In this paper, a new time discontinuous expanded mixed finite element method is proposed and analyzed for two-order convection-dominated diffusion problem. The proofs of the stability of the proposed scheme and the uniqueness of the discrete solution are given. Moreover, the error estimates of the scalar unknown, its gradient and its flux in the L∞(J̄ , L(Ω)-norm are obtained. Keywords—Convectio...

für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution 4.0 International License. Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namen...

Rapidly rotating Rayleigh-Bénard convection is studied by combining results from direct numerical simulations (DNS), laboratory experiments, and asymptotic modeling. The asymptotic theory is shown to provide a good description of the bulk dynamics at low, but finite Rossby number. However, large deviations from the asymptotically predicted heat transfer scaling are found, with laboratory experi...

The onset of thermal convection in a finite rotating cylinder is investigated using direct numerical simulations of the Navier–Stokes equations with the Boussinesq approximation in a regime in which spatio-temporal complexity is observed directly after onset. The system is examined in the non-physical limit of zero centrifugal force as well as with an experimentally realizable centrifugal force...

We calculate the excitation of low frequency gravity waves by turbulent convection in the sun and the effect of the angular momentum carried by these waves on the rotation profile of the sun’s radiative interior. We find that the gravity waves generated by convection in the sun provide a very efficient means of coupling the rotation in the radiative interior to that of the convection zone. In a...

We summarise recent results form direct numerical simulations of both non-rotating helically forced and rotating convection driven MHD equations in spherical wedge-shape domains. In the former, using perfect-conductor boundary conditions along the latitudinal boundaries we observe oscillations, polarity reversals and equatorward migration of the large-scale magnetic fields. In the latter we obt...

Rolls in finite Prandtl number rotating convection with free-slip top and bottom boundary conditions are shown to be unstable with respect to small angle perturbations for any value of the rotation rate. This instability is driven by the horizontal mean flow whose estimation requires a special singular perturbation analysis. PACS numbers: 47.27.Te, 47.20.Bp, 47.32.-y, 47.20.-Lz

We have used the results of recent smoothed particle hydrodynamic simulations of colliding stars to create models appropriate for input into a stellar evolution code. In evolving these models, we find that little or no surface convec-tion occurs, precluding angular momentum loss via a magnetically-driven stellar wind as a viable mechanism for slowing rapidly rotating blue stragglers which have ...

The three components of the heat-flux vector F = ρCp〈uT 〉 are numerically computed for a stratified rotating turbulent convection using the NIRVANA code in a flat box. The latitudinal component Fθ proves to be negative (positive) in the northern (southern) hemisphere so that the heat always flows towards the poles. As a surprise, the radial heat-flux Fr peaks at the equator rather than at the p...

Most CMIP5 models unrealistically form Antarctic Bottom Water by open ocean deep convection in the Weddell and Ross Seas. To identify the triggering mechanisms leading to Southern Ocean deep convection in models, we perform sensitivity experiments on the ocean model NEMO forced by prescribed atmospheric fluxes. We vary the ver-5 tical velocity scale of the Langmuir turbulence, the fraction of t...