Streamline representation of the time-averaged flow field for a) the deactivated array and b) the operating array for an applied gas flow rate of 250sccm. c) shows a digitally magnified view (spatially deformed) of the array surface region while the array is operating, highlighting the near-surface flow structures. The flow fields are averaged over 1000 images at a camera recording frequency of 5297 Hz. For flow calculation close to the array surface, the array was at room temperature in this special case, as thermal convection would induce buoyancy of the seeding particles and prevent meaningful evaluation in this zone.