There have been tried many types of liquids with different ranges of viscosity values that have been tested to form a single cavitation bubble. The purpose of these experiments was to observe the behaviour of cavitation bubbles in media with different ranges of absorbance. The most of the method was based on spark to induced superheat limit of liquid. Here we used arrangement of the laser-induced breakdown (LIB) method. There were described the set cavitation setting that affects the size bubble in media with different absorbance. We visualized the cavitation bubble with a 60 kHz high speed camera. We used here shadowgraphy setup for the bubble visualization. There were observed time development and bubble extinction in various media, where the size of the bubble in the silicone oil was extremely small, due to the absorbance size of silicon oil.
Abstract. There has been tried many methods how to generate single cavitation bubble. The purpose of these experiments is to observe the surface impact of collapsing cavitating bubbles. The most of method are based on spark to induced superheat limit of liquid. Here we compare the one of these methods -laser induced breakdown (LIB) with more correct mechanical way using ultrasound as generator. There is described the setup for ultrasound cavitation effecting the sessile bubble as well as random generated and moving bubble. We visualize the cavitation bubble using high speed camera of speed 180 kHz. There are observed interface instabilities as the ultrasound response.
The velocity field around the standard Rushton turbine was investigated by the Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV) measurements. The mean ensembleaveraged velocity profiles and root mean square values of fluctuations were evaluated at two different regions. The first one was in the discharge stream in the radial direction from the impeller where the radial flow is dominant and it is commonly modelled as a swirling turbulent jet. The validity range of the turbulent jet model was studied. The second evaluated region is under the impeller where flow seems to be at first sight rather rigorous but obtained results show nonnegligible values of fluctuation velocity.
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