Dynamics of liquid argon flow around carbon nanotube

Abstract

In this work non-equilibrium molecular dynamics (MD) simulations were performed to investigate the liquid argon flow passing a stationary carbon nanotube and to estimate kinetic energy of the flow and flow forces exerted on the nanotube. Effects of different factors were also investigated. CFD simulations of flow around a circular cylinder were also performed to compare the results with those of MD around the carbon nanotube. In molecular dynamics simulation, the fluid forces on the body are calculated directly from the summation of the molecular forces exerted on solid atoms by fluid atoms. In this work, this method is used to investigate the effects of different flow parameters such as flow velocity, flow temperature on the flow behavior over the carbon nanotube, atom positioning around the nanotube and forces exerted on it. The simulation is 3D, and the computational domain consists of a maximum of 33,700 liquid argon atoms as the fluid and 240 atoms of carbon which represent the solid nanotube. A single-walled carbon nanotube is simulated as a rigid body of fixed carbon atoms, and both argon-argon and argon-carbon interactions are modeled by the standard Lennard-Jonnes potential function. Flow is driven by rescaling fluid particles velocities at the inlet region with a length of 3% of the domain length in that direction every 50-time steps. Based on the information given, a parallel code was developed, and investigations have been conducted using this code. Results show that among all the parameters which were investigated in this paper, the flow velocity has the most significant effects on the exerted forces and kinetic energy on the carbon nanotube and the drag force is increased with an increment of the flow inlet velocity in all cases. Lift fluctuates around zero in all cases of the stationary carbon nanotube. Inlet flow velocities and temperatures have also changed atoms positioning in the vicinity of the nanotube and so atomic density in the nearby bins which is used to further clarify the difference in the drag force.