摘要:

The separation of sidewall boundary layers in a rotating annulus of homogeneous fluid is studied experimentally. The flow is driven by a differentially rotating lid, and a very small uniform slope of the bottom causes a weak mountain vortex pair to form in the interior, away from the sidewalls. A necessary condition for aerodynamic separation of the sidewall boundary layers is derived and compared with the experimental results. The laboratory flow separates for parameters that are just slightly more inviscid than those required by the necessary condition for the existence of adverse pressure gradients at the wall. As the bottom friction is decreased further, the flow becomes unsteady and chaotic. The most interesting aspect of this problem is that chaotic interior behavior, associated with the separated boundary layer, is observed for parameter values for which the interior topographically forced flow is, by itself, essentially linear.

ISSN:0309-1929    

DOI:10.1080/03091929008208935

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Fluxes of angular momentum produced by turbulence in rotating fluids are derived with the effects of a magnetic field included. It is assumed that the rotation is slow but that the magnetic field is of arbitrary strength. A mean magnetic field is shown to produce qualitative changes of the sources of the differential rotation rather than the quenching of differential rotation usually expected. A new equatorward flux of angular momentum arises through the influence of the toroidal magnetic field. The possibility of interpreting the torsional oscillations of the Sun as a consequence of the magnetic perturbations of the turbulent angular momentum fluxes is discussed.

ISSN:0309-1929    

DOI:10.1080/03091929008208936

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The underlying reasons for the band structures seen in the atmospheres of Jupiter and Saturn are still incompletely understood. This paper gives quantitative support to a proposal made by Busse (1983), namely that the bands signal the presence of columnar convection rolls in the planetary atmospheres, such rolls being characteristic of convection in a highly rotating medium. The planetary atmosphere is, for simplicity, modeled by a barotropic annulus.

ISSN:0309-1929    

DOI:10.1080/03091929008208937

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A single active layer thermodynamic reduced gravity upper ocean circulation model is presented. The model is forced by prescribed surface heat flux (via the air temperature distribution) and wind stress and describes motions on the season to inter-annual time scale, with horizontal length scales of the order of 1000km.

ISSN:0309-1929    

DOI:10.1080/03091929008208938

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A 2-dimensional steady state latitude/depth advective-diffusive ocean model is formulated. The advecting flow is an idealized thermohaline circulation with upwelling at the low latitudes and downwelling at the high latitudes. Diffusion may occur along geopotential co-ordinates, or along isopycnal surfaces with a constant slope. The latter introduces an anistropy in the governing advection-diffusion equation for a passive tracer. The model is forced at the top with a specified tracer distribution. The sides and bottom are insulating. The equation is scaled to yield two non-dimensional parameters: the Peclet number(Pe), and an isopycnal slope parameter(γ). General results are derived analytically for the diffusive limit(Pe→0). A parameter study is carried out using numerical integration for the non-diffusive cases(Pe≠0). The results are interpreted in terms of the diffusive and advective fluxes, and the homogenization properties of the tracer field.

ISSN:0309-1929    

DOI:10.1080/03091929008208939

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

In their numerical analysis of convection driven by centrifugal buoyancy in a rotating cylindrical annulus Or and Busse (1987) found that sideband instabilities played an important role. These instabilities correspond to a finite value of the Floquet parameterdand have the tendency to modulate the periodic convection pattern. Since the Galerkin method is not suitable for the study of the convection flow as the sideband instabilities with their small Floquet wavenumberdgrow to finite amplitudes, it was suggested (Busse, 1986) that amplitude equations for the principal modes are investigated to gain at least a qualitative understanding of the problem. The amplitude equations which retain interaction terms up to the cubic order of the amplitude appear to give a fairly accurate description of the symmetric convection columns (Busse and Or, 1986) and of the mean flow solution occurring at higher Rayleigh numbers (Linet al., 1989). The plan was thus conceived to extend the analysis to the case of incommensurate wavenumbers in the azimuthal direction.

ISSN:0309-1929    

DOI:10.1080/03091929008208940

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A spectral low-order model is proposed in order to investigate some effects of bottom corrugation on the dynamics of forced and free Rossby waves. The analysis of the interaction between the waves and the topographic modes in the linear version of the model shows that the natural frequencies lie between the corresponding Rossby wave frequencies for a flat bottom and those applying in the “topographic limit” when the beta-effect is zero. There is a possibility of standing or eastward-travelling free waves when the integrated topograhic effect exceeds the planetary beta-effect.

ISSN:0309-1929    

DOI:10.1080/03091929008208941

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor