Abstract
The effects of the fine spiral grooves of the disk surface on the flow over an enclosed rotating disk were shown in the case of narrow axial clearance, experimentally. The measurements of the frictional moment of the disk with fine spiral grooves were conducted in the non-dimensional axial clearance (s/a)=0.011 and 0.033. The number and the depth of grooves on the surface were 150〜160 and 0.1〜0.2mm, respectively. It was seen that the drag reduction occurred in the Reynolds number range 10^5〜6x10^5 at the non-dimensional axial clearance ratio (s/a)=0.011, the maximum drag reduction ratio was about 15%. The drag reduction depends on the number of the grooves and the non-dimensional axial clearance. If we consider as the riblets drag reduction for the phenomena, the value of s^+ and h^+ are 40〜200 and 6〜30, respectively.
