O Connor Joseph, Revell Alistair, Mandal Parthasarathi, Day Philip
School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL, UK.
School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL, UK.
J Biomech. 2016 Jul 26;49(11):2143-2151. doi: 10.1016/j.jbiomech.2015.11.057. Epub 2015 Dec 11.
Complex fluid-structure interactions between elastic filaments, or cilia, immersed in viscous flows are commonplace in nature and bear important roles. Some biological systems have evolved to interpret flow-induced motion into signals for the purpose of feedback response. Given the challenges associated with extracting meaningful experimental data at this scale, there has been particular focus on the numerical study of these effects. Porous models have proven useful where cilia arrangements are relatively dense, but for more sparse configurations the dynamic interactions of individual structures play a greater role and direct modelling becomes increasingly necessary. The present study reports efforts towards explicit modelling of regularly spaced wall-mounted cilia using a lattice Boltzmann-immersed boundary method. Both steady and forced unsteady 2D channel flows at different Reynolds numbers are investigated, with and without the presence of a periodic array of elastic inextensible filaments. It is demonstrated that the structure response depends significantly on Reynolds number. For low Reynolds flow, the recirculation vortex aft of successive filaments is small relative to the cilia spacing and does not fully bridge the gap, in which case the structure lags the flow. At higher Reynolds number, when this gap is fully bridged the structure and flow move in phase. The trapping of vortices between cilia is associated with relatively lower wall shear stress. At low to intermediate Reynolds, vortex bridging is incomplete and large deflection is still possible, which is reflected in the tip dynamics and wall shear stress profiles.
浸没在粘性流中的弹性细丝（即纤毛）之间复杂的流固相互作用在自然界中很常见且具有重要作用。一些生物系统已经进化到能够将流动诱导的运动转化为信号，以进行反馈响应。鉴于在这个尺度上提取有意义的实验数据存在挑战，人们特别关注这些效应的数值研究。在纤毛排列相对密集的情况下，多孔模型已被证明是有用的，但对于更稀疏的配置，单个结构的动态相互作用起着更大的作用，直接建模变得越来越必要。本研究报告了使用格子玻尔兹曼-浸入边界方法对规则排列的壁面纤毛进行显式建模的工作。研究了不同雷诺数下的稳态和强迫非稳态二维通道流，有无周期性排列的弹性不可伸长细丝。结果表明，结构响应显著依赖于雷诺数。对于低雷诺数流动，连续细丝后方的回流涡相对于纤毛间距较小，且不能完全跨越间隙，在这种情况下，结构滞后于流动。在较高雷诺数下，当这个间隙被完全跨越时，结构和流动同相运动。纤毛之间的涡旋捕获与相对较低的壁面剪应力有关。在低到中等雷诺数时，涡旋桥接不完全，仍然可能有大的偏转，这反映在尖端动力学和壁面剪应力分布中。
