Utilizing particle image velocimetry, the flow field inside an impinging flow reactor was measured, and the fluid dynamic characteristics including flow patterns, flow velocity, turbulence kinetic energy, turbulent eddy scale, and turbulent vortex structures under different turbulent conditions and impingement distances were analyzed. The results demonstrate that the fundamental flow pattern in the impinging flow reactor involves two fluid jets impinging and then diffusing to the sides of the chamber, generating internal circulation. The velocity is lowest at the impingement center and gradually increases after diffusion. Increasing flow rates (Q) and reducing impingement distances (L) result in stronger radial motion of the fluid after impingement. Within the studied range (Q: 0.42 m³/h to 0.82 m³/h, L: 30mm to 70mm), micron-scale vortices can be generated inside the impinging flow reactor at any impingement distance and flow rate. Increasing flow rates and decreasing impingement distances lead to a reduction in the global turbulent eddy scale, which becomes more pronounced along the centerline of the jet. The turbulent eddy scale exhibits its smallest value at the impingement center and along the jet periphery, attributed to increased turbulence due to the velocity difference between the jet region and its surroundings. A symmetric set of vortices around the impingement center exists near the nozzle outlet. An upward shift in the vortex structure is observed as the impingement distance increases. This phenomenon may be attributed to the increased impingement distance, which results in insufficient radial energy for flowback over longer distances. Analyzing the characteristics of flow field in the impinging flow reactor will contribute valuable insights for the application of impinging flow technology in fine particle recovery flotation devices.
 

impinging flow,turbulent eddy scale,vortex structure,process enhancement