The typical flow structures in the corotating disks were clarified about the influence of Reynolds number and disk geometry by using Particle Image Velocimetry and Laser Doppler Velocimetry The secondary vortices keeping the phase lag against the disk rotating speed are induced outside of the forced vortex formed near the disk center The number and the size of the vortices determine the core radius and the core shape mode of the forced vortex As the increase of the Re number and the gap of the disks, the core radius is smaller But, in the case with the shroud around the disks, the vortices disappear and the core radius becomes large nearby the disk edge
