RANS simulations of terrain-disrupted turbulent airflow at Hong Kong International Airport

During a tropical cyclone, windshear can occur at Hong Kong International Airport (HKIA) owing to interactions between strong winds and the complex topography of the neighboring Lantau Island. For aviation safety, it is crucial to understand how such interactions arise under realistic but controlled meteorological conditions. In this study, we numerically simulate the turbulent airflow over Lantau Island and HKIA using OpenFOAM, an open-source platform for computational fluid dynamics. We use the platform to solve the Reynolds-averaged Navier–Stokes equations via the finite volume method of discretization. We impose a neutrally stratified atmospheric boundary layer as the upwind condition, which is initialized with a logarithmic velocity profile in three different wind directions: southerly, southeasterly and easterly. For all three directions, we find multiple high-speed ∨-shaped jets emanating from the mountain gaps of Lantau Island, giving rise to headwind and crosswind variations along the glide paths of HKIA. However, we find that it is primarily the southerly and southeasterly winds that are the most conducive to windshear. For these two wind directions, we find that windshear is most likely to occur along the glide paths of the two existing runways because these are the closest to Lantau Island itself. The third runway, which is currently under construction, is the least likely to suffer from windshear. By showing how airflow disturbances arise from the complex topography of Lantau Island, this study contributes to safer and more efficient flight operations at HKIA.