摘要:

An experimental study was carried out to investigate the effect of rotation on turbulent mixing in a stratified fluid when the turbulence in the mixed layer is generated by an oscillating grid. Two types of experiments were carried out: one of them is concerned with the deepening of the upper mixed layer in a stable, two-fluid system, and the other deals with the interaction between a stabilizing buoyancy flux and turbulence.

ISSN:0309-1929    

DOI:10.1080/03091929008208925

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The onset of convection in a polytropic atmosphere with rotation and magnetic field is considered in a geometry such that rotation, magnetic field and gravity are mutually perpendicular. The anelastic approximation is used together with the low diffusion magnetogeostrophic approximation. The factors determining the pattern of convection are discussed, with particular reference to the question of whether convection rolls are primarily aligned with the rotation axis or the magnetic field. As in the Boussinesq problem, the global Elsasser number ℬ2/2μρΩη plays a key role.

ISSN:0309-1929    

DOI:10.1080/03091929008208926

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The linearised Boussinesq equations, which describe two-dimensional convection in a rotating layer of fluid, can support multiple instabilities associated with the same as well as different wavenumbers. These instabilities involve both steady and oscillatory convection rolls, and the most complicated situations involve triple interactions between two steady and one oscillatory or two oscillatory and one steady mode. In this paper we consider the weakly nonlinear dynamics of a triple instability involving a steady and an oscillatory roll of wavenumberk2and an oscillatory mode of wavenumberk1. The methods of centre manifolds and normal forms are used to derive equations for the evolving wave amplitudes and bifurcation theory is employed to find and analyse the stability of the equilibrium states. Periodic, quasi-periodic and period-doubling bifurcations are all possible close to the codimension three point. This paper forms the first part of a two-part presentation of the results of our investigation and only the periodic and quasi-periodic solutions are discussed here. The period-doubling behaviour together with a more complete scenario, placing the results in a physical context, will be discussed elsewhere.

ISSN:0309-1929    

DOI:10.1080/03091929008208927

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor