scholarly journals A Finite Volume-Complete Flux Scheme for a Polluted Groundwater Site

2016 ◽  
Vol 2016 ◽  
pp. 1-12
Author(s):  
M. F. P. ten Eikelder ◽  
J. H. M. ten Thije Boonkkamp ◽  
M. P. T. Moonen ◽  
B. V. Rathish Kumar
Keyword(s):  
Time Integration ◽  
Stability Result ◽  
Coupled System ◽  
Diffusion Reaction ◽  
Advection Diffusion ◽  
Guarani Aquifer ◽  
Space Discretization ◽  
Reaction Equations ◽  
Advection Diffusion Reaction Equations ◽  
Good Agreement

We present a model of a polluted groundwater site. The model consists of a coupled system of advection-diffusion-reaction equations for the groundwater level and the concentration of the pollutant. We use the complete flux scheme for the space discretization in combination with the ϑ-method for time integration and we prove a new stability result for the scheme. Numerical results are computed for the Guarani Aquifer in South America and they show good agreement with results in literature.

scholarly journals Second Order Fully Semi-Lagrangian Discretizations of Advection-Diffusion-Reaction Systems

2021 ◽  
Vol 88 (1) ◽  
Author(s):  
Luca Bonaventura ◽  
Elisa Calzola ◽  
Elisabetta Carlini ◽  
Roberto Ferretti
Keyword(s):  
Time Discretization ◽  
Second Order ◽  
Dirichlet Boundary Conditions ◽  
Diffusion Reaction ◽  
Implicit Time ◽  
Advection Diffusion ◽  
Space Discretization ◽  
Reaction Equations ◽  
Advection Diffusion Reaction Equations ◽  
Large Linear Systems

AbstractWe propose a second order, fully semi-Lagrangian method for the numerical solution of systems of advection-diffusion-reaction equations, which is based on a semi-Lagrangian approach to approximate in time both the advective and the diffusive terms. The proposed method allows to use large time steps, while avoiding the solution of large linear systems, which would be required by implicit time discretization techniques. Standard interpolation procedures are used for the space discretization on structured and unstructured meshes. A novel extrapolation technique is proposed to enforce second-order accurate Dirichlet boundary conditions. We include a theoretical analysis of the scheme, along with numerical experiments which demonstrate the effectiveness of the proposed approach and its superior efficiency with respect to more conventional explicit and implicit time discretizations.

scholarly journals Estimating the extent of glioblastoma invasion

2021 ◽  
Vol 82 (1-2) ◽  
Author(s):  
Christian Engwer ◽  
Michael Wenske
Keyword(s):  
Analytic Solution ◽  
Glioma Cells ◽  
Diffusion Reaction ◽  
Kpp Equation ◽  
Advection Diffusion ◽  
Clinical Interest ◽  
Inhomogeneous Diffusion ◽  
Reaction Equations ◽  
Advection Diffusion Reaction Equations ◽  
Tumor Extent

AbstractGlioblastoma Multiforme is a malignant brain tumor with poor prognosis. There have been numerous attempts to model the invasion of tumorous glioma cells via partial differential equations in the form of advection–diffusion–reaction equations. The patient-wise parametrization of these models, and their validation via experimental data has been found to be difficult, as time sequence measurements are mostly missing. Also the clinical interest lies in the actual (invisible) tumor extent for a particular MRI/DTI scan and not in a predictive estimate. Therefore we propose a stationalized approach to estimate the extent of glioblastoma (GBM) invasion at the time of a given MRI/DTI scan. The underlying dynamics can be derived from an instationary GBM model, falling into the wide class of advection-diffusion-reaction equations. The stationalization is introduced via an analytic solution of the Fisher-KPP equation, the simplest model in the considered model class. We investigate the applicability in 1D and 2D, in the presence of inhomogeneous diffusion coefficients and on a real 3D DTI-dataset.

scholarly journals Well-posedness of time-fractional advection-diffusion-reaction equations

2019 ◽  
Vol 22 (4) ◽  
pp. 918-944 ◽  
Author(s):  
William McLean ◽  
Kassem Mustapha ◽  
Raed Ali ◽  
Omar Knio
Keyword(s):  
Linear Time ◽  
Initial Boundary ◽  
Initial Boundary Value Problem ◽  
Diffusion Reaction ◽  
Fractional Integrals ◽  
Well Posedness ◽  
Advection Diffusion ◽  
Initial Boundary Value ◽  
Reaction Equations ◽  
Advection Diffusion Reaction Equations

Abstract We establish the well-posedness of an initial-boundary value problem for a general class of linear time-fractional, advection-diffusion-reaction equations, allowing space- and time-dependent coefficients as well as initial data that may have low regularity. Our analysis relies on novel energy methods in combination with a fractional Gronwall inequality and properties of fractional integrals.

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