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以往对于壁面附近气泡动态特性的研究均是针对完整壁面进行的, 而对带破口壁面附近气泡运动特性的研究很少, 例如舰船结构在遭受药包爆炸冲击波作用后形成破口, 其仍可能会遭受随后生成气泡的二次打击, 破口的存在必定会影响爆炸生成气泡的动力学行为. 本文采用电火花气泡生成与观察实验装置, 对带有破口的壁面附近气泡脉动和射流特性进行研究.通过实验发现, 当气泡在破口同心位置生成时, 破口的存在会使气泡靠近破口一侧形成"腔吸现象", 并使气泡形成对射流. 在此基础上分析了破口大小和无量纲距离对破口附近气泡的影响规律, 最后讨论气泡在破口偏心位置生成时的运动特性, 结果发现破口附近气泡的二次打击威力随偏心距离的增加而增加, 文章旨在为不同边界附近气泡运动规律研究提供参考.
关键词:
气泡
实验
破口
射流 相似文献
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假设气泡周围流场为无黏、无旋、不可压缩的理想流体,建立气泡群相互作用的三维数值模型.将多极快速傅里叶变换方法(FFTM)与高阶边界元法(HOBEM)相结合求解气泡群的运动,在达到同样计算精度时显著加快了边界积分方程的求解速度,可以在合理的时间内模拟气泡群的动态物理特性.同时为维持气泡群模拟过程中的数值稳定性,引入了弹性网格技术(EMT),并用算例验证了数值模型及算法的有效性.基于建立的数值模型,研究了不同组合的气泡群之间的相互作用,模拟和解释了各类气泡运动的物理现象,讨论了影响气泡群膨胀、坍塌、迁移及射流
关键词:
气泡群
FFTM
射流
三维 相似文献
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在2 m×2 m×2 m的实验水箱中开展小当量PETN炸药水中爆炸气泡脉动实验时,利用弹性波从声阻抗高的物质传入声阻抗低的物质时的“减震缓冲”原理,采用在水箱壁贴低声阻抗材料的方法,有效降低了水箱壁反射冲击波对气泡脉动过程的影响,获得了清晰的气泡脉动过程图像、气泡水射流形成过程图像和气泡脉动压力曲线。将水箱实验结果与8 kg TNT当量爆炸水池实验结果对比,得到的最大相对误差仅为5.1%,验证了水箱实验方法的准确性,为炸药水中爆炸气泡脉动现象研究提供了一种简便有效的实验方法。 相似文献
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通过对竖直放置直接甲醇燃料电池水平流道内扩散层壁面上CO_2气泡的受力分析,建立描述气泡生长动力学方程,获得CO_2气泡生长速率和气泡脱离直径的计算方法。计算结果表明:CO_2气泡生长和脱离主要受浮力、曳力、剪切升力和表面张力的控制;气泡生长速率随电流密度和接触环直径的增大而增大;甲醇溶液流速增加,气泡脱离直径变小,且流速对气泡脱离直径的影响随接触环直径减小而变大;电池放电电流密度的变化对气泡脱离直径几乎没有影响;温度和甲醇浓度增加,均使气泡脱离直径略有减小;扩散层表面润湿性越好,气泡的脱离直径越小。 相似文献
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气泡在不同边界附近运动时,其运动特性与在自由场中相比会发生很大变化,特别是当气泡在近自由面附近运动时, 与自由面发生强烈的耦合作用而产生极其复杂的水面现象.为探究其规律,在前人研究的基础上, 采用电火花生成气泡,利用高速摄影系统对气泡与自由液面的相互作用进行了实验观察和研究. 通过对大量实验数据的分析和整理,总结了自由液面的存在对气泡最大半径、脉动周期、射流时间以及射流宽度的影响, 并初步拟合了放电电压与气泡最大半径的关系.对不同水冢现象的具体过程进行了分类和详细的描述, 得出了发生不同水冢现象的决定因素,同时统计得到相同初始条件下水柱最大高度随无量纲距离的变化规律, 为气泡与自由液面相互作用的研究提供了参考. 相似文献
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The time-averaged interaction force exerted by a sound field between a gas bubble and a solid spherical particle is examined. An approach is developed allowing the force to be calculated for small separations between the bubble and the particle. The results obtained are compared with the existing asymptotic equation derived for large separations. It is shown that when the bubble and the particle are closely spaced, both the magnitude and the sign of the force are different from those predicted by the asymptotic equation, resulting in new interesting effects. 相似文献
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The interaction between spherical cavitation bubble and flat wall is transformed into that between the real bubble and imaging bubble by the method of images. Firstly, we investigate the dynamics of real bubble and matched, inversed or mis-matched imaging bubble driven by a small amplitude ultrasound, revealing the characteristics of the interaction between cavitation bubble and rigid, soft and impedance walls. Then, we emphatically study the dynamics of real bubble and mis-matched imaging bubble driven by a finite amplitude ultrasound, and the interaction characteristics between cavitation bubble and real impedance wall are revealed. The results show that the cavitation bubble is always close to the rigid wall and far away from the soft wall; For the impedance wall, whether the cavitation bubble is far away or close depends on the specific wall parameters. Moreover, the direction and magnitude of bubble's translation velocity can be changed by adjusting the driving parameters. Understanding the interaction between cavitation bubble and impedance wall is of great significance for efficient application of ultrasonic cavitation. 相似文献
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Theoretical analysis of interaction between a particle and an oscillating bubble driven by ultrasound waves in liquid 下载免费PDF全文
A theoretical model is developed to describe the interaction of a particle and an oscillating bubble at arbitrary separation between them. The derivation of the model is based on the multipole expansion of the particle and bubble velocity potentials and the use of Lagrangian mechanics. The model consists of three coupled ordinary differential equations. One of them accounts for the pulsation of the bubble and the other two describe the translation of the bubble and particle in an infinite, incompressible liquid. The model here is accurate to order 1/d~(10), where d is the distance between the centers of the particle and bubble. The effects of the size and density of the particle are investigated, namely, the interaction between the particle and bubble changes from repulsion to attraction with the increment of the particle density, and the increment of the particle size makes the interaction between the particle and bubble stronger. It is demonstrated that the driving frequency and acoustic pressure amplitude can affect the interaction of the particle and bubble. It is shown that the correct modeling of the translational dynamics of the bubble and particle at small separation distances requires terms accurate up to the tenth order. 相似文献
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Based on the potential flow theory, the vortex ring is introduced to simulate the toroidal bubble, and the boundary element
method is applied to simulate the evolution of the bubble. Elastic-plasticity of structure being taken into account, the interaction
between the bubble and the elastic-plastic structure is computed by combining the boundary element method (BEM) and the finite
element method (FEM), and a corresponding 3D computing program is developed. This program is used to simulate the three-dimensional
bubble dynamics in free field, near wall and near the elastic-plastic structure, and the numerical results are compared with
the existing experimental results. The error is within 10%. The effects of different boundaries upon the bubble dynamics are
presented by studying the bubble dynamics near different boundaries.
