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Effects of time-varying flexibility on the propulsion performance of a flapping foil
Physics of Fluids ( IF 4.6 ) Pub Date : 2020-12-24 , DOI: 10.1063/5.0027927
Guangyu Shi 1 , Qing Xiao 1 , Qiang Zhu 2
Affiliation  

In this paper, we numerically investigate the effects of time-varying bending stiffness on the propulsion performance of a flapping foil using a fully coupled fluid-structure interaction model. The flow field is simulated using a Navier–Stokes solver while the structural dynamics is resolved by a nonlinear beam model. The force generation, the passive deformation, and the flow field of the flexible foil are significantly affected by the time dependency of flexibility. Here, both the actuation at the leading edge and the stiffness of the foil vary sinusoidally, and the phase ϕ between them plays an important role in determining the performance of the foil. At ϕ = 0°, the maximum time-averaged thrust coefficient can be increased by ∼52% whereas the highest propulsion efficiency remains almost the same as that of the foil with a constant flexibility. This is of significance when the size of the wing is often constrained. In addition, the foil with time-varying stiffness generates considerable lift force, which is attributed to the non-symmetrical deformations and deflected vortex-shedding patterns. Finally, the force generation due to added mass is discussed using a simplified model.

中文翻译:

时变柔韧性对拍打箔片推进性能的影响

在本文中,我们使用完全耦合的流固耦合模型,数值研究了时变弯曲刚度对拍打箔片推进性能的影响。使用Navier-Stokes求解器模拟流场,同时通过非线性梁模型求解结构动力学。挠性箔片的力产生,被动变形和流场受挠性的时间依赖性显着影响。在此,在前缘处的致动和箔片的刚度都以正弦曲线形式变化,并且它们之间的相位φ在确定箔片的性能中起重要作用。在ϕ= 0°时,最大时均推力系数可增加约52%,而最高推进效率与具有恒定挠性的箔几乎保持相同。当机翼的尺寸经常受到限制时,这很重要。另外,具有随时间变化的刚度的箔片产生相当大的升力,这归因于非对称变形和偏斜的涡流脱落图案。最后,使用简化模型讨论了由于增加的质量而产生的力。
更新日期:2020-12-30
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