Non-Newtonian hydrodynamics in EPS-rich systems
Exopolymers (EPS) secreted primarily by algae and bacteria modify the mechanical properties of water. EPS-rich regions are more viscous than the surrounding water and often exhibit non-Newtonian, viscoelastic behavior, shifting local hydrodynamics away from the Newtonian regime. Consequently, particles sinking in EPS-rich water experience enhanced drag, viscoelasticity-induced reorientation, and altered wake structures and velocity fields.
Particle hydrodynamics in EPS-rich systems is an emerging research area that contributes to understanding particulate matter dynamics in regions affected by algal blooms. This interdisciplinary field integrates physics, chemistry, and biology, and its relevance extends to industrial applications where EPS are used as rheology modifiers.
Spheres (diameter = 5 mm) sinking in doublet in EPS-rich water, PIV measurement
Particle motion in stratified fluid
Density stratification in seas and lakes, driven by salinity and temperature gradients, strongly affects sedimentation processes. Organic aggregates and other biogeochemically relevant particles, including faecal pellets, minerals, and pollutants such as microplastics, experience buoyancy effects that reduce sinking velocities, alter orientation, and promote aggregation. Stratified layers often become hotspots for organic matter and plankton, forming thin layers or mucilage mats. Particle hydrodynamics in stratified aquatic systems is a rapidly growing field that advances our understanding of microscale processes, biogeochemical cycling, and sedimentation dynamics. Relevance of basic physical processess in stratified systems extend to the atmosphere and industrial systems.
Magdalena Mrokowska - biogeophysics | soft matter in hydro-environment 