摘要:
使用格子Boltzmann方法对零质量射流激励下液体的相变演化过程进行了数值模拟和分析。首先,提出了此特定零质量射流进出口边界的处理格式。然后,结合Shan和Doolen提出的单组分多相模型,模拟了方腔内液体受到此零质量射流激励而诱发产生空化的过程,着重分析了三个重要射流参数ε/T , T和vout/vin对方腔内液体相变的影响。分析表明:演化过程中方腔内气相节点数量在初始阶段急剧增长,然后经振荡趋于一个稳定值。由于ε/T和vout/vin可以反映射流在出入方腔两个过程间相互转换时的急剧变化,所以能够影响方腔中的液体相变的演化;而改变参数T并不影响射流速度的变化程度,所以T对液体相变的影响较弱。对于本文给定的参数取值,ε/T较小时,方腔内液体相变生成的孤立气泡脱离壁面;较大的ε/T下产生附着于方腔壁面的气泡,并且能够加速液体的相变进程;vout/vin的增加使方腔内相应的孤立气泡所覆盖的范围略有减小。研究结果揭示了零质量射流激励诱发的液体相变过程,为进一步探索液体空化的控制途径奠定了基础。
Abstract:
The phase transition in liquid due to the excitation of zero-net-mass-flux jet is simulated using the lattice Boltzmann method. First, the scheme for inlet/outlet boundary of the specific zero-net-mass-flux jet is derived. Then, with the model proposed by Shan and Doolen for single component and multiphase flow, the process of a single bubble formation in a liquid-filled square cavity is simulated, with the excitation of zero-net-mass-flux jet taken into consideration. Further, the investigation of the effects of three significant parameters,ε/T , T and vout/vin, on phase transition in the square cavity is carried out. The results show that the number of vapor nodes increases rapidly in the early stage of phase transition, and then achieves a constant after a long term fluctuation. In some sense, the previously mentioned parameters except T reflect the rapid change of jet velocity when the stages of inflow and outflow are transformed into each other. Thus the evolution of phase transition in liquid can be affected by the parametersε/T and vout/vin mainly, but by parameter T negligibly. When ε/T is small, the single bubble resulting from phase transition is separated from the boundary. On the contrary, when ε/T is large, the corresponding single bubble attaches to the bottom boundary, and the process of phase transition is accelerated. Moreover, with vout/vin increases, the domain filled by vapor phase in the square cavity, decreases slightly. In summary, this study reveals the details of phase transition process in liquid subjected to the zero-net-mass-flux jet.