Tuulivirtaus

Tuulivirtaus is Finnish for wind flow or air flow. In meteorology and fluid dynamics it refers to the movement of air relative to the Earth's surface. The term encompasses both large-scale atmospheric transport and localized flows around terrain, urban canyons, vegetation, and buildings. The word combines tuuli (wind) and virtaus (flow).

Physically, tuulivirtaus is governed by the same principles as other fluid flows. In the atmosphere, wind is driven primarily by horizontal pressure gradients created by differences in temperature and air mass distribution. Coriolis force from Earth's rotation and surface friction modify the flow, producing patterns such as geostrophic winds aloft and a shallow boundary layer near the ground. Most natural wind flows are turbulent, containing a range of eddies and fluctuations.

Observation and modeling of tuulivirtaus rely on various methods. Measurements include cup and sonic anemometers for speed and direction, weather stations, wind profilers, and Doppler LiDAR. Computational fluid dynamics and atmospheric models simulate wind flow using the equations of motion (Navier–Stokes) and turbulence models (for example, k-ε or large-eddy simulation). In some cases, simplified or potential-flow approaches are used for specific, idealized scenarios.

Applications and relevance of tuulivirtaus span weather forecasting, wind energy siting, building design to withstand wind loads and ensure ventilation, urban planning, and the dispersion of pollutants. Wind patterns also affect ecological processes such as pollination, seed dispersal, and microclimates within landscapes and cities.