Study of fluid flow behavior in smooth and rough nanochannels through oscillatory wall by molecular dynamics simulation

• A simulation for the behavior of Argon flow in oscillatory Couette flow of flat and rough nanochannels has been proposed.
• In this type of flow, the slip length depends on the wall velocity, and the frequency and period of the oscillations.
• Applying rectangular and triangular roughness to lower wall reduces the fluid slip.
• The current study is assumed to be more accurate and comprehensive in comparison with previous studies in oscillating Couette flows.

The method of molecular dynamics simulation is applied in order to study the behavior of liquid Argon flow within oscillatory Couette flows, in both smooth and rough nanochannels. To accomplish this study, the fluid velocity and the fluid slip in oscillatory Couette flows were used to assess the effects of: oscillatory velocity amplitude, speed frequency rate, channel height, wall density, and the amount of interaction between fluid and wall particles. Both smooth and rough walls were modelled in order to investigate the effect on the fluid patterns as well. Rectangular and triangular wall roughnesses in different dimensions were used to study this effect. The results indicate that an increase in the velocity amplitude increases the fluid slip, and decreases the fluid velocity fluctuations near the walls. Similar to the steady-state Couette flow, in oscillatory flow we observe a decrease in fluid slip by reducing the wall density. Moreover, by reducing the energy parameter between the fluid and wall, the fluid slip increases, and by reducing the length parameter the fluid slip decreases. Implementing the rectangular and triangular roughness to the bottom wall in the oscillatory flow results in a decrease in fluid slip, which is also similar to the usual non-oscillating flows.