The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. The distribution of pressure disturbance on disks has relation to flow structure. To investigate the flow structure, the circumferential velocity was obtained using hot-wire measurements for the flow between the center pair of four disks of common radius R2 co-rotating at angular velocity σ in a fixed cylindrical enclosure. Disk radius is about 4 times larger than usual one of HDD to detect detail velocity profile. Hot-wire supporter acts as an obstruction in this case. The effects of rotating speed on large flow oscillation in outer region with hotwire supporter were investigated.