A new model for bubble cluster dynamics in a viscoelastic media.

Bubble cluster dynamics in viscoelastic media is instructive for ultrasound diagnosis and therapy. In this paper, we propose a statistical model for bubble cluster dynamics in viscoelastic media considering the radius distribution of bubble nuclei. By investigating and comparing the response for a bubble in three conditions: single bubble; multi-bubble with the same radius; multi-bubble with different radius, the following rules are found: The promotion or suppression of the bubble cluster on the bubble vibration is not monotonous with the increase of the number of bubbles. The promotion or suppression of the bubble cluster on the bubble vibration varies alternately with the frequency. The effect of bubble cluster on bubble vibration is mostly suppressed when the driving acoustic pressure amplitude pa is high (5000 kPa). Usually, the bubble cluster promotes the vibration of the large bubbles (R0 = 10 µm) more, or suppresses it less.

Study on the real-time variation laws and mechanism of oil sample viscosity during ultrasonic irradiation.

It is rather significant to reveal the real-time variation of oil sample viscosity during ultrasonic irradiation to research the mechanism of viscosity change. In this paper, we first simulate the acoustic field distribution law in the reaction chamber by using the finite element method and orthogonal experiment method, then measure the viscosity of the oil sample with temperature by vibration type viscometer and get the corresponding function equation by fitting. On this basis, we measure the viscosity of the oil sample with ultrasonic irradiation time and electric power change in real-time and in situ, and finally analyze the mechanism of oil sample viscosity variation by using a temperature recorder and cavitation noise method. The results show that the greatest influence on the acoustic pressure in the reaction chamber is the change of the transducer probe in the height Z direction, followed by the width X direction and the depth Y direction. The viscosity of the oil sample shows an exponential decay with the increase in temperature. With the increase of ultrasonic irradiation time and electric power, the viscosity of the oil sample is gradually reduced. By comparing the effect of heating and ultrasonic irradiation on viscosity, it is found that ultrasonic irradiation not only changes the viscosity through thermal effect but also the cavitation noise analysis and the phenomena observed in the experiment confirm that the cavitation effect and mechanical effect exist all the time.