Fluidstrahl

Fluidstrahl is a term used in fluid dynamics and engineering to denote a focused jet of liquid discharged from a nozzle. The jet's characteristics—velocity, coherence, and spread—are determined by the fluid’s properties (density, viscosity), the driving pressure, and the nozzle geometry. In many languages, including German, Fluidstrahl literally means fluid jet, and the term is used in both academic texts and industrial descriptions to describe a liquid stream that can be refined or focused for processing tasks.

Underlying physics: The behavior is described by conservation of mass and momentum (Navier–Stokes), with dimensionless numbers such as the Reynolds number indicating laminar versus turbulent flow. Nozzle design, including flared, convergent, or converging-diverging shapes, controls the jet diameter and its initial velocity. Boundary-layer development, entrainment of surrounding fluid, and air entrainment influence the jet spread. In specialized variants, gaseous sheaths or pulsing can modify impact pressure.

Applications: high-pressure water jets for cutting and shaping materials (including abrasive water jets using suspended abrasive particles), precision cleaning and surface finishing, microfluidic dispensing, and cooling or lubrication delivery in industrial systems. In spray technology, the jet can be atomized or shaped to form a spray pattern. Micro-fluid jets are studied in biomedical devices and analytical instrumentation.

History and status: The concept has been studied since early hydraulic engineering and became widely used with advances in high-pressure pumps and nozzle technology in the late 20th century. Today, fluid jets are central to manufacturing, material processing, and experimental fluid dynamics, and ongoing research explores jet stability, control, and interaction with fluids and solids.