Sheltering efficiency of wind barriers on bridges

Sheltering efficiency of wind barriers on viaducts was experimentally studied in a boundary layer wind tunnel. Effects of wind incidence angle on flow field characteristics in the wake of a wind barrier were reported. Mean velocity fields and vorticity fields were determined using the Particle Image Velocimetry (PIV) technique. Freestream velocities were measured using hot-wire and Pitot tube. Results indicate a possibility of wind-induced instability of high-sided vehicles at larger vertical incidence angles, especially in the traffic lane close to trailing edge of the bridge, as velocity fluctuations and mean freestream velocities approach the road surface when increasing the vertical incidence angle. Removing elements from the wind barrier causes very large local velocities immediately downstream from a barrier and strong vorticity in the entire area in the wake of a wind barrier. Variations in horizontal incidence angle do not seem to affect flow field characteristics significantly. Without a wind barrier, wind velocities on bridges reach 80% of the freestream velocity at height as low as 1 m full-scale along with very strong vorticity in the immediate vicinity of the road surface.