Aerodynamic Structural Noise - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 206

region;.wherein.at.least.a.portion.of.the.blade.is.formed.from.a.cellular.mate-
rial.and.where.the.cellular.material.portion.deines.a.portion.of.an.exposed.
surface.of.the.blade.
Different.wind.velocities.in.the.top-Vp.and.bottom-Vb.points.of.blades.at.
an.elevation.of.approximately.200.m.creates.turbulence.and.vibration.
The.ratio.of.reduction.air.velocity.is.represented.in.equation.(7.7).

Vt - Vb
Vb

α 1 =

. . (7.7).

and.power.is.given.by:

. P.=.0.5ρA.V mid. (V.-.Vp). (7.8)

= Vt - Vb
2

V

Here:. . (7.9)

mid

This.phenomenon.will.be.increased.noise.(Figure 7.7).
For.reduced.noise.between.lange.ingers.bush.and.hub,.we.install.shock.
absorbers. (see. Figure 7.7).. Shock. absorber. pads. dampen. vibrations. and.
reduce.noise..Shock.absorbers.are.seen.in.Figure 7.8. 5 .
Another.solution.can.be.plate.springs.or.nylon.bushes..But,.the.advantage.of.
shock.absorbers.is.the. automatic .regulation.of.vibration.and.noise..Pneumatic.

Wind turbine blade, aerodynamic aspect

FIGURE 7.7
Assembly.blades.with.shock.absorber.