Multiphase coupling analysis of the aerodynamic characteristics of 155 mm howitzer shell flow in a heavy rain environment

Abstract:

To investigate the flow field and aerodynamic characteristics of a projectile during flight under adverse weather conditions, this study applies the two-way momentum-coupled Eulerian-Lagrangian method to analyze the aerodynamic performance of a 155 mm howitzer shell in a heavy rain environment based on the Marshall-Palmer raindrop spectrum. The unsteady tracking of raindrop particle trajectories is conducted using the discrete phase model (DPM), while the random walk diffusion model is incorporated to simulate the effects of turbulent diffusion in the continuous phase on raindrop motion. A novel methodology is proposed that combines the Lagrangian multiphase flow (LMF) model with the Lagrangian wall film (LWF) model to simulate the formation and evolution of wall films resulting from raindrop impacts on the projectile surface. The results show that raindrop impacts lead to the formation of wall films that exhibit flow trajectories, with the films predominantly distributed on the windward surface (particularly around the projectile nose and band regions). The maximum wall film thickness reaches approximately 0.02 mm, and the maximum film mass is about 0.16 mg; The formation of wall films increases the surface roughness, significantly raising the shear stress, the maximum shear stress escalates from 666 Pa in rain-free conditions to 2 350 Pa under heavy rain,and the maximum value increasing from 0.008 to 0.025; Rainfall also adversely affects the projectile′s aerodynamic coefficients, with the maximum drag coefficient increasing by 6.75% , while the lift coefficient experiences a slight reduction, with a maximum decrease of 1.9%. This approach effectively captures the dynamic evolution of wall films on the projectile surface under heavy rain conditions and their impact on aerodynamic performance, providing theoretical support for the projectile design and performance optimization in complex environmental conditions.