Purpose

Goal for the present research is investigating the axisymmetric wave propagation behaviors of fluid-filled carbon nanotubes (CNTs) with low slenderness ratios when the nanoscale effects contributed by CNT and fluid flow are considered together.

Method

An elastic shell model for fluid-conveying CNTs is established based on theory of nonlocal elasticity and nonlocal fluid dynamics. The effects of stress non-locality and strain gradient at nanoscale are simulated by applying nonlocal stress and strain gradient theories to CNTs and nonlocal fluid dynamics to fluid flow inside the CNTs, respectively. The equilibrium equations of axisymmetric wave motion in fluid-conveying CNTs are derived. By solving the governing equations, the relationships between wave frequency and all small-scale parameters, as well as the effects caused by fluid flow on different wave modes, are analyzed.

Results

The numerical simulation indicates that nonlocal stress effects damp first-mode waves but promote propagation of second-mode waves. The strain gradient effect promotes propagation of first-mode waves but has no influence on second-mode waves. The nonlocal fluid effect only causes damping of second-mode waves and has no influence on first-mode waves. Damping caused by nonlocal effects are most affect on waves with short wavelength, and the effect induced by strain gradient almost promotes the propagation of wave with all wavelengths.

中文翻译：

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基于非局部流体动力学和非局部应变梯度理论的流体传输碳纳米管中轴对称波的传播行为

目的

本研究的目标是研究将细长的碳纳米管（CNT）与流体流动共同作用的纳米尺度效应综合考虑时的低细长比流体填充碳纳米管（CNT）的轴对称波传播行为。

方法

基于非局部弹性理论和非局部流体动力学理论，建立了流体传输碳纳米管的弹性壳模型。通过将非局部应力和应变梯度理论分别应用于CNT和将非局部流体动力学应用于CNT内部的流体，来模拟纳米级应力非局部性和应变梯度的影响。推导了流体传输碳纳米管中轴对称波动的平衡方程。通过求解控制方程，分析了波浪频率与所有小尺度参数之间的关系，以及流体流动对不同波浪模式的影响。

结果

数值模拟表明，非局部应力影响了第一波的衰减，但促进了第二波的传播。应变梯度效应促进第一模式波的传播，但对第二模式波没有影响。非局部流体效应仅引起第二模式波的衰减，而对第一模式波没有影响。非局部效应引起的阻尼对短波长的波影响最大，应变梯度引起的效应几乎促进了所有波长的波的传播。