WaterSubject

This paper is the fourth in a series of efforts intended to yield complete, rigorous, closed models that describe transport phenomena in multiscale porous medium systems using the thermodynamically constrained averaging theory (TCAT) approach. The first paper provides an overview of the general TCAT approach, which is built on averaged conservation and thermodynamic equations that constrain an entropy inequality. The second paper provides the mathematical fundamentals and theorems that are used to generate needed macroscale equations. The third paper illustrates the application ... Read More

Dunes are the most common bed form structures in sandy rivers. Knowledge of the turbulence characteristics of the complex flow regimes found over typical bed forms or dunes must be known to predict the behavior of many natural phenomena. Dunes in bed load-dominated and/or laboratory environments are often asymmetric having low-sloping upstream side (stoss) and steep lee faces, while those in suspended load dominated environments are often more symmetric with relatively low angle lee faces. The bed forms, such as ripples and ... Read More

Many codes are available for the modeling of fluid flow and heat transport. A recent overview is given by Anderson. We used the program SHEMAT for the modeling of deep groundwater and heat transport in a sedimentary basin. This program uses a finite volume method (FVM) on an orthogonal grid. Geometrically complex three-dimensional flow domains often cannot be represented well by a rectangular spatial discretization, because the geometry is approximated by steps. Therefore, a more flexible, non-orthogonal discretization was implemented into this ... Read More

Numerical simulation is commonly used to study flow and transport in porous media in a wide range of applications in environmental sciences and reservoir modeling. The complexity and size of numerical models has increased with the ever increasing speed and memory of computers, accompanied by advances in the numerical algorithms available in the simulation software. The ability to represent hydrostratigraphic details such as thin confining layers and faults has improved with high resolution models [3]. The capability of assessing and controlling numerical ... Read More

At present, the almost universal practice in the oil industry is to use empirical models to predict three-phase flow properties, such as capillary pressure and relative permeability, that are extrapolations from two-phase measurements. However, the three-phase relative permeability is known to be a function of two saturations and the displacement path, indicating that a finite number of measurements is unlikely to reproduce the full range of behavior. One simplifying hypothesis is to propose that the relative permeability is a unique function of ... Read More

Time Domain Random Walk (TDRW) methods have become very appealing for simulating mass transport in media with huge contrasts in their hydrodynamic properties. For instance, fractured rocks can be depicted as Discrete Fracture Networks (DFN) made up of connected 1D bonds, e.g. Properties in each bond are constant but may vary from one bond to the other. In the same way, complex flow (involving, e.g., non-Newtonian fluids) or Darcian flow in heterogeneous porous media can be mimicked by percolation networks or handled ... Read More

Kalman filter (KF), a sequential data assimilation technique, and its extensions such as extended Kalman filter (EKF) and ensemble Kalman filter (EnKF), have been extensively used in hydrological modeling. This includes but not limited to soil moisture and temperature retrieval, aquifer parameter identification, and simultaneous state and parameter estimation. The common purpose of these applications is to quantify and manipulate uncertainties and errors involved in model structure, parameter and observation, given that the statistical properties of both model and observation errors are ... Read More

A short look to any handbook of hydraulic engineering or to classical textbooks on free surface flows is sufficient to guess the importance of the concepts of specific energy and total force in the crucial aspects of open channel flows. For example, the complex and rich physics of fluid motion around obstacles, at abrupt contractions or expansions of the channel width, near localized steps or sudden changes in bed elevation, in flowing out from different hydraulic structures, at the occurrence of a ... Read More

The transport of adsorptive solutes in soils and aquifers plays an important role in a variety of fields, including leaching of agrochemicals from soil surface to groundwater, uptake of soil nutrients by plant roots and remediation of contaminated soils and aquifers; and how to model it has been an interest over the past few decades. Traditional mathematical models treat movement and adsorptive reaction of solute as two separated processes, with the transport parameters associated with the movement determined from displacement experiment and ... Read More

A short look to any handbook of hydraulic engineering or to classical textbooks on free surface flows is sufficient to guess the importance of the concepts of specific energy and total force in the crucial aspects of open channel flows. For example, the complex and rich physics of fluid motion around obstacles, at abrupt contractions or expansions of the channel width, near localized steps or sudden changes in bed elevation, in flowing out from different hydraulic structures, at the occurrence of a ... Read More