Windkanal

A windkanal, commonly known in English as a wind tunnel, is a facility used to study the aerodynamics of objects by producing a controlled flow of air around a model. By varying speed, pressure, and flow conditions, researchers observe forces, pressures, and flow patterns to understand performance and stability.

There are open-circuit and closed-circuit wind tunnels, and operating regimes ranging from subsonic to transonic and supersonic. Open-circuit tunnels draw air from the surroundings, pass it through the test section, and exhaust it back to the environment. Closed-circuit tunnels recirculate a fixed air volume, often with enhanced control over flow quality and temperature.

Key components include a test section where the model is placed, a contraction or nozzle that accelerates the flow, a diffuser that slows it for measurement, and a drive system such as fans or compressors. Flow conditioning elements, like screens and honeycomb structures, improve uniformity. Instrumentation for data collection—pressure sensors, force balances, and visualization tools—complements advanced measurement systems.

Measurements typically include lift, drag, and moment coefficients obtained from force balances and pressure taps, as well as velocity and turbulence data from techniques such as hot-wire anemometry, laser Doppler velocimetry, or particle image velocimetry. Visualization methods using smoke, tufts, or oil flows help reveal flow structures.

Applications span aerospace (aircraft and rotorcraft design), automotive engineering, civil and wind engineering (buildings and bridges), sports equipment, and aerodynamic research. History highlights include the first wind tunnel built in 1871 by Francis Wenham and subsequent development of larger subsonic, transonic, and supersonic facilities. While computational fluid dynamics complements wind-tunnel testing, wind tunnels remain essential for empirical validation and complex flow studies.