Study On Dynamic Characteristics Of Microchannel Fluid-solid Coupling Systems In Microscale Stress Fields

Since the development of technology for smart machenics and microelectronic,microchannels are widely used in the areas of industry,agriculture,bioengineering,electronic information technology and other fields,so it is more and more important to study the flow characteristics of fluids in microchannels.However,since fluid flow and heat transfer in the micro scale is different from the one at normal scales,the theory for macrofluids is not appropriate for micro scale fluids,and new rules need to be explored to explain microscale fluid flow characteristics.Due to the complexity of micro-flows,the analytical study on the laws of microfluidic flow is not perfect and even contradictory.Therefore,it is very important to study the basic theory of microfluidic fluids.In this paper,the non-local stress/strain gradient coupled constitutive model is emploied to analyze and study various dynamic characteristics of micro channel system.Firstly,the research background is discussed,the current research methods and results of structural features,mechanical properties and application prospects of micro channels are summarized.Furthermore,the non-local stress/strain gradient models are established based on the classical beam theory.The governing equations of motion for free vibration and wave propagation are derived according to Euler-Bernoulli beam and Timoshenko beam theories.By solving the governing equations,the small scale effects contributed by micro-pipe and inner fluid are simulated by non-local stress effect,strain gradient effect and non-local scale effect of fluid respectively.The dynamic behaviors of fluid-filling microchannel are analized when considering the small-scale effect by fluid and solid respectively.According to the numerical results based on the Euler-Bernoulli beam model,the effects of various scales have different effects on the dynamical characteristics of the system.The non-local elastic effect of microchannel dampens the wave propagation,especially for the wave with a short wavelength.In contrary,the promoted effect for wave propagation caused by strain gradient is found at all wavelength range.The non-local effect and the strain gradient effect on the stiffness of micro channel also indicated reverse results.Non-local effect leads to stiffness decreasing,when strain gradient effect leads to stiffness enhancement.The analysis on fluid-structure interaction dynamics system of micro components based on Timoshenko beam model show that the strain gradient effect and non-local stress effect by fluid can promote the vibration and the fluctuation of the system;when the non-local effect by solid can cause wave damping.When the non-local scale parameters of fluid and solid increased to a critical value,the system vibration and wave propagation will no longer have an interation.