High-resolution simulation of a severe case of low-level windshear at the Hong Kong International Airport: Turbulence intensity and sensitivity to turbulence parameterization scheme

Large eddy simulations are performed for a severe windshear case of terrain-induced airflow disturbances at the Hong Kong International Airport. The objectives of the study include: (i) to investigate the performance of large eddy simulation in capturing the turbulence intensity to be encountered by the aircraft; and (ii) to find out the impact of the choice of turbulence parameterization scheme on the simulation results. The structure functions of the headwind profiles are calculated, and the simulated velocity and the LIDAR data are found to have similar behavior. The cube root of eddy dissipation rate is also calculated, which is taken to be the metric of turbulence intensity in aviation application. All EDR calculated has similar behavior. They have good correlation, but the best-fit-straight-line of the scatter plot is found to have a slope far away from unity. The reason for this needs to be studied further. Finally, a simulation with the use of Smagorinsky scheme is performed. It is found to have better performance in capturing pilot windshear reports in terms of the relative operating characteristic curve. The use of Smagorinsky scheme alone may be an alternative in the choice of turbulence parameterization scheme in the alerting of windshear using large eddy dissipation, but the computational cost is too expensive. It is important to note that the present results are based on one case only and more cases would need to be studied in order to establish the robustness of the conclusions. More experiments would also need to be conducted, for example, in which nest(s) to use the Smagorinsky scheme.