Blade loads on tidal turbines in planar oscillatory flow
Blade loads on tidal turbines in planar oscillatory flow
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DOI：
10.1016/j.oceaneng.2012.12.027
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发表时间：
2013-03
影响因子：
5
通讯作者：
I. Milne;A. Day;Rajnish N. Sharma;R. Flay
中科院分区：
文献类型：
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作者：
I. Milne;A. Day;Rajnish N. Sharma;R. Flay
非定常水动力载荷的表征对于准确预测潮汐涡轮叶片的疲劳寿命和极限载荷是至关重要的。本文分析了流体动力叶片根部平面外弯矩对平面振荡运动响应的一组实验测试，它被选为波浪和湍流所赋予的不稳定的理想表示。观察到了与动态失速相关的现象，这些现象对振荡频率和速度幅值很敏感。流动分离所产生的载荷明显大于恒定流下的载荷。在流动再附着后，载荷周期与Theodorsen的二维翼片在升沉中振荡的理论相比较好，这表明，降流尾迹引起的环流主导了与加速度同相的不稳定，超过了附加质量的影响。对于附着流，非恒定度的影响相对较小。与高频时的滞后相比，低频时观测到的相位超前于速度。文中还简要讨论了多频振荡问题。使用恒定流测量和单频测量的多频响应重建显示，对于较低的频率组合，当流被附着时，多频响应提供了相对较好的拟合。
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.