论文标题
间歇性不稳定的推进，并结合起来和俯仰箔
Intermittent Unsteady Propulsion with a Combined Heaving and Pitching Foil
论文作者
论文摘要
刻薄的计算是通过连接到使用连续和间歇性动作的组合膨胀和俯仰箔的自动虚拟体的。可以确定，当无量纲的升高比为$ h^* <0.7 $时，间歇性游泳可以提高效率，而它降低了$ h^* \ geq 0.7 $的效率。这是由于俯仰主导（$ h^* <0.5 $）和以主导（$ h^*> 0.5 $）动作的力量产生的物理起源的结果。基于从经典不稳定的薄机翼理论中获得的洞察力，发现倾斜主导的动作是由基于质量的推力产生驱动的，在这些动作中，自propelled效率以高降低的频率最大化，而较高的主导运动则由循环基于循环的推力产生驱动，从而最大程度地减少了频率，而低降低了频率的最大化。不管无量纲的重量比如何，小幅度运动，高灯塔数量和低占空比周期的频率降低，反之亦然。此外，在间歇性游泳期间，在爆裂和沿海阶段的交界处脱落的停止涡流变得可忽略不计，$ h^* <0.5 $和$ a^* = 0.4 $的小幅度运动。这项研究提供了对生物学或生物启发的游泳者不断或间歇地使用堆积和俯仰水翼的合并的机械权衡的见解。
Inviscid computations are presented of a self-propelled virtual body connected to a combined heaving and pitching foil that uses continuous and intermittent motions. It is determined that intermittent swimming can improve efficiency when the dimensionless heave ratio is $h^* < 0.7$ while it degrades efficiency for $h^* \geq 0.7$. This is a consequence of the physical origins of the force production for pitch-dominated ($h^* < 0.5$) and heave-dominated ($h^* > 0.5$) motions. Based on insight derived from classic unsteady thin airfoil theory, it is discovered that pitch-dominated motions are driven by added-mass-based thrust production where self-propelled efficiency is maximized for high reduced frequencies, while heave-dominated motions are driven by circulatory-based thrust production where self-propelled efficiency is maximized by low reduced frequencies. Regardless of the dimensionless heave ratio the reduced frequency is high for small amplitude motions, high Lighthill numbers, and low duty cycles and vice versa. Moreover, during intermittent swimming, the stopping vortex that is shed at the junction of the bursting and coasting phases becomes negligibly weak for $h^* < 0.5$ and small amplitude motions of $A^* = 0.4$. This study provides insight into the mechanistic trade-offs that occur when biological or bio-inspired swimmers continuously or intermittently use combined heaving and pitching hydrofoils.
