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Andrew T. Myers, PhD, PE, Assistant Professor Vahid Valamanesh , Graduate Student Department of Civil and Environmental Engineering Northeastern University. The Influence of Aerodynamic Damping in the Seismic Response of HAWTs. Presentation Outline. Motivation

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slide1
Andrew T. Myers, PhD, PE, Assistant Professor

VahidValamanesh, Graduate Student

Department of Civil and Environmental Engineering

Northeastern University

The Influence of Aerodynamic Damping in the Seismic Response of HAWTs

slide2

Presentation Outline

  • Motivation
  • Dimensions of utility-scale HAWTs
  • Vulnerability to earthquakes
  • Derivation of aerodynamic damping
    • Fore-aft direction
    • Side-to-side direction
  • Numerical example – 1.5 MW NREL baseline turbine
  • Conclusions
slide3

Motivation: Exposure of HAWTs to Earthquakes

  • Installed wind capacity map as of Jan 2011

United States National Seismic Hazard Map

slide4

Dimensions and Period of HAWTs

Approximate dimensions of a utility-scale HAWT

First Period ~ 3 s

slide5

Vulnerability to Earthquakes

  • No redundancy in the support structure
  • Slender hollow sections (D/t as high as 280)
  • Farms consisting of many nearly identical structures
  • Large directional affect due to aerodynamic damping

Side-to-side

Fore-aft

slide6

Aerodynamic Damping of HAWTs in the Fore-Aft Direction

  • Forces based on blade element momentum theory (BEM)
  • Flexibility of rotor is omitted
  • Wind direction is along fore-aft direction
  • Steady wind
  • First mode of vibration is considered
slide9

Numerical Example – 1.5 MW Baseline Turbine by NREL

Aerodynamic damping in the fore-aft direction with W=20 rpm and b=7.5ᵒ

slide10

Numerical Example – 1.5 MW Baseline Turbine by NREL

Aerodynamic damping in the side-to-side direction with W=20 rpm and b=7.5ᵒ

slide11

Numerical Example – 1.5 MW Baseline Turbine by NREL

Aerodynamic damping in the fore-aft direction with b=7.5ᵒ (left) and W=20 rpm (right)

slide12

Numerical Example – 1.5 MW Baseline Turbine by NREL

Aerodynamic damping in the side-to-side direction with b=7.5ᵒ (left) and W=20 rpm (right)

slide13

Numerical Example – 1.5 MW Baseline Turbine by NREL

Validation with FAST in the fore-aft direction with b=7.5ᵒ and W=20 rpm

FAST

Derivation

slide14

Numerical Example – 1.5 MW Baseline Turbine by NREL

Effect of aerodynamic damping on the seismic response with W=20 rpm

slide15

Conclusions

  • Aerodynamic damping of operational wind turbines strongly depends on wind speed. For the considered example (1.5 MW turbine, W = 20 rpm, b = 7.5˚, wind speed between cut-in and cut-out):
    • The fore-aft aerodynamic damping varies between 2.6% and 6.4%
    • The side-to-side aerodynamic damping varies between -0.1% and 0.9%
  • For this same operational case, the derivative of the lift coefficient with respect to the angle of attack is the most influential parameter in aerodynamic damping in the fore-aft direction
  • The blade pitch angle and rotational speed also influence the aerodynamic damping in both the fore-aft and side-to-side directions
  • The directional effect strongly influences the seismic response, with median spectral drift predicted to be as much as 70% larger in the side-to-side direction than in the fore-aft direction