Effect of suction flow in water vortex unit on maximum suction force and flow field

Water vortex unit (WVU) is a non-contact negative pressure generation device that uses water as the working fluid. It operates by injecting fluid into a cylindrical chamber through a nozzle, generating negative pressure and suction force through rotational flow. However, high-velocity swirling flow is confined near the cylinder wall, resulting in a pressure distribution characterized by a steep drop near the periphery and a relatively flat profile in the central region. This phenomenon limits further enhancement of suction force. This study redesigned the hydraulic circuit, allowing water that would have leaked to circulate within the hydraulic system. This modification resulted in a WVU with a steeper F–Q curve. Nevertheless, due to a reduction in the maximum flow rate, the maximum suction force only increased by 12%. The paper further proposes a new WVU structure that introduces a suction chamber. By drawing water through tangential suction holes on the suction chamber, the maximum flow rate of the WVU is increased, leading to an additional 83% increase in the maximum suction force. Finally, the role of the critical structural parameter, the suction chamber diameter, was analyzed. The results indicate that both excessively small and large suction chamber diameters can have adverse effects on the WVU.