Fog droplets drift right on the wind and strike a vertical mesh of wire strands. Capture depends on the Stokes number (droplet inertia vs. wire size) and on the shade coefficient (too dense a mesh deflects airflow around it, too sparse lets droplets slip through the gaps). Captured water beads, drips down the wires and collects in the trough.
Droplet capture efficiency vs. mesh geometry and wind speed