部分回転円板による高分子水溶液の容器内旋回流れにおけるリング渦の可視化観察(流体工学,流体機械)

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Confined swirling flows of aqueous polymer solutions due to a partially rotating disc in a cylindrical casing have been investigated using a flow visualization technique. The ratio of rotating disc radius R_d to container radius R_c, σ=R_d/R_c, was 0.4, 0.6 and 1.0. As the aqueous polymer solution, 0.5, 0.8 and 1.0wt% polyacrylamide (PAA) solutions were used. It was observed that at σ=0.4 and 0.6, the ring vortex was formed near the partial rotating disc and it was shed periodically for all the solution concentrations C tested, as well as at σ=1.0. Regardless of σ, the period of the vortex shedding seemed to increase with the Reynolds number Re_0. The diameter of the ring vortex B, which increased with the increase of Re_0, was roughly between 0.2 and 0.4 times the outer diameter of the rotating disc. Regardless of C or σ, the height of the vortex h was about 0.1 times the diameter of the rotating disc. The relation between the lower-critical Reynolds number for the ring vortex (Re_0)_c and the elastic number E_0 could be expressed by the equation, (Re_0)_c=10E_0^<-3/5> which was independent of σ.
2010-01-25