Coupled Effects of Gap Width and Tube Length on Water Transport through Disjoint Carbon Nanotubes

Fracture-induced discontinuities are ubiquitous in realistic nanofluidic systems, yet their influence on molecular water transport remains not fully understood. Using molecular dynamics simulations, we investigate the coupled effects of gap width and tube length on water flow through disjoint single-walled carbon nanotubes. For a fixed nanogap, the water flux displays a distinct three-stage evolution with increasing tube length: an initial decline, a partial recovery, and a slow decay at large lengths. This nonmonotonic trend arises from the competing roles of confinement and hydrogen-bond connectivity across the fractured region. In short nanotubes, when the gap separation exceeds approximately twice the hydrogen-bond length (≈ 0.5 nm), the water bridge spanning the gap becomes unstable, leading to a pronounced flux drop in short tubes. Extending the tube length partially restores hydrogen-bond continuity, thereby enhancing bridge stability and sustaining steady transport. These findings demonstrate the interdependent influence of geometric parameters on nanoscale water mobility and reveal a microscopic mechanism linking structural discontinuity to interfacial hydrogen bonding, offering guidance for the rational design of fractured nanofluidic channels.