Forming Jet Surface Velocity Profile Measurements with High Speed Digital Imaging, 2000 Engineering Conference Proceedings

Katsumasa Ono, Hanjiang Xu, Chang Park, Paul McKay, Cyrus Aidun, Minami Yoda--Measuring the forming jet velocity profile is important in process control and in controlling the physical properties of the sheet including basis weight, fiber orientation, and uniformity. Images of the random topography of the turbulent jet free surface were taken by a high-speed video camera at framing rates up to 1 kHz. Cross-correlation techniques were used with these images to determine the displacement of topographic features. Since the jet surface topography does not change significantly over 1 msec, the resultant displacement of topographic features for two images spaced 1 msec apart is a direct measurement of the surface velocity profile of the forming jet. In this paper, we present details of this surface velocity measurement technique, named surface pattern image velocimetry (SPIV),and demonstrate that this method has sufficient accuracy to monitor and diagnose jet quality problems in commercial headbox flows.