Sudden flow induced by mountain ridges beside windbreaks in a railway and its mitigation measures

The impact of a mountain ridge (MR) on the wind speed distribution and flow structures along a railway, under crosswinds beside a windbreak at attack angles of 90 ° and 105 °, is studied in this paper. Based on the observed flow field deterioration mechanism, mitigation measures are proposed and the corresponding effects are compared, from which the preferred mitigation scheme is determined. For the original MR, the wind speed coefficient U is larger than 1.2 in the range below the train height at both wind angles. With the implementation of the flow field mitigation measures, as the distance (L) increases from the MR to the windbreak, the wind speed decreases linearly for the 90 ° wind angle and quadratically for the 105 ° wind angle. When the mitigation measure with L/h = 8.1 (h is the train height) is adopted, the wind speed coefficient U fluctuates very slightly in the MR area, with-0.2<U<0.05 at both wind angles. Therefore, L/h = 8.1 is recommended to protect the operation safety of trains travelling under strong crosswinds.