Energy Extracting Stream-tube of a WindTurbine

Aerodynamics of Horizontal-Axis Wind Turbines

To study the aerodynamics of wind turbines some knowledge of fluid dynamics in general is necessary and, in particular, aircraft aerodynamics, we can use Bernoulli theorem for steady, incom pressible flow is required together with the concept of continuity, and then use The Biot亡avart law, which will be familiar to those with a knowledge of electric and magnetic fields, is used to determine velocities induced by vortices


Aerodynamics of Horizontal-Axis Wind Turbines



As the air passes through the rotor disc, by design, there is a drop in static pressure such that, on leaving, the air is below the atmospheric pressure level. The air then proceeds downstream with reduced speed and static pressure ・this region
of the flow is called the wake. Eventually, far downstream, the static pressure in the wake must return to the atmospheric level for equilibrium to be achieved. The rise in static pressure is at the expense of the kinetic energy and so causes a further slowing down of the wind. Thus, between the far upstream and far wake conditions, no changein static pressure exists but there is a reduction in kinetic energy.