共查询到19条相似文献,搜索用时 125 毫秒
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通过自行研制的光偏转测试系统对黏性液体中激光空泡脉动特性进行了实验,获得了激光等离子体空泡前两次脉动全过程,从而判定了空泡在脉动过程中对应的最大和最小泡半径;并将不同黏性系数下空泡脉动结果与基于空泡溃灭理论的计算结果进行了对比.结果表明:液体黏性对空泡生存周期、空泡半径,以及泡壁的运动速度等均有影响.受液体黏性影响,空泡膨胀或收缩过程明显变缓,其相应的生存周期也越长.这一研究结果不仅可促进空化研究的深入,也可为合理利用空化现象提供参考.
关键词:
激光泡
脉动特性
黏性
光纤传感器 相似文献
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基于空泡生长和溃灭理论分析不同环境压强对空泡膨胀的最大泡半径、收缩的最小泡半径、膨胀与收缩速度的影响.同时,利用高功率激光与液体物质相互作用产生空泡,采用高速照相机、高频测量水听器实验研究不同环境压强下液体中空泡运动规律,并将实验结果与计算结果进行对比.结果表明:环境压强对空泡脉动特性有较大影响.相同激光能量击穿液体介质时,随着外界环境压强的增加,空泡脉动周期呈现递减趋势;空泡第一次脉动的最大泡半径同脉动周期的变化趋势一致,且数值由快到慢递减;随着外界压强的增加,空泡溃灭的速度越快.随着压强的增大,空泡膨胀与收缩更为剧烈,持续时间更短. 相似文献
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分析了含气量对粘性液体中球形单空泡脉动特性的影响。研究结果表明:随着泡内初始含气量的增加,空泡达到最大泡半径的时间延长;空泡膨胀的最大泡半径、收缩的最小泡半径和脉动周期均随初始含气量的增加而增加;同时,空泡膨胀和溃灭时泡壁的运动速度均随空泡初始含气量的变化而变化。无论含气量如何,在空泡收缩到最小泡半径附近,泡壁运动速度(收缩或膨胀)要明显快于其在最大泡半径附近;此外,受液体粘性影响,空泡膨胀和收缩过程明显变缓。 相似文献
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Acoustic cavitation is a very important hydrodynamic phenomenon, and is often implicated in a myriad of industrial, medical, and daily living applications. In these applications, the effect mechanism of liquid surface tension on improving the efficiency of acoustic cavitation is a crucial concern for researchers. In this study, the effects of liquid surface tension on the dynamics of an ultrasonic driven bubble near a rigid wall, which could be the main mechanism of efficiency improvement in the applications of acoustic cavitation, were investigated at the microscale level. A synchronous high-speed microscopic imaging method was used to clearly record the temporary evolution of single acoustic cavitation bubble in the liquids with different surface tension. Meanwhile, the bubble dynamic characteristics, such as the position and time of bubble collapse, the size and stability of the bubbles, the speed of bubble boundaries and the micro-jets, were analyzed and compared. In the case of the single bubbles near a rigid wall, it was found that low surface tension reduces the stability of the bubbles in the liquid medium. Meanwhile, the bubbles collapse earlier and farther from the rigid wall in the liquids with lower surface tension. In addition, the surface tension has no significant influence on the speed of the first micro-jet, but it can substantially increase the speed of second and the third micro-jets after the first collapse of the bubble. These effects of liquid surface tension on the bubble dynamics can explain the mechanism of surfactants in numerous fields of acoustic cavitation for facilitating its optimization and application. 相似文献
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通过自行研制的光纤传感器对不同黏度液体中材料靶后的力学作用进行研究,获得了液体黏度变化对等离子体烧蚀力、射流冲击力及空泡生存周期的影响. 实验结果表明:液体黏度相同时,靶材所受冲击力幅值随作用激光能量的增加单调上升;液体黏度增加时,靶材所受的冲击力减小,靶材的空化空蚀程度亦减小;受液体黏度增大的影响,空泡膨胀或收缩过程减缓,相应的生存周期也增大. 此外,对空泡溃灭周期公式进行修正, 结果表明修正后的理论估算值与实验值的一致性较好. 相似文献
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The theory of local electrification of cavitation bubbles has been generalised. The major cases for a local electrification of bubbles in a cavitation field were considered; i.e., fragmentation and deformation of cavitation bubbles. The splitting of cavitation bubbles was considered taking into account surface tension, bubble perturbation, Stokes force and electrostatic forces between like charges on the wall of the collapsing neck of the fragment bubble. The problem of the uncompensated charge on the surface of the deformed cavitation bubble is solved. For this purpose radial deformations are considered in terms of the paraboloid of rotation and axial deformation approximated by one cavity hyperboloid of rotation. The maximum electric strength is accounted for. An explanation for some physical and physico-chemical effects in cavitation fields is proposed in terms of the electrical theory of the local electrification of cavitation bubbles. 相似文献
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In this work, a comparison between the temperatures/pressures within acoustic cavitation bubble in an imidazolium-based room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium bis(triflluoromethyl-sulfonyl)imide ([BMIM][NTf2]), and in water has been made for a wide range of cavitation parameters including frequency (140–1000 kHz), acoustic intensity (0.5–1 W cm−2), liquid temperature (20–50 °C) and external static pressure (0.7–1.5 atm). The used cavitation model takes into account the liquid compressibility as well as the surface tension and the viscosity of the medium. It was found that the bubble temperatures and pressures were always much higher in the ionic liquid compared to those predicted in water. The valuable effect of [BMIM][NTf2] on the bubble temperature was more pronounced at higher acoustic intensity and liquid temperature and lower frequency and external static pressure. However, confrontation between the predicted and the experimental estimated temperatures in ionic liquids showed an opposite trend as the temperatures measured in some pure ionic liquids are of the same order as those observed in water. The injection of liquid droplets into cavitation bubbles, the pyrolysis of ionic liquids at the bubble-solution interface as well as the lower number of collapsing bubbles in the ionic liquid may be the responsible for the lower measured bubble temperatures in ionic liquids, as compared with water. 相似文献
