超声速侧向喷流干扰流场的稀薄效应研究

The rarefaction effects on the supersonic lateral jet/freestream interaction

反作用控制系统(RCS)具有响应快速、控制灵活的特点,在临近空间飞行任务中可实现飞行器的精准姿轨控制,然而连续流区建立的侧向喷流干扰在稀薄流域逐渐弱化甚至失效。为了解决这一问题,针对平板和楔形块两种构型,采用直接模拟蒙特卡罗方法(DSMC)开展了超声速侧向喷流/高超声速来流相互干扰流场的稀薄效应研究。结果表明:平板和楔形块喷流干扰流场均出现经典干扰结构,如多涡、多激波等;特别地,楔形块构型中出现类似马赫杆的特殊弓形激波结构,其由大入射角前缘激波与喷流弓形激波相互干扰而形成。随着流动逐渐变得稀薄,喷口前涡结构逐渐减小至消失,激波增厚且干扰减弱,特殊弓形激波结构逐渐消失。基于壁面压力、切应力和热流系数分别定义了3种无量纲干扰强度和干扰区长度,均与克努森数呈近似幂律递减关系。超声速喷流干扰作用对平板与楔形块壁面热流的增长最显著,受到的稀薄效应抑制作用也最强;干扰区长度与气动特性参数无关,与本文的两种几何构型也无关。

The reaction control system(RCS)relies on the interaction between the lateral jet and the freestream to achieve precise attitude control,quick response,and flexible flow field control in near space.However,these advantages in the continuum region will not be evident in rarefied flows.This paper utilizes direct simulation Monte Carlo(DSMC)to investigate the effects of rarefaction on the supersonic lateral jet/hypersonic freestream interaction over a flat plate and a wedge.Typical flow structures,such as vortical structures and shock waves,are observed in the continuous flow fields for both the flat-plate and wedge configurations.Additionally,a distinct bow shock similar to the Mach stem emerges in the flow field above the wedge,resulting from the interaction between the shock wave at the leading edge with a significant incident angle and the jet's bow shock wave.In rarefied flow fields,vortical structures downstream of the jet disappear,the shock wave thickens,and the distinct bow shock gradually diminishes.Three dimensionless interaction strength groups and the length of the interaction region,quantified by the wall pressure,shear stress,and heat flux,respectively,decrease exponentially with the global Knudsen number.Specifically,the interaction of the supersonic jet has the most significant impact on the increase in wall heat flux for both the flat-plate and wedge configurations.