## 7 Conclusions
As the final goal of the flow-induced noise study of centrifugal pumps, the noise optimization design is mainly realized by changing the pump structures to reduce the rotor-stator interaction intensity. However, different structures have different effects on the flow-induced noise. Therefore, it is required to consider the impacts of various structure variables and to combine the evaluationcriteria of noise with that of hydraulic performance, then carry out multi-objective comprehensive optimization design. * Based on the current study status, the in-depth study of the generation mechanism of flow-induced noise, the improvement of the fluid-vibration-acoustic-coupling method, the analysis model establishment of the generation, distribution and propagation mechanism for flow-induced noise and the development of high precision and fast numerical simulation method, as well as the development of noise visualization experiment need to be focused in future. [PERSON] proposed the idea for the article; [PERSON] performed the literature research and data analysis; [PERSON] wrote the manuscript; [PERSON] and [PERSON] revised the manuscript. All authors have read and agreed to the published version of the manuscript. This research was funded by Key Research and Development Project of Shandong Province, grant number 2019 GSF109084. And the APC was funded by Key Research and Development Project of Shandong Province. The authors* _[PERSON] et al. (2001)_ [PERSON]; [PERSON]; [PERSON] _Occupational Exposure to Noise Evaluation, Prevention and Control_; World Health Organization: Geneva, Switzerland, 2001; pp. 80-81. * _[PERSON] et al. (2011)_ [PERSON]; [PERSON]; [PERSON]; [PERSON] Review and outlook of studying on noise of centrifugal pumps. _[PERSON]. Vib. Shock_**2011**, _30_, 77-84. (In Chinese)
* _[PERSON] et al. (1995)_ [PERSON]; [PERSON]; [PERSON] [PERSON] Relationship between unsteady flow, pressure fluctuation, and noise in a centrifugal pump--Part A: Use of PDV data to compute the pressure field. _J. Fluid Eng._**1995**, _117_, 24-29. [CrossRef]
* _[PERSON] et al. (1995)_ [PERSON]; [PERSON]; [PERSON] [PERSON] Relationship between unsteady flow, pressure fluctuation, and noise in a centrifugal pump--Part B: Effects of blade-tongue interactions. _J. Fluid Eng._**1995**, _117_, 30-35. [CrossRef]
* _[PERSON] et al. (2002)_ [PERSON]; [PERSON]; [PERSON]; [PERSON] Numerical simulation of the dynamic effects due to impeller-volute interaction in a centrifugal pump. _J. Fluid. Eng._**2002**, _124_, 348-355. * _[PERSON] (2014)_ [PERSON] _Cavitation and Bubble Dynamics_; Cambridge University Press: New York, NY, USA, 2014; pp. 59-83. * _[PERSON] et al. (2018)_ [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] An experimental study on the cavitation vibration characteristics of a centrifugal pump at normal flow rate. _J. Mech. Sci. Technol._**2018**, _32_, 4711-4720. [CrossRef]
* _[PERSON] et al. (2019)_ [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Experimental analysis of cavitation in a centrifugal pump using acoustic emission, vibration measurements and flow visualization. _Eup. J. Mech. B-Fluid._**2019**, _75_, 300-311. * _[PERSON] et al. (2003)_ [PERSON]; [PERSON]; [PERSON] Experiments on the unsteady flow field and noise generation in a centrifugal pump impeller. _J. Sound Vib._**2003**, _263_, 493-514. [CrossRef]
* _[PERSON] (2014)_ [PERSON] Numerical and Experimental Study on Flow-Induced Noise in Centrifugal Pumps. Master's Thesis, Jiangsu University, Zhenjiang, China, June 2014. (In Chinese)
* _[PERSON] et al. (2013)_ [PERSON]; [PERSON]; [PERSON]; [PERSON] Investigation on flow-induced noise impacted by backflow in low specific speed centrifugal pumps. _Adv. Mech. Eng._**2013**. [CrossRef]
* _[PERSON] et al. (2015)_ [PERSON]; [PERSON]; [PERSON]; [PERSON] Overview of rotating stall in centrifugal pumps with vaned diffuser. _J. Drain. Irig. Mach. Eng._**2015**, _33_, 369-373. (In Chinese)
* _[PERSON] (2015)_ [PERSON] Research on Rotating Stall Characteristics in Centrifugal Pumps.