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Numerical exploration on buckling instability for directional control in flagellar propulsion.
Soft Matter ( IF 2.9 ) Pub Date : 2020-01-22 , DOI: 10.1039/c9sm01843c
Weicheng Huang 1 , M K Jawed
Affiliation  

We report a numerical method to control the swimming direction by exploiting buckling instability in uniflagellar bacteria and bio-inspired soft robots. Our model system is comprised of a spherical rigid head and a helical elastic flagellum. The rotation of the flagellum in low Reynolds environment generates a propulsive force that allows the system to swim in fluid. The locomotion is an intricate interplay between the elasticity of the flagellum, the hydrodynamic loading, and the flow generated by the moving head. We use the Discrete Elastic Rods algorithm to capture the geometrically nonlinear deformation in the flagellum, Lighthills Slender Body Theory to simulate the hydrodynamics, and Higdons model for the spherical head in motion within viscous fluid. This flagellated system follows a straight path if the angular velocity of the flagellum is below a critical threshold. Buckling ensues in the flagellum beyond this threshold angular velocity and the system takes a nonlinear trajectory. We consider the angular velocity as the control parameter and solve the inverse problem of computing the angular velocity, that varies with time, given a desired nonlinear trajectory. Our results indicate that bacteria can exploit buckling in flagellum to precisely control their swimming direction.

中文翻译:

鞭毛推进方向控制屈曲不稳定性的数值研究。

我们报告了一种数值方法,通过利用单鞭毛细菌和生物启发的软机器人中的屈曲不稳定性来控制游泳方向。我们的模型系统由球形刚性头和螺旋弹性鞭毛组成。在低雷诺环境下鞭毛的旋转会产生推动力,使系统在液体中游动。运动是鞭毛的弹性,流体动力载荷和动头产生的流量之间的复杂相互作用。我们使用离散弹性杆算法来捕获鞭毛中的几何非线性变形,使用Lighthills细长体理论来模拟流体力学,并使用Higdons模型来研究在粘性流体中运动的球形头。如果鞭毛的角速度低于临界阈值,则该鞭毛系统遵循直线路径。鞭毛随后在该阈值角速度之后发生屈曲,并且系统采用非线性轨迹。我们将角速度视为控制参数,并解决了在给定所需的非线性轨迹的情况下计算随时间变化的角速度的反问题。我们的结果表明细菌可以利用鞭毛屈曲来精确控制其游泳方向。给定所需的非线性轨迹。我们的结果表明细菌可以利用鞭毛屈曲来精确控制其游泳方向。给定所需的非线性轨迹。我们的结果表明细菌可以利用鞭毛屈曲来精确控制其游泳方向。
更新日期:2019-12-25
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