## 1 Introduction
Cavitation in a vortex hydrodynamic cavitation generator can be generated without moving parts. Numerical simulations of the absolute pressure in a vortex cavitation generator were performed by [PERSON] et al. [13]. The mass concentration of hydroxyl radicals generated by the vortex cavitation generator was detected with the methylene blue method, revealing that the inducer can create a negative pressure zone with low pressure in local areas where significant cavitation effects can be observed. However, it is noted that this generator is only applicable on a laboratory scale and is not suitable for practical application. Composed of a stator and a rotor, the rotary hydrodynamic cavitation generator utilizes the centrifugal force and shear force from relative motion against the wall to induce cavitation. The rotor surface is designed with various types of grooves or protrusions to create localized high-speed flow regions. The advantages of the rotary hydrodynamic cavitation generator lie in its ability to induce cavitation continuously and efficiently, thereby enhancing cavitation efficiency and output, which contributes to its applicability for industrial production. Based on a high-precision compact difference scheme and the N-S equations, numerical models for the rotary hydrodynamic cavitation generator were established by [PERSON] et al. [14] and [PERSON] et al. [15] to investigate the effects of parameters such as angle, speed, and pressure on the cavitation performance. Experimental visualization and numerical simulations [16; 17] revealed that a tilt angle of 8\({}^{\circ}\) resulted in higher cavitation intensity, while higher rotational speeds led to more stable flow, higher number of vortices generated, and better cavitation effect. Designed by [PERSON] et al. [18; 19; 20], a toothed rotary hydrodynamic cavitation generator was simulated for its internal flow field using a hybrid multiphase flow model combined with the Zwart cavitation model. It was found that the cavitation rate of the square tooth was higher than that of the round tooth and the presence of the tooth side leveling angle improved the cavitation effect. It was discovered that the cavitation rate of the square tooth was higher than that of the round tooth, and the presence of tooth side angles enhanced the cavitation effects. However, the impact of structural parameters on cavitation performance has not been thoroughly studied. Based on these findings, a multiphase flow model for numerical simulations is established and the integrated experimental dye wastewater degradation tests are conducted in this paper to investigate the effects of structural parameters such as tooth row numbers, single tooth counts, generator outer diameter, and tooth face angle on cavitation performance. The research target is to optimize generator structure, which holds engineering significance for the application of rotary hydrodynamic cavitation generators in wastewater treatment. The main contributions of this paper can be summarized as follows: (1) A numerical model of the shear hydrodynamic cavitation generator is established, and the applicability of the mixed multiphase flow model and the Zwart model to the shear hydrodynamic cavitation generator is verified by comparing the numerical simulation with the experimental results. (2) The influence of different structural parameters on the cavitation performance is investigated by numerical simulation. (3) The cavitation mechanism for shear-induced cavitation bubble generation is obtained by analyzing the diagrams of pressure and velocity clouds. The paper is organized as follows: Section 2 establishes the structural model of the shear hydrodynamic cavitation generator, determines the methodology and boundary conditions of the numerical model, and verifies the accuracy of the numerical model experimentally.