On the dynamics of tail fins and wind vanes

Ebert, P.; Wood, David

doi:10.1016/0167-6105(94)00088-u

Cited by 14 publications

(19 citation statements)

References 10 publications

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“…There are very few ex perim ental data on w hich to assess the accuracy of these analy ses. Ebert & Wood (1995) found the natural frequency of some fins w as considerably different from that predicted by USB theory. Nevertheless, the yaw behaviour of delta-w ing fins of varying a spect ra tio and boom length, w as that of a linear, second order sy stem in ag reem ent with the assumptions of both quasi-steady and USB analy ses.…”

Section: Introductionmentioning

confidence: 63%

“…40-50°, w hich is insufficient for protection. However, the wind tunnel tests of Ebert & Wood (1995) indicated that the fixed twin fins had high yaw dam ping, w ell in excess of that predicted by the analy sis in the nex t Section, and w ell in excess of that of single fins. D espite the angle of attack on at least one fin being high for a ny g , and the theory being limited to sm all g , the predicted second order linear response w as observed for twin fins a t release angles up to 50°.…”

Section: Introductionmentioning

confidence: 83%

“…This w ill be called the "pseudo-static" assumption. Its limitations w ere show n clearly by the wind tunnel tests of Ebert & Wood (1995). They studied model tail fins without a nacelle or rotor, by yawing the fin to a certain angle and releasing it w hile k eeping U constant.…”

Section: Introductionmentioning

confidence: 99%

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Modelling the Yaw Behaviour of a Small Wind Turbine

et al. 2002

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This paper develops a mathematical model for a small wind turbine responding to changes in the wind direction. Here “small” implies that the turbine has a tail fin. Good yaw behaviour, in terms of tracking the changes in wind direction, is necessary to maximize power extraction. However large rates of change of yaw can lead to large stresses in the turbine components. The unsteady tail fin loads are more complex than implied by the “pseudo-static” assumption that the steady-state lift and drag act instantaneously. The aerodynamic model is applied first to data obtained from a 5 kW experimental turbine when it was not extracting power, because this almost removes the effect of the blades from the yaw behaviour. MATLAB's systems identification toolbox was used to optimise the fit of the model parameters to the data. The resulting values of a number of the parameters are shown to be in good agreement with earlier wind tunnel tests of the tail fin design. Some details of the comparisons, mainly in terms of the higher frequency components, suggest the need to characterise similarly the dynamics of wind vanes. When the turbine was extracting power, the flexible blades were deflected backwards by the aerodynamic loads. A blade element analysis suggests that the stabilizing moment due to this “coning” does not alter the form of the yaw response equation. The optimised fit of the model equations gave changes in the parameters broadly in agreement with the blade element analysis, but the quasi-steady analysis did not predict the measured increase in the damping associated with power extraction.

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Section: Introductionmentioning

confidence: 63%

Section: Introductionmentioning

confidence: 83%

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Modelling the Yaw Behaviour of a Small Wind Turbine

et al. 2002

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“…and Bechly et al [5] based on unsteady slender body (USB) theory, which shows surprisingly accurate prediction of the moments and yaw rates using only the lift acting on the tail vane, even at high yaw angles.…”

Section: Experimental Apparatus and Methodsmentioning

confidence: 98%

Yaw Behavior of Horizontal-Axis Small Wind Turbines in an Urban Area

et al. 2009

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This paper reports the experimental study on passive yaw behavior of a horizontal axis small wind turbines.The yaw angle velocity in a small wind turbine is one of the significant design values and IEC61400-2 Ed.2 prescribes its maximum value should be less than 3 rad/s. However, in practice, in the case of small wind turbines with diameters under 2 m, the yaw angular velocity may exceed the limit of 3 rad/s. The authors conducted a theoretical evaluation as well as a wind tunnel test to examine the possible maximum yaw velocity. The model wind turbine has a diameter of 1 m, blade number of 5, solidity of 0.26 and 2 types of tail fins (large and small). For each tail fin size, the yaw behavior was studied for a range of rotational speeds and wind speeds.The results show that the yaw angular velocity becomes larger with increasing wind velocity and tail fin area. The larger the rotor rotational speed, the smaller the yaw angular velocity. Furthermore, a maximum yaw angular velocity of 3.84 rad/s was observed at a wind speed of 10 m/s, which exceeds the conventional design value of 3 rad/s.

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“…2) Equations: Many approaches have been adopted in the literature to model the behaviour of a weather vane but, in general terms, the angular response when exposed to wind can be assimilated to the response of a second-order system [4]. This result can be found in applying the fundamental principle of dynamics to the wind vane system.…”

Section: Input Datamentioning

confidence: 99%

Methodology for optimal wind vane design

Kerhascoet

Laurent

Cerqueus

et al. 2016

OCEANS 2016 - Shanghai

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International audienceMeasurements of wind direction are sought after by a multitude of professionals in many different domains. Whether to recalibrate meteorological models or simply for leisure activities, the demand for accurate and responsive wind measurements is widespread. This study was motivated by the need to improve the responsiveness of direction measurements on yachts. Here we argue that the ideal form factor of the wind sensor can be determined using digital tools, rather than empirically, with the aim of improving the mechanical response of the wind vane. Then we present the results obtained by applying a predictive filter method tailored to the specified form factor. We have developed and experimentally validate a mathematical model describing the dynamic behavior of a wind vane. This model is then used to determine the form factor of the vane that will give the best possible response to perturbations it will encounter. To do so we use operational research tools, specifying the mechanical characteristics of the vane and by providing the future use conditions of the sensor, in the form of a wind speed spectral density. The design built from this optimization methodology helps reduce the response time of the vane by 44% compared to to designs currently in use. We then work on digital signal processing by using a predictive filter which takes into account the dynamic characteristics of the vane previously determined by the mathematical model. This step vastly improves the quality and sensitivity of the signal, leading to another reduction in response time of 83%. This brings the total decrease in response time at 90%. There is therefore not only an improvement in the quality of wind direction measurements, but also with respect to the set of data that is derived from this information. In the context of single-handed racing boats, the performance of the automatic pilot directly benefits from this improvement in responsiveness

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On the dynamics of tail fins and wind vanes

Cited by 14 publications

References 10 publications

Modelling the Yaw Behaviour of a Small Wind Turbine

Modelling the Yaw Behaviour of a Small Wind Turbine

Yaw Behavior of Horizontal-Axis Small Wind Turbines in an Urban Area

Methodology for optimal wind vane design

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