共查询到20条相似文献,搜索用时 0 毫秒
1.
High-power ultrasonic horns operating at low frequency are known to generate a cone-shaped cavitation bubble cloud beneath them. The exact physical processes resulting in the conical structure are still unclear mainly due to challenges associated with their visualization. Herein, we address the onset of the cavitation cloud by exploiting high-speed X-ray phase contrast imaging. It reveals that the cone formation is not immediate but results from a three-step phenomenology: (i) inception and oscillation of single bubbles, (ii) individual cloud formation under splitting or lens effects, and (iii) cloud merging leading to the formation of a bubble layer and, eventually, to the cone structure due to the radial pressure gradient on the horn tip. 相似文献
2.
Chemical activation of ultrasonic cavitation 总被引:2,自引:0,他引:2
Bogdan Niemczewski 《Ultrasonics sonochemistry》1999,6(4):1682
A method for intensifying ultrasonic cavitation in water and aqueous solutions has been proposed, which consists of a chemical fixation of dissolved oxygen. The influence of selected reducing agents on the intensity of cavitation in water and alkaline solutions has been investigated. 相似文献
3.
4.
P. Kruus 《Ultrasonics》1983,21(5):201-204
Polymerization due to ultrasonically induced cavitation is reported for a number of compounds: bromobenzene, styrene, isoprene, and methyl methacrylate. The molecular weight of the polymethylmethacrylate produced through ultrasound is considerably lower than that due to normal aging. The bromobenzene and styrene products are dark friable solids. The isoprene product has an ultra-violet absorption suggesting a conjugated system of about ten carbon-carbon bonds in length. 相似文献
5.
将由速度势叠加原理得到的双泡超声空化动力学微分方程归一化,通过matlab语言编程计算,分析了水中空化泡的线度、双泡间距、声压幅值、声波频率等因素对空化过程的影响. 在双泡超声空化动力学微分方程中引入双频超声,探讨了双泡双频超声问题. 研究表明泡的线度是决定空化特性的主要因素,声压幅值对空化特性的影响最大,其次是超声波的频率;双泡间的相互作用影响空化特性,这种影响随双泡间距的增大而减弱;双频超声对双泡空化特性的影响有限,这种影响在两超声分量的声压幅值相等时较强.
关键词:
超声空化
双泡
双频超声 相似文献
6.
J. Sponer 《Czechoslovak Journal of Physics》1990,40(10):1123-1132
A theoretical prediction of the dependence of the ultrasonic cavitation threshold for sonoluminescence on the acoustic frequency is presented. Data were obtained from the numerical solution of nonlinear oscillations of a single isolated gas-filled bubble in a viscous compressible liquid. Principal reasons for the increase of cavitation threshold with acoustic frequency and liquid viscosity are also briefly discussed.The author wishes to thank professor Ivo Hrazdira for permanent support of this work. All calculations were run on ICL 2950/10 computer of the Regional Computing Centre of the Czechoslovak Academy of Sciences, Brno. 相似文献
7.
Cone-like bubble formation in ultrasonic cavitation field 总被引:9,自引:0,他引:9
A new phenomenon in ultrasonic cavitation field is reported. Cavitation bubbles are observed to self-arrange in a cone-like macrostructure in the vicinity of transducer radiating surface. The cone-like macrostructure is stable while its branch-like pattern microstructure changes rapidly. The structure is constituted by moving bubbles which undergo attractive and repulsive Bjerknes forces caused by high acoustic pressure gradients and strongly nonlinear oscillations of cavitation bubbles. The cone-like bubble structure is a chemically active formation. Its remarkably high activity is confirmed by chemiluminescence experiments. 相似文献
8.
B Niemczewski 《Ultrasonics》1980,18(3):107-110
Cavitation intensity in 37 organic liquids is compared with cavitation intensity in water under the same conditions. Temperature ranges are established over which cavitation intensities in these liquids are at their highest. 相似文献
9.
The paper reports the enhanced effect of multi-frequency ultrasonic irradiation on cavitation yield. The cavitation yield is characterized by electrical conductivity determination, fluorescence intensity determination and iodine release method. Two-frequency (28 kHz/0.87 MHz) orthogonal continuous ultrasound, two-frequency (28 kHz/0.87 MHz) orthogonal pulse ultrasound and three-frequency (28 kHz/1.0 MHz/1.87 MHz) orthogonal continuous ultrasound have been used. It has been found that the combined irradiation of two or more frequencies of ultrasound can produce a significant increase in cavitation yield compared with single frequency irradiation. The possible mechanisms of the enhanced effect are briefly discussed. 相似文献
10.
