Blade loads on tidal turbines in planar oscillatory flow

I.A. Milne, Alexander Day, R.N. Sharma, R.G.J. Flay

Research output: Contribution to journalArticle

37 Citations (Scopus)
18 Downloads (Pure)

Abstract

Characterisation of the unsteady hydrodynamic loads is essential for accurate predictions of the fatigue life and ultimate loads of tidal turbine blades. This paper analyses a set of experimental tests of the hydrodynamic blade root out-of-plane bending moment response to planar oscillatory motion, chosen as an idealised representation of the unsteadiness imparted by waves and turbulence. Phenomena associated with dynamic stall are observed which are sensitive to the oscillatory frequency and velocity amplitude. Flow separation is shown to result in loads significantly greater in magnitude than that for steady flow. Following flow reattachment, the load cycles compare relatively well with Theodorsen’s theory for a two-dimensional foil oscillating in heave, suggesting that circulation due to the shed wake dominates the unsteadiness in phase with acceleration, over added mass effects. For attached flow, the effect of unsteadiness is comparatively much smaller. At low frequencies a phase lead over the velocity is observed, compared to a lag at higher frequencies. Multiple frequency oscillations are also briefly considered. Reconstruction of the multi-frequency response using both the steady flow measurements, and the single frequency measured response, is shown to offer a relatively good fit when the flow is attached, for lower frequency combinations
Original languageEnglish
Pages (from-to)163-174
Number of pages12
JournalOcean Engineering
Volume60
Early online date26 Jan 2013
DOIs
Publication statusPublished - 1 Mar 2013

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Steady flow
Turbomachine blades
Frequency response
Turbines
Hydrodynamics
Flow separation
Flow measurement
Bending moments
Metal foil
Turbulence
Fatigue of materials

Keywords

  • tidal turbine
  • unsteady hydrodynamics
  • dynamic staff
  • added mass
  • rotor aerodynamics

Cite this

Milne, I.A. ; Day, Alexander ; Sharma, R.N. ; Flay, R.G.J. . / Blade loads on tidal turbines in planar oscillatory flow. In: Ocean Engineering. 2013 ; Vol. 60. pp. 163-174.
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Blade loads on tidal turbines in planar oscillatory flow. / Milne, I.A.; Day, Alexander; Sharma, R.N.; Flay, R.G.J. .

In: Ocean Engineering, Vol. 60, 01.03.2013, p. 163-174.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Blade loads on tidal turbines in planar oscillatory flow

AU - Milne, I.A.

AU - Day, Alexander

AU - Sharma, R.N.

AU - Flay, R.G.J.

PY - 2013/3/1

Y1 - 2013/3/1

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AB - Characterisation of the unsteady hydrodynamic loads is essential for accurate predictions of the fatigue life and ultimate loads of tidal turbine blades. This paper analyses a set of experimental tests of the hydrodynamic blade root out-of-plane bending moment response to planar oscillatory motion, chosen as an idealised representation of the unsteadiness imparted by waves and turbulence. Phenomena associated with dynamic stall are observed which are sensitive to the oscillatory frequency and velocity amplitude. Flow separation is shown to result in loads significantly greater in magnitude than that for steady flow. Following flow reattachment, the load cycles compare relatively well with Theodorsen’s theory for a two-dimensional foil oscillating in heave, suggesting that circulation due to the shed wake dominates the unsteadiness in phase with acceleration, over added mass effects. For attached flow, the effect of unsteadiness is comparatively much smaller. At low frequencies a phase lead over the velocity is observed, compared to a lag at higher frequencies. Multiple frequency oscillations are also briefly considered. Reconstruction of the multi-frequency response using both the steady flow measurements, and the single frequency measured response, is shown to offer a relatively good fit when the flow is attached, for lower frequency combinations

KW - tidal turbine

KW - unsteady hydrodynamics

KW - dynamic staff

KW - added mass

KW - rotor aerodynamics

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SN - 0029-8018

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