Research On Surface Erosion Characteristics And Application Based On Ultrasonic Cavitation

Cavitation is observed widely in medium and high-speed fluid engineering,and it is also one of the research focuses of fluid mechanics.The collapse of cavitation bubbles erodes structural components in the fluid environment,thereby shortening the life of these components and causing accidents.It's necessary to conduct a study on its flow characteristics and erosion mechanism.In this paper,the ultrasonic cavitation caused by the ultrasonic emitter is used to accelerate the erosion process,shorten the experimental period,and combine the numerical simulation method to study the erosion characteristics of ultrasonic cavitation.At the same time,the cavitation erosion is applied to the fabrication of superhydrophobic surfaces,so that the damage becomes a beneficial effect.(1)The bubble dynamics and the mechanism of ultrasonic cavitation were studied,and a numerical model of ultrasonic cavitation was established.The effects of viscosity,turbulence and surface tension in the flow process were analyzed,and a two-phase flow model was established.The cavitation phase transition was defined by the transmission equation,the equation of state was corrected by temperature,and the speed of sound formula was added to abtain the ultrasonic cavitation model.(2)The accuracy of the model was verified by Fluent and the flow characteristics of ultrasonic cavitation were clarified.For the two cases of single bubble and ultrasonic bubble group,the numerical results were matched well with theoretical results and experimental results,confirming the accurate tracking ability of the new model.The ultrasonic cavitation dynamics reveal the relationship between erosion behavior and shock waves.A prediction model of erosion region based on bubble number density was proposed.(3)The erosion mechanism of ultrasonic cavitation was explored through experimental research.An ultrasonic cavitation test platform was designed and built.The cavitation erosion surface was characterized through surface morphology,surface roughness and volume loss.The cavitation damage process and mechanism were discussed.The high erosion rate in the edge region was found,which further confirmed the numerical results.A high synergistic effect of chemical corrosion and cavitation mechanical erosion was found in NaCl solution.It has been found that cavitation increased the hydrophobicity of the surface and promote heterogeneous nucleation.(4)The superhydrophobicity was achieved on copper alloy,stainless steel,copper foam and sponge through cavitation,and stability and repairability were tested.The effects of substance concentration,reaction time and cavitation erosion time on surface wettability were discussed.The stability of the samples was tested in ultraviolet,outdoor,water and corrosive liquids.The attached SiO2 particles gave the surface durability and repairability.The new process was applied to copper foamed and sponge to achieve 3D superhydrophobicity and oil-water separation.