Wind field characteristics of stationary and moving downburst lines based on numerical simulation and impinging jet experiments

A downburst line is a linear high-wind system formed by multiple downburst cells, and the interaction among their near-surface outflows can produce a strongly unsteady and spatially non-uniform wind field. This study combines cooling source large-eddy simulation with an improved twin-outlet impinging jet experiment driven by a single power source to investigate stationary and moving downburst lines, focusing on the evolution process, time-varying near-surface wind speed, spatial distribution, interaction-region wind field, and the storm-cell spacing effect. The results show that ambient wind significantly changes the near-surface wind field distribution. In the stationary case, the wind field remains relatively symmetric, with high-wind regions mainly located near the outer edges of the cells and in the interaction region. In the moving case, the high-wind region persistently shifts toward the forward side, making the leading and trailing edges more distinct. For the 1200 m spacing case, the maximum wind speed increases from 58 m/s in the stationary case to 66 m/s in the moving case, corresponding to an increase in approximately 13.8%, and the peak time is delayed from 390 to 430 s. The wind speed in the interaction region is 0.94–1.12 times the linear superposition of the stationary wind field and ambient wind, indicating that the moving downburst-line wind field cannot be fully described by simple translational superposition. As cell spacing increases, the two cells become more independent, the continuous high-wind band weakens, the wind speed near the interaction center decreases, and the turbulence intensity increases.