暴雨环境下155 mm榴弹气动特性多相流耦合分析

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

摘要:

为研究恶劣气候条件下弹丸飞行过程中的绕流流场和气动特性,基于Marshall-Palmer雨滴谱,采用双向动量耦合Eulerian-Lagrangian方法研究了某155 mm榴弹在暴雨环境中的气动性能。利用离散相模型（DPM）对雨滴粒子的运动轨迹进行非稳态追踪,并结合随机游走扩散模型模拟连续相湍流对雨滴扩散的影响。提出了一种拉格朗日多相流（LMF）与拉格朗日壁膜（LWF）相结合的方法,研究雨滴撞击弹体表面后液膜的形成和演化规律。结果表明,雨滴撞击弹体表面形成液膜并呈现流动轨迹,液膜主要分布在迎风面（尤其是弹头区域及弹带前缘）,最大厚度约0.02 mm,最大质量接近0.16 mg；液膜的形成增大了弹体表面的粗糙度,使最大剪切应力从无雨环境下的666 Pa增至暴雨条件下的2 350 Pa,最大摩擦系数从0.008增至0.025；暴雨对弹丸的气动系数也会产生不利影响,最大阻力系数较无雨条件下增加了6.75%,而升力系数略有下降,最大下降了1.9%。该研究可有效捕捉暴雨环境下弹体表面液膜的动态变化及其气动效应,为复杂环境下弹丸设计与性能优化提供理论支持。

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.