## 3 Results and Discussion
### The High Weber Number Conditions  
Under high _We_ conditions, the deformation and breakup behavior of droplets, as well as the underlying physical mechanisms governing these phenomena, will display significant deviations from their low _We_ counterparts. When _We_ is further increased to 184, the droplet undergoes sheet-thinning breakup, as shown in Figure 7a. In the droplet deformation step (\(\tau\) = 0-0.818), the droplet continues to shrink toward the center and flattens out. At \(\tau\) = 0.511, the droplet experiences a simultaneous contraction of the windward and leeward sides towards the center. However, the compression and deformation rate of the leeward side is noticeably greater than that of the windward side. As a result, the tail end of the leeward side evolves into a disk shape, appearing as a straight line on the image, while the curvature of the windward side remains curved. Following this, the windward side of the droplet grows in the direction of the vertical gas flow, wraps the droplet in the direction of the downstream gas flow, and wraps the droplet completely at \(\tau\) = 0.818. For the breakup step (\(\tau\) = 0.818-), the \"sheet-thinning\" mechanism and the development of R-T instability successively dominate the droplet breakup process. During the period of \(\tau\) = 0.818-1.267, the sheet continuously grows from the edge of the windward side and continues to grow and progressively stretches in the direction of the gas flow. Between \(\tau\) = 1.267-1.568, the gas flow fractures the sheet and produces liquid ligaments and filaments that then break up into a liquid mist. Concurrently, there is a clear piercing behavior of the gas flow toward the inside of the droplet at the windward edge so that it can be considered R-T instability. As the breakup process continues to progress (\(\tau\) = 1.568-), the droplet's windward edge gradually sheds into a dense liquid mist cluster and further breakup. This instability results in the stripping of a significant fraction of the droplet mass, governing the subsequent stages of the breakup process. Figure 6: Schematic of droplet breakup morphology characteristics taken by Shi (_We_ = 21). Figure 7b illustrates the morphological characteristics of the hundred-micron droplet catastrophic breakup process at _We_ = 696. Compared with the _We_ =184 condition, the similarity in the evolution process is primarily reflected in the following aspects: (1) the windward side remains; (2) the flattening trend of the droplets continues until the generated liquid mist obscures the main body of the droplets; (3) R-T instability exists at the windward edge of the droplets. The differences in the evolutionary process can be reflected in the following aspects: (1) the droplets are broken after experiencing slight compression deformation, and their deformation duration is significantly shortened; (2) the sheet is broken into liquid filaments and ligaments before breakup into small droplets in the _We_ = 184 condition, while the liquid mist is directly dislodged from the liquid surface under the action of shear force; (3) in the droplet breakup step, no folds can be observed on the windward side at _We_ = 184, while at _We_ = 696, the increased air velocity makes the droplets appear as folds on the windward side, and the comparison diagram is shown in Figure 8.  
Figure 8: The windward comparison diagram of sheet-thinning breakup and catastrophic breakup. Figure 7: Schematic of droplet breakup morphology characteristics. (**a**) sheet-thinning breakup, (**b**) catastrophic breakup. As the front end of the droplet evolves from a smooth surface to a fluctuating state in front of the windward side, there are bumps and fluctuating behaviors, but no obvious piercing behaviors are observed. This suggests that R-T instability is not the dominant factor in the breakup of this region. This is consistent with the experimental findings of [PERSON] et al. [6]. It should be noted that [PERSON] et al.