Abstract
An image processing system applicable to flow visualization experiments has been developed for making a quantitative estimation of unsteady two-dimensional flow fields. The flow with which we are concerned is that past a circular cylinder at Reynolds numbers around 100. The flow visualization is conducted in a towing water tank by means of a tracer method, and produces photographs of particle streaks. These photographic images are then put into an optical scanning process followed by computerized digital image analysis. This generates an instantaneous velocity distribution of the flow concerned; the mesh point velocity is interpolated from among several to several tens of local velocity vectors, and numerical calculations are made with thee distributions of stream function, vorticity and pressure. Distributions are presented in the form of contour lines.
