Tracking of macroscopic particle motions in flow visualization images Available to Purchase

A novel flow-visualization/digital-image-analysis technique to obtain quantitative information on individual mono-dispersed silica-sand particle motions in a wind-generated turbulent boundary-layer has been developed. This information is relevant to the understanding of the physics associated with the mass-transfer process across a fluid-surface interface, such as the wind erosion of toxic material or fertile agricultural land in an open environment or the sedimentation of materials in streams and rivers. The technique involves recording particle trajectories, which have been illuminated with a strobed plane of light generated via a He-Ne laser, on 35 mm black and white film, converting the negatives into 512 x 512 digital images, enhancing these images via Fast Fourier Transforms, extracting ‘dashed’ particle lines and then linking the lines together to reconstruct the particle trajectory. The result is a Lagrangian description of the particle path of flight, obtained with the aid of the basic principles of computer vision/artificial intelligence. The technique was developed on a Sun 3/180 computer and subsequently implemented on a Cray X-MP/22 supercomputer.