A volume of fluid-enhanced-discrete phase model algorithm for water dropping simulation of firefighting aircraft

The water-dropping of firefighting aircraft is a complex gas–liquid two-phase process generating multi-scale droplets, and its accurate simulation is vital for assessing fire-extinguishing performance. Mesh-based methods (Volume of Fluid, VOF) capture interfaces accurately but are computationally expensive for large-scale problems, whereas meshless methods, such as the discrete phase model (DPM), efficiently simulate droplet motion but fail to describe breakup dynamics. This study proposes an enhanced DPM that incorporates a Weber number-based breakup criterion, allowing droplet splitting and a more realistic splashing evolution. The model is validated against water jet experiments, which show high consistency in liquid column formation and droplet breakup. A VOF-enhanced-DPM algorithm is further established to simulate the overall water-dropping morphology of firefighting aircraft, and the enhanced-DPM is independently applied to analyze water landing distribution under varying discharge volumes, heights and velocities, and to compare the effective fire-extinguishing range. Results demonstrate that the VOF-enhanced-DPM algorithm provides reliable precision simulations. In addition, the enhanced-DPM achieves a balance between computational efficiency and predictive accuracy in large-scale water-dropping applications.