摘要:

In this paper we examine the behaviour of oceanic unsteady flow impinging on isolated topography by means of numerical simulation. The ocean model is quasigeostrophic and forced by an oscillatory mean flow. The fluid domain is of the channel type and open-boundary numerical conditions are used to represent downstream and upstream flow.

ISSN:0309-1929    

DOI:10.1080/03091928608245895

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

It is shown that surfaces ∑αof discontinuity in the torsion α in a force-free field (whose existence was established in the previous paper) have special properties. There is a discontinuity in the magnetic field (i.e. a current sheet) associated with ∑αif the extension of ∑αalong the field is terminated anywhere within the fluid, or if two or more ∑αintersect. If the ∑αdo not terminate, they extend arbitrarily far along the field from the location of the arbitrary change in winding pattern that produces them. In that case there would be as many ∑αas changes in winding pattern, each ∑αoriented arbitrarily with respect to the others. Intersections would be unavoidable, and discontinuities (current sheets) inevitable companions of the ∑α. Hence sequences of arbitrary patterns of winding and wrapping of the lines of force generally produce current sheets.

ISSN:0309-1929    

DOI:10.1080/03091928608245896

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A series of experiments has been undertaken to investigate the onset of convection in a rapidly rotating fluid filled sphere. The boundary is subjected to a time varying temperature allowing the simulation of radial temperature profiles associated with internal heating. The system is similar to that treated theoretically by Roberts (1968), Busse (1970) and Soward (1977). It is found that Busse's modification of Roberts' linear analysis, taking into account velocity perturbations which are antisymmetric about the equatorial plane, provides a good estimate of the temperature gradient required to initiate convection. As observed in the experiments of Carrigan and Busse (1983) and predicted by linear theory, convection appears in the form of rolls or columns, aligned parallel to the rotation axis. As in earlier experiments, observed azimuthal wavenumbers are consistently smaller than predicted which we postulate to be a consequence of nonlinear effects. Owing to the presence of a centrifugally driven thermal wind, the predicted azimuthal drift of the rolls has not been observed.

ISSN:0309-1929    

DOI:10.1080/03091928608245897

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

An inviscid, electrically conducting fluid is contained between two rigid horizontal planes and bounded laterally by two vertical walls. The fluid is permeated by a strong uniform horizontal magnetic field aligned with the side wall boundaries and the entire system rotates rapidly about a vertical axis. The ratio of the magnitudes of the Lorentz and Coriolis forces is characterized by the Elsasser number, A, and the ratio of the thermal and magnetic diffusivities,q.By heating the fluid from below and cooling from above the system becomes unstable to small perturbations when the adverse density gradient as measured by the Rayleigh number,R, is sufficiently large.

ISSN:0309-1929    

DOI:10.1080/03091928608245898

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The variational lower boundv> 0.39π2determined by Ivers (1984) for the infimum decay rate v of axisymmetric poloidal magnetic fields is corroborated numerically and an upper boundv< 0.66°2established. This is achieved by correcting and extending results for certain flows considered by Chandrasekhar (1956).

ISSN:0309-1929    

DOI:10.1080/03091928608245899

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

by L. R. Lyons and D. J. Williams. D. Reidel Publishing Co., .231 pages (ISBN 90-2771663-3). Price 130.00 DFL (1984).

ISSN:0309-1929    

DOI:10.1080/03091928608245900

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor