luftstrøm

Luftstrøm is a term meaning the movement of air, the fluid that fills spaces and environments, and is used in fields such as physics, engineering, and building science. It describes how air flows through a space, the rate at which it moves, and the direction and speed of that movement. The concept is used both for natural ventilation and for mechanically driven systems.

In technical terms, airflow is described by the flow rate Q, the volume of air that passes a cross-section per unit time, typically measured in cubic meters per second (m3/s) or liters per second (L/s). It relates to velocity v and cross-sectional area A through Q = vA. The density and viscosity of air, along with surface roughness and obstacles, influence whether the flow is laminar or turbulent and determine pressure losses along ducts or channels.

Airflow is driven by pressure differences created by fans, ventilation systems, winds, or buoyancy (stack effect). In ducts and passages, friction, fittings, and changes in cross-section cause pressure drops that must be overcome to achieve the desired Q. Measurements are made with devices such as anemometers or pitot tubes. In buildings, the air exchange rate (ACH) expresses how often indoor air is replaced per hour and is a key indicator of ventilation quality.

In addition to practical applications in HVAC and indoor air quality, luftstrøm is analyzed in aerodynamics, where the Reynolds number helps determine whether flow is laminar or turbulent around objects.