气泡生长及脱离过程的格子玻尔兹曼模拟

Lattice Boltzmann Simulation of Bubble Growth and Detachment

为了研究气液相变过程中重力加速度、壁面温度以及成核点间距离对气泡生长及脱离的影响,课题组在Shan-Chen伪势格子Boltzmann模型的基础上,通过将密度分布函数与温度分布函数进行耦合求解的方式建立了气液相变模型。同时采用此模型计算得到了液滴内外压差与液滴半径倒数之间的关系,发现其符合Young-Laplace定律,从而验证了模型的正确性。进而利用此模型对气液相变现象中的气泡生长及脱离过程进行了二维数值模拟。结果表明:气泡脱离直径会随着重力加速度的增大而呈现出逐渐减小的规律,而且气泡生长及脱离的过程与文献结果甚为相符,此外将模拟得到的气泡脱离直径进行了非线性拟合,发现其结果与新的经验关系式吻合良好;同时较高的壁面温度会增大气泡断裂颈部与壁面之间的距离,而且壁面温度的升高会增大气泡的脱离直径;还发现随着成核点间距离的增加,气泡的脱离直径会呈现出先减小而后增大的趋势。

In order to study the effects of gravity acceleration,wall temperature and distance between nucleation points on bubble growth and detachment in vapor-liquid phase-change,a vapor-liquid phase-change model was established by coupling density distribution function and temperature distribution function on the basis of Shan-Chen pseudo-potential lattice Boltzmann model.At the same time,the relationship between the pressure difference inside and outside the droplet and the reciprocal radius of the droplet was obtained by using the model.It was found that the model conforms to Young-Laplace law,thus verifying the correctness of the model.Then,the two-dimensional numerical simulation of bubble growth and detachment in vapor-liquid phase-change was carried out by using this model.The calculation results show that the bubble detachment diameter decreases gradually with the increase of gravity acceleration,and the process of bubble growth and detachment is in good agreement with the literature results.In addition,the simulated bubble detachment diameter is fitted by non-linear method and the results are in good agreement with the new empirical formula;at the same time,the higher wall temperature will increase the distance between the bubble neck and wall,and the increase of wall temperature will increase the detachment diameter of bubbles.The detachment diameter of bubbles decreases first and then increases with the increase of the distance between nucleation points.