Inhomogeneous airflow and heat transfer characteristics of buoyancy-driven airflow in aircraft cockpits

Abstract

ABSTRACT In-flight airflow and temperature distributions are key parameters for the thermal design of aircraft cockpit. In real working conditions, the effect of gravitational acceleration on flow and heat transfer characteristics is crucial but has long been ignored in the cockpit study. Gravitational acceleration also induces buoyant force and inhomogeneous thermal transport, which gives rise to thermal challenges of aircraft cockpit. To address this challenge, an SST k-ω turbulence model was well validated with 94% prediction accuracy to evaluate the inhomogeneous characteristics. The results indicated that the buoyancy-driven temperature distribution became progressively more inhomogeneous as gravitational acceleration increased. It was also found that the nonlinear variations in temperature were observed in the vertical direction from 0 to 1.5 m. Besides, a dimensionless parameter Gr* (∝107) was used to quantitatively assess the buoyant force. The results showed that the buoyancy force was considerably similar at 2.0 g and 4.0 g, and largely different from the trend at 1.0 g. Indeed, a common characteristic of these three conditions is the presence of a large inhomogeneity coefficient R in the top region of the cockpit. Therefore, an important limitation when designing the thermal structure of cockpit is the inhomogeneous feature of which the follow-up study needs to be carried out.