A Simple laboratory Model for investigating the Dynamic Instability of a Nearly Two-dimentional Jet in a Rotating Fluid

Abstract

An experimental study of the dynamic instability in a rotating system is presented. The basic jet is made by rubbing the free surface of water in rigid rotation with a solid plate. The structure of the basic jet is studied by a linear theory on the vertical free shear layers. The beta-effect is simulated by variation of the fluid depth.
When the Rossby number exceeds a certain critical value, the zonal jet becomes unstable and a disturbance with a specific wave number appears. By comparing the observed wave numbers with relevant linear theories, the following results are obtained.
(i) The observed marginal state better fits the theory in which the jet is stabilized by the beta-effect than the theory in which the jet is stabilized by the internal viscosity.
(ii) The observed results show that the westerly jet is more stable than the easterly jet.
(iii) The observed wave number rapidly decreases from the linear mode, when the Rossby number increases from the critical value.