Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 28 for “"advection-diffusion equation"”.
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A fast characteristic finite difference method for fractional advection-diffusion equations with non-linear reaction.
… can be modeled with fractional differential equations. This approach results in early arrival of contaminants and heavy-tail distributions observed in field experiments. The implicit finite difference scheme with the shifted Grunwald approximation discritizing the fractional …
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Numerical modelling of solute transport processes using higher order accurate finite difference schemes. Numerical treatment of flooding and drying in tidal flow simulations and higher order accurate finite difference modelling of the advection diffusion equation for solute transport predictions.
The modelling of the processes of advection and dispersion-diffusion is the most crucial factor in solute transport simulations. It is generally appreciated that the first order upwind difference scheme gives rise to excessive numerical diffusion, whereas the conventional second order central …
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Massively parallel solver for the high-order Galerkin Least-Squares method
… high-order discretization of the Poisson equation, the advection-diffusion equation, and the Euler equation. The Robin-Robin interface condition is extended to the Euler equation using the entropy-symmetrized variables. The BDDC method maintains scalability for the high-order …
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Solution of the advection equation using finite difference schemes and the method of characteristics
… a prediction is achieved by the solution of the advection-diffusion equation. At present, there exist many numerical techniques which can be used to solve the advection-diffusion equation. The major difficulty when considering undertaking such a simulation, is what method should be used to …
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A finite volume discretization method for flow on structured and unstructured anisotropic meshes
This project is concerned with advection discretization technology within the field of Computational Fluid Dynamics (CFD). To this end, two novel methods are proposed which are dubbed the Enhanced Taylor (ET) Schemes. The model equation for this work is the advection-diffusion equation with the …
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A Web-based finite element model for heat transfer
… is reviewed and the technique applied to the advection-diffusion equation for the transport of temperature. The Java code and graphical interface used to implement the solver for use on the Internet is discussed.
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Interactions and orientation in concentrated suspensions of rigid rods: Theory and experiment
… via probability density function whose transport equation has the form of a generalized advection-diffusion equation with a orientation dependent diffusion. This equation is solved using a finite difference scheme and the results are presented versus experiments with suspensions with planar …
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Implicit-explicit methods for time-dependent PDE’s
… discretized time-dependent partial differential equations. For problems with terms of different types, implicit-explicit (IMEX) schemes have been used, especially in conjunction with spectral methods. For convection-diffusion problems, for example, one would use an explicit scheme for the …
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The Distance to Uncontrollability via Linear Matrix Inequalities
… element discretization of the one-dimensional advection-diffusion equation. Here our objective is to test these algorithms for larger problems that originate in PDE-control.
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On the Potential Impact of Curved Meshing for Higher-order Adaptive Mesh Simulations
… the solution to partial differential equations (PDEs). In this thesis, we consider the potential advantages of incorporating higher-order element shapes, i.e. curved meshes, into an adaptive process through the use of a mesh-based, geometric mapping. While previous work has considered …
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Development of a flow-condition-based interpolation 9-node element for incompressible flows
The Navier-Stokes equations are widely used for the analysis of incompressible laminar flows. If the Reynolds number is increased to certain values, oscillations appear in the finite element solution of the Navier-Stokes equations. In order to solve for high Reynolds number flows and avoid the …
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An unstructured finite volume simulator for multiphase flow through fractured-porous media
… distribution) is captured by the traditional advection-diffusion equation using a highly discretized system. Today. many macroscopic flow models are being developed which account for the non-Fickian. non-local flow more accurately and efficiently with less computation. The finite volume …
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A direct numerical simulation of fully developed turbulent channel flow with passive heat transfer
… time-dependent three-dimensional Navier-Stokes equations and advection-diffusion equation are solved numerically using a pseudospectral technique with 1,064,960 grid points in physical space (128 x 65 x 128 in x, y, z). No subgrid scale model is employed since all essential turbulence scales are …
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Finite element solution of interface and free surface three-dimensional fluid flow problems using flow-condition-based interpolation
… and even coarse meshes. The continuum mechanics equations are formulated, and the Navier-Stokes equations are solved using a 'flow-condition-based interpolation' (FCBI) scheme. The FCBI method uses exponential interpolations derived from the analytical solution of the 1-dimensional …
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A mathematical model of the nitrogen cycle in a constructed wetland
… and a jump condition is modeled for nutrient diffusion through the sediment-water interface. A hyperbolic advection-settling equation models the transport and deposition of sediment-bound organic nitrogen; mineralization of deposited nitrogen is modeled. A parabolic advection-diffusion …
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Diagnostics of diapycnal diffusion in z-level ocean models
… ocean circulation models (OGCMs) diapycnal diffusion arises not<br/>only from the discretisation of the explicit diffusion, but also by numerically<br/>induced diffusion, caused, e.g., by common discretisations of advective<br/>transport.<br/>In the present study, three different diagnostics …
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Stabilized Finite Element Formulations for Flow Problems
… to numerically modeling the Navier-Stokes equations, we begin with a study of the Stokes and advection-diffusion equations. From our study of the Stokes equations we learn that stabilized methods based on enriching the velocity trial function space with bubble functions are only stable for …
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Multi-Scale Probing of Colloidal Sedimentation Dynamics in Active Suspensions
… particles-an alteration describable through an advection-diffusion equation with an added population dynamics term. Subsequently, I characterize the sedimentation speed of spherical particles across different bacterial concentrations, unveiling the emergence of two sedimentation fronts: …
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Effects of ocean turbulence on the large-scale stratification and Small-Scale Particle Distributions
… on the particle, and the resulting stochastic equations are reduced via perturbation analysis to a single advection-diffusion equation for the spatial distribution of particles. We verify and test the resulting model in several sample flows and begin to quantify the many inertial and stochastic …
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Dynamics of quasi-two-dimensional turbulent jets
… jets we use a time-dependent advection--diffusion equation, with a mixing length hypothesis accounting for the turbulent eddy diffusivity. The model is supported by experimental releases of dye in jets or numerical releases of virtual passive tracers in experimentally-measured …
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