Hydrodynamic simulation of air bubble implosion using a level set approach
Hydrodynamic simulation of air bubble implosion using a level set approach
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DOI：
10.1016/j.jcp.2005.10.020
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发表时间：
2006-06-10
影响因子：
4.1
通讯作者：
Akhatov, I
中科院分区：
文献类型：
--
作者：
Nagrath, S;Jansen, K;Akhatov, I
采用三维直接数值模拟（DNS）研究了水中小气泡（直径10 μ m）内爆和反弹的流体动力学。为了研究这个问题，我们开发了一种新的稳定化有限元方法（FEM）采用鬼流体和水平集方法相结合。该配方将空气和水都视为可压缩流体。使用这种方法，获得了内爆的瞬态三维（3-D）解（即，破裂）和气泡的反弹。这些模拟得到的结果是定性相似的观察/预测在以前的实验/数值研究。三维模拟表明，气泡内的条件几乎是均匀的，直到收敛的压力波足够强，以创建非常大的温度和压力附近的气泡的中心。这些动态发生在非常小的空间（0.1-0.7 μ m）和时间（ns）尺度。在初始阶段的内爆的空气/水界面的运动被认为是一致的，使用瑞利-Plesset模型的预测。然而，模拟结果表明，在高能内爆的最后阶段，气泡可以成为不对称的，这是相反的球对称性假设在许多以前的数值研究气泡动力学。直接数值模拟预测两种不同的不稳定性，即瑞利-泰勒型界面/表面和形状不稳定性。在剧烈坍缩阶段，气泡偏离球形对称，变形为椭球形气泡。基于球谐函数的线性稳定性分析也表明，可以预期椭圆形气泡形状。此外，界面不稳定性也出现在后期的内爆过程。区分这些现象的帮助下，数值模拟打开了新的机会，了解最近的实验声致发光和声融合的许多功能。(c)2005年爱思唯尔公司All rights reserved.
The hydrodynamics of the implosion and rebound of a small (10 mu m diameter) air bubble in water was studied using a three-dimensional direct numerical simulation (DNS). To study this problem, we developed a novel stabilized finite element method (FEM) employing a combination of ghost fluid and level set approaches. This formulation treats both the air and water as compressible fluids. Using this method, a transient three-dimensional (3-D) solution was obtained for the implosion (i.e., collapse) and rebound of an air bubble. These simulation results obtained were qualitatively similar to those observed/predicted in previous experimental/numerical studies. The 3-D simulations show that the conditions within the bubble are nearly uniform until the converging pressure wave is strong enough to create very large temperatures and pressures near the center of the bubble. These dynamics occur on very small spatial (0.1-0.7 mu m), and time (ns) scales. The motion of the air/water interface during the initial stages of the implosion was found to be consistent with predictions using a Rayleigh-Plesset model. However, the simulations showed that during the final stage of energetic implosions, the bubble can become asymmetric, which is contrary to the spherical symmetry assumed in many previous numerical studies of bubble dynamics. The direct numerical simulations predicted two different instabilities, namely Rayleigh-Taylor type interfacial/surface and shape instabilities. During the violent collapse stage, the bubble deviates from spherical symmetry and deforms into an ellipsoidal-shaped bubble. A linear stability analysis based on spherical harmonics also indicates that an ellipsoidal bubble shape could be expected. Moreover, interfacial instabilities also appear during the later stage of the implosion process. Distinguishing these phenomena with the help of numerical simulations opens new opportunities to understand many features of recent experiments on sonoluminescence and sonofusion. (c) 2005 Elsevier Inc. All rights reserved.