ISSN:0309-1929    

DOI:10.1080/03091927708240367

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Continental shelf waves are examined in the long wavelength limit, and the effects of weak topographic dispersion calculated. These dispersive effects are then balanced against nonlinear terms and a Korteweg-de Vries equation is derived to describe the evolution of the wave amplitude. Two particular cases are worked in detail.

ISSN:0309-1929    

DOI:10.1080/03091927708240368

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The problem of onset of convection in spherical fluid shells is considered in the limit of high rotation rates. Solutions are obtained as a function of the distance s from the axis, the Prandtl number, and the radius ratio η of the spherical boundaries. Analytical results are derived in the thin shell limit η → 1. The main result of the paper is the qualitative difference of convection modes inside and outside the cylindrical surface touching the inner spherical boundary at the equator. This feature was used earlier (Busse, 1976) to explain the difference in cloud formations at low and high latitudes of the Jovian atmosphere.

ISSN:0309-1929    

DOI:10.1080/03091927708240369

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

There are many examples of fluid motions that give kinematic dynamos in an infinite medium, but very few cases of dynamos in an electrical conductor of bounded extent. This curious observation is investigated by numerical calculation. Two significant effects are revealed. An insulating boundary is found to cause a current sheet to form near it and this inhibits magnetic field generation. Also the ratio of poloidal to toroidal component of fluid flow must lie in a certain range for dynamo action to occur, because otherwise the diffusive effects of the separate components dominate the regeneration mechanism which requires a combination of both. These two effects help account for some of the difficulties encountered in constructing kinematic dynamo models, and are relevant to the problem of generation of magnetic field by thermal convection in a rotating system.

ISSN:0309-1929    

DOI:10.1080/03091927708240370

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A primitive equation, solar driven, thermospheric model is derived which has applications to the neutral gas components on Mars and Venus. The full effects of molecular viscosity and thermal conductivity are included, necessitating the development of a combined analytic and numerical solution technique. The model is applied to Venus in order to understand how thermospheric rotation, if present, would affect the dynamics. Results indicate that rotation periods of eight days or less should be observable. Application of the model to Mars indicates that the perturbation solar heating and the atmospheric response have primarily a diurnal component for which typical temperature and zonal wind maximum amplitudes are 20 K and 30 m/sec respectively. Because of uncertainty in the solar heating efficiency, calculations were made varying this parameter by an order of magnitude. The results imply that the response due to solar forcing alone is probably too small to account for observed concentrations of the minor constituents CO and O. An upper limit estimate is made of the upward propagation of wave energy from the lower atmosphere and the resulting response of the thermosphere.

ISSN:0309-1929    

DOI:10.1080/03091927708240371

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0309-1929    

DOI:10.1080/03091927708240372

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Convection in a rotating spherical shell has wide application for understanding the dynamics of the atmospheres and interiors of many celestial bodies. In this paper we review linear results for convection in a shell of finite depth at substantial but not asymptotically large Taylor numbers, present nonlinear multimode calculations for similar conditions, and discuss the model and results in the context of the problem of solar convection and differential rotation. Detailed nonlinear calculations are presented for Taylor numberT= 105, Prandtl numberP= 1, and Rayleigh numberRbetween 1 |MX 104and 4 |MX 104(which is between about 4 and 16 times critical) for a shell of depth 20% of the outer radius. Sixteen longitudinal wave numbers are usually included (all even wave numbersmbetween 0 and 30) the amplitudes of which are computed on a staggered grid in the meridian plane.

ISSN:0309-1929    

DOI:10.1080/03091927708240373

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Measurements have been made of the net horizontal force F acting on a sphere moving with horizontal velocity U (Reynolds numbers in the range 102-104) through a stratified fluid rotating about a vertical axis with uniform angular velocity Ω. In both homogeneous and stratified rotating fluids with small Rossby numberR(R=U/Ωa≲ 1 whereais the radius of the sphere) the force F is of magnitude 2ΩρUV(where ρ is the density of the fluid andVis the volume of the sphere). In a homogeneous fluid the relative directions of F and U were found to depend on the quantity F = 8Ωa2/UD(whereDis the depth of the fluid in which the object is placed (Mason, 1975)). In a rotating stratified fluid the relative directions of F and U are found to depend on the inverse Froude numberk(k=Na/UwhereN2= (g/δ)∂ρ/∂z) providedD> 4aΩ/N.In a homogeneous fluid with F ≲ 1 the force F is mainly in the U direction (a drag force due to inertial wave radiation) and is ∼ −0.4 |MX 2ΩρUVFor F ≲ 1 a “Taylor column” occurs and the force, in correspondence with theoretical expectations, is ∼ - 2Ω |MX UρVIn a rotating stratified fluid withN∼2Ω andk≲ 1 the force F is mainly in the U direction but is roughly one half of that occurring in the homogeneous situation with F ≲ 1 (tentatively explained as due to the evanescence of inertia-gravity disturbances). In a rotating stratified fluid withk≫ 1 the flow should have no vertical motion (as with F ≫ 1) and again in correspondence with theoretical expectations the drag is ∼ −2 Ω |MX UρV.In a non-rotating stratified fluid the drag coefficientCD(CD= F U/½∂ρU2) was measured in the rangek= 0.1 to 10 and had a maximum value ∼ 1.2 fork∼ 3.

ISSN:0309-1929    

DOI:10.1080/03091927708240374

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A spectrum of oscillations covering a wide range of wave numbers is specified for a homogeneous fluid in a finite volume. Considering the range dominated by gravity and low wave number acoustic modes, a correspondence is established between the latter and a certain field associated with the former. It is shown that these two forms of oscillations are governed by the Helmholtz equation, with gravity modes as the driving source. This equation is solved by Green's function methods and a point source solution is derived from which the eigensolutions can be constructed.

ISSN:0309-1929    

DOI:10.1080/03091927708240375

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0309-1929    

DOI:10.1080/03091927708240376

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor