A video-based monitor for assessing free-fall droplet motion

Abstract

A newly video-based monitoring technique was developed in this study to characterize the shape and free-fall velocity of water droplets. The free-fall droplet monitoring system integrates three main components which are containing the CCD image sensor for capturing video images, the backlight source for illuminating the water droplets, and the computation unit for the image acquisition and function control. Subsequently, the high-speed CCD image sensor was used to capture images in 200 fps and the exposure time was set at 100 μs. With high contrast images, we mark out every droplet by detecting its contour. Later, a series of droplet detection and tracking algorithms were executed to obtain the velocity of the free-fall droplets. In the simulation experiments, the glass balls and the water droplets ejected from a sprinkler were both introduced for the verification of the system performance. The experimental results support the proposed free-fall droplet monitoring system including the combination of droplet detection and droplet tracking algorithms are capable to provide a promising approach for the measurement of the free-fall droplets. Additionally, this apparatus could be improved by replacing a CCD image sensor with larger sensing area or the faster sampling rate in our next attempt.