Abstract
Instantaneous flow fields in open-channel flows with a horizontal dead zone, in which the aspect ratio (=streamwise length/spanwise length of the dead zone, i. e., L/Bw) is changed to 3, 5 and 10, were measured by making use of PIV (Particle Image Velocimetry). In the case of the aspect ratio of 3, the horizontal vortex exists stably. In contrast, in the case of the aspect ratio of 5, the vortices which are generated by the shear instability, i. e., Kelvin-Helmholtz instability, become larger in the downstream direction. In the case of the aspect ratio of 10, the reattachment phenomenon can be seen. The space-time correlation of the spanwise turbulence components decreases with an increase of the aspect ratio L/Bw.
