Variation of leading-edge suction during stall for unsteady aerofoil motions
Variation of leading-edge suction during stall for unsteady aerofoil motions
复制标题
不稳定翼型运动失速期间前缘吸力的变化
DOI：
10.1017/jfm.2020.467
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发表时间：
2020
影响因子：
3.7
通讯作者：
J. Edwards
中科院分区：
文献类型：
--
作者：
S. Narsipur;Pranav Hosangadi;Ashok Gopalarathnam;J. Edwards
摘要圆头翼型前缘的吸力是前缘流动状态的重要指标，通常也是整个翼型流动状态的重要指标。前缘吸力参数（LESP）是该力的无量纲形式。在最近的工作中，从非定常翼型理论计算低雷诺数（10 000-100 000）下附着流的LESP具有良好的精度。与这种“无粘性”LESP相反，粘性计算和实验结果用于计算在低亚音速下进行俯仰运动的翼型上的“粘性”LESP。LESP公式也被更新以考虑翼型的净速度。跨越多个翼型，雷诺数和运动学，情况下，包括动态失速发生或没有前缘涡（LEV）形成的运动。前缘附近的表面压力和表面摩擦分布的拐点被证明是LEV启动的可靠指标。临界LESP，这是LEV启动时的LESP值，被发现是几乎独立的枢轴位置，弱依赖于俯仰速率和强烈依赖于雷诺数。粘性LESP被认为是下降到接近零的值时，流在前缘分离，LEV的形成无关。这种行为被证明与由于流动分离而导致的前缘流线曲率损失有很好的相关性。这些发现有助于提高我们的理解，并扩展了从早期工作中获得的前缘吸力特性的适用性。
Abstract The suction force at the leading edge of a round-nosed aerofoil is an important indicator of the state of the flow over the leading edge and, often, the entire aerofoil. The leading-edge suction parameter (LESP) is a non-dimensional version of this force. In recent works, the LESP was calculated with good accuracy for attached flows at low Reynolds numbers (10 000–100 000) from unsteady aerofoil theory. In contrast to this ‘inviscid’ LESP, results from viscous computations and experiments are used here to calculate the ‘viscous’ LESP on aerofoils undergoing pitching motions at low subsonic speeds. The LESP formulation is also updated to account for the net velocity of the aerofoil. Spanning multiple aerofoils, Reynolds numbers and kinematics, the cases include motions in which dynamic stall occurs with or without leading-edge vortex (LEV) formation. Inflections in the surface pressure and skin-friction distributions near the leading edge are shown to be reliable indicators of LEV initiation. Critical LESP, which is the LESP value at LEV initiation, was found to be nearly independent of pivot location, weakly dependent on pitch rate and strongly dependent on Reynolds number. The viscous LESP was seen to drop to near-zero values when the flow is separated at the leading edge, irrespective of LEV formation. This behaviour was shown to correlate well with the loss of streamline curvature at the leading edge due to flow separation. These findings serve to improve our understanding and extend the applicability of the leading-edge suction behaviour gained from earlier works.
薄翼型非定常流中的前缘吸力和驻点位置
影响因子：
3.7
作者：
Ramesh K
通讯作者：
Ramesh K