Multi-objective optimization study on the structure of self-excited oscillating pulse cavitation jet nozzles in submerged environments

Mud circulation tanks efficiently remove accumulated mud cake and impurities from the tank, stabilizing drilling fluid performance and directly ensuring drilling safety and efficiency. Automatic cleaning of these tanks is critical for modern drilling operations. This paper designs an integrated optimization system applied to self-excited cavitation jet nozzles to enhance their comprehensive cleaning performance on mud tanks in submerged environments. Using inlet radius, cavity diameter, cavity length, and lower-nozzle diameter as design variables and pressure peak, amplitude, and frequency as objective variables, orthogonal experiments and range analysis were conducted to obtain optimized structural parameters under orthogonal analysis and identify key structural variables. Subsequently, the discrete optimization space, constructed from key structural parameters, was mapped to the continuous optimization space of the machine learning model. A multi-objective particle swarm optimization algorithm was employed to obtain the Pareto front. Finally, the optimal structures were ranked using the technique for order preference by similarity to an ideal solution method. Compared to the orthogonal analysis results, the optimized structure achieved improvements of 69.79 %, 78.60 %, and 11.77 % in pressure peak, amplitude, and frequency, respectively. Overall cleaning capacity increased by 77.39 %. Simulations of the optimal structure obtained through the integrated optimization system revealed that the nozzle's optimal configuration generates a distinct pulsed cavitation jet. The cavitation zone within the nozzle cavity undergoes periodic contraction and expansion over time, validating the optimization results. The self-excited cavitation jet nozzle structure designed via the integrated optimization system significantly enhances its overall cleaning performance, providing an effective solution for the automatic cleaning of mud circulation tanks.