摘要:

The linear instability of a narrow current flowing eastward between two semi-infinite watr masses of different mean stratification is studied with a multi-mode quasi-geostrophic model. The mean stratification in each domain has an exponential profile. The current is symmetric about the vertical plane separating the two water masses and its vertical profile is determined by the difference between the mean stratification of the two domains, as imposed by the thermal-wind equation.

ISSN:0309-1929    

DOI:10.1080/03091929708208977

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In the paper we develop an alluvial hydraulic theory for the flow of an alluvial river around the base of a bridge pier. General results are established and then the cases of particular pier geometries are considered. Finally, the effects of flow separation on the hydraulic theory are assessed.

ISSN:0309-1929    

DOI:10.1080/03091929708208978

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The structure and collapse of linear three-dimensional magnetic neutral points is studied by varying the four parameters (p, q,j|,j⊥) that define, in general, the linear field of a neutral point. The effect of these parameters on both the skeleton structure (i.e. the fan and spine) and the actual field line structure of the null is considered. It is found that one current component (j⊥) causes the skeleton structure of the null to fold up from its potential state, whereas the other current component (j|;) causes the field lines to bend. The two other parameters (p,q) determine the potential structure of the null and cause the null to transform from a three-dimensional null to a two-dimensional null and from a positive (type B) null to a negative (type A) null.

ISSN:0309-1929    

DOI:10.1080/03091929708208979

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We apply the theory of continuous group transformations to equations governing optically thin gaseous media in the isobaric limit in order to find the class of self-similar solutions admitted of such equations. Depending on the character of the diffusivity (linear or nonlinear) three types of self-similar variables are found generating (i) the well-known root-mean-square law of heat transfer, (ii) a power-law enhanced or de-pressed by nonlinearity of diffusivity or radiation losses, and (iii) progressive wave type of solutions, respectively. The constraints on the form of the source (i.e., cooling) function have been determined for each solution. These results have been applied to the study of the nonlinear evolution of a thermal instability of a plasma as an example of astrophysical interest. We find that the nonlinear phase of the thermal instability leads to the formation of conductive/cooling fronts in the medium if a thermally unstable equilibrium point does exist. The specific dependence of diffusivity on temperature was shown to determine the shape of cooling/conductive fronts, while radiative losses influence the temporal behavior of perturbations. The transition between different types of self-similar solutions are discussed along with their stability.

ISSN:0309-1929    

DOI:10.1080/03091929708208980

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Edited by J.-P. Zhan and J. Zinn-Justin, Elsevier, 1993. XXIV+ 615 pp., US$248.50, hardbound (ISBN-0-444-81797-2).

ISSN:0309-1929    

DOI:10.1080/03091929708208981

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

By, U. Frisch, Cambridge University Press, 1995, XIII + 295 pp., US$ 29.95, GB£15.95, paperback (ISBN 0-521-45713-0), US$ 80.00, GB£45.00, hardbound (ISBN 0-521-45103-5)

ISSN:0309-1929    

DOI:10.1080/03091929708208982

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor