Display omitted •Effects of CGU structure on ARHCR performance are studied by CFD.•ARHCRs with rotor–stator interactions are far superior to non-interaction ones.•Hemisphere-shaped CGUs show the best performance among other common structures.•Effects of diameter, distance, height, and inclination angle are revealed.•This work offers a viable way to design high-performance ARHCRs. The advanced rotational hydrodynamic cavitation reactors (ARHCRs) that appeared recently have shown obvious advantages compared with conventional devices in various process intensifications. In ARHCRs, the cavitation generation unit (CGU) located on the rotor and stator basically determines their performance. For the first time, the present study investigated the effect of the CGU structure on the performance of a representative ARHCR by utilizing computational fluid dynamics. The amount of generated cavitation and required torque of the axis for various shapes, diameters, interaction distances, heights, and inclination angles of the CGU were analyzed. The results indicate that the interaction-type ARHCR (cavitation is generated by stator-rotor interaction) was far superior to the non-interaction type one. In addition, the hemisphere-shaped CGU demonstrates the best performance compared with that with cone-cylinder, cone, and cylinder shapes. Moreover, by evaluating the effects of various geometrical factors, the hemisphere-shaped CGU with a diameter of 12 mm, an interaction distance of 1 mm, a height of 1 mm, and an inclination angle of 10° achieved the highest performance. The reasons leading to different performance were elaborated in accordance with the flow and pressure field distributions, as well as the generated cavitation patterns. The findings of this work can strongly support the fundamental understanding, design, and application of ARHCRs for process intensifications.