Abstract:

Boundary slip is one of the key features of micro-flow,and it provides a new way for flow control bychanging the slip status of flow channel.Based on the slip effect adjacent to the wall in the micro-gap and the Navierslip boundary condition,a model of exact solution to the shear flow in the two-dimensional micro-gap with a lyophilicand lyophobic wall is constructed. Then,the reliability of the proposed mathematical model is verified by establishinga simulation model of micro-flow based on the computational fluid dynamics method,and it is used to investigatethe micro-flow laws in the micro-gaps with different slip properties according to the slip parameters obtainedfrom the experimental results in relevant literatures.The results show that ( 1) the slip flow in the micro-gap variesrapidly with the wall movement,and it tends to be steady within milliseconds or below; ( 2) the lyophilic stationarywall is of a stronger adsorption ability to liquid in comparison with the moving one,while the motion status of thelyophobic wall has a small impact on the slip flow; and ( 3) in nano-scale gaps,the integration of the superlyophilicstationary wall with the super-lyophobic moving wall causes a strong adsorption of liquid on the lyophilicwall to occur.

Key words: micro /nano gap, shear flow, complicated boundary slip, unsteady flow