Linear spin-up in a sliced cylinder

Spin-up and spin-down in a circular tank with a uniformly sloping bottom ar e studied experimentally and numerically for small values of the relative c hange in the angular velocity of the tank. Generally, the initial single-ce ll flow evolves into a number of smaller vortices. The evolution is compare d with an analytical model based on an expansion of the flow held in linear Rossby waves (Pedlosky and Greenspan, 1967). Although it is possible to tu ne the experimental parameters in such a way that agreement with the theory is found, in most cases the experiments show shedding of vortices in the i nitial stage of the spin-up or spin-down, a phenomenon not described by the analytical model. Nonetheless, in such cases the analytical model still ac counts for other observations: the alternating generation of cyclonic and a nticyclonic vortices in the eastern part of the tank and their subsequent w estward motion.