| With the rapid progress of the global industrialization,water pollution is increasing highlighted.In the last decades,the research field of water purification and wastewater treatment has been vastly growing due to the stringent water quality control and regulations against hazardous pollutants.Hydrodynamic cavitation(HC)system has been applied successfully for the degradation of recalcitrant pollutants.Numerical and experimental investigations of hydrodynamic cavitation generated by orifice plate have been implemented in the present study,aiming at investigating the effect of hydrodynamic cavitaion on the degradation of pollutants and discussing the effects of different structural parameters on degradation process.The main research contents and conclusions are as follow:(1)A more applicable numerical calculation method of orifice plate has been established.The optimal number of grid is proposed using the grid independent identification.The boundary conditions have been input into simulation software in the form of function in order to be consistent with the boundary conditions in experiments,and the accuracy of the numerical method has been verified by comparing the numerical and experimental results.(2)An optimization method of structural parameters of the venturi tube in orifice plate with emphasis on surrogate-based model has been established.The optimization method is divided into the following steps: the establishment of the problem,design of test points,calculation of the true value,choice of the approximation method,error evaluation,global sensitivity assessment,optimization,experimental verification and selection of the optimal value,and all steps are given in detail.(3)The optimum solution set of orifice plate has been obtained using surrogate-based optimization method.Using the surrogate model optimization method for the two numerical optimization,and three representative optimum points have been selected from the optimal solution.The optimum point 1 represents the orifice plate with largest cavitation area and low flow rate,the optimum point 2 represents the orifice plate with large cavitation area and big flow rate,and the he optimum point 3 represents the orifice plate with small cavitation area and biggest flow rate.It is suggested that the area of cavitation zone and the flow rate in point 2 are both more than original orifice plate,the other two points respectively in the area of cavitation zone and the flow rate is more than the original orifice,and the optimal value can not be selected only using the numerical results,the experiment of degradation should be conducted to verify the numerical optimization results.(4)Combined with the experimental and numerical results,the orifice plate with the best water treatment effect is selected.Three representative points in numerical study and the original orifice plate are selected to investigate the methylene blue degradation experiment.It can be concluded that the effect of Methylene Blue degradation by using hydrodynamic cavitation method alone is not obvious in the present hydrodynamic cavitation system,and the amount of methylene blue degradation keep stable after 60 min.In terms of amount of degradation,the orifice plate of point 2 can achieve the maximum amount of methylene blue degradation,while the total amount of degradation in orifice plate of point 1 is less than the other two points since the degradation of a single work cycle is high but the flow rate is too small,the amount of degradation in orifice plate of point 3 is less than point 2 in a single work cycle.In terms of energy consumption,the point 1 can achieve the lowest energy consumption in the same condition,while the point 2 can achieve the second lowest energy consumption.In summary,the orifice plate of point 2 is the optimum value in the present study. |
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