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- Aeroelastic evaluations
While the rotor blades for the sub mega-watt class usually had been designed
with high stiffness in regard to aerodynamic instabilities, the need to
reduce the specific weight of rotor blades for the multi-megawatt class of
wind turbines increased the possibility of unsteady aerodynamic behaviour,
known since the late 1940's as the "flutter"-effect in aircraft design.
Due to the highly complex and unsteady relation between the aerodynamic
forces and the structural response, aeroelastic evaluation usually still
is a topic for dedicated scientific institutes. Based on research activities
of the German Society of Aeronautical Research (DLR), WINDnovation's engineers
have developed their own code for the aeroelastic stability analysis of rotor blades.
Above all, the background knowledge in this field is of great value when it
is available right from the start of a new rotor blade design. The earlier
all critical factors can be taken into account the less likely real problems
will occur later. The use of a fast but sufficiently detailed aeroelasic
evaluation allows its integration into the design optimization loop, once
again improving the reliability of the final design.
In the design loop, the aeroelastic evaluation of a rotor blade design allows
for example to calculate the maximum allowable rotational speed of the rotor for
safe operation of the wind turbine or - vice versa - the margin of a rotor blade
turning with a defined rotational speed to the flutter limits.
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