基于分子动力学模拟的流体剪切力学特性分析

考虑固体壁面对流体分子作用力的影响，建立了两平行壁面-流体系统的分子动力学模型，模拟了壁面切向运动对流体的剪切过程，分析了壁面速度对不同离壁距离流体层微观剪切力学特性的影响，研究了剪应变率、工作压力和温度对流体宏观剪切力学特性的作用规律.研究表明:受到分子无规则热运动的影响，不同离壁距离流体层的剪切应力呈现出波动变化状态，但随着流体剪切运动的增强，剪切应力的波动幅值逐渐减小；当壁面切向运动较大时，近壁层流体在运动速度上与壁面之间易出现较大的滑动，壁面-流体出现边界滑移；工作压力及温度影响着分子间距离，压力升高与温度降低都将减小分子间的距离，从而引起流体黏度与剪切应力的增大. 

Fluid Shear Mechanical Property Analysis Based on Molecular Dynamic Simulation

Taking the wall force effect into consideration, a molecular dynamic model for two-paralleled walls-fluid system was built and the related shear process was simulated by changing the tangential motion of wall. Under different wall velocity conditions, the shear mechanical property of fluid level at different positions from wall was studied. And the effects of shear rate, pressure and temperature, on macro shear mechanical property were investigated. Results show that the random thermal motion of molecules can lead to the fluctuation of shear stress for different fluid levels, and with the increase of shear velocity, the fluctuation decreases. In the condition of large tangential velocity of wall, the large velocity slip between surficial fluid and the surface occurs, as responses to the step increase of shear force. Pressure and temperature have great effects on molecular distance, thus increasing pressure or decreasing temperature can decrease distance, as results in the rising for both viscosity and shear force.