Micromixers play a crucial role in improving fluid mixing in microfluidic systems. Due to their
small dimensions, effective mixing is often not achieved in these devices. Therefore, enhancing
mixing efficiency in such systems has become one of the main challenges. In this study, the
impact of jet flow on mixing performance in a passive micromixer is investigated through
numerical simulations. The geometry of the micromixer consists of two coaxial pipes, with
fluids entering through the inner and outer pipes, and exiting through the space between the
two pipes. In the range of Reynolds numbers studied, three distinct jet flow patterns were
observed, which had a significant impact on the flow and mixing of the two fluids. As the
Reynolds number increases, the penetration depth of the fluid jet into the main flow increases,
and the jet deflection becomes more pronounced, leading to an improvement in the mixing
performance of the two fluids.