Ventilation and heat exchange characteristics in aircraft cabin considering buoyancy-driven flow and pressure-induced variations

During flight, aerodynamic heating and multiple internal heat loads create a high-temperature low-pressure extreme environment. The flow and heat transfer mechanisms there differ from those in atmospheric sealed chambers, posing substantial challenges to thermal control design. Most existing studies tend to decouple multiple influencing factors and fail to fully describe the complex heat exchange phenomena within cabins. To address this issue, a full-scale aircraft cabin ground test platform was built for combined simulation and experimental analyses to investigate the buoyancy-driven flow and its pressure-induced effects. Under a fixed mass flow rate, the dimensionless flow structure remains unchanged with pressure when forced convection dominates, and the wall heat transfer characteristics remain stable. Once buoyancy-driven flow is introduced, jet deflection intensifies with rising pressure or falling flow rate. The deflection displacement y is proportional to P e 2 /m 2 . At atmospheric pressure, the jet deflects rapidly and impinges on the cabin walls, producing vertical temperature stratification. As the pressure decreases, flow symmetry gradually recovers. At 24 kPa, the spatial standard deviation of temperature drops by 15.8%, indicating considerable thermal control improvement, although the improvement saturates gradually. Obstacles and non-uniform wall temperatures amplify buoyancy asymmetry, altering jet deflection paths. Additionally, jet deflection angles were quantified and a critical mass flow criterion for jet-wall impingement was proposed. These findings on flow and thermal phenomena, which systematically characterize the coupled effects of buoyancy and pressure, were validated through steady-state experiments. The results support optimizing cabin ventilation and thermal control at high altitudes and serve as reference for design for ground tests.