Supported by the National Natural Science Foundation of China (Grant No. 50779007), the National Science Foundation for Young
Scientists of China (Grant No. 50809018), the Specialized Research Fund for the Doctoral Program of Higher Education of China
(Grant No. 20070217074), the Defense Advanced Research Program of Science and Technology of Ship Industry (Grant No. 07J1.1.6),
and Harbin Engineering University Foundation (Grant No. HEUFT07069) 相似文献
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示踪粒子在(高)超声速流场中的动力学响应是粒子成像测速等粒子示踪测量技术的关键问题之一.现有文献对粒子动力学响应的试验测量往往是通过单个斜激波响应的测量方法.然而,当示踪粒子用于测量高速飞行器发动机内部复杂的激波串流场时,粒子将经历由多道激波导致的速度、压力、黏性等剧烈变化.本文结合目前(高)超声速飞行器的研究热潮,重点关注示踪粒子在应用于发动机内部具有连续激波的复杂流场测量中存在的跟随性评估方面,开展了一系列的相关试验研究.包括测量超声速风洞的喷管出口速度分布以验证测试系统的性能,在马赫4.2和3.0流场中测量了粒子对二维10°和15°单斜劈绕流中的斜激波动力响应,并测量了模拟发动机内部连续梯度的双斜劈粒子斜激波动力响应.结合粒子动力学的理论模型,得到了各状态的粒子弛豫时间、弛豫距离、Stokes数.基于图像方法、统计学规律分析了激波非定常抖动对测量结果的影响,并对测量结果进行了修正.结果显示,相同斜劈角度下,马赫数越高,粒子的弛豫时间、弛豫距离就越大.但是在相同的来流马赫数下,斜劈角度越大,粒子的弛豫时间、弛豫距离反而减小.在强梯度之后由于流场的雷诺数和黏性系数变化剧烈,粒子的跟随性降低了大约5.7%,stokes数增加了约1%.虽然在本文条件下Stokes数仍满足超声速流场对粒子跟随性的要求,但粒子响应的降低无疑是值得关注的,尤其是当其被应用于具有更多连续梯度的复杂流场测量中. 相似文献
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A high-speed digital camera is used to record the saltation of three sand samples(diameter range:300–500,200–300 and100–125μm).This is followed by an overlapping particle tracking algorithm to reconstruct the saltating trajectory and the differential scheme to abstract the kinetic parameters of saltating grains.The velocity results confirm the propagating feature of saltation in maintaining near-face aeolian sand transport.Moreover,the acceleration of saltating sand grains was obtained directly from the reconstructed trajectory,and the results reveal that the climbing stage of the saltating trajectory represents an critical process of energy transfer while the sand grains travel through air. 相似文献
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建立了二维双组分两相流的大密度比格子玻尔兹曼方法 (lattice Boltzmann method, LBM)模型. 该模型基于改进的Shan-Chen伪势多相流LBM模型, 结合采用不同时间步长的方法, 实现密度比达800以上的气液两相流模拟. 为了对模型进行验证, 模拟了在不同气液相互作用系数和密度比条件下气泡内外压力差与其半径之间的关系, 其结果满足Laplace定律. 将所建立的大密度比LBM与介观尺度的元胞自动机(cellular automaton, CA)和有限差分法(FDM)相耦合, 用LBM模拟气液两相流, 用CA方法模拟固相生长, 用有限差分法模拟温度场, 采用LBM-CA-FDM耦合模型对定向凝固过程中凝固前沿的气泡与液-固界面之间的相互作用进行模拟研究. 结果表明, 绝热气泡的存在影响了温度场分布, 使得凝固前沿接近气泡时, 液-固界面凸起, 在不同的固相生长速度条件下, 出现凝固前沿淹没气泡或气泡脱离凝固前沿的不同情况, 模拟结果与实验结果符合良好.
关键词:
格子玻尔兹曼方法
元胞自动机
凝固
气泡 相似文献
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