Abstract
This work presents guidelines for controlling and intensifying mixing in oscillatory opposed-jet mixers, focusing on Confined Impinging Jets (CIJs) as a model system where flow behavior is primarily governed by oscillatory parameters, decoupled from geometric complexity. Computational Fluid Dynamics (CFD) simulations were used to investigate the effects of oscillation amplitude and frequency on mixing. The results show that at high amplitudes, mixing is robust across a broad frequency range, as energy injection is sufficient to promote vortex formation and their propagation to the reactor's outlet. At low amplitudes, mixing is highly sensitive to the oscillation frequency and occurs only near the resonance frequency, the specific frequency at which the flow's response to the applied oscillation is maximized. At low amplitude, lower frequencies fail to inject sufficient energy, while higher frequencies promote flow segregation. Remarkably, effective vortex propagation and mixing were achieved even at very low net Reynolds numbers (Re_net=25), increasing the residence time from 0.042 s at Re_net=300 to 0.5 s at Re_net=25. Two quantitative mixing metrics corroborate the qualitative flow observations and were instrumental in defining practical guidelines for process intensification. These findings provide new insights into how oscillatory forcing can be tuned to control mixing scales, enabling efficient mixing under a wide range of operating conditions, including shear-sensitive processes. The study offers a foundation for the model-based design and optimization of intensified static mixers, linking oscillation parameters, Reynolds number, and residence time to application-specific mixing performance.