Wind field characteristics of stationary and moving downbursts based on the test of impinging jet with a movable nozzle

Abstract

Affected by the large-scale boundary layer wind, thunderstorm clouds are often accompanied by a horizontal movement while producing downdrafts. However, previous studies mainly focused on the stationary downburst. Hence, the understanding of the wind field characteristics of moving downbursts is still insufficient. To study the influence of a storm's movement on the downburst wind field, based on the impinging jet test device with a movable nozzle, the stationary and moving downburst are simulated. Firstly, the moving average method is used to process the wind speed time history, and according to various existing criteria, a reasonable moving average time is determined. Afterwards, the vertical, radial, and lateral wind profiles are respectively given, and the influence of the parameter η – which represents the ratio of the storm translating speed (Vtr) to the jet velocity (Vjet) – on the wind profile is studied. Moreover, the applicability of the vector sum method is verified. Finally, turbulence properties including turbulence intensity, power spectral density function (PSD), and probability density distribution function (PDF) are furthermore analyzed.