Wei Zhao

Under low-density hypersonic flight conditions, conventional aerodynamic control authority is markedly reduced, making transverse jets a promising approach for direct force control. However, the interaction mechanisms of multiple jets under such conditions remain unclear. In this paper, numerical simulations were employed to investigate the flowfield structure, aerodynamic characteristics, and their coupling-induced variations in twin transverse jets under low-density hypersonic crossflow. The results show that the twin-jet flow is not a simple superposition of two isolated single jets, but exhibits distinct near-wall separation, compression, and wake evolution patterns induced by jet–jet interaction. The upstream jet aerodynamically shields the downstream injector, modifies its local crossflow conditions, and consequently enhances downstream jet penetration and wake development. Conversely, the downstream jet affects the upstream flow through the near-wall boundary layer by pushing the primary separation region farther upstream, restricting the free expansion of the upstream jet, and intensifying compression and recirculation in the inter-jet and near-wake regions. Macroscopically, the aerodynamic force analysis reveals that the control force coefficient increases with jet strength, whereas the control force amplification factor decreases continuously. Compared with a single-jet configuration at matched total jet mass flow rate, the twin-jet configuration yields a higher control force and a lower total moment. These findings provide fundamental physical insights into the design and optimization of multi-jet direct force control systems under low-density hypersonic flows.

Oblique detonation waves (ODWs) are hypersonic combustion phenomena induced by oblique shock waves. When applied to air-breathing engines, ODWs offer high thermal cycle efficiency, adaptability to a wide range of flight Mach numbers, and the advantage of a short combustion chamber, making them highly promising for hypersonic propulsion applications. Despite numerous numerical studies on the heat release and multi-wave flow mechanisms of ODWs, practical applications of oblique detonation engines (ODEs) remain limited due to several technical challenges. These challenges include generating the required high-velocity test environments, achieving effective fuel and oxidant mixing, and measuring the flow field structure in hyper-velocity and high-temperature flows. These limitations hinder the development of ODEs, underscoring the importance of experimental research, particularly for understanding the initiation and propagation mechanisms of ODWs. One of the primary experimental techniques involves inducing oblique detonation using high-velocity models. This method is extensively used to study the initiation process, shock structure, initiation criteria, and ODW propagation. It is advantageous because the state of the experimental mixture is controllable, and the model state can be precisely measured. This paper reviews studies on oblique detonation induced by hyper-velocity projectiles, presenting advances in experimental methods, detonation wave structures, unsteady processes, and initiation characteristics. Additionally, we discuss the deficiencies in existing studies, noting that the current measurement methods fall short of the requirements for observing the ODW initiation process, propagation process, and fine structure. The application of advanced combustion diagnostic techniques and the exploration of the relationship between initiation processes and criteria are crucial for advancing our understanding of ODW initiation and stabilization mechanisms. Finally, we summarize the current state of experimental facilities and measurement techniques, providing suggestions for future research on the measurement of shock waves and chemical reaction zones.

A two-stage light gas gun driven by gaseous detonation was newly constructed, which can make up for the disadvantages of the insufficient driving capability of high-pressure gas and the constraints of gunpowder. The performance of the gas gun was investigated through experiments and a quasi-one-dimensional modeling of it was also developed and described in detail. The model accounts for the friction and heat transfer to the tube wall for gases by adding a source term. An improved model has been established to consider the inertial loads in the piston or projectile and model the friction force with the tube wall. Besides, the effects of pump tube pressure on the performance of the gas gun are also investigated numerically. Simulations of the pressure histories in the pump tube and the piston and projectile velocities were conducted. A good agreement was observed between the computational predictions and experimental results. The results showed that the friction between the piston and wall had only small influence on the piston velocity. The proposed numerical approach is suitable for the development of two-stage light gas guns and tests of the operating conditions.