Liquid Flow Characteristics In Nanochannels And Contact Angle Molecular Dynamics Simulation

The liquid flow characteristics in nanochannels play an important role in the separation and purification of porous membranes,the research and manufacture of microfluidic chips and microelectromechanical systems,and the development of unconventional oil and gas resources.At present,the research on the characteristics of liquid flow at the micro and nano-scale is mainly concentrated on the micro scale.There are few studies on the characteristics of oil flow and oil-water two-phase flow at the nano-scale.The flow mechanism is still unclear.In order to study the liquid flow characteristics at the nano-scale,molecular dynamics simulation of solid wall oil contact angle,the flow characteristics of oil in the nano-channel array and the unsteady water flooding flow characteristics of the nano-channel array were carried out in this paper.The results of molecular dynamics simulation and experiment show that: using molecular dynamics simulation as a means to simulate the oil contact angle on the solid wall,it is found that the wall thickness and the number of oil droplets have little influence on the oil drop contact angle at the nanometer scale,and the oil drop contact angle decreases linearly as the potential energy of the wall interaction increases.The flow characteristics of oil in the nano-channel experiment showed that the flow of single-phase oil in the nano-channel conforms to the linear characteristics described by the traditional hagen-poiseuille equation,but the volume flow rate of the experiment is smaller than the theoretical volume flow rate;Boundary layer of nonlinear reduce with the increase of pressure gradient,and finally tends to a constant value,when the shear rate to converge to zero,the experimental results consistent with theory,the boundary layer of equal to 1,the boundary layer of rapidly reduce with the increase of shear rate,the boundary layer of decreases slowly with the increase of shear rate,and tend to be the same;When the pressure gradient is the same,the drag coefficient ratio decreases with the increase of the diameter of nano-channel,and in the same nano-channel,the drag coefficient ratio decreases with the increase of pressure gradient and tends to a constant value.The flow of single-phase oil in the nano-channel has a pseudo-start-up pressure gradient,and the pseudo-start-up pressure gradient decreases as the nano-channel's diameter increases.The flow characteristics of unsteady and constant pressure water flooding oil in the nano-channel show that the volume flow of water flooding oil in the nano-channel decreases linearly as the displacement time increases,and the volume flow of single-phase oil and single-phase water under the same flow rate is always the same.In the process of water flooding in nano-channel,there is obvious fluctuation region time,and the fluctuation time length decreases with the increase of pipe diameter.The characteristics of water flooding in nanochannels are similar to those of columnar standard core water flooding below ultra-low permeability.It can be used as an auxiliary means for water flooding development and yield prediction in ultra-low permeability reservoirs,and provide reference for further in-depth research by scholars engaged in relevant research.