Abstract
We investigate the flow between co-rotating disks with a narrow gap, enclosed by a stationary shroud at their circumferences, using the flow visualisation with PIV analysis. Experiments are conducted concerning non-dimensional hub radius κ in wide ranges of two system parameters, that is, disk-tip Reynolds number Re and gap aspect ratio δ. As a result, we reveal stability diagrams concerning core-shape modes of the flow, where we find out a new core-shape mode with a modal number m of unity at large Re and δ and at κ = 0.50. This core-shape mode 1 is the mode where there exists only one bulk of the fluid in rigidly-rotational motion in the azimuthal direction. Except for m = ∞, m decreases with increasing κ, as well as increasing Re and increasing δ. Especially at δ > 0.2, the influence of κ upon m is remarkable.
