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1975 .

(3 publications)

R. Sadourny. Compressible Model Flows on the Sphere. Journal of Atmospheric Sciences, 32:2103-2110, November 1975. [ bib | DOI | ADS link ]

The effect of potential enstrophy conservation in finite-difference model flows on the stability of large- scale Rossby waves is investigated. It is also shown that cylindrical coordinates can be used successfully in global numerical experiments. Coherent boundary conditions at the poles are derived and tested on Rossby waves allowing cross-polar flow.

C. Basdevant and R. Sadourny. Ergodic properties of inviscid truncated models of two-dimensional incompressible flows. Journal of Fluid Mechanics, 69:673-688, June 1975. [ bib | DOI | ADS link ]

The equilibrium spectra of two-dimensional numerical model flows are studied from the viewpoint of microcanonical ensemble averages. The method leads to accurate numerical verification of the ergodic, or mixing, hypothesis in the case of systems constrained to a finite number of degrees of freedom.

R. Sadourny. The Dynamics of Finite-Difference Models of the Shallow-Water Equations. Journal of Atmospheric Sciences, 32:680-689, April 1975. [ bib | DOI | ADS link ]

Two simple numerical models of the shallow-water equations identical in all respects but for their con-servation properties have been tested regarding their internal mixing processes. The experiments show that violation of enstrophy conservation results in a spurious accumulation of rotational energy in the smaller scales, reflected by an unrealistic increase of enstrophy, which ultimately produces a finite rate of energy dissipation in the zero viscosity limit, thus violating the well-known dynamics of two-dimensional flow. Further, the experiments show a tendency to equipartition of the kinetic energy of the divergent part of the flow in the inviscid limit, suggesting the possibility of a divergent energy cascade in the physical system, as well as a possible influence of the energy mixing on the process of adjustment toward balanced flow.

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