Abstract
The transient flow in a cylindrical enclosure with fixed sidewall is studied numerically. The initial motion due to uniform rotation of the lower endwall is disturbed by setting the top endwall to corotate impulsively with a small angular velocity. The flow parameter values are chosen so as to induce a vortex breakdown in the initial steady state. The unsteady rotationally-symmetric Navier-Stokes equations are solved iteratively using a combination of second-order and fourth order compact difference schemes. At higher values of the Reynolds number, upwind differencing is used in the convective terms. The breakdown bubble in the initial steady state occurs between the stationary top end wall and the mid-plane. The numerical soulution shows that at the early stage of the transient flow the breakdown bubble enlarges in size, and in subsequent time the bubble occurs between the mid-plane and the faster rotating endwall. The role of the azimuthal component of vorticity in the breakdown phenomena is analysed. The torque on the lower endwall is obtained at several values of non-dimensional time during the transient flow.
Published Version
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