No abstract

In this study, a calculation model was proposed to predict the motion locus of particles moving to a wall in boundary layers. The velocity of soft abrasive flow and the incident angle of the particles were obtained based on the results calculated by the mixture model and realizable k–ε model. After the model formed, the distributions of the dynamic pressure and the volume fraction of abrasive particles were analyzed and compared to experimental results. After analysis, it was found that the amount of removed material is positively correlated with the incident velocity and the volume fraction of abrasive particles, as well as the dynamic pressure on the surface of the workpiece. In addition, the comparison shows that the numerical simulation method is feasible to predict the flow field and effect of soft abrasive flow. In addition, it was found that the simulation results are consistent with the flow field distribution and machining effect. Therefore, this model can be used in design of constrained modules.

Microjets caused by the cavitation effect in microchannels can affect the motion trajectory of solid particles in microchannels under ultrasonic conditions. The optimal parameters for an observation experiment were obtained through simulations, and an experiment was designed to verify these parameters. When the cavitation bubbles collapse in the near-wall area, the solid particles in the microchannel can be displaced along the expected motion trajectory. Using fluent software to simulate the bubble collapse process, it can be seen that, when an ultrasonic sound pressure acts on a bubble near the wall, the pressure causes the top of the bubble wall to sink inward and eventually penetrate the bottom of the bubble wall, forming a high-speed microjet. The maximum speed of the jet can reach nearly 28 m/s, and the liquid near the top of the bubble also moves at a high speed, driving the particles in the liquid towards the wall. A high-speed camera was used to observe the ultrasonic cavitation process of bubbles in the water to verify the simulation results. A comparison of particle motion with and without ultrasonic waves proved the feasibility of using the ultrasonic cavitation effect to guide small particles towards the wall. This method provides a novel experimental basis for changing the fluid layer state in the microchannel and improving precision machining.