# Review on the Recent Numerical Studies of Liquid Atomization
## 4 Particle Tracking
### Application Cases  
Using the particle tracking method, multiple researchers studied the transportation phenomenon of liquid droplets including trajectory, heat transfer, and evaporation. Recently, [PERSON] et al. [56] simulated the evaporation of desulphurization wastewater in flue gas using the commercial code CFX. [PERSON] et al. [57] investigated the dust capture using liquid spray in mineral excavation face by Fluent. The influence of atmosphere pressure on the metal-powder production through liquid metal atomization has been discussed in [PERSON] et al. [58], where a wave break model integrated into Fluent was adopted. In these studies, not much attention has been paid to the atomization core where breakup models function. [PERSON] et al. [59] simulated the gasoline spray in direct injection spark ignition engines using Star-CD. Before the primary breakup length, the HG model and KH model competed depending on whether the turbulence or the aerodynamic force dominated. After the primary region, it is assumed the fast-growing wavelength may come from KH instability or RT instability, upon which KH or RT breakup model was chosen. A grid space of 1.5 mm and time step of 0.01 ms were applied, which apparently would not cost as much computer resource as the interface capturing method. After validation of the spray penetration length with experiment, the influence of injection pressure and ambient pressure were discussed. Sometime cavitation may occur upstream of the nozzle because the local pressure reaches below the saturation status. The cavitation may produce turbulence energy strong enough to alter the atomization outside the nozzle. Therefore, an aerodynamic-cavitation-turbulence (ACT) model was developed to precisely predict the turbulence energy at the nozzle exit. The pure KH model, KH-ACT hybrid model and KH-WF hybrid model were evaluated by [PERSON] and [PERSON] [60] in their simulation of diesel injection with Converge. Comparison of the predicted spray structure among the three spray models and against available measurements helps identify a set of experimental conditions and \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Model Name** & **Application Scenario** & **Core Mechanism** & **Advantages** & **Disadvantages** \\ \hline Huh–Gosman (HG) & Primary breakup in high-pressure nozzles & Turbulent eddy-driven interface instability & 1. Directly links nozzle turbulence parameters 2. High engineering usability & 1. Relies on empirical constants (C1–C4) 2. Fails to capture secondary breakup 1. Requires precise nozzle exit \\ Wu–Faeth (WF) & Primary breakup in transverse jets & Turbulence-surface wave coupling & 1. Incorporated material scales 2. Suitable for non-axisymmetric flows & 1. Replies on empirical numbers (We > 500) 1. Neglects shear-dominated breakup 2. Inapplicable to high-viscosity fluids (Oh > 0.1) 1. Neglects acceleration effects \\ KH & High Weber numbers (We > 100) & Shear-induced surface wave instability & 1. Passibility intuitive 2. Switable for fuel injection & 1. Neglects shear-dominated breakup 2. Inapplicable to high-viscosity fluids (Oh > 0.1) 1. Neglects acceleration effects \\ KH-RT & High-speed, high-pressure multiphase flows (e.g., IC engines) & Shear (KH) + acceleration (RT) instability & 1. Dual-mechanism coupling improves accuracy 2. Industrially validated & 1. High computational complexity 2. Requires manual liquid core region (L) definition \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison table of breakup models. measurements that are needed to inform the development of improved atomization and spray breakup models. In a review made by [PERSON] et al. [61] on atomization of diesel injection, comprehensive breakup modes of liquid column at different flow speeds and breakup regimes at different locations are covered.