池沸腾中气泡生长过程的格子Boltzmann方法模拟

Simulation of bubble growth process in pool boiling using lattice Boltzmann method

在通过引入精确差分方法的单组分多相格子Boltzmann模型的基础上耦合能量方程,并考虑流体与固壁间的相互作用力来调节气泡与固壁间的接触角,从而建立了一种新的描述气液相变的格子Boltzmann理论模型.为验证该模型的正确性,利用其对工质为水的相变过程进行了模拟,发现模拟结果与实验值符合良好;进而利用其验证Laplace定律,发现计算所得的水的表面张力与实验值甚为符合.为考察该模型处理复杂相变问题的能力,利用其对工质为水的池沸腾中的气泡生长过程进行模拟,发现气泡脱离直径与g-0.5成正比,脱离频率与g0.75成正比(g均为重力加速度),这与经验关系式及文献结果符合良好;此外,接触角的变化对气泡脱离直径影响不大,但气泡脱离频率与接触角成指数关系.

In this paper,a new single-component lattice Boltzmann model,which is based on exact difference method and extended with an energy transfer equation to model heat transfer,is proposed to describe liquid-vapor phase transition process.The wettability of the heated wall is modeled by an interaction force between solid wall and fluid.This new model is validated through the simulation of water phase transition process.It is found that the simulation results are in good agreement with the experimental data.The surface tension of water,which is obtained from simulation results at different temperatures,is closed to experimental data.These results are in agree ment with those obtained from Laplace law.In order to demonstrate the availability of this model for dealing with phase transition and two-phase problems,the bubble growth process on a heated surface is simulated in pool boiling.It is found that the bubble departure diameter is proportional to g-0.5 and the release frequency scales with g0.75,where g is the gravitational acceleration.These results are in good agreement with those obtained from the empirical relationship and reference results.Finally,simulation results show no relationship between the bubble departure diameter and the static contact angle,but the bubble release frequency increases exponentially with the latter.