ORCID Profile
0000-0002-7710-5148
Current Organisation
University of Adelaide
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Cambridge University Press (CUP)
Date: 06-1972
DOI: 10.1017/S002237780000684X
Abstract: The influence of resistivity and Hall current on the Rayleigh-Taylor problem involving two superposed fluids of finite density in the presence of gravitational and magnetic fields normal to the fluid interface is examined. Unlike the related problem in which the magnetic field is parallel to the interface, it appears that the dispersion relation does not exhibit singular behaviour in the zero resistivity limit. The ‘potentially stable’ situation is considered throughout. The results are compared with earlier ideal and resistive theories, and an apparent anomaly regarding the existence of normal modes in such systems is resolved.
Publisher: Informa UK Limited
Date: 11-1993
Publisher: Cambridge University Press (CUP)
Date: 12-1968
DOI: 10.1017/S0022377800004074
Abstract: Recent calculations for hydromagnetic analogues of the classical Rayleigh– Taylor problem with Hall effect are compared. It is shown that an early calculation is the limiting situation of the work of Taiwar & Kaira, which confirms that the Hall effect introduces new instabilities.
Publisher: Wiley
Date: 12-04-2007
DOI: 10.1002/MMA.871
Publisher: Cambridge University Press (CUP)
Date: 09-1985
DOI: 10.1017/S0022112085002646
Abstract: The propagation of flexural waves in floating ice plates is governed by two restoring forces – elastic bending of the plate, and the tendency of gravity to make the upper surface of the supporting water horizontal. This paper studies steady wave patterns generated by a steadily moving source on a water–ice system that is assumed to be homogeneous and of infinite horizontal extent, using asymptotic Fourier analysis to give a simple description of the wave pattern far from the source. Short-wavelength elastic waves propagate ahead, while the long gravity waves appear behind and, depending on the system parameters, one, two or no caustics may appear. Wavecrest patterns are shown, and the litude variation with direction from the source is given. Where the two caustics just merge together, a special mathematical function analogous to the Airy function is introduced to describe wave litudes. These waves can be detected by a strainmeter embedded in the ice, and we compare its theoretical response with some experimental measurements.
Publisher: Cambridge University Press (CUP)
Date: 13-06-2017
DOI: 10.1017/JOG.2017.27
Publisher: Cambridge University Press (CUP)
Date: 10-1979
DOI: 10.1017/S0022377800010138
Abstract: The stability of cylindrical flux surfaces in the presence of finite resistivity and parallel ion viscosity is reconsidered, and in particular the increment in the logarithmic derivative Δ( Q ) over the inner dissipative region. Correction of the viscosity coefficient removes the branch-point behaviour at large growth rates reported earlier. Numerical results for real Q in the high-beta hard-core pinch are supported by mathematical analysis to show that parallel ion viscosity renders Δ( Q ) positive definite provided D 0, with a positive minimum increasing with temperature. This stabilization is associated with coupling of the parallel plasma motion in the presence of magnetic field curvature. The viscous compressible value of Δ( Q ) is somewhat less than its inviscid compressible counterpart at small real Q , so that relative to purely compressible theory parallel ion viscosity can be slightly destabilizing.
Publisher: AIP Publishing
Date: 08-1967
DOI: 10.1063/1.1762342
Abstract: Calculations for the finite conductivity ``tearing'' instability in the hard-core pinch with constant applied axial magnetic field are described. Cylindrical effects in the ``outer'' region, where the plasma remains effectively coupled to the magnetic field, are fully allowed for through a numerical solution of the boundary value problem. It is seen that there is quite good agreement with recent experimental measurements on the hard-core configuration, even though plasma compressibility is ignored. In particular, the fact that the m = 1 mode is not generally the fastest growing is accounted for by the use of cylindrical geometry in the outer region. A second result is that an increase in the ratio of azimuthal to axial magnetic field appears to be a somewhat better means of stabilization against ``tearing'' modes than one might have anticipated. A criterion for the validity of the plane approximation in the ``outer'' region is developed analytically.
Publisher: Cambridge University Press (CUP)
Date: 25-02-1999
DOI: 10.1017/S0022112098003875
Abstract: The time-dependent response of a floating flexible plate to an impulsively started steadily moving load defines the time taken to approach a steady-state deflection due to the load, or indeed whether such a steady state is achieved at all. The asymptotic analysis for large time reported here, for both a concentrated point load and a uniformly distributed circular load, confirms that a steady-state deflection is achieved at both subcritical and supercritical load speeds. This analysis also predicts a logarithmically growing response near the critical speed corresponding to the minimum phase speed of the hybrid waves generated, but an eventual steady-state response when the load speed moves at the shallow water wave speed. These results are supported by numerical computation.
Publisher: American Physical Society (APS)
Date: 27-09-1965
Publisher: Springer Science and Business Media LLC
Date: 10-1970
DOI: 10.1007/BF00649953
Publisher: Global Science Press
Date: 11-2012
DOI: 10.4208/EAJAM.290712.261012A
Abstract: An infinite Bernoulli-Euler beam (representing the “combined rail” consisting of the rail and longitudinal sleeper) mounted on periodic flexible point supports (representing the railpads) has already proven to be a suitable mathematical model for the floating ladder track (FLT), to define its natural vibrations and its forced response due to a moving load. Adopting deliberately conservative parameters for the existing FLT design, we present further results for the response to a steadily (uniformly) moving load when the periodic supports are assumed to be elastic, and then introduce the mass and viscous d ing of the periodic supports. Typical support d ing significantly moderates the resulting steady deflexion at any load speed, and in particular substantially reduces the magnitude of the resonant response at the critical speed. The linear mathematical analysis is then extended to include the inertia of the load that otherwise moves uniformly along the beam, generating overstability at supercritical speeds – i.e. at load speeds notably above the critical speed predicted for the resonant response when the load inertia is neglected. Neither the resonance nor the overstability should prevent the safe implementation of the FLT design in modern high speed rail systems.
