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Experimental and Numerical Investigations of Cavitation Control Using Cavitating-bubble Generators
Cavitation is a physical phenomenon which consists of evaporation, bubble formation and collapse and plays an important role in many technical fields. Cavitation appears in ship technology due to its erosive effect on the ship’s rudder and propeller as a result of the collapse of cavitation bubbles near the wall surface. Cavitation can cause structural vibrations, noise emissions, and hydrodynamic efficiency reduction in the maritime sector and in hydraulic machinery systems. Measures to reduce or avoid undesirable cavitation-related consequences may importantly contribute to a better economic operation of ships and hydraulic machinery. This thesis deals with developing efficient passive flow control methods to control and suppress the deleterious effects of cavitation in different regimes. For this aim, a wedge-type miniature vortex generator so-called Cavitating-bubble Generator (CG) was developed and cylindrical-type miniature vortex generators so-called Cylindrical Cavitating-bubble Generators (CCGs) was proposed to control the cavitation and to stabilize the cavitation-induced instabilities. In this work, experimental investigations of these two cavitation passive control measures under different cavitation conditions such as cavitation inception, quasi-steady partial cavitation, unsteady cloud cavitation and cavitation surge regimes were performed. First, a high-speed visualization of cavitation around two test cases without cavitation control was performed to analyze the cavitation dynamics. Second, a particle image velocity technique was applied to measure the mean flow velocity profiles around the surface and in the wake region. Third, a hydroacoustic measurement was carried out to record local pressure pulsations in the wake region of the test cases. Then, the effects of the passive flow control methods on the qualitative parameters such as cavity structures in different cavitating regimes were studied by means of high-speed imaging. Finally, the effects of the cavitation control on the quantitative ...
Experimental and Numerical Investigations of Cavitation Control Using Cavitating-bubble Generators
Cavitation is a physical phenomenon which consists of evaporation, bubble formation and collapse and plays an important role in many technical fields. Cavitation appears in ship technology due to its erosive effect on the ship’s rudder and propeller as a result of the collapse of cavitation bubbles near the wall surface. Cavitation can cause structural vibrations, noise emissions, and hydrodynamic efficiency reduction in the maritime sector and in hydraulic machinery systems. Measures to reduce or avoid undesirable cavitation-related consequences may importantly contribute to a better economic operation of ships and hydraulic machinery. This thesis deals with developing efficient passive flow control methods to control and suppress the deleterious effects of cavitation in different regimes. For this aim, a wedge-type miniature vortex generator so-called Cavitating-bubble Generator (CG) was developed and cylindrical-type miniature vortex generators so-called Cylindrical Cavitating-bubble Generators (CCGs) was proposed to control the cavitation and to stabilize the cavitation-induced instabilities. In this work, experimental investigations of these two cavitation passive control measures under different cavitation conditions such as cavitation inception, quasi-steady partial cavitation, unsteady cloud cavitation and cavitation surge regimes were performed. First, a high-speed visualization of cavitation around two test cases without cavitation control was performed to analyze the cavitation dynamics. Second, a particle image velocity technique was applied to measure the mean flow velocity profiles around the surface and in the wake region. Third, a hydroacoustic measurement was carried out to record local pressure pulsations in the wake region of the test cases. Then, the effects of the passive flow control methods on the qualitative parameters such as cavity structures in different cavitating regimes were studied by means of high-speed imaging. Finally, the effects of the cavitation control on the quantitative ...
Experimental and Numerical Investigations of Cavitation Control Using Cavitating-bubble Generators
Kadivar, Ebrahim (author) / el Moctar, Bettar Ould
2020-11-03
Theses
Electronic Resource
English
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