ИССЛЕДОВАНИЕ ЗАВИСИМОСТИ АКТИВНОСТИ АКУСТИЧЕСКОЙ КАВИТАЦИИ ОТ ТЕМПЕРАТУРЫ жидкости

Cavitation activity in non-homogeneous ultrasonic field have been studied. It has been shown that the character of temperature dependencies of cavitation activity is different for different points of the field. For example, cavitation activity at the surface of the radiator and at the liquid - gas surface decreases with temperature. There are points in the volume of the liquid where temperature dependencies are curves with maximum, i.e. it grows with temperature, achieves maximal value and then decreases.Исследовалась активность кавитации в неоднородном ультразвуковом поле. Показано, что характер зависимости активности кавитации от температуры существенно зависит от того, в какой точке поля проводится измерение. В частности, вблизи поверхности излучателя и вблизи границы раздела жидкость-газ активность кавитации уменьшается с ростом температуры, а в объеме жидкости имеются точки, в которых зависимости активности кавитации от температуры имеют вид кривой с максимумом

Исследование связи эрозионной активности кавитации и интенсивности кавитационного шума

The study of the erosion activity of cavitation is of considerable interest for clarifying the mechanism of the effect of cavitation on biological tissues and cells. This paper proposes an improved technique for assessing the erosion activity of acoustic cavitation. The results of testing this technique in relation to the problem of studying the distribution of erosion activity in the cavitation region, generated by a radiator with a rod waveguide, are presented. The experiments were carried out using a submersible emitter with a resonant frequency of 32 kHz. It was found that erosion activity rapidly decreases with distance from the emitter and depends on the distance to the emitter L as 1/L3 when the diameter of the emitter is less than or of the order of the wavelength in the used liquid. It was shown that there is a correlation between the erosion activity of cavitation and the readings of the cavitometer with the output signal being the integral intensity of the highfrequency component of the cavitation noise in the frequency range up to 10 MHz. Piezoelectric sensors were used to register cavitation noise. In particular, in liquids characterized by a higher level of erosion activity, the output signal of the cavitometer is also higher. In this case, the readings of the cavitometer change depending on the distance to the radiator as 1/L. Based on the data obtained, a method is proposed for assessing the erosion activity of cavitation by the magnitude of the intensity of cavitation noise in a cube. It is shown that this parameter is linearly related to the results of measurements of the erosional activity of cavitation. The results obtained will be used in the development of a specialized cavitometer designed to assess the erosion activity of cavitation during in vitro studies of the effect of ultrasound on cells.Исследование эрозионной активности кавитации представляет значительный интерес для уточнения механизма воздействия кавитации на биологические ткани и клетки. В работе предложена усовершенствованная методика оценки эрозионной активности акустической кавитации. Приводятся результаты апробации данной методики применительно к задаче исследования распределения эрозионной активности в кавитационной области, генерируемой излучателем со стержневым волноводом. Эксперименты проводились с использованием погружного излучателя с резонансной частотой 32 кГц. Установлено, что при диаметре излучателя меньше или порядка длины волны в используемой жидкости эрозионная активность быстро уменьшается по мере удаления от излучателя и зависит от расстояния до излучателя L как 1/L3 . Показано, что имеет место корреляция эрозионной активности кавитации и показаний кавитометра, выходным сигналом которого является интегральная интенсивность высокочастотной составляющей кавитационного шума в диапазоне частот до 10 МГц. Для регистрации кавитационного шума использовались пьезоэлектрические датчики. В частности, в жидкостях, характеризующихся более высоким уровнем эрозионной активности, выходной сигнал кавитометра также выше. Показания кавитометра при этом изменяются в зависимости от расстояния до излучателя как 1/L. Исходя из полученных данных, предложен метод оценки эрозионной активности кавитации по величине интенсивности кавитационного шума в кубе. Показано, что этот параметр линейно связан с результатами измерений эрозионной активности кавитации. Полученные результаты будут использоваться при разработке специализированного кавитометра, предназначенного для оценки активности кавитации в ходе исследований воздействия ультразвука на клетки in vitro

STUDY INTO DEPENDENCE OF CAVITATION ACTIVITY ON LIQUID TEMPERATURE

Cavitation activity in non-homogeneous ultrasonic field have been studied. It has been shown that the character of temperature dependencies of cavitation activity is different for different points of the field. For example, cavitation activity at the surface of the radiator and at the liquid - gas surface decreases with temperature. There are points in the volume of the liquid where temperature dependencies are curves with maximum, i.e. it grows with temperature, achieves maximal value and then decreases

