Graviteitsstromen

Graviteitsstromen are flows driven by density differences between fluids in a gravitational field. In these events a denser, heavier fluid propagates into a lighter ambient fluid, typically along a boundary such as a seabed or a horizontal plane, causing a self-sustained current that advances downslope or along the interface. The motion is governed by buoyancy forces associated with the density contrast rather than by external forcing.

In two-layer configurations, the strength of a gravity current is characterized by the reduced gravity g' = g(Δρ/ρ0), where Δρ is the density difference and ρ0 is a reference density. The dynamics are often described using shallow-water or two-layer models with the Boussinesq approximation for small density variations. The front of the current typically travels with a velocity that scales with the square root of g' and a characteristic height, while entrainment of ambient fluid modifies density, thickness, and speed and can lead to a transition from laminar to turbulent flow.

Graviteitsstromen occur in natural and engineered settings. Oceanic turbidity currents transport sediments along continental margins and submarine canyons; saline gravity currents arise when dense saline water moves into fresher water, for example in estuaries or fjords. In the atmosphere and on land, gravity currents include cold-air outflows from storms, pyroclastic or debris density currents associated with volcanic eruptions, and dense slurry flows in steep channels. These flows play a crucial role in sediment transport, hazard assessment, and understanding past geological processes.

Modeling and observation rely on laboratory experiments, field measurements, and numerical simulations. Key concepts include density contrasts, entrainment, front speed, turbulence, and the governing equations of fluid dynamics under buoyancy-dominated conditions.