Transition of cavitating flow to supercavitation

Bakalárska práca sa skladá z dvoch častí. Prvá časť sa venuje rešerši. Zaoberá sa objasnením základných pojmov kavitácie a súčasnému poznaniu v oblasti super- kavitácie. V druhej experimentálnej časti sa venuje procesom prúdenia Venturiho dýzou pri prechode z vyvinutej kavitácie do superkavitácie. Cieľom bolo preskúmať hysteréziu, ktorá nastáva zmenou smeru prechodu. Na objasnenie javu sa porovnali statické a dynamické charakteristiky získané z merania a vizualizácie na hydraulickom okruhu s kavitačnou tryskou.Bachelor thesis consists of two parts. The first part is dedicated to research. It deals with clarifying the basic concepts of cavitation and current knowledge in the field of supercavitation. The second, experimental part is devoted to flow in Venturi nozzle in the transition from developed cavitation to supercavitation. The aim was to examine the hysteresis that occurs with a change of transition direction. To clarify the phenomenon were compared static and dynamic characteristics acquired from the measurement and visualization on the hydraulic circuit with cavitation jet.

Transition of cavitating flow to supercavitation within Venturi nozzle – hysteresis investigation

Cavitation is usually considered as undesirable phenomena. On the other hand, it can be utilized in many applications. One of the technical applications is using cavitation in water treatment, where hydrodynamic cavitation seems to be effective way how to reduce cyanobacteria within large bulks of water. The main scope of this paper is investigation of the cavitation within Venturi nozzle during the transition from fully developed cavitation to supercavitation regime and vice versa. Dynamics of cavitation was investigated using experimental data of pressure pulsations and analysis of high speed videos, where FFT of the pixel intensity and Proper Orthogonal Decomposition (POD) of the records were done to identify dominant frequencies connected with the presence of cavitation. The methodology of the high speed (HS) records semiautomated analysis using the FFT was described. Obtained results were correlated and above that the possible presence of hysteresis was discussed