River plumes have a direct influence on coastal environments, impacting coastal planktonic and benthic communities, including fishery resources. In general, the main drivers of river plume dynamics are the river discharge and the alongshore wind stress, whereas the tides and topography play a secondary role. In central Chile, rivers flowing into the eastern Pacific have a relatively short path on land, with a high slope and a mixed snow–rain regime. This study aims to understand the interannual variability in the plumes of the Maipo and Rapel rivers in the coastal/shelf area off central Chile and their influence on local ocean dynamics. We used the Coastal and Regional Ocean Community (CROCO) model, with 1 km horizontal resolution and 20 sigma levels, to simulate the ocean dynamics for the period 2003–2011. The results show that the plume's area coverage and coastal ocean salinity are strongly correlated with the river discharges. The predominant northeastward winds control the plumes' orientation toward the northwest. However, episodes of southeastward winds in winter can reverse the plumes' direction, promoting their attachment to the coast and southward transport. Results also show a salification trend linked to the severe droughts hitting central Chile during the studied period. This salification determines a change in local dynamics which could be more frequent in future scenarios of climate change with a significant lack of rain and river discharges along central Chile.

Although Kepler’s laws can be empirically proven by applying Newton’s laws to the dynamics of two particles attracted by gravitational interaction, an explicit formula for the motion as a function of time remains undefined. This paper proposes a quasi-analytical solution to address this challenge. It approximates the real dynamics of celestial bodies with a satisfactory degree of accuracy and minimal computational cost. This problem is closely related to Kepler’s equation, as solving the equations of motion as a function of time also provides a solution to Kepler’s equation. The results are presented for each planet of the solar system, including Pluto, and the solution is compared against real orbits.

This paper describes a low-cost laboratory experiment designed to demonstrate the applicability of the refractive index to study stratification in fluids. The laser refractography method was applied to a linearly vertical density profile of a salt (NaCl) stratified water column. Next, an image processing procedure was performed, consisting of the binarization and edge detection of the laser beam and its subsequent second-order polynomial best fit. Quantitatively, the whole-field results compared well with the respective measured density profiles. This method allows one to obtain quantitative measurements of density profiles in stratified fluids with good accuracy, making it a suitable experimental method for laboratory demonstrations on fluids.

In this experimental work, sloshing tests were performed with containers filled 1 with water at 50% of their volume capacity. Two boundary conditions were considered: un- 2 coated containers and containers with hydrophobic coated walls such as in [1]. In addition, 3 several aspect ratios λ (container width over length) were considered. We characterized two 4 regimes: the first one when the container is periodically forced at a frequency lower than its 5 resonant frequency and the second one after the forcing is suddenly stopped. In each case, 6 the amplitude of the waves was measured. Several surprising results were found. First, in 7 the forced regime, the sloshing amplitude was lower in the hydrophobic containers than in 8 the nonhydrophobic walls, despite the free-slip condition in the former case. Second, the 9 free damping after sudden stoppage was much higher with the hydrophobic walls than 10 with the uncoated containers. This behavior is explained by the collision of waves with 11 oil-coated walls, which decreases the load pressure. Finally, it was found that the damping 12 depends on the dimension of the container through λ and is greater when λ = 1.0. These 13 experimental findings open the way for further innovative research.

It is often expected that hydrophobic walls reduce viscous dissipation. However, our experimental results show that they instead increase the damping of shallow-water sloshing while leaving the natural oscillation frequency essentially unchanged. Two geometrically identical acrylic containers, differing only in wall wettability, are impulsively excited and the subsequent free-surface decay is recorded using a smartphone camera. Contrary to intuitive expectations, the hydrophobic container exhibits a decay time nearly three times shorter than the hydrophilic container. A shallow-water model reduces the dynamics to a damped harmonic oscillator, allowing students to extract frequency and decay rate independently through nonlinear regression and spectral analysis. The experiment provides a clear and accessible laboratory activity for upper-level undergraduate courses, illustrating the separation between restoring forces and dissipative mechanisms, the role of boundary conditions, and the exponential decay of mechanical energy in oscillatory systems.