[1] Experiments were completed in a laboratory-scale, porous media tank to study the transport patterns of a saltwater wedge in a freshwater aquifer. Three types of experiments were performed to develop: (1) steady state salt-wedge data observed under different hydraulic gradient conditions; (2) transient salt-wedge data observed under intruding-wedge conditions; and (3) transient salt-wedge data observed under receding-wedge conditions. Furthermore, flux measurements were made to quantify the flow characteristics of three distinct steady state experiments. The saltwater intrusion model SEAWAT was used to simulate these data sets. The model results along with the experimental data are presented as benchmark problems for testing density-coupled groundwater flow models. A worthiness analysis was completed to test the sensitivity of these experimental problems to density-coupling effects. The results of our analysis show that the proposed benchmark is a more robust alternative to the traditional Henry problem. These new experimental data sets can be used to assess the performance of saltwater intrusion models under both steady state and transient conditions.Citation: Goswami, R. R., and T. P. Clement (2007), Laboratory-scale investigation of saltwater intrusion dynamics, Water Resour.

No abstract

Zero-valent iron nanoparticles (INP) were synthesized and stabilized using poly acrylic acid (PAA) to yield stabilized INP (S-INP). A two-dimensional physical model was used to study the fate and transport of the INP and S-INP in porous media under saturated, steady-state flow conditions. Transport data for a nonreactive tracer, INP, and S-INP were collected under similar flow conditions. The results show that unstabilized INP cannot be transported into groundwater systems. On the other hand, the S-INP can be transported like a tracer without significant retardation. However, the S-INP plume migrated downward as it moved horizontally in the physical model, indicating that small density gradients have significant influence on two-dimensional transport. The variable-density groundwater flow model SEAWAT was used to model the observed density-driven transport patterns. This is the first time a two-dimensional transport data set is reported for demonstrating the multidimensional transport characteristics of nanoparticles. The data shows the importance of density effects, which cannot be fully discerned using one-dimensional, column experiments. Finally, we also demonstrate that the numerical model SEAWAT can be used to predict the density-driven transport characteristics of S-INP in groundwater aquifers.

We computationally investigate the dynamics of a self-propelled Janus probe in crowded environments. The crowding is caused by the presence of viscoelastic polymers or non- viscoelastic disconnected monomers. Our simulations...

In this work, we have considered the crystallisation behaviour of supercooled water in the presence of surface defects of varying size (surface fraction, α from 1 to 0.5). Ice nucleation on Ag exposed β-AgI (0001 plane) surface is investigated by molecular dynamics simulation at a temperature of 240 K. For systems with α > 0.67, the surface layers crystallise within 150 ns. In the system with defects, we observe two distinct stacking patterns in the layers near the surface and find that systems with AA stacking cause a monotonic decrease in the early nucleation dynamics with an increase in defect size.Where AB stacking (α = 0.833) is observed, the effect of the defect is diminished and the dynamics are similar to the plain AgI surface. This is supported by the variation in the orientational dynamics, hydrogen bond network stability, and tetrahedrality with respect to the defects. We quantify results in terms of the network topology using double-diamond cages (DDCs) and hexagonal cages (HCs). The configurations of the initially formed layers of ice strongly affect the subsequent growth even at long timescales. We assert that the retarded ice growth due to defects can be explained by the relative increase in DDCs with respect to HCs.

As the global health crisis unfolded, many academic conferences moved online in 2020. This move has been hailed as a positive step towards inclusivity in its attenuation of economic, physical, and legal barriers and effectively enabled many individuals from groups that have traditionally been underrepresented to join and participate. A number of studies have outlined how moving online made it possible to gather a more global community and has increased opportunities for individuals with various constraints, e.g., caregiving responsibilities. Yet, the mere existence of online conferences is no guarantee that everyone can attend and participate meaningfully. In fact, many elements of an online conference are still significant barriers to truly diverse participation: the tools used can be inaccessible for some individuals; the scheduling choices can favour some geographical locations; the set-up of the conference can provide more visibility to well-established researchers and reduce opportunities for early-career researchers. While acknowledging the benefits of an online setting, especially for individuals who have traditionally been underrepresented or excluded, we recognize that fostering social justice requires inclusivity to actively be centered in every aspect of online conference design. Here, we draw from the literature and from our own experiences to identify practices that purposefully encourage a diverse community to attend, participate in, and lead online conferences. Reflecting on how to design more inclusive online events is especially important as multiple scientific organizations have announced that they will continue offering an online version of their event when in-person conferences can resume.

Image analysis (IA) techniques are increasingly being used in porous media experiments to measure system properties such as concentration and water content. The values of system properties estimated using IA techniques can be influenced by various types of experimental errors. These errors are generally quantified by using global mass balance calculations or by comparing the dispersion coefficient value obtained from the IA data against an accepted value. We used a theoretical test problem to show that both of these error quantification methods have severe limitations. Hence, we developed an alternative statistics‐based method for quantifying IA errors. The applicability of the new method was verified using the theoretical test problem. In addition to quantifying errors, the method can also be used as a design tool for selecting optimal concentration ranges for conducting contaminant transport experiments with minimal errors. We conducted a dense‐tracer transport experiment to demonstrate the use of the proposed error analysis method.

A community of developers has formed to modernize the Fortran ecosystem. In this article, we describe the high-level features of Fortran that continue to make it a good choice for scientists and engineers in the 21st century. Ongoing efforts include the development of a Fortran standard library and package manager, the fostering of a friendly and welcoming online community, improved compiler support, and language feature development. The lessons learned are common across contemporary programming languages and help reduce the learning curve and increase adoption of Fortran.