Ausströmprofil

Ausströmprofil, literally “outflow profile,” refers to the spatial distribution of fluid velocity at the boundary where a flow exits a conduit, nozzle, or orifice and into the surrounding region. It describes how the cross-sectional velocity varies across the exit plane and into the initial portion of the downstream jet. The term is widely used in fluid dynamics, nozzle design, ventilation, spray systems and related applications.

The shape of the ausströmprofil is determined by factors such as upstream flow conditions, outlet geometry, boundary-layer development, and whether the flow is laminar or turbulent. In a smooth, long tube with laminar, fully developed flow, the cross-sectional velocity is close to parabolic. At the exit of sharp-edged orifices or short passages, the profile can be more nonuniform, with a concentrated core and a shear layer. Turbulent exits tend to produce flatter, more self-similar profiles in the near field, which then evolve downstream toward a characteristic jet profile. The exact profile influences how the jet spreads, entrains surrounding fluid, mixes species, and generates noise or erosion.

Measurement and modelling of ausströmprofil rely on experimental techniques such as particle image velocimetry (PIV), laser Doppler anemometry (LDA), and hot-wire anemometry, as well as numerical simulations solving the Navier–Stokes equations with appropriate boundary conditions. In practice, simplified profiles (parabolic for laminar exit, top-hat or plug-like for jets) are often used for engineering calculations, alongside more detailed, location-specific data.

See also: velocity profile, jet, boundary layer, nozzle design, flow field.