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Investigation of cavitation bubble collapse in hydrophobic concave using the pseudopotential multi-relaxation-time lattice Boltzmann method 下载免费PDF全文
《中国物理 B》2021,(4)
The interaction between cavitation bubble and solid surface is a fundamental topic which is deeply concerned for the utilization or avoidance of cavitation effect.The complexity of this topic is that the cavitation bubble collapse includes many extreme physical phenomena and variability of different solid surface properties.In the present work,the cavitation bubble collapse in hydrophobic concave is studied using the pseudopotential multi-relaxation-time lattice Boltzmann model(MRT-LB).The model is modified by involving the piecewise linear equation of state and improved forcing scheme.The fluid-solid interaction in the model is employed to adjust the wettability of solid surface.Moreover,the validity of the model is verified by comparison with experimental results and grid-independence verification.Finally,the cavitation bubble collapse in a hydrophobic concave is studied by investigating density field,pressure field,collapse time,and jet velocity.The superimposed effect of the surface hydrophobicity and concave geometry is analyzed and explained in the framework of the pseudopotential LBM.The study shows that the hydrophobic concave can enhance cavitation effect by decreasing cavitation threshold,accelerating collapse and increasing jet velocity. 相似文献
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Due to the tunability in mass transfer, solvation and solubility, gas-expanded liquids show advantages over traditional organic solvents in many characteristics. Ultrasonication is a commonly used method to promote heat and mass transfer. The introduction of ultrasonic technology into the gas-expanded liquid system can promote the polymerization of polymer monomers, enhance extraction efficiency, and control the growth size of nanocrystals, etc. Although acoustic cavitation has been extensively explored in aqueous solutions, there are still few studies on cavitation in organic liquids, especially in gas-expanded liquid systems. In this article, the development of cavitation bubble cloud structure in CO2-expanded N, N-dimethylformamide (DMF) was observed by a high-speed camera, and the cavitation intensity was recorded using a spherical hydrophone. It was found that the magnitude of the transient cavitation energy was not only related to input power, but also closely related to CO2 content. The combination of ultrasound (causing a rapid alternation of gas solubility) and gas-expanded liquid system (causing a decrease in viscosity and surface tension of liquids) is expected to provide a perfect platform for high-speed mass transfer. 相似文献
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Effect of surface tension on a liquid-jet produced by the collapse of a laser-induced bubble against a rigid boundary 总被引:1,自引:0,他引:1
The effect of surface tension on the behavior of a liquid-jet is investigated experimentally by means of a fiber-coupled optical beam deflection (OBD) technique. It is found that a target under water is impacted in turn by a laser-plasma ablation force and by a high-speed liquid-jet impulse induced by bubble collapse in the vicinity of a rigid boundary. The liquid-jet impact is found to be the main damage mechanism in cavitation erosion. Furthermore, the liquid-jet increases monotonously with surface tension, so cavitation erosion rises sharply with increasing surface tension. Surface tension also reduces bubble collapse duration. From the experimental results and the modified Rayleigh theory, the maximum bubble radius is obtained and it is found to reduce with increasing surface tension. 相似文献
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采用理论分析的方法考察了磁场中非理想流体中Rayleigh-Taylor(RT)不稳定性气泡的演化过程,在与磁场垂直的平面中,综合考虑流体黏性和表面张力的影响,推导了二维非理想磁流体RT不稳定性气泡运动的控制方程组,给出了不同情况下气泡速度的渐近解和数值解,分析了流体黏性、表面张力和磁场对气泡发展的影响,分析结果表明:流体黏性和表面张力能够降低气泡速度和振幅,即能够抑制RT不稳定性;而磁场对RT不稳定性的影响是由非线性部分引起的,并且磁场非线性部分的方向决定了磁场是促进还是抑制RT不稳定性的发展, 相似文献