Flow around a wind turbine
Induction region
Vortex sheet theory Medici et al. 2011
Wake
Near wake
Far wake
periodic helicoidal vortex
structures shedding
tip vortices
root vortices
tip vortices are more "persistent"
Wind-Turbine and Wind-Farm Flows: A Review, Fernando Porté-Agel et al.
Breakdowns
tip votices can reduce
flow entrainment in the near wake by separating this region from the outer flow
have some random fluctuations
vortex wandering or
vortex jittering
mutual inductance instability
Hub vortex
Mean flow distribution
mean flow distribution
velocity distribution
turbulence intensity distribution
slight Gaussian distribution
self similarity
Wake recovery
heavily influenced by influenced by roughness length
'rougher flows' induce greater turbulence intensity.
Greater turbulence intensity = quicker recovery
Ultimately affects "capacity density"
Generally high turbulence, especially in the upper part of the wake. Also, Kinzel shows power transport due to kinetic energy flux is dominant in the upper part of the wake, compared to that of the lower part of the wake
if uniform inflow conditions, I_w has a double gaussian profile. Max values occur at the edge of the wakes
Streamwise turbulence intensity
Turbulent momentum flux
entrainment of air from the outer flow
towards the wake centre
Turbulent kinetic energy
Wake Meandering
wake meandering does not occur unless turbulent eddies much larger than the turbine rotor diameter exist in the incoming flow
Yawed flow
Wake deflection
Yaw angle
Thrust coefficient
Incoming turbulence intensity
thermal stability
Thermal effects
Convective boundary layer
Neutral atmospheric boundary layer
stable boundary layer
Relatively higher turbulence intensity in the convective boundary layer
Enhanced turbulent mixing, flow entrainment, wake meanduring, and wake recovery