Research

Earth system and life are inseparably linked to water. In the face of pressing global changes, understanding water motions, transformation, and interaction with fragile landscapes and ecosystems is critical to its protection and sustainable management. To support this principle, we delve into the physics of aquatic systems to develop mechanistic models and mathematical frameworks to characterize the pathways of water in nature.

Sandball genesis from drops

Raindrops do more than splash—on dry, sloped soils, individual drops can roll downslope like miniature snowballs, sweeping up grains and building compact aggregates we call “sandballs.” This rolling-and-gathering pathway can boost the amount of soil moved by a single drop by roughly an order of magnitude, highlighting a strong and underappreciated erosion mechanism. Understanding water–soil interactions at this small scale can improve models of landscape evolution, soil loss, and agricultural impacts, and may also inform ideas in areas such as bioengineering, food processing, and the physics of snow and other soft granular materials.

Optical altimetry for microscale sediment layers

We introduce a simple optical technique to measure very thin layers of sediment or microparticles with grain-size detail. Instead of specialized instruments, it uses a standard digital camera and the light scattered by the particle layer. The approach includes a straightforward way to correct for uneven or imperfect lighting, making it flexible and easy to apply in different settings. The method can resolve features at micrometer scales both across the surface and in layer thickness, and it is demonstrated by measuring underwater ripple patterns made of fine organic particles. The technique could be used to study granular sediment layers, biofilms, and dust deposition.

Active carpets in layered aquatic microenvironments

Microbes often form dense “active carpets” at interfaces in layered fluids, such as the ocean’s surface microlayer, where they stir the fluid and enhance transport. Using theory and simulations, we show that layer thickness and viscosity contrast control both the intensity and direction of the resulting fluctuations and how passive tracers move. Fluctuations are directional: vertical motions dominate near the carpet and internal interface, become more isotropic farther away, and shift to horizontal dominance near the free surface. Under strong confinement, the flow organizes into coherent vortex rolls whose size is set by layer thickness and whose strength depends on how sharply viscosity changes. These may aid biofilm control and microfluidic design.

Convection, but how fast does fluid mix in hydrothermal systems?

Earth’s internal heat creates temperature gradients that drive convection in confined hydrothermal systems such as mid-ocean ridges and geothermal reservoirs. There, hot fluids rise and mix with colder water flowing through fractures, producing complex mixing patterns. Using energy-based theory and lab experiments, we derive formulas to estimate mixing rates in faulted and fractured environments, with implications for understanding crustal fluid flow and improving geothermal and subsurface storage technologies.

Scaling particle-size segregation in wide-ranging sheared granular flows

We test whether standard scaling laws for shear-driven size segregation remain valid under nonuniform shear. Using DEM simulations across a wide range of conditions, we find the usual scaling between segregation speed and local rheology holds only for moderate inertial numbers and fails in quasi-static and strongly collisional regimes. Consequently, continuum models based on this scaling can mispredict segregation rates in bidisperse mixtures, motivating more general laws that work across shear regimes. 

Energy transformation of bidisperse granular flows

We present a continuum framework for analyzing the energetics of particle-size segregation in bidisperse granular flows. Applied to shear-driven flows, it reveals two key phases: the onset of segregation and diffusive remixing. Numerical simulations, validated by experimental data, show that energy balances at steady state follow predictable scaling laws. We also propose a model for the degree of mixing, offering a practical tool for predicting and controlling segregation-mixing states in engineering and geophysical applications.

 Note: GPE stands for Gravitational Potential Energy

Floating Active Carpet in Aquatic Systems

We investigate how communities of swimming microorganisms known as “active carpets” influence their aquatic environment by driving biogenic transport in their surrounding. We combine theory and simulations to examine fundamental metrics, including diffusivity, particle encounters, and particle aggregation. The findings reveal that the hydrodynamic fluctuations generated by active carpets promote particles encounters and aggregation processes. Our study emphasizes the role of biologically driven fluctuations in the transport of essential elements in biogeochemical cycles within aquatic systems. Learn more in the following link:

Transition regimes in confined thermal convection

The phenomenon of thermal convection governs crucial natural and engineered systems, including oceans, hydrothermal systems, and heat exchangers. These systems are all geometrically confined, resulting in restricted convective fluid motions. Our introduction of the “degree of confinement” as a universal parameter characterizes the impact of lateral control on thermal convection, encapsulating fluid properties, system geometry, and thermal forcing. Laboratory experiments demonstrate that the degree of confinement plays a critical role in determining the local and global dynamics of thermal plumes, the fundamental manifestation of convection. Our study connects the classic problem of “Rayleigh–Bénard convection” with various natural and engineering thermo-fluid systems distinguished by their degrees of confinement. For more info and awesome videos, check out the link below:

Convective transport of dissolved gases

The debate over littoral influence on lake gas dynamics persists due to limited quantification of lateral gas transport, as diffusive horizontal transport assumptions fail to explain observed anomalies in pelagic gas concentrations. We reveal, via field experiments, that daily convective horizontal circulation drives significant littoral-pelagic advective gas fluxes, challenging traditional models and emphasizing the need to integrate convective transport into gas budgets in aquatic systems.

Tracking swarms of swimming organisms

Simple and frugal method for tracking occluded self-propelled organisms in densely populated water bodies. We apply the method to monitor swarms of Daphnia Magna in an aquatic laboratory, facilitating the acquisition of comprehensive statistics on swimming behaviours, like flapping frequency and sinking velocity, across a wide range of swimmer sizes.

Stratified Horizontal Convection

Driven by Differential Heating

Laboratory experiments and theory characterizing the fluid dynamics of stratified fluids subject to differential heating at their surface. Learn more:

Convection in Confined Domains

Theoretical, numerical and experimental characterization of thermal and solutal convection in confined domains like faults, fractured media, and porous media. Learn more:

Radiatively Driven Convection

Theory, field and numerical experiments characterising the convective dynamics driven by sunlight in ice-covered waters. Learn more:

Topographically and Thermally Driven

Convective Flows

Characterization of topographically and thermally driven convetive modes of motions in aquatic systems like nearshore waters in seas and lakes. Learn more:

Flows Across Sloping Boundaries

Theory, field and numerical experiments characterising thermally, wind and tidally driven cross-shore flow. Learn more:

Resonance in Enclosed Waterbodies 

Characterization of resonance dynamics of basin-scale interfacial gravity waves induced by wind and modualted by Coriolis acceleration via field, laboratory and numerical studies. Learn more:

Characterization of the dynamic and energy regimes of rotating internal gravity waves in stratified water basins via field, laboratory and numerical experiments. Video: Direct numerical simulation of a Kelvin waves. Learn more:

Hydrodynamics, Mixing and Ecology

of Lakes

Hydrodynamics and mixing in lakes is controlled mainly by wind and heat fluxes. For temperate lakes, deep mixing occurs typically from fall to winter and is one of the essential physical processes supporting the supply of nutrients from deep to near-surface waters and the primary production during the productive season. Modelling the vertical and lateral mass transport is critical to assess the quality of natural waters. Learn more:

Image: Lake Llanquihue, Patagonia, Chile. Video: Numerical simulation of Lagrangian particles in Lake Llanquihue.