is studied from the point of view of starting from general principles, and proceeding to specific constitutive equation which contain known physical effects.
Abstract: The process of determining appropriate constitutive equations for multidimensional time averaged two-phase flow equations is studied from the point of view of starting from general principles, and proceeding to specific constitutive equations which contain known physical effects. Energetic effects and phase change are not considered. Models are given for the interfacial momentum transfer, the laminar and turbulent (Reynolds) stresses, and the pressure differences between the phases, and between a given phase pressure and the interfacial average pressure.
225 citations
TL;DR: In this paper, a model for deposition of particles and droplets from turbulent gas streams is presented, which is largely free of the assumption and limitations of earlier methods, providing for the possibiity that the eddy and particle motion are not identical.
Abstract: This paper presents a model for deposition of particles and droplets from turbulent gas streams which is largely free of the assumption and limitations of earlier methods. In particular, the model provides for the possibiity that the eddy and particle motion are not identical, that the random process associated with the turbulence results in particle motions in all directions and that the process of penetration in the wall region is also a stochastic process. The theory is tested against data which cover a wide range of conditions including particle size from 0.8–125 μ; Reynolds number from 5 × 10 3 to 3 × 10 5 ; gas to particle density ratio of 1·6 × 10 −4 to 1·5 × 10 −3 ; and tube sizes fro 0·375 to 2·5 in. in dia. Agreement is quite satisfactory in all cases. The rate of deposition is shown to depend on the Reynolds number, the particle to tube diameter ratio, the gas to particle density ratio and the distance down the tube, measured in tube diameters.
200 citations