Molecular Dynamics Study On Fluid Flow And Heat Transfer In Nanochannel With A Janus Interface

The molecular dynamics method is used to investigate fluid flow and heat transfer in nanochannels with the asymmetric situations of wettability.The effects of driving force,asymmetric wettability and surface nanostructure on fluid velocity slip and temperature jump were studied.The effect of asymmetric wettability on the fluid Energy Transfer Process are analyzed.The Results of this paper is as follows:In a confined space,the fluid density distribution near the wall will delaminate,which is closely related to wall wettability and nanostructures.And it is not centrosymmetric because of the asymmetric wall wettability.The fluid near the hydrophilic wall is relatively dense,its density distribution fluctuates more than the fluid density distribution near the hydrophobic wall.Nanostructures expand the area of influence of solids on the fluid and increase the area where fluid densities are stratified.The velocity of the fluid flow under an external force in a nanochannel in a bulk region is of a parabolic distribution.But the parabolic distribution is not centrosymmetric because of the centrosymmetric density profile.Viscous dissipation due to shear flow will increase the fluid temperature.So the wettability of the cold wall hardly affects the velocity of the fluid near the hot wall,and the slip velocity is almost constant.The locking boundary will take place at the fluid-solid interface near the hot wall.But the velocity of the fluid near the cold wall comes up with the increasing hydrophobicity of the cold wall,and the slip velocity increases.At this time,the fluid temperature near the cold wall gradually exceeds the fluid temperature near the hot wall.The inverted temperature profile of the fluid will appear.And the internal heat flow of the fluid will be reversed.The inverted temperature profile is more obvious with increasing the degree of asymmetric wettability.The driving force is the energy source for the fluid flow in the nanochannel,which will inevitably affect the flow and heat transfer law of the fluid in the nanochannel.As the driving force increases gradually,the fluid velocity in the channel rapidly increases along the direction of driving force.However,The fluid in the near wall area is affected differently by the driving force because of the asymmetric wall wettability.The locking boundary will take place at the fluid-solid interface near the hot wall.As the driving force increases,the absolute value of slip speed increases rapidly,but the slip length changes gently.The slip boundary will take place at the fluid-solid interface near the hot wall,The slip speed increases gradually with the increase of driving force,while the slip length of the interface decreases slightly.In the process of increasing driving force,the fluid temperature near the cold wall gradually exceeds the fluid temperature near the hot wall.The inverted temperature profile of the fluid will appear.And the internal heat flow of the fluid will be reversed.The inverted temperature profile is more obvious with the increase of driving force.Nanostructures can affect the flow of the fluid near the wall.So it can change the flow and heat transfer.Compared to the smooth surface,the presence of nanostructures in the wall significantly reduces the fluid flow velocity and the temperature.The inverted temperature profile of the fluid in smooth nanochannel will appear.As the height of the wall nanostructures increases,the velocity and temperature of the fluid near both sides wall decrease slightly.And the temperature of the fluid near the cold wall is gradually lower than the temperature of the fluid near the hot wall,and the inverted temperature profile in a bulk region will disappear.