スピンアップおよびスピンダウン過程における円筒容器内の渦崩壊の数値シミュレーション

抄録

Numerical study is performed on the vortex breakdown within a cylindrical container for the cases of spin-up from and spin-down to rest of an endwall disk. This flow problem is characterized by two non-dimensional physical parameters, i. e., the Reynolds number Re≡ΩR²/ν and the container aspect ratio H/R, here Ω, R, H and ν denote the angular frequency of the rotating endwall disk, the radius and height of the container, and the kinematic viscosity of the working fluid, respectively. In the present numerical investigation, the axisymmetry of the flow is assumed and the governing equations are solved by a finite difference method for the cases of H/R=2.00, 2.25 and 2.50, and Re=1.97×10³∼2.46×10³. Numerical results are discussed by comparing with flow visualizations. The appearance of oscillating vortex breakdown(s) and the damping to a steady state in the spin-up process and also the disappearance of vortex breakdown(s) and the appearance of a secondary recirculating zone in the spin-down process are demonstrated. Necessary condition for the appearance of the vortex breakdown suggested by Brown and Lopez is confirmed to extend for the spin-up process.