模拟射流雾化过程的VOF-LPT耦合方法

doi:10.19596/j.cnki.1001-246x.8460

摘要/Abstract

摘要：

探讨模拟射流雾化的若干典型VOF(Volume of Fluid)界面重构方法, 并在开源流体力学计算软件OpenFOAM中运用VOF-LPT(Lagrangian Particle Tracking)耦合算法; 该算法兼顾模拟的准确性和计算效率, 可较为准确地模拟从连续液体到离散小液滴的射流雾化过程, 并为更大尺度的模拟提供了一种可行的高效模拟方案。

关键词: 射流雾化, VolumeofFluid, 多相流, 拉格朗日跟踪

Abstract:

We evaluate several VOF(Volume of Fluid) methods for interfacial reconstruction. A VOF-LPT(Lagrangian Particle Tracking) coupling method is applied in OpenFOAM, an open source CFD package, to achieve both simulation accuracy and computational efficiency. This method simulates accurately from continuous liquid to discrete small droplets for jet atomization. It provides a feasible and efficient simulation scheme for simulation of jet atomization process on large scales.

Key words: jet atomization, volume of fluid, multiphase flow, Lagrangian particle tracking

李子丰, 杨宁. 模拟射流雾化过程的VOF-LPT耦合方法[J]. 计算物理, 2022, 39(4): 440-452.

Zi-feng LI, Ning YANG. A VOF-LPT Coupling Method for Simulating Jet Atomization[J]. Chinese Journal of Computational Physics, 2022, 39(4): 440-452.

图/表 16

图1 3D耦合算法(相场阈值αt = 0.1，计算时刻t = ti) (a)初始相场；(b)标记液体网格；(c)液滴识别与编号

Fig.1 3D coupling algorithm (phase field threshold αt = 0.1, computing time t = ti) (a) initial phase field; (b) labeling liquid grid; (c) droplet identification and numbering

图2 3D耦合算法

Fig.2 Algorithm logic diagram of VOF-LPT

图3 溃坝算例的初始条件

Fig.3 Initial condition of dambreak simulation

表1 不同重构方法(计算核数为6)在不同级别精度网格下的计算时间(单位：s)

Table 1 CPU time (in unit: s) of interface reconstruction methods (with 6 cores) at different mesh resolution

	粗网格(9070 Cells)	中等网格(36288 Cells)	细网格(145152 Cells)
MULES	20.2	483.2	5 032
Isoadvector	68.3	397.7	5 373
PLIC-RD	43.6	400.2	4 202

图4 不同界面重构方法的溃坝模拟(a) 中等网格；(b) 细网格

Fig.4 Dambreak simulation with different interface reconstruction method (a) medium grid; (b) fine grid

图5 不同界面捕捉方法下的相场守恒性误差参数Ev

Fig.5 Phase field conservation error parameters in different interface capture methods

图6 射流雾化模拟的网格及边界条件

Fig.6 Mesh and boundary conditions in jet atomization simulation

表2 模拟来流雾化物理时间0.03 s所需的计算时间(计算核数为10)

Table 2 Computation time for 0.03 s physical time in jet atomization simulation (with 10 cores)

界面重构方法	计算时间/s
MULES	52 667
Isoadvector	39 326
PLIC-RDF	48 539

图7 不同界面重构方法模拟的射流雾化(a) 相场云图；(b) 相场0.5的等值面(颜色表示x方向速度值Ux。)

Fig.7 Jet atomization simulation with different interfacial reconstruction methods (a) phase field ɑ; (b) contours of ɑ = 0.5 colored by velocity Ux

图8 满足阈值转化条件的离散液滴(a) 转化前VOF结果; (b) 转化后的液滴分布

Fig.8 Discrete droplets satisfying transformation threshold (a) VOF results before transformation; (b) droplet distribution after transformation

图9 (a) 离散液滴在(Ux, Uz) 速度平面内的数密度概率分布; (b) Ux速度分布

Fig.9 (a) Number density distribution in (Ux, Uz) plane; (b) Ux velocity distribution of discrete droplets

图10 对撞射流模拟初始条件(D = 635 m， Uj = 18.5 m ·s-1，2α = 60°，We = 2 987，Re = 11 724)

Fig.10 Initial conditions for the simulation of impact jet flow (D = 635 m, Uj=18.5 m ·s-1, 2α = 60°, We = 2 987, Re = 11 724)

图11 撞击流的VOF-LPT模拟(a) Chen等的纯VOF模拟；(b) 本文VOF-LPT模拟；(c) Ryan等的实验结果

Fig.11 VOF-LPT simulation of impact jet flow (a) pure VOF of Chen et al; (b) VOF-LPT in this work; (c) experiment of Ryan et al

图12 识别与捕捉离散液滴前后的液体结构(a) VOF；(b) VOF-LPT

Fig.12 Liquid structure before or after the identification and capture of discrete droplets (a) VOF; (b) VOF-LPT

图13 (a) 离散液滴各速度分量的概率密度分布；(b) 离散液滴两两组合各方向速度的联合概率密度分布

Fig.13 (a) Droplet probability density distributions of discrete droplet velocity components; (b) Joint density distributions of pairwise combination of velocities of discrete droplets

图14 梯级利用纯VOF、VOF-LPT和纯LPT模拟射流雾化过程

Fig.14 Scale-dependent coupling of VOF, VOF-LPT and LPT simulation for jet atomization

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