粗糙纳通道内流体流动与传热的分子动力学模拟研究

Molecular dynamics simulation on fluid flow and heat transfer in rough nanochannels

为研究粗糙表面对纳尺度流体流动和传热及其流固界面速度滑移与温度阶跃的影响,本文建立了粗糙纳通道内流体流动和传热耦合过程的分子动力学模型,模拟研究了粗糙通道内流体的微观结构、速度和温度分布、速度滑移和温度阶跃并与光滑通道进行了比较,并分析了固液相互作用强度和壁面刚度对界面处速度滑移和温度阶跃的影响规律.研究结果表明,在外力作用下,纳通道主流区域的速度分布呈抛物线分布,由于流体流动导致的黏性耗散使得纳通道内的温度分布呈四次方分布.并且,在固体壁面处存在速度滑移与温度阶跃.表面粗糙度的存在使得流体剪切流动产生了额外的黏性耗散,使得粗糙纳通道内的流体速度水平小于光滑通道,温度水平高于光滑通道,并且粗糙表面的速度滑移与温度阶跃均小于光滑通道.另外,固液相互作用强度的增大和壁面刚度的减小均可导致界面处速度滑移和温度阶跃程度降低.

Fluid flow and heat transfer in a microstructure may depart from the traditional behavior due to the scale effect, and its velocity slip and temperature jump will occur at the fluid-solid interface. A molecular dynamics model of coupled fluid flow and heat transfer in rough nanochannels is developed to investigate the effect of surface roughness on nanoscale fluid flow and heat transfer, as well as velocity slip and temperature jump at the fluid-solid interface. The fluid microscopic structure, velocity and temperature distributions, interfacial velocity slip and temperature jump in a rough nanochannel are evaluated and compared with the corresponding smooth nanochannel. Effects of solid-liquid interaction and wall stiffness on the velocity slip and temperature jump are analyzed. Results indicate that the velocity of the fluid flow under an external force in a nanochannel in a bulk region is of a parabolic distribution, and the viscous dissipation due to shear flow induces the fourth-order temperature profile in the nanochannel. And the velocity slip and temperature jump will occur at the fluid-solid interface. The presence of roughness may introduce an extra viscous dissipation in shear flow,leading to a reduction of overall velocity and an increase in temperature in the nanochannel when compared with the smooth nanochannel. In addition, the degree of velocity slip and temperature jump at a rough liquid-solid interface is smaller than that at a smooth interface. In particular, the increase in fluid-solid interaction strength and reduction in wall stiffness will lead to a small velocity slip and temperature jump.