共查询到15条相似文献,搜索用时 93 毫秒
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采用两套光偏转测试装置对不同表面张力液体中激光空泡脉动及溃灭特性进行了实验研究,获得了液体表面张力改变对固壁近旁空泡生长和溃灭过程的影响.结果表明,表面张力延缓了空泡的膨胀过程,加速了空泡的溃灭;表面张力对空泡溃灭的影响要强于对膨胀的影响;液体张力越大,空泡脉动周期越短,且空泡对应的最大泡半径越小而收缩所能达到的最小泡半径亦越小.此外,液体张力越大,射流所产生的瞬时冲击力越大,即表面张力加强了液体射流对固壁的空蚀作用.研究结果可为水下激光加工、激光医疗、空化空蚀相关流体力学的研究提供一定的理论和实验支持. 相似文献
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采用光偏转测试系统研究了不同温度纯净水中激光空泡脉动过程,通过实验获得了激光空泡在靶表面膨胀和收缩全过程,确定了空泡的最大、最小泡半径、脉动周期和泡壁运动速度。实验采用0℃到70℃的纯净水,测量了空泡的泡半径和脉动周期等特征参量变化情况。实验结果表明,液体温度是影响空泡脉动的一个非常重要的因素,随着液体温度的增加空泡的最大泡半径和溃灭周期均呈增加趋势。给出了相应的理论解释。 相似文献
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环境压强是影响空泡脉动的一个重要因素.为了研究环境压强对激光空泡声波特性的影响,采用理想液体中单空泡运动的理论模型,对不同环境压强下液体中空泡运动过程进行了数值模拟,并通过充气泵精确调节高压水箱内的气压,采用高速照相机、高频测量水听器,得到了在不同压强条件下,空泡脉动特性的序列图像和声谱图,根据实验数据研究了不同环境压强下液体中激光诱导产生的空泡脉动规律与声波特性.结果表明:环境压强的改变影响了空泡生存周期和脉动的剧烈程度,但对声波的强度和声谱分布没有影响.辐射的频率集中在0~50 kHz 范围内,所辐射的声波能量主要集中在0~20 kHz 频段范围,并在2 kHz 与8 kHz 有两个明显的频率峰值. 相似文献
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液体辅助红外激光消融硬生物组织的准确性和兼容性均优于机械工具,而在骨科手术中往往会遇到骨组织自然曲面位置的钻切需求。系统研究了波长约为2μm的中红外激光诱导空泡在自然骨曲面边界附近的演化行为规律,总结了不同无量纲距离(γ)空泡的非球形演变规律和空泡脉动周期的时间长度的变化趋势,并对空泡收缩过程进行了数值模拟分析。发现了空泡演化行为受骨曲面边界影响的机制,自然骨曲面边界的不对称性使空泡收缩时两侧泡壁处的压力梯度和移动速度不同,导致空泡在收缩时质心与两侧泡壁向自然骨曲面边界较高的一侧发生偏移,并引起空泡微射流向相同方向偏移。给出了用于补偿微射流作用点定位误差的光纤预置偏移量,得到了自然骨曲面附近0.2≤γ≤0.6的空泡产生的微射流速度。 相似文献
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不同黏性液体激光击穿声辐射特性研究 总被引:1,自引:0,他引:1
激光与液体介质相互作用时,在不同液体参数情况下,光击穿辐射声信号具有较大的差异性.为研究液体黏性、饱和蒸汽压等特性对激光击穿形成的空泡辐射声波的影响,推导了激光空泡壁的运动方程,构建了激光击穿声辐射测量系统,实验研究了不同液体参数对光击穿辐射声信号的影响.结论:液体饱和蒸汽压越高.激光空泡膨胀辐射的声波强度越低;液体黏性系数越大,将减缓空泡溃灭的速率,导致空泡牛存周期增长,并使空泡溃灭辐射的声波强度降低. 相似文献
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采用2套基于光偏转原理的光纤传感器(OBD),测量了激光空泡脉动全过程及空泡溃灭对靶材造成的破坏。通过实验获得了激光空泡在靶表面2次膨胀收缩的全过程,判定了空泡在2次脉动中对应的最大、最小泡半径和溃灭周期,并推算了空泡泡壁速度随时间的变化关系。实验发现,在脉冲激光作用下,水中靶材依次受到激光烧蚀压力和射流冲击力作用,且射流冲击力是造成靶材破坏的主要原因。 相似文献
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A modified Rayleigh-Plesset equation is derived to model the oscillation of a contrast agent microbubble attached to an elastic wall. The obtained equation shows that contact with the wall affects the bubble oscillation as if the bubble oscillated in a liquid with a changed (effective) density. Depending on the wall properties, the effective density can be either higher or lower than the real liquid density and hence the natural frequency of the attached bubble can be either lower or higher than the natural frequency of the same bubble in an unbounded liquid. Numerical simulations are made for a contrast bubble with shell properties similar to those used in the Marmottant shell model. The cases of a rigid wall and a plastic wall are compared. The properties of the plastic wall are set to correspond to walls of OptiCell chambers commonly used in experiments. It is shown that contact with the rigid wall decreases the natural frequency of the bubble as