420 research outputs found
A mathematical model for thermal single-phase flow and reactive transport in fractured porous media
In this paper we present a mathematical model and a numerical workflow for
the simulation of a thermal single-phase flow with reactive transport in porous
media, in the presence of fractures. The latter are thin regions which might
behave as high or low permeability channels depending on their physical
parameters, and are thus of paramount importance in underground flow problems.
Chemical reactions may alter the local properties of the porous media as well
as the fracture walls, changing the flow path and possibly occluding some
portions of the fractures or zones in the porous media. To solve numerically
the coupled problem we propose a temporal splitting scheme so that the
equations describing each physical process are solved sequentially. Numerical
tests shows the accuracy of the proposed model and the ability to capture
complex phenomena, where one or multiple fractures are present
A multi-layer reduced model for flow in porous media with a fault and surrounding damage zones
In this work we present a new conceptual model to describe fluid flow in a
porous media system in presence of a large fault. Geological faults are often
modeled simply as interfaces in the rock matrix, but they are complex structure
where the high strain core is surrounded by the so called damage zones,
characterized by the presence of smaller fractures which enhance the
permeability of the medium. To obtain reliable simulation outcomes these damage
zone, as well as the fault, have to be accurately described. The new model
proposed in this work considers both these two regions as lower dimensional and
embedded in the rock matrix. The model is presented, analyzed, and tested in
several configurations to prove its robustness and ability to capture many
important features, such as hight contrast and heterogeneity of permeability
Performances of the mixed virtual element method on complex grids for underground flow
The numerical simulation of physical processes in the underground frequently
entails challenges related to the geometry and/or data. The former are mainly
due to the shape of sedimentary layers and the presence of fractures and
faults, while the latter are connected to the properties of the rock matrix
which might vary abruptly in space. The development of approximation schemes
has recently focused on the overcoming of such difficulties with the objective
of obtaining numerical schemes with good approximation properties. In this work
we carry out a numerical study on the performances of the Mixed Virtual Element
Method (MVEM) for the solution of a single-phase flow model in fractured porous
media. This method is able to handle grid cells of polytopal type and treat
hybrid dimensional problems. It has been proven to be robust with respect to
the variation of the permeability field and of the shape of the elements. Our
numerical experiments focus on two test cases that cover several of the
aforementioned critical aspects
A multi-layer reactive transport model for fractured porous media
An accurate modeling of reactive flows in fractured porous media is a key
ingredient to obtain reliable numerical simulations of several industrial and
environmental applications. For some values of the physical parameters we can
observe the formation of a narrow region or layer around the fractures where
chemical reactions are focused. Here the transported solute may precipitate and
form a salt, or vice-versa. This phenomenon has been observed and reported in
real outcrops. By changing its physical properties this layer might
substantially alter the global flow response of the system and thus the actual
transport of solute: the problem is thus non-linear and fully coupled. The aim
of this work is to propose a new mathematical model for reactive flow in
fractured porous media, by approximating both the fracture and these
surrounding layers via a reduced model. In particular, our main goal is to
describe the layer thickness evolution with a new mathematical model, and
compare it to a fully resolved equidimensional model for validation. As
concerns numerical approximation we extend an operator splitting scheme in time
to solve sequentially, at each time step, each physical process thus avoiding
the need for a non-linear monolithic solver, which might be challenging due to
the non-smoothness of the reaction rate. We consider bi- and tridimensional
numerical test cases to asses the accuracy and benefit of the proposed model in
realistic scenarios
A reduced model for Darcy’s problem in networks of fractures
Subsurface flows are influenced by the presence of faults and large fractures which act
as preferential paths or barriers for the flow. In literature models were proposed to
handle fractures in a porous medium as objects of codimension 1. In this work we consider
the case of a network of intersecting fractures, with the aim of deriving physically
consistent and effective interface conditions to impose at the intersection between
fractures. This new model accounts for the angle between fractures at the intersections
and allows for jumps of pressure across intersections. This fact permits to describe the
flow when fractures are characterized by different properties more accurately with respect
to other models that impose pressure continuity. The main mathematical properties of the
model, derived in the two-dimensional setting, are analyzed. As concerns the numerical
discretization we allow the grids of the fractures to be independent, thus in general
non-matching at the intersection, by means of the extended finite element method
(XFEM). This increases the flexibility of the method in the case of complex
geometries characterized by a high number of fractures
Comment on \u201cApplication of PK/PD Modeling in Veterinary Field: Dose Optimization and Drug Resistance Prediction\u201d
Comment on \u201cApplication of PK/PD Modeling in Veterinary Field: Dose Optimization and Drug Resistance Prediction\u201
Comment on “Application of PK/PD Modeling in Veterinary Field: Dose Optimization and Drug Resistance Prediction”
Comment on “Application of PK/PD Modeling in Veterinary Field: Dose Optimization and Drug Resistance Prediction
The Mixed Virtual Element Method on curved edges in two dimensions
In this work, we propose an extension of the mixed Virtual Element Method
(VEM) for bi-dimensional computational grids with curvilinear edge elements.
The approximation by means of rectilinear edges of a domain with curvilinear
geometrical feature, such as a portion of domain boundary or an internal
interface, may introduce a geometrical error that degrades the expected order
of convergence of the scheme. In the present work a suitable VEM approximation
space is proposed to consistently handle curvilinear geometrical objects, thus
recovering optimal convergence rates. The resulting numerical scheme is
presented along with its theoretical analysis and several numerical test cases
to validate the proposed approach
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