Abstract
The Dean's hydrodynamic instability in curved rectangular channels having the aspect ratio of 12 has been examined by flow visualiztion technics, Using a dye injection and an electrolytic coloring methods, the effect of curvature ratio on the critical Dean number has been determined over the range of curvature ratio from 0.0125 to 0.25. The results of photographs indicate that the critical Dean number for the onset of instability increases with increase of the curvature ratio for the region above the threshold point of 0.1, wheras it is nearly constant over the range of lower curvature ratio. The pair of vortices due to the two side walls is quite clear but is confined into the corners near the side walls.
The results also show that the wave number of secondary flow becomes large for Dean number well over the critical value indicating transition to the next stage of the oscillatory phenomenon.