Study of the relationship of cavitation erosion activity and cavitation noise intensity

The study of the erosion activity of cavitation is of considerable interest for clarifying the mechanism of the effect of cavitation on biological tissues and cells. This paper proposes an improved technique for assessing the erosion activity of acoustic cavitation. The results of testing this technique in relation to the problem of studying the distribution of erosion activity in the cavitation region, generated by a radiator with a rod waveguide, are presented. The experiments were carried out using a submersible emitter with a resonant frequency of 32 kHz. It was found that erosion activity rapidly decreases with distance from the emitter and depends on the distance to the emitter L as 1/L3 when the diameter of the emitter is less than or of the order of the wavelength in the used liquid. It was shown that there is a correlation between the erosion activity of cavitation and the readings of the cavitometer with the output signal being the integral intensity of the highfrequency component of the cavitation noise in the frequency range up to 10 MHz. Piezoelectric sensors were used to register cavitation noise. In particular, in liquids characterized by a higher level of erosion activity, the output signal of the cavitometer is also higher. In this case, the readings of the cavitometer change depending on the distance to the radiator as 1/L. Based on the data obtained, a method is proposed for assessing the erosion activity of cavitation by the magnitude of the intensity of cavitation noise in a cube. It is shown that this parameter is linearly related to the results of measurements of the erosional activity of cavitation. The results obtained will be used in the development of a specialized cavitometer designed to assess the erosion activity of cavitation during in vitro studies of the effect of ultrasound on cells

Combined method for acoustic cavitation research

At present, the field of applications of powerful ultrasound is expanding intensively, and the improvement of equipment and technological processes continues. With that, the key factor in the effect of ultrasonic vibrations on processes in liquids and liquid-like media is cavitation, i.e. the phenomenon of formation, pulsation and collapse of gas microbubbles under the influence of variable pressure. The widespread introduction of promising ultrasound technologies is largely constrained by the fact that the patterns of cavitation generation are not well understood, and the data known in the literature are contradictory and are characterized by low reproducibility. This paper describes an innovative method for studying ultrasonic cavitation. In order to increase the reproducibility of the results and the reliability of the conclusions about the correlation of various cavitation effects, it is proposed to register simultaneously the parameters characterizing these effects. An installation designed to implement this method has been developed and tested. The installation provides the ability to register the full output signal of the hydrophone, the intensity of the glow generated in the cavitation region - sound luminescence, the cavitation noise spectrum and its individual components. Technical characteristics of the installation allow you to adjust the rate of development of the cavitation region by varying the duration and period of the ultrasound pulses. It is possible to conduct experiments both in low-frequency (LF) and high-frequency (HF) fields as well as in interacting HF and LF ultrasonic fields. During the testing of the installation, the results were obtained that are of considerable interest from the point of view of refining the ideas about the mechanism for generating cavitation effects. It was found that preliminary treatment of the liquid in an ultrasonic field with the aim of its degassing for 15–20 min provides a significant increase in the reproducibility of measurements, especially for liquids with a high gas content. Based on a comparison of the time dependences of the signals of the cavitation sensor and the photomultiplier output, the characteristic stages of the development of the cavitation region are distinguished, which differ in the dynamics of the development of the cavitation region and in the composition of the cavitation noise spectra recorded

Study into the Dynamics of the HIFU Cavitation Zone Development

It has been studied the dynamics of the cavitation zone development. Cavitation zone was generated by high intensity focused ultrasound (HIFU) in pulsed mode. Three stages of the process were identified. Sonoluminescence (SL) is absent at the first stage. The output signal of the hydrophone which is placed above the focal point of the transducer, is constant if the voltage applied to the transducer is constant. It is increased linearly if the ultrasound intensity is increased linearly. The sonoluminescence is appeared at the second stage. Its intensity is increased slowly at this stage. At the third stage a jump-like increase of SL is observed. The acoustic transparency of the cavitation zone is decreased simultaneously. Cavitation noise spectra are changed significantly with stages of that cavitation zone development. This is indicative that the different regimes of sonication could be identified by spectral analysis of cavitation noise

Enhancing the repropducibilty of cavitation conditions in vitro

Cavitation conditions reproducibility dependence on different paramenters have been studied experimentaly. en shown that the most strongly influencing factors are as following: uncontrolled deviation of the e frequency of the transducer (transducers) from the freq

Cavitation in pulsed and continuous ultrasound fields

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