Using the DPIV video sequences, tentacles on one side of the medusa were digitized as series of points using ImageJ 1.44 (developed by the NIH) software.
Frames were extracted from the DPIV video sequences at 0.02-s time intervals (t), and medusa motion was measured from sequential changes in position (x, y) of the anteriormost point of the exumbrellar surface.
where [u.sub.w,y,i] was the component of water velocity (obtained from the DPIV output) in a direction perpendicular to the tentacle at point i.
7), as well as with observations of particle motions in the DPIV video sequences.
Bress and Dowling (15) used digital particle image velocimetry (DPIV
) to measure midplane velocity vector fields throughout the mold filling process.
Mean and instantaneous DPIV
vector fields showed an unsteady spanwise (CD) vortex forming in the corner formed by the top nozzle wall and knife.
These more recent studies, however, do not provide the full-field velocity data of polymer melts that is possible with DPIV.
Interestingly, these experimental conditions provide both benefits and challenges to the implementation of planar DPIV in molten plastics, and these considerations are described in this section.
In addition, the current implementation of DPIV lacked the frame rate and resolution to measure the center-plane flow near the gate where it is predominantly radial and the largest center-plane velocity gradients exist.