compared to its natural frequency in an unbounded liquid, whereas contact with the OptiCell wall increases the natural frequency of the bubble. Bubble resonance curves for three cases are compared: the bubble in an unbounded liquid; the bubble at a distance from an OptiCell wall; the bubble in contact with an OptiCell wall. Results obtained for a 2- μm -radius bubble insonified with a 10-cycle, 40 kPa, 2.1 MHz Gaussian pulse show that contact with the OptiCell wall leads to the following effects. The amplitude of the radial oscillation of the attached bubble is decreased by about 70% as compared to that of the same bubble in an unbounded liquid. The fundamental component in the spectrum of the scattered pressure of the attached bubble is decreased by 12 dB. A strong second harmonic appears in the spectrum of the scattered pressure of the attached bubble; its magnitude is about 11.5 dB higher than the level corresponding to the case of an unbounded liquid. 相似文献
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Bojie Xu Qianbin Wang Qing'an Meng Meijin He Cheng Guo Lei Jiang Huan Liu 《Advanced functional materials》2019,29(20)
Bubbles, a typical air‐in‐liquid system including both underwater and in‐air bubbles, are important phenomena involved in our daily life and engineering fields. So far, the fundamental and dynamics for in‐air bubbles largely remain unclear. Here, two typical in‐air wetting states of the bubble are revealed: the bubble‐phobic state in which a bubble with a perfect spherical shape stays on the liquid surface but without coalescence with the liquid; and the bubble‐philic state in which a bubble on the liquid substrate gives a quasi‐hemispherical shape. It is proposed that the bubble phobicity is a typical high‐energy state where the air cushion at the bubble/liquid interface plays a crucial role in preventing their coalescence by generating an energy barrier. By applying an external force to overcome the energy barrier, the bubble will distort and finally be stabilized in a bubble‐philic state. It is demonstrated that superhydrophilic substrates enable manipulating bubbles in air: a superhydrophilic surface with microscale hairy textures shows robust in‐air repellence to the bubbles, while a hemispherical bubble is capable of transport directionally in air on a superhydrophilic conical fiber. Here, the concept of superwetting into air‐in‐air system (liquid films) is promoted, which may open a new perspective in surface and interface chemistry. 相似文献
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在实际舰船尾流激光探测过程中,激光探测系统与目标气泡层之间会存在杂质(气泡群、悬浮粒子),导致气泡回波信号信噪比降低。为了提高实际舰船尾流探测的信噪比,采用蒙特卡洛方法,仿真模拟了不同气泡层特性遮挡的情况,通过改变遮挡气泡层的厚度、数密度来探究其对目标气泡回波特性的影响,仿真得到:当遮挡气泡层存在时,回波信号会明显降低,且降低趋势随着遮挡气泡层厚度和数密度的增加而更为剧烈。搭建了实验室条件下的模拟舰船尾流激光探测系统,对不同气泡层特性遮挡的情况进行了验证,得到了遮挡效应会随着气泡层的厚度、数密度增大而不断变强的变化规律。对测试数据进行归一化处理,实现了仿真与实验的相互验证,可为舰船尾流激光探测工程化提供支撑。 相似文献