Fig. 6. Digital particle image velocimetry (DPIV) was used to measure variations in velocity and turbulence levels with the wind tunnel set at an equivalent airspeed of 5 m s^-1 along the x dimension (axis of airflow). The DPIV system uses a YAG laser and synchronized stereo video cameras to measure velocities U, V and W, corresponding to the x, y and z axes, respectively, of particles suspended in the moving air column. Variation in true airspeed (U) was relative to a mean of 5.54 m s^-1. Total turbulence (T) varied about a mean of 0.23 %.