Influence of flight/jet parameters on drag and heat reduction characteristics of opposing jet under real gas effect

High-speed flight of hypersonic vehicles generates significant aerodynamic drag and thermal loads, where the vibrational and electronic energy excitation of surrounding gas molecules, along with chemical reactions such as dissociation and ionization, make the real gas effect non-negligible. The opposing jet technology, as a novel active thermal protection method for vehicles, has attracted considerable research attention. Thus, it is essential to conduct a detailed investigation of the drag and heat reduction capabilities of the opposing jet under real gas effects. This study employs two-dimensional compressible Navier-Stokes equations and a non-equilibrium thermochemical gas model to simulate the flow field of the opposing jet system under various flight conditions. The effects of real gas effects and flight/jet-flow parameters on the flow field structure, aerodynamic drag, and heat of a blunt body are investigated. The results indicate that an increase in flight Mach number significantly raises the total temperature and pressure, with the total drag coefficient increasing by 29.30% and the total heat flux increasing by 8.53 times when the flight Mach number increases from 8 to 12. The presence of a flight angle of attack disrupts the symmetry of the flow field, with a wall pressure difference of 2.57 times and a heat flux difference of up to 16.17 times between the windward and leeward sides at an angle of attack of 10°. Increasing flight altitude decreases the total pressure of the free-flow, resulting in reduced free-flow intensity and enhanced jet-flow penetration capability. As the flight altitude increases from 32 km to 36 km, the maximum pressure of the blunt body decreases by 36.34 kPa, and the maximum heat flux decreases by 1.32 MW/m². Increasing the jet pressure ratio significantly improves the total drag and heat flux. When the jet pressure ratio is 0.014, the system demonstrates optimal drag and heat flux reduction, with the total drag coefficient and heat flux reduced by 41.32% and 73.55%, respectively, compared to no-jet conditions. Changes in jet temperature have a significant impact on the near-wall temperature distribution. While increasing the jet temperature has little effect on the total drag coefficient, the total heat flux increases, reducing the overall drag and heat reduction efficiency of the system.