Abstract:

Based on the theory of pseudo-potential, an isothermal lattice-Boltzmann model for multiphase pulsatile flow in capillary tube was established. By selecting the appropriate dimensionless parameters, the simulation unit was loaded into an actual unit. Simulation results obtained by this model, such as surface tension of static drop, shape of rising bubble in large space and narrow space, were compared with theory and other scholars’ research results, and the reliability of this model was verified. Bubbly flow driven by the sinusoidal pressure wave in capillary tube was simulated. The relationship between pressure wave amplitude and periodic variation of liquid phase Re number and bubble displacement was investigated. Shape changes of vapor-liquid interface in the periodic pulsatile process was obtained. The oscillation of Re number near the boundary area was observed when the direction of liquid velocity on the boundary was changed.  The reason for this phenomenon was discussed in this paper. The effect of gravity on the pulsatile process was analyzed. Simulation results validated the empirical law that the flow pattern in the capillary tube was affected by gravity if Bond number (ratio of buoyancy force to surface tension force) Bo >2. The movement and interface form of a single liquid slug was alsoinvestigated by using numerical simulation. The research result agreed with experimental results from literatures. These simulation results provided the basis for the research of pulsatile heat pipe with capillary tube as its main component.

摘要：

基于伪势模型理论，建立毛细管内汽液两相工质脉动流动的等温格子-Boltzmann模型。将利用该模型取得的静态液滴形态以及表面张力、大空间和窄空间内气泡浮升运动时的形态模拟结果与文献的研究结果进行对比，验证了模型的可靠性。对毛细管内泡状流和柱塞流两种流型在边界正弦压力波作用下绝热脉动流动情况进行了数值模拟。通过模拟研究了毛细管内不同压力波振幅下液相Reynolds数和气泡位移幅度周期性变化规律；获得了汽液界面形态在脉动过程中的变化；观察到在边界液相速度方向发生改变时，边界附近区域的Reynolds数振荡现象；分析了重力对脉动运动过程的影响。模拟结果为分析以毛细管为主要构件的脉动热管内汽液两相工质的工作过程提供了一定依据。