Figure 1.

Experimental setup for visualizing the wake of the flying swift. The tunnel is filled with a thin fog that is illuminated by the pulsed laser emitting 200 pulse pairs per second. The laser is synchronized with the two CMOS DPIV cameras that capture images of the smoke at each laser pulse. The images are stored in the host PC. The light emitted from the laser is guided via an optical arm that by the end of it has a lens that spreads the light beam into a thin light sheet. The light sheet was for this experiment positioned perpendicular to U. The position camera is used for recording the flight behaviour of the bird and its location relative to the laser sheet during measurements. The laser and the cameras are triggered and synchronized by the high-speed controller box (HSC).