回転円板間流れへのハブの影響について

概要

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We investigate the flow between co-rotating disks with a narrow gap, enclosed by a stationary shroud at their circumferences, using flow visualisations with PIV analyses. Experiments are conducted at three values of non-dimensional hub radius κ in wide ranges of other two system parameters, namely, disk-tip Reynolds number Re and gap aspect ratio δ. As a result, we reveal stability diagrams concerning core-shape modes of the flow defined by the modal number m. Except for the 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. Besides, we find out a new core-shape mode with m of unity, at large Re, large δ and large κ. This core-shape mode 1 is the mode where there exists only one bulk of the fluid in rigidly-rotational motion, which is attached to the hub and travels in the azimuthal direction with a rotation speed less than the disks.