. Average drop sizes produced by the needles
were 2.6, 3.7, and 5.1 mm volume equivalent diameters with standard
deviations of 0.16, 0.19, and 0.19 mm, respectively. The results presented
in this manuscript are based upon the analysis of total of 360 drops
(10 drops per station per each drop size × 12 stations × 3 drop sizes).
A high-speed camera (Fastec-Troubleshooter) was used to capture
the sequence of frames with a 1000 frames per second rate as the
drops passed through the camera view frame. The captured images
were 640 pixels (92 mm) in the horizontal direction and 480 pixels
(69 mm) in the vertical direction. Generated drops fell within a circle
of 7 cm diameter at the focal plane, which ensured the image quality
and measurement accuracy as it is discussed below. More than 1000
frames have been used for the analysis of each drop size. A halogen
light bulb was used as the light source to illuminate the drop from behind
(see Testik et al., 2006; Testik, 2009; Testik et al., 2011). Typical
drop images obtained using this technique are shown in Fig. 3.