Airakseleration

Airakseleration, in the context of fluid dynamics, is the acceleration of air—that is, the rate at which the velocity of air changes with time at a point in a flow. In formal terms, the acceleration of a parcel of air is the substantial derivative of the velocity field, a = Dv/Dt = ∂v/∂t + (v · ∇)v. This decomposition separates the local (temporal) change from the convective change caused by movement through spatial variations in the flow. The magnitude of air acceleration has units of meters per second squared (m/s^2).

In compressible and incompressible flows, air acceleration is related to pressure gradients and body forces via the governing equations of fluid dynamics. A common form is Dv/Dt = - (1/ρ) ∇p + f, where ρ is air density, p is pressure, and f represents external body forces. This formulation underpins how changes in velocity arise from gusts, turbine or propeller action, and pressure distributions around objects.

Air acceleration is important in engineering and meteorology. It influences aircraft loads during gusts, the performance of propulsion systems that ingest and accelerate air, and the behavior of wind and weather patterns. Measuring and predicting air acceleration uses velocity-field data from experiments or simulations, obtained through methods such as hot-wire anemometry, particle image velocimetry, Doppler radar, LIDAR, or computational fluid dynamics.