Hypersonic shock wave and turbulent boundary layer interaction in a sharp cone/flare model

A direct numerical simulation of hypersonic Shock wave and Turbulent Boundary Layer Interaction(STBLI) at Mach 6.0 on a sharp 7° half-angle circular cone/flare configuration at zero angle of attack is performed. The flare angle is 34° and the momentum thickness Reynolds number based on the incoming turbulent boundary layer on the sharp circular cone is Re_θ = 2506. It is found that the mean flow is separated and the separation bubble occurring near the corner exhibits unsteadiness. The Reynolds analogy factor changes dramatically across the interaction, and varies between 1.06 and 1.27 in the downstream region, while the QP85 scaling factor has a nearly constant value of 0.5 across the interaction. The evolution of the reattached boundary layer is characterized in terms of the mean profiles, the Reynolds stress components, the anisotropy tensor and the turbulence kinetic energy. It is argued that the recovery is incomplete and the near-wall asymptotic behavior does not occur for the hypersonic interaction. In addition, mean skin friction decomposition in an axisymmetric turbulent boundary layer is carried out for the first time. Downstream of the interaction, the contributions of transverse curvature and body divergence are negligible, whereas the positive contribution associated with the turbulence kinetic energy production and the negative spatial-growth contribution are dominant. Based on scale decomposition, the positive contribution is further divided into terms with different spanwise length scales. The negative contribution is analyzed by comparing the convective term, the streamwise-heterogeneity term and the pressure gradient term.     

Study of aerodynamic and inertial forces of a experimental and numerical methods

The force-generation mechanism of a dovelike flapping-wing micro air vehicle was studied by numerical simulation and experiment. To obtain the real deformation pattern of the flapping wing, the digital image correlation technology was used to measure the dynamic deformation of the wing. The dynamic deformation data were subsequently interpolated and embedded into the CFD solver to account for the aeroelastic effects. The dynamic deformation data were further used to calculate the inertial forces...     

临近空间高超声速稀薄流中梯形缝隙绕流分析

针对高超声速飞行器表面不规则缝隙的构型特征，将其简化为梯形缝隙模型；采用直接模拟蒙特卡洛(DSMC)方法对高超声速稀薄流中的缝隙绕流问题进行数值模拟；研究了不同的缝隙壁面倾角对流场结构以及壁面参数的影响，为航天器结构设计以及热防护设计提供了数值支持。结果表明：改变倾角会改变流场结构，当倾角减小时，外部流场会更深入缝隙内部，使得缝隙内流场和表面的气动参数增强，且倾角越小，影响的程度越深。同时，倾角减小也会减小缝隙内的旋涡强度，当倾角小于30°时，缝隙内的旋涡区域完全消失。     

一种基于学习的高超声速飞行器智能控制方法

针对吸气式高超声速飞行器的飞行控制问题，提出一种基于学习的智能控制方法。为便于控制器设计，将飞行器动力学模型划分为速度子系统和高度子系统：为解决速度子系统控制输入受限的问题，提出一种基于强化学习的智能控制方案；对于考虑有限通信资源的高度子系统跟踪控制问题，提出一种基于事件触发的确定学习控制方案。该方案包含离线学习训练和在线触发控制两个阶段。首先在本地离线学习训练阶段获取并存储系统的未知动态知识，随后利用所获取的经验知识设计基于事件触发机制的在线触发控制器。本文所提方案基于学习的思想将离线学习训练获取的智能体和经验知识应用于在线控制，使得所提方案能够快速计算控制指令且通信资源占用少。仿真结果说明了所提出方法的有效性。     

基于任务协同的有人机/无人机 对海攻击作战效能评估研究

通过分析攻击敌海上舰船目标过程中有人机/无人机编队的作战使用方式及影响其作战效能的主要因素,建立了有人机/无人机编队协同攻击海上目标的作战效能评估指标体系,运用ADC法构建了有人机/无人机混合编队攻击敌舰船目标作战效能评估模型,通过算例证明了该方法适应于有人机/无人机编队的作战效能评估,为有人机/无人机协同作战决策提供了有效的参考依据。     

Mahalanobis distance-based fading cubature Kalman filter with augmented mechanism for hypersonic vehicle INS/CNS autonomous integration

Inertial Navigation System/Celestial Navigation System(INS/CNS) integration, especially for the tightly-coupled mode, provides a promising autonomous tactics for Hypersonic Vehicle(HV) in military demands. However, INS/CNS integration is a challenging research task due to its special characteristics such as strong nonlinearity, non-additive noise and dynamic complexity.This paper presents a novel nonlinear filtering method for INS/CNS integration by adopting the emerging Cubature Kalman Filter(C...     

A novel adaptive lateral reentry guidance algorithm with complex distributed no-fly zones constraints

Aimed at complex distributed no-fly zones avoidance problems, a novel adaptive lateral reentry guidance algorithm is proposed. Firstly, by introducing the improved attractive and repulsive potential fields, an improved artificial potential field method is developed. Combined with the proposed judgment criterion for whether a no-fly zone has been avoided, the proposed improved artificial potential field method effectively solves the reference heading angle determination problem under the constrai...     

Autonomous mission reconstruction during the ascending flight of launch vehicles under typical propulsion system failures

In recent years, Chinese Long March(LM) launchers have experienced several launch failures, most of which occurred in their propulsion systems, and this paper studies Autonomous Mission Reconstruction(AMRC) technology to alleviate losses due to these failures. The status of the techniques related to AMRC, including trajectory and mission planning, guidance methods,and fault tolerant technologies, are reviewed, and their features are compared, which reflect the challenges faced by AMRC technology...     

A power and thermal management system for long endurance hypersonic vehicle

Due to the pneumatic heating and combustion effect, the scramjet engine of hypersonic vehicle faces high temperature challenge. It is necessary to comprehensively consider its thermal management and power generation together. A new Power and Thermal Management System (PTMS) combined with Supercritical Carbon Dioxide (SCO₂) closed Brayton cycle and fuel vapor turbine is proposed and discussed in this paper. The new PTMS can meet the cooling requirement of hypersonic vehicle at Mach number 6–7, and avoid the coking and scrapping in the scramjet cooling channels. Compared with the PTMS only based on fuel vapor turbine, the new PTMS utilizes the waste heat of scramjet to generate more electricity. In addition, it can reduce the use of fuel sink for cooling, and the additional weight penalty can be compensated for long endurance hypersonic flight.     

Oblique detonation wave triggered by a double wedge in hypersonic flow

Pressure-gain combustion has gained attention for airbreathing ramjet engine applications owing to its better thermodynamic efficiency and fuel consumption rate. In contrast with traditional detonation induced by a single wedge, the present study considers oblique shock interactions attached to double wedges in a hypersonic combustible flow. The temperature/pressure increases sharply across the interaction zone that initiates an exothermic reaction, finally resulting in an Oblique Detonation Wav...