The paper presents the results of the study of flow in hydrodynamic cavitators. There was designed and manufactured models of hydrodynamic cavitation with various configuration for studying legitimacy appearance of cavitation. For their research, a stand was developed and created, which allows to obtain the flow characteristics of elements that are being tested and to visualize the flow in the throttling elements of the cavitators. The dependence of the discharge coefficient for the throttling element of the cavitator model on the Reynolds number is determined. The models of cavitators of various configurations are studied and pictures of the emerging cavitation are obtained by the method of visualization and the appearance of the luminescence phenomenon in a cavitating fluid flow is noted. On the basis of the obtained dependence for the coefficient of flow, a scheme with a mechatronic structure is proposed which provides a cavitation mode in the device when the working conditions change. The results of studies are analyzed and hypotheses of the appearance of luminescence based on similar physical phenomena and effects, which have a similar in nature and nature of radiation and spectrum according to the Planck diagram, are considered. Mathematical dependences of the flow coefficient on the Reynolds number and fluid flow on temperature and time are obtained.