Crosswind-induced aero-performance deterioration of a vehicle passing by a hill with different windproof measures

Abstract

In crosswind conditions, the vehicle's aerodynamic performance significantly deteriorates when passing by a hill, impacting driving stability. Roadside windproof measures are effective in mitigating this performance deterioration. This study aims to explore the changes in aerodynamic performance of vehicles as they pass by a hill under three distinct scenarios: without wind barrier, solid wind barrier, and ventilation wind barrier. A three-dimensional computational fluid dynamics (CFD) model of the hill–embankment–wind barrier–vehicle–air, integrating the improved delayed detached eddy simulation (IDDES) turbulence model and a porous medium model, is established. The correctness of the numerical simulation is verified through field tests and wind tunnel experiments. The main conclusions are as follows: (1) When the vehicle passes by a hill under the crosswind, its aerodynamic loads undergo complex and significantly increased variations. ΔCx, ΔCy, ΔCz, ΔCmx, ΔCmy, and ΔCmz in the hill section without wind barrier are 2.79, 4.42, 5.18, 3.73, 4.45, and 2.73 times higher than those in the flat section. (2) The fluctuation amplitude of the aerodynamic loads and the maximum value of power spectral density (PSD) are the greatest under the solid wind barrier. Under the solid wind barrier, ΔCx, ΔCy, ΔCz, ΔCmx, ΔCmy, and ΔCmz are 3.63, 2.16, 4.34, 2.93, 2.00, and 3.21 times that with ventilation wind barrier. (3) Crosswinds cause flow separation on the leeward side and alter wind speed due to the hill's shelter without wind barrier. Ventilated barriers lessen these effects, while solid wind barrier reverses the crosswind direction, increases turbulence, and results in more erratic wind patterns and pressure changes on the vehicle's surface. (4) Without wind barrier, more vortex structures form on the leeward side and rear of the vehicle, which are smaller and less numerous with ventilation wind barrier. Solid wind barrier causes continuous changes in vortex structure position and size, resulting in the most significant aerodynamic load variations. This study provides valuable insights for selecting wind protection measures in hill sections of expressways.