Effect of electric charging on the velocity of water flow in CNT.

The role of electrical charge in controlling the velocity of water molecules in a finite single-walled carbon nanotube (CNT) was studied in detail using molecular dynamics simulation. Different test cases were examined to determine the parameters affecting the control of water-flow velocity in CNT upon electrically charging the surface of a CNT. The results showed that charge magnitude and volume, as well as the charging scenario, are the parameters having greatest effect. The implementation of electric charge on the surface of a CNT was demonstrated to decrease the resistance of CNT to incoming water flow at the entrance, but to increase friction-type resistance to flow along the CNT. Therefore, through controlling the magnitude of electric charge, water flow through the CNT may be accelerated, or decelerated. The results show that the velocity of molecular flow in the CNT increases to a maximum value, and then decreases with electric charge regardless of its sign. In the case studied here, this maximum velocity occurs at electric charging of ±0.25e/atom. It was also shown that, to reach similar flow velocities in a CNT, it is not sufficient to merely implement equal volumes of electric charge, where the volume of electric charging is defined as charge magnitude × charging time. In fact , both magnitude of charging and volume of electric charging must be equal to each other. These findings, together with options to implement scenarios with alternative charging, provide the means to effectively adjust desired velocities in a CNT.