Preliminary results of a field experiment to characterize wind flow through a vertical plane

Verholek, M.G.

doi:10.2172/6722047

Cited by 10 publications

(9 citation statements)

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“…The inflow conditions obviously have a significant impact on the turbine load response (Elliott and Cadogan, 1990;Eggers et al, 2003;Antoniou et al, 2007;Wagner et al, 2011;St. Martin et al, 2016).…”

Section: Problem Discussionmentioning

confidence: 99%

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Pedersen¹

2018

Preprint

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In this paper, inflow information is extracted from a measurement database and used for aeroelastic simulations to investigate if using more accurate inflow descriptions improves the accuracy of the simulated wind-turbine fatigue loads.The inflow information is extracted from nearby meteorological masts (met masts) and a blade-mounted fivehole pitot tube. The met masts provide measurements of the inflow at fixed positions some distance away from the turbine, whereas the pitot tube measures the inflow while rotating with the rotor.The met mast measures the free-inflow velocity; however the measured turbulence may evolve on its way to the turbine, pass beside the turbine or the mast may be in the wake of the turbine. The inflow measured by the pitot tube, in comparison, is very representative of the wind that acts on the turbine, as it is measured close to the blades and also includes variations within the rotor plane. Nevertheless, this inflow is affected by the presence of the turbine; therefore, an aerodynamic model is used to estimate the free-inflow velocities that would have occurred at the same time and position without the presence of the turbine.The inflow information used for the simulations includes the mean wind speed field and trend, the turbulence intensity, the wind-speed shear profile, atmospheric stability-dependent turbulence parameters, and the azimuthal variations within the rotor plane. In addition, instantaneously measured wind speeds are used to constrain the turbulence.It is concluded that the period-specific turbulence intensity must be used in the aeroelastic simulations to make the range of the simulated fatigue loads representative for the range of the measured fatigue loads. Furthermore, it is found that the one-to-one correspondence between the measured and simulated fatigue loads is improved considerably by using inflow characteristics extracted from the pitot tube instead of using the met-mast-based sensors as input for the simulations. Finally, the use of pitot-tube-recorded wind speeds to constrain the inflow turbulence is found to significantly decrease the variation of the simulated loads due to different turbulence realizations (seeds), whereby the need for multiple simulations is reduced.Published by Copernicus Publications on behalf of the European Academy of Wind Energy e.V.

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Section: Problem Discussionmentioning

confidence: 99%

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Pedersen¹

2018

Preprint

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“…The damping force vector, {F DAMP (t)}, created by the presence of the single damper placed at the top of the tower, is given by (16) which when transferred into modal coordinates condenses into (17) Taking a Fourier transform of equation (17) in which equations (2) and (9) are inserted yields (18) Equation (1) is expressed in its modal canonical form as (19) where C -…”

Section: Theoretical Formulation Response Of Tower Including Blade/tomentioning

confidence: 99%

“…Due to the rotation of the blades, the spectral energy distribution is altered, with variance shifting from the lower frequencies to peaks located at integer multiples of the rotational frequency. Although literature on this topic is limited, some relevant work have been reported by Madsen and Frandsen, 17 Verholek, 18 Hardesty et al 19 and Sørensen et al 20 Rotationally sampled spectra were created as outlined in Murtagh et al 12,15 and were converted to a time-domain representation via the discrete Fourier transform. The mode acceleration method was then employed to estimate the flapping acceleration response time histories of the rotating blades, which allowed their fore-aft base shear time histories to be calculated for use in the coupling process.…”

Section: Introductionmentioning

confidence: 99%

Passive control of wind turbine vibrations including blade/tower interaction and rotationally sampled turbulence

et al. 2007

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This paper investigates the use of a passive control device, namely, a tuned mass damper (TMD), for the mitigation of vibrations due to the along-wind forced vibration response of a simplified wind turbine.The wind turbine assembly consists of three rotating uniform rotor blades connected to the top of a flexible uniform annular tower, constituting a multi-body dynamic system.First,the free vibration properties of the tower and rotating blades are each obtained separately using a discrete parameter approach, with those of the tower including the presence of a rigid mass at the top, representing the nacelle, and those of the blade including the effects of centrifugal stiffening due to blade rotation and self-weight. Dragbased loading is assumed to act on the rotating blades, in which the phenomenon of rotationally sampled wind turbulence is included. Blade response time histories are obtained using the mode acceleration method, allowing base shear forces due to flapping motion for the three blades to be calculated. The resultant base shear is imparted into the top of the tower. Wind drag loading on the tower is also considered, and includes Davenport-type spatial coherence information. The tower/nacelle is then coupled with the rotating blades by combining their equations of motion. A TMD is placed at the top of the tower, and when added to the formulation, a Fourier transform approach allows for the solution of the displacement at the top of the tower under compatibility of response conditions. An inverse Fourier transform of this frequency domain response yields the response time history of the coupled blades/tower/damper system. A numerical example is included to qualitatively investigate the influence of the damper. Figure 4. Transfer function for the coupled tower/nacelle and rotating blades model (Ω = 15 rev min -1 ) including and excluding the TMD 314 P. J. Murtagh et al.Figure 7. Simulated displacement response at the top of the tower coupled tower/nacelle and rotating blades model (Ω = 30 rev min -1 ) including and excluding the TMD 316 P. J. Murtagh et al.

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“…The stresses on the rotating blade caused by instantaneous wind shears encountered by the blade within each revolution have been found to be more severe and more difficult to understand than previously expected. Since 1977, the Pacific Northwest Laboratory (PNL) has qeen conducting a program of measuring the wind as seen by a rotating horizontal axis wind turbine (HAWT) blade, using fixed arrays of towers and anemometers (Verholek 1978;Connell 1981), known as vertical plane arrays (VPA).…”

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confidence: 99%

Rotationally sampled wind characteristics and correlations with MOD-OA wind turbine response

George¹,

Connell²

1984

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PNL-5238 UC-60 DISCLAIM ER Th is report was prepared as an account of work sponsored by an age ncy of the Un ite d States Gove rn ment. Neit her t he Un ited States Gove rnm ent no r any age ncy t hereof, nor any of their employees, makes any warran ty, ex press or im p lied, o r ass umes any legal lia bi lity or responsibility fo r t he accu ra cy, completeness, or usef ulness o f an y informa t ion, appa ratus, produ ct, or p rocess disclosed, or represe nts that its use wou ld not infringe privately ow ned r ig hts. Reference herein to an y specifi c co m m ercial p roduct, pro cess, or service by t rade name, trademark, manu facturer, or otherwise, does not necessa rily co nst itu te or im ply its endorsement, recommen d at ion, or favoring by the U n ite d Sta tes Government o r any agency thereo f. The vie ws and opi ni o ns of authors expressed herei n do not necessarily state or reflect th ose o f the United States Governme nt o r an y agency thereof.

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Preliminary results of a field experiment to characterize wind flow through a vertical plane

Cited by 10 publications

References 0 publications

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Passive control of wind turbine vibrations including blade/tower interaction and rotationally sampled turbulence

Rotationally sampled wind characteristics and correlations with MOD-OA wind turbine response

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