Tropfenfluss

Tropfenfluss is a term in fluid mechanics describing a two-phase flow regime in which discrete droplets are advected through a continuous carrier fluid. The flow consists of spatially separated droplets that travel with a carrier stream and retain coherence over a finite distance, unlike a homogeneous suspension.

Formation and dynamics: Droplets form by breakup of jets, ligaments or liquid films due to shear, instabilities, or atomization. They can be produced at nozzles or by microfluidic generators. After formation, droplets move under flow, gravity and external fields, and are deformed by viscous and inertial forces. Coalescence or breakup at interfaces affects spacing and size.

Characterization and measurement: Tropfenfluss is described with dimensionless numbers such as Reynolds, Weber, Capillary, and Bond numbers. Experimental methods include high-speed imaging, phase Doppler anemometry, and laser-induced fluorescence to determine droplet size, velocity and inter-droplet distance.

Occurrence: It appears in microfluidic devices, inkjet printing, agricultural sprays, spray cooling and combustion engines. Natural processes like rain can be viewed as droplet flow under gravity and air drag.

Applications and implications: Understanding Tropfenfluss informs nozzle and channel design to control droplet formation and transport, with implications for coating, cooling, and emissions control. Controlling droplet size distribution and interactions improves mixing, transfer and efficiency while reducing losses from coalescence or deposition.