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首页> 美国卫生研究院文献>PLoS Clinical Trials >Normalized Lift: An Energy Interpretation of the Lift Coefficient Simplifies Comparisons of the Lifting Ability of Rotating and Flapping Surfaces
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Normalized Lift: An Energy Interpretation of the Lift Coefficient Simplifies Comparisons of the Lifting Ability of Rotating and Flapping Surfaces

机译：归一化提升：提升系数的能量解释简化了旋转和拍打表面提升能力的比较

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For a century, researchers have used the standard lift coefficient CL to evaluate the lift, L, generated by fixed wings over an area S against dynamic pressure, ½ρv 2, where v is the effective velocity of the wing. Because the lift coefficient was developed initially for fixed wings in steady flow, its application to other lifting systems requires either simplifying assumptions or complex adjustments as is the case for flapping wings and rotating cylinders.This paper interprets the standard lift coefficient of a fixed wing slightly differently, as the work exerted by the wing on the surrounding flow field (L/ρ·S), compared against the total kinetic energy required for generating said lift, ½v2. This reinterpreted coefficient, the normalized lift, is derived from the work-energy theorem and compares the lifting capabilities of dissimilar lift systems on a similar energy footing. The normalized lift is the same as the standard lift coefficient for fixed wings, but differs for wings with more complex motions; it also accounts for such complex motions explicitly and without complex modifications or adjustments. We compare the normalized lift with the previously-reported values of lift coefficient for a rotating cylinder in Magnus effect, a bat during hovering and forward flight, and a hovering dipteran.The maximum standard lift coefficient for a fixed wing without flaps in steady flow is around 1.5, yet for a rotating cylinder it may exceed 9.0, a value that implies that a rotating cylinder generates nearly 6 times the maximum lift of a wing. The maximum normalized lift for a rotating cylinder is 1.5. We suggest that the normalized lift can be used to evaluate propellers, rotors, flapping wings of animals and micro air vehicles, and underwater thrust-generating fins in the same way the lift coefficient is currently used to evaluate fixed wings.
机译：一个世纪以来，研究人员一直使用标准升力系数CL来评估面积S上固定机翼抵抗动压½ρv 2 产生的升力L，其中v是机翼的有效速度。由于升力系数最初是为固定翼在稳定流动中发展而来的，因此将其应用于其他升力系统需要简化假设或进行复杂的调整（如拍打襟翼和旋转油缸的情况）。本文略微解释了固定翼的标准升力系数不同的是，与机翼在周围流场上施加的功（L /ρ·S）相比，产生所述升力所需的总动能½v 2 。重新解释的系数，归一化升程，是从功能定理得出的，它在相似的能量基础上比较了不同升程系统的升程能力。归一化升力与固定机翼的标准升力系数相同，但对于运动较为复杂的机翼则有所不同。它也明确地说明了这种复杂的动作，而无需进行复杂的修改或调整。我们将归一化的升力与先前报告的马格努斯效应中旋转圆柱体的升力系数值，悬停和向前飞行中的蝙蝠以及悬停的斜翼进行比较。在稳定流动中不带襟翼的固定翼的最大标准升力系数为约为1.5，但对于旋转圆柱体，它可能会超过9.0，该值表示旋转圆柱体产生的机翼最大升力接近6倍。旋转气缸的最大归一化升程为1.5。我们建议归一化升力可用于评估螺旋桨，旋翼，动物和微型飞行器的襟翼以及水下推力产生的鳍片，其升力系数目前可用于评估固定翼。

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