Global instability of the rotating disk boundary layer

Lecturer: Prof. Jonathan Healey, Keele University, Anglie
Date: May 19, 2010, 10:00 -11:00 Wednesday
Location: Institute of Thermomechanics AS CR, v. v. i., Dolejškova 5, Prague, lecture room A

When a disk rotates at constant angular velocity in otherwise still fluid a boundary layer flow is established close to the disk. Obviously the local velocity of the disk increases with radius, but to a first approximation, this radial variation of the basic flow can be neglected to produce a "local" parallel-flow linear stability theory. The local stability theory predicts that the flow becomes absolutely unstable beyond a certain radius. However, it was found that the full radially-dependent "global" stability theory predicts global decay of disturbances, contrary to the local results, and more recent experiments appear to confirm this global decay. In this paper we present a new mechanism for global instability of this flow, and show that it correctly predicts the qualitative behaviour of laminar-turbulent transition observed in experiments.

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