基于水下凹壁面上双油滴撞壁-聚并过程分析

doi:10.11949/0438-1157.20241002

摘要/Abstract

摘要：

利用CLSVOF模型和动态自适应网格数值模拟了静水中双油滴撞击凹壁面及聚并过程。结果表明，双油滴撞击水下疏油凹壁面滚动下滑过程中碰撞产生聚并行为，水下亲油表面上双油滴撞壁后铺展边缘接触产生聚并行为。对凹壁面上油滴铺展直径d、近端点距离δ和最大铺展因子β研究表明：β≤3.1聚并形成单液桥；β>3.1，δ/d<3，右侧油滴撞击凹壁面形成空心环，内边缘存在较高压力，导致油滴铺展面积扩张，促使形成双液桥；当β>3.1，δ/d≥3时形成环孔单液桥，但聚并后油滴与凹壁面的润湿面积存在波动。双油滴聚并形成的单液桥无量纲流通面积较大，稳定性优于双液桥，但双液桥缩短了撞壁-聚并的时长。研究可为深入理解旋流器近壁面非均相聚并机理提供理论支持。

关键词: 水下双油滴, 凹壁面, CLSVOF, 撞壁, 聚并, 液桥

Abstract:

The CLSVOF model and dynamic adaptive grid were used to numerically simulate the impact-coalescence process of double droplets on the concave-wall in still water. The results indicate that double droplet coalescence behavior occurred during the rolling and sliding process on the concave-wall with the underwater oleophobic materials, the droplet spreading edges contacted and coalescented after impact on the underwater oleophilic surface. The spreading diameter d, the endpoint distance of double droplets on the concave-wall δ, and the maximum spreading factor β were used to classify three liquid bridge forms. For β≤3.1, droplets coaled and formed a single liquid bridge. For β>3.1 and δ/d<3, a hollow ring with high pressure at the inner edge was formed when the right droplet impacted on concave-wall, and double liquid bridges were formed because of the expansion of the oil droplet spreading area. For β>3.1 and δ/d≥3, a single liquid bridge with a hollow ring was formed, but the wetting area fluctuated after coalescence. The single liquid bridge formed by the coalescence of double droplets has a larger dimensionless flow area. The single liquid bridge was more stable than the double liquid bridge. However, double liquid bridge shortened the duration of the impact wall to coalescence. The discoveries provided a useful theory for understanding the collision and coalescence mechanisms of heterogeneous phases near the cyclone wall. The shortcoming of the coalescence theory on discrete phase droplets was supplemented.

Key words: underwater double droplets, concave-wall, CLSVOF, impact wall, coalescence, liquid bridge

中图分类号:

O 35

张静, 杨光, 菅爱博, 程思淼, 王绍哲, 龚斌. 基于水下凹壁面上双油滴撞壁-聚并过程分析[J]. 化工学报, 2025, 76(3): 1029-1039.

Jing ZHANG, Guang YANG, Aibo JIAN, Simiao CHENG, Shaozhe WANG, Bin GONG. Analysis of double droplets impact-coalescence process based on underwater concave-wall[J]. CIESC Journal, 2025, 76(3): 1029-1039.

图/表 16

图1 双油滴撞击凹壁面计算模型

Fig.1 Computational modeling of a concave-wall impacted by double droplets

表1 结构参数和初始油滴参数

Table 1 Structure size and initial droplet parameter

参数/mm	数值
计算域宽度B	60
计算域直边高度H	75
凹壁面曲率半径R	75
下落高度h₀	115
左侧油滴偏心距e_l	65
右侧油滴偏心距e_r	33.0~58.5
油滴初始粒径d₀	2.2~6.4

表2 网格方案

Table 2 Grid plans

网格方案	油水界面细化阈值	流体域粗化阈值	最小网格尺寸/mm	最多网格数量/个	网格最大增量/%
Plan-0	无	无	1	367360	—
Plan-1	10^-2	10^-3	0.0129	528969	43.9
Plan-2	10^-2	10^-4	0.0133	532805	44.9
Plan-3	10^-3	10^-4	0.0143	531363	44.5
Plan-4	10^-4	10^-4	0.0143	591962	61.0

图2 自适应网格（S0=10 mm，d0=4.6 mm）

Fig.2 Adaptive mesh (S0=10 mm, d0=4.6 mm)

图3 网格无关性（S0=10 mm，d0=4.6 mm）

Fig.3 Independence of grid (S0=10 mm, d0=4.6 mm)

表3 连续相和离散相物性参数（293.15 K）

Table 3 Parameters of continuous-phase and discrete-phase at293.15 K

参数	数值
连续相密度ρ_c/（kg/m³）	998.2
连续相黏度μ_c/(kg/(m·s))	1.003×10^-3
离散相密度ρ_d/(kg/m³)	1595.0
离散相黏度μ_d/(kg/(m·s))	9.69×10^-4
界面张力σ/(N/m)	4.57×10^-2
重力加速度g/(m/s²)	9.81

图4 双油滴撞击凹壁面实验装置1—水封四氯化碳;2—蠕动泵;3—针头;4—摄像机;5—微距镜头;6—灯板;7—水箱;8—凹壁面;9—CCD相机;10—相机支架

Fig.4 Experimental setup for double droplets impact on concave-wall1—water-sealed CCl4; 2—peristaltic pump; 3—needle; 4—camera; 5—macro lens; 6—lamp plate; 7—tank; 8—concave-wall; 9—CCD camera; 10—camera bracket

图5 双油滴撞击凹壁面实验与数值模拟对比（S0=10 mm，d0=4.6 mm）

Fig.5 Comparison of experimental results with numerical simulation (S0=10 mm, d0=4.6 mm)

图6 双油滴撞击凹壁面过程分析（S0=10 mm，d0=4.6 mm）

Fig.6 Analysis of double droplets impact process on concave-wall (S0=10 mm, d0=4.6 mm)

图7 不同接触角壁面对双油滴润湿面积的影响（S0=10 mm，d0=4.6 mm）

Fig.7 Effect of contact angle on the wetting area (S0=10 mm, d0=4.6 mm)

图8 双油滴初始粒径对润湿面积的影响（S0=10 mm, θ=30°）

Fig.8 Effect of initial droplet size on the wetting area (S0=10 mm, θ=30°)

图9 初始中心距对双油滴润湿面积的影响（d0=4.6 mm，θ=30°）

Fig.9 Effect of initial center distance on the wetting area (d0=4.6 mm, θ=30°)

图10 油滴铺展参数

Fig.10 Droplet spreading parameters

图11 液桥形式对撞壁-聚并特性的影响

Fig.11 Effect of liquid bridge on impact-coalescence

图12 油滴聚并前后连续相流场分析

Fig.12 Continuous-phase flow analysis during droplet coalescence

图13 油滴聚并时刻内部速度分析

Fig.13 Distribution of velocity at droplet coalescence

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