水下火炮燃气后效流场特性研究

目的 研究水下火炮发射过程中炮口燃气后效及其对高速射弹超空化流场的影响。方法 基于CFD软件FLUENT，运用UDF和动网格技术，考虑空化效应，建立水下火炮发射炮口燃气后效多相流数值计算模型。针对1 m水深条件下水下火炮发射炮口后效期运动过程进行数值模拟，获得了炮口气泡发展特性、压力脉动规律，分析炮口气泡对高速射弹空泡发展的影响。结果 炮口气泡经历了膨胀、收缩、拉断等发展历程，在发展初期能够加速射弹运动。射流中心处的压力特性最为复杂，随着远离射流中心，脉动幅值减小。高速射弹入水初期迅速形成超空泡，随后燃气泡与空泡发展融合，高压燃气进入形成的气\汽混合空腔，抑制了空化的发展，运动5倍弹长后，形成闭合空泡。对比火炮水下发射实验验证了仿真模型的准确性，空泡结果与实验一致性较好。结论 水下发射炮口流场复杂，影响高速射弹空泡的发展，同时还会使得火炮平台承受高载荷冲击的威胁，需要采取炮口降载措施。

Characteristics of Gas After-effect Flow Field of Underwater Artillery

This paper aims to study the after-effect of muzzle gas and its influence on the supercavitating flow field of high-speed projectile during Artillery underwater firing. Considering the cavitation model, based on the CFD software FLUENT, the technology of UDF and dynamic mesh was used to establish the numerical calculation model of multiphase flow of gas in the muzzle of underwater Artillery. The numerical simulation is carried out aiming at the aftereffect movement of underwater Artillery muzzle under the condition of 1m water depth, the development characteristics of muzzle bubbles and the law of pressure fluctuation are obtained, the influence of muzzle bubble on the development of cavitation in high-speed projectile is analyzed. The muzzle bubble has experienced the development process of expansion, contraction, and rupture, and can accelerate the projectile movement in the early stage of development. The pressure characteristics at the center of the jet are the most complex, with increasing the distance from the jet center, pulsation amplitude decreases. At the initial stage of high-speed projectile entering the water, supercavitation is rapidly formed, and then the gas bubble and cavitation develop and integrate, and the high-pressure gas enters the formed gas/vapor mixed cavity, which inhibits the development of cavition, a closed cavity is formed when projectile moves five times the spring length. Compared with the underwater firing experiment of artillery, the accuracy of the simulation model is verified, and the cavition simulation results are in good agreement with the experiment. The complex flow field of underwater firing will not only after the development of high-speed projectile cavitation, but also make the artillery platform endure the threat of high load impact, so it is necessary to take muzzle load reduction measures