摘要:
为研究多发动机并联火箭橇的复杂尾流场特性，本文重点分析了喷管水平中心距与冲击高度对流动结构与地面效应的作用机制。通过对比大间距（l=7d）、小间距（l=1d）、低冲击高度（h=2d）及高冲击高度（h=5.5d）四种工况，系统揭示了不同构型下流场结构、压力分布与对地面的热冲刷行为。结果表明：小间距布局在无地效时会诱发强烈的射流干涉，导致压力恢复呈现“多波峰-慢恢复”特性，显著延缓了流场弛豫过程。地面效应与干涉的耦合作用由冲击高度主导：低冲击高度工况下，射流冲击地面诱发涡结构剧烈重组与破碎，形成速度高达960 m/s的壁面射流，地表温度峰值达1286.6 K且持续高温，轨道烧蚀风险显著增大；而高冲击高度可有效抑制地效作用，流场结构更趋均匀稳定，地表温度峰值降低约65%，最大流速降低58%，烧蚀风险显著缓解。火箭橇起始段（0-8 m）为热-力载荷最恶劣区间，该阶段平均加速度高达832.7 m/s²且单位距离作用时间长为1.84 ms/m，与瞬态复杂流场耦合，构成了轨道烧蚀的极高风险。数值模拟结果与高速摄影试验结果在流场形态、冲击高度及涡核位置等方面高度吻合，验证了所建立“内弹道-外弹道-流场”耦合模型的可靠性。本研究阐明了多喷管并联系统在强约束条件下的复杂流动规律，为高加速度、大载荷火箭橇试验系统的结构布局优化与热防护设计提供了重要的理论依据与设计参数。
Abstract:
To investigate the complex wake field characteristics of multi-motor parallel rocket sleds, this study focuses on analyzing the mechanisms by which horizontal nozzle center distance and impact height influence flow structures and ground effects. By comparing four operating conditions including large spacing (l=7d), small spacing (l=1d), low impact height (h=2d), and high impact height (h=5.5d)，this study systematically reveals the flow field structure, pressure distribution, and thermal erosion behavior on the ground under different configurations. Results indicate：(1) The small-spacing layout induces strong jet interference in the absence of ground effect, resulting in a “multi-peak-slow-recovery” pressure recovery characteristic that significantly delays the flow field relaxation process. (2) The coupling effect between ground effect and interference is dominated by impact height. At low impact height, jet impact induces violent vortex restructuring and fragmentation, forming wall jets with velocities up to 960 m/s. Peak surface temperatures reach 1286.6 K with sustained high temperatures, significantly increasing track ablation risks. In contrast, high impact heights effectively suppress ground effects, leading to a more uniform and stable flow field structure. Peak surface temperatures decrease by approximately 65%, maximum flow velocities reduce by 58%, and ablation risks are significantly mitigated. (3) The rocket skid initial phase (0-8 m) represents the most severe thermal-mechanical loading zone. During this stage, the average acceleration reaches 832.7 m/s², coupled with a prolonged duration per unit distance of 1.84 ms/m. This interaction with transient complex flow fields constitutes the highest risk for orbital ablation. Numerical simulation results closely matched high-speed photography test outcomes in flow field morphology, shock height, and vortex core location, validating the reliability of the established “internal ballistics-external ballistics-flow field” coupled model. This study elucidates the complex flow patterns of a multi-nozzle parallel system under severe constraints, providing crucial theoretical foundations and design parameters for structural layout optimization and thermal protection design in high-acceleration, heavy-load rocket sled test systems.
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