The cavitation-bubble pump: a non-mechanical approach to fluid transport using asymmetric bubble collapse.

The asymmetric collapse of cavitation bubbles near a rigid boundary generates high-speed microjets, which, when confined by a perforated boundary, possess the potential to drive directional fluid transport. However, existing studies have long treated this pumping effect as a subordinate phenomenon within cavitation bubble dynamics, and no independent theoretical framework or performance evaluation system has been established for engineering applications. This paper formally defines the"Cavitation-Bubble Pump (CBP)"as an independent fluid transport technology. We systematically investigate the asymmetric collapse morphology, microjet characteristics, and near-orifice flow field of single bubbles under the constraints of orifice diameter Φ (2-19 mm) and dimensionless distance γ (0-2.0). The transient response of the liquid column and the buildup of macroscopic head under continuous bubble excitation are analyzed, and the evolution of steady-state headHs, time-averaged flow rateQt, and energy conversion efficiency with Φ and γ is quantitatively evaluated. The results show that orifice size is one of the main determinants of macroscopic pumping performance: the steady-state head decreases monotonically with increasing orifice diameter, whereas the flow rate first increases and then decreases, leading to an optimal operating condition and a critical dead-head state. The standoff distance also plays a key role, with the experimentally identified optimum agreeing well with the geometric tangency condition. Cross-scale analysis indicates that the microjet is the primary source of momentum injection, while shock waves provide an auxiliary contribution. Experiments using variable cross-section channels further reveal that the pumping head is determined by the orifice diameter at the injection boundary rather than by the tube diameter, enabling an impedance-matching design strategy that decouples the driving and transport sections. Based on time-averaged impulse balance and forced liquid-column oscillation dynamics, a theoretical model is developed to describe the H-Q characteristics and liquid-column motion. The results provide a theoretical foundation and design basis for the development of novel fluid transport devices.