当双泡中心间距足够小时,由于气泡间辐射压力波的存在,作用在气泡上的压力不等于外部驱动压力.通过考虑双泡之间的辐射压力波,利用改进的Keller-Miksis方程,分别计算了不同大小、不同间距、含不同惰性气体的双泡在声空化过程中半径的变化、次Bjerknes力的变化和双泡内温度的变化.计算结果表明,当双泡大小不同时,小气泡受到的抑制作用较强,温度变化也比较大.随着双泡间距离从100μm增大到1 cm时,气泡间的次Bjerknes力的数量级从10~(-4)N减小到10~(-8)N.含不同惰性气体的耦合双泡在回弹阶段表现出明显不同的振荡规律. 相似文献
11.
An alkali-catalyzed biodiesel production method with power ultrasonic (19.7 kHz) has been developed that allows a short reaction time and high yield because of emulsification and cavitation of the liquid-liquid immiscible system. Orthogonality experiments were employed to evaluate the effects of synthesis parameters. Furthermore, hydrodynamic cavitation was used for biodiesel production in comparison to ultrasonic method. Both methods were proved to be efficient, and time and energy saving for the preparation of biodiesel by transesterification of soybean oil. 相似文献
12.
13.
14.
Ultrasonic electroplating produces various effects, including refinement of the plating film structure, by generating localized agitation through cavitation bubbles. However, details of the agitation mechanism have not been clarified because ultrasonic cavitation is very small in scale and occurs rapidly, and its reproducibility is low. Therefore, using laser-induced cavitation, which can generate cavitation similar to ultrasonic waves with high reproducibility, the author attempted to elucidate the conditions and frequency of cavitation generation that affect the agitation phenomenon in ultrasonic electroplating. By controlling the laser irradiation position, three different cavitation conditions were established, and the microstructures of the plated films produced were compared. Microstructural refinement was the most advanced under the condition of microjet generation. The frequency of cavitation generation at any position in the ultrasonic electroplating was estimated to be < 1 Hz. 相似文献
15.
Birkin PR Offin DG Vian CJ Leighton TG Maksimov AO 《The Journal of the Acoustical Society of America》2011,130(5):3297-3308
This paper reports on noninertial cavitation that occurs beyond the zone close to the horn tip to which the inertial cavitation is confined. The noninertial cavitation is characterized by collating the data from a range of measurements of bubbles trapped on a solid surface in this noninertial zone. Specifically, the electrochemical measurement of mass transfer to an electrode is compared with high-speed video of the bubble oscillation. This gas bubble is shown to be a "noninertial" event by electrochemical surface erosion measurements and "ring-down" experiments showing the activity and motion of the bubble as the sound excitation was terminated. These measurements enable characterization of the complex environment produced below an operating ultrasonic horn outside of the region where inertial collapse can be detected. The extent to which solid boundaries in the liquid cause the frequencies and shapes of oscillatory modes on the bubble wall to differ from their free field values is discussed. 相似文献
16.
17.
随着制造业的不断发展,对产品的加工精度要求愈来愈高,然而微小毛刺的去除仍然是十分困难的。毛刺虽小但危害巨大。因此,有效去除毛刺已成为加工中不可或缺的工序。而超声波去毛刺法可以有效快速的去除复杂零件的微小毛刺,具有很高的实用价值。尽管超声波的相关理论日趋完善,但是超声去毛刺机理以及空化产生的高压对毛刺的影响缺乏一些理论参考。此文阐述了超声波去毛刺的基本原理,利用有限元软件ABAQUS对单个空化泡在毛刺上的溃灭过程进行数值仿真,证明了超声波去毛刺的可行性,通过实验验证,超声波能够有效的去除毛刺。其研究结果为进一步研究超声波去毛刺的理论提供了参考。 相似文献
18.
Thus far, studies conducted to assess the safety of diagnostic ultrasound have employed sinusoidal sound fields. To evaluate the influence of nonlinearly distorted acoustic fields, this article compares the responses of microbubbles of variable size, exposed to (1) a sinusoidal pulse and (2) a sawtooth pulse. The nonlinear oscillations of a spherical bubble in a viscous compressible liquid stimulated into motion by an ultrasonic pulse are predicted, using a theoretical model for bubble dynamics. The maximum gas pressures inside the bubble when it collapses under the influence of a sinusoid or a sawtooth are deduced. Experimental work on Drosophila larvae exposed to sinusoidal and to sawtooth fields is consistent with the theoretical analysis. 相似文献
19.
The electrochemical behaviors of passive film of stainless steel 0Cr13Ni5Mo under the condition of static state (quiescence) and ultrasonic cavitation in the HCl solution have been studied by means of polarization curve, electrochemical impedance spectroscopy (EIS) and capacitance potential measurement. The results indicate that the passive film shows a multi layer structure distribution, and presents a p-type semiconductor property under the condition of quiescence. The stability of passive film decreases, the semiconducting property changes to an n-type semiconductor in the presence of cavitation. The amount of transition electrons from valence band because of cavitation is related to the height of Fermi level of passive film semiconductor. 相似文献