Numerical investigation of the spin-up of a two-layer fluid

The spin-up of a two-layer fluid with a free surface in a cylindrical conta iner rotating about a vertical axis is investigated numerically, using axis ymmetric finite differences. As Linden & van Heijst (1984) have shown, the flow inside the viscous boundary layer at the bottom leads to the accumulat ion of the heavier lower-layer fluid near the side wall. Thereby, a bare sp ot in which the light fluid is in direct contact with the bottom is formed around the aa:is, The present simulation gives new insight into the interna l structures and interaction of the two fluids. Preliminary results indicat e strong mixing inside the region of heavy fluid.