Publisher: Cambridge University Press (CUP)
Date: 02-1975
DOI: 10.1017/S002237780002585X
Abstract: A closed solution for the increment in the logarithmic derivative & dgr ( Q ) over the inner (‘resistivity’) region for resistive tearing theory in cylindrical geometry including ‘parallel’ viscosity is compared with an earlier numerical solution. The singular point Q crit about which δ( Q ) exhibits branch-point behaviour in the presence of compressibility is identified modification of the viscous theory, to include (for ex le) finite Larmor radius effects, is suggested. In the incompressible limit, a familiar (inviscid) stability criterion is recovered, in the presence of ‘parallel’ viscosity.
Publisher: Cambridge University Press (CUP)
Date: 25-12-2004
Publisher: Cambridge University Press (CUP)
Date: 09-1970
DOI: 10.1017/S0022377800005158
Abstract: The stability of a non-conducting, compressible fluid (gas) flowing across the surface of incompressible conducting fluid (liquid) is discussed. Finite resistivity and Hall current are included in the hydromagnetic equations, together with surface tension. Both subsonic and supersonic flows are treated and some new instabilities are found, together with modifications to real and oscillatory modes obtained in earlier treatments.
Publisher: WORLD SCIENTIFIC
Date: 12-2009
Publisher: Elsevier BV
Date: 04-2004
Publisher: AIP Publishing
Date: 1970
DOI: 10.1063/1.1692782
Abstract: The influence of compressibility on the real growth rates of the resistive “tearing” instability in the hard-core pinch is considered. Numerical calculations indicate that the growth rates differ little for the chosen physical parameters from those given by incompressible theory. The difference is considerably less than an order of magnitude. Inclusion of terms involving the perturbed field in the direction of the field is found to have the most noticeable stabilizing effect particularly when the ratio of azimuthal to axial field is increased. In many cases, the high m modes are found to be the more unstable.
Publisher: Elsevier BV
Date: 05-1976
Publisher: Elsevier BV
Date: 1974
Publisher: Hindawi Limited
Date: 2001
DOI: 10.1155/S1173912600000079
Abstract: In the most common mathematical model for a moving load on a continuously- supported flexible plate, the plate is assumed thin and elastic. An exception is the inclusion of viscoelasticity in the theory for the response of a floating ice plate, where the deflexion at the critical load speed corresponding to the minimum phase speed of hybrid flexural-gravity waves consequently approaches a steady state. This is in contrast to the elastic theory, where the response is predicted to grow continuously at this critical load speed. In the theory for a floating ice plate, the dominant pressure due to the underlying water is inertial, introduced via a velocity potential and the Bernoulli equation (assuming non-cavitation at the plate-water interface). On the other hand, the classical Winkler representation used in early railway engineering analysis corresponds to retaining a term which is generally negligible in the ice plate context. Critical load speeds are consequently predicted to be much higher, at wavelengths correspondingly much lower, for commonly accepted railway engineering parameters. Other models might be considered.
Publisher: IOP Publishing
Date: 05-1973
Publisher: Elsevier BV
Date: 10-1986
Publisher: IOP Publishing
Date: 09-1973
Publisher: Cambridge University Press (CUP)
Date: 02-12-2005
Publisher: AIP Publishing
Date: 03-1967
DOI: 10.1063/1.1762152
Abstract: A self-gravitating, infinite cylinder of conducting, homogeneous, incompressible fluid in an axial magnetic field is considered with Hall effect included. In the case of axisymmetric modes, an asymptotic analysis for small, nonzero Hall current indicates a destabilizing effect of O(ε), where ε is the perturbation parameter. It appears that the increased instability is due to the electron-ion diffusion current, which contributes a radial Lorentz force that is absent in the single-fluid theory. This radial Lorentz force increases the tendency for the cylinder to break up into lengths defined by the perturbation wavenumber.
Publisher: IOP Publishing
Date: 02-2008
Publisher: American Physical Society (APS)
Date: 23-08-1965
Publisher: Springer Singapore
Date: 2016
Publisher: Cambridge University Press (CUP)
Date: 11-1988
DOI: 10.1017/S0022112088002757
Abstract: Viscoelastic theory is used to describe the response of a floating ice sheet to a moving vehicle. We adopt a two-parameter memory function to describe the behaviour of the ice, subjected to a steadily moving line or point load. The viscoelastic dissipation produces an asymmetric quasi-static response at subcritical speed, renders a finite response at the critical speed, and d s the shorter leading waves rather more severely than the longer trailing waves at supercritical speed. We extend earlier asymptotic theory to consider the anisotropic d ing of the flexural waves. There is enhanced agreement between theory and experiment.
Publisher: Cambridge University Press (CUP)
Date: 07-1987
No related grants have been discovered for Roger Hosking.