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中文核心期刊

近刚性壁面异相双气泡耦合及射流增强效应研究

STUDY ON THE INTERACTION AND JET ENHANCEMENT EFFECT OF TWO OUT-OF-PHASE BUBBLES NEAR A RIGID BOUNDARY

  • 摘要: 气泡广泛存在于自然界和工程应用中, 由于其往往不是孤立存在的, 在多气泡耦合作用下会出现更为复杂有趣的气泡动力学现象和射流行为. 近刚性边界水下脉动气泡在坍塌过程中会产生朝向结构的高速射流, 严重威胁结构的局部强度安全. 通过多气泡耦合作用能够调控气泡的坍塌模式、射流方向和砰击速度, 其中异相双气泡耦合作用下形成的射流增强效应有着广阔的应用前景. 本文联合气泡动力学理论和边界积分法, 建立了近刚性壁面异相双气泡非线性耦合数值模型, 能够准确模拟气泡的初生、膨胀、坍塌和射流等动力学行为, 并预报双气泡的耦合方式和坍塌模式, 数值计算结果很好地再现了实验中的气泡动力学行为, 验证了模型的有效性. 然后, 系统研究了较大参数空间内的双气泡耦合动力学行为, 着重分析了射流增强效应, 并借助压力场、速度场等信息揭示了其中的力学机理. 研究发现, 气泡延迟生成时间τ极大地影响了双气泡耦合射流增强程度, 近壁面气泡的射流砰击速度随τ的增大先增大再减小, 在τ = 2附近达到极大值, 并得到了有效的射流增强参数区间. 旨在为多发水下爆炸武器的攻击策略及其它多气泡相关领域提供理论支撑.

     

    Abstract: Bubbles widely exist in nature and engineering applications. Bubbles usually do not appear in isolation and therefore more complex and interesting bubble dynamics and jet behaviors occur under multi-bubble coupling. The collapse of underwater pulsating bubble near rigid boundary will produce high-speed jet towards the structure, which will seriously threaten the local strength safety of the structure. The interaction of multiple bubbles can regulate and control the bubble collapse mode, jet direction, jet impact velocity, etc. in which the jet enhancement effect of out-of-phase double bubbles has a broad application prospect. In this work, a numerical model of nonlinear coupling of two out-of-phase bubbles near rigid boundary is established by combining bubble dynamics theory and boundary integral method. It can accurately simulate the dynamic behavior of the nascent, expansion and collapse jet of the bubble, and predict the coupling mode and collapse mode of the two bubbles. By comparing the numerical results with the experimental results, the favorable agreement is achieved which validates this numerical model. Using the numerical model as is mentioned above, the dynamic behavior of two bubbles is studied systematically in a large parameter space, and the enhancement effect of the jet is analyzed emphatically. With the aid of the pressure and velocity information of flow field, the mechanical mechanism is revealed. It is found that the delay time of bubbles formation τ greatly affects the jet enhancement degree of double bubbles coupling. The jet impact velocity of the near-wall bubble increases first and then decreases with the increase of τ , and reaches the maximum value nearby τ = 2. The effective parameter range of jet enhancement is obtained, which aims to provide new ideas and theoretical support for the attack strategy of multiple underwater explosive weapons.

     

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