Abrasive-assisted bidirectional volume alternating cavitation: Flow characteristics and wall-loading mechanisms in microchannels

The polishing quality of cavitation–abrasive synergistic processes critically depend on the flow characteristics and its wall-loading mechanisms. In this study, a bidirectional volume alternating cavitation (BVAC) method for generating global cavitation in microchannels was proposed. By introducing low-concentration abrasives without altering the overall hydrodynamic performance, a novel abrasive-assisted bidirectional volume alternating cavitation (A-BVAC) method was established. Numerical simulations and visualization experiments were carried out to comparatively investigate the multiphase flow characteristics and wall-loading mechanisms in microchannels of L/D = 20 and D = Ø1 mm, with and without abrasives. The results show that the presence of abrasives significantly enhances cavitation intensity and greatly increases wall-loading strength. Moreover, it promotes flow unsteadiness while improving the spatial uniformity of cavitation and induces multi-scale vortex structures. Compared with the BVAC, the maximum vapor volume fraction, flow velocity, and wall shear stress in the A-BVAC flow field increased to 0.55, 13.04 m/s, and 1739.47 Pa, respectively. The good agreement between simulations and visualization experiments confirms the accuracy of the model and provides theoretical guidance for elucidating the polishing mechanism of A-BVAC in complex microchannels with large length-to-diameter ratios (L/D ≥ 20).