We report a transition from a curved texture to an angular texture in Rayleigh-B enard convection in a mixture of ethanol and water. The transition occurs as the Rayleigh number is reduced from a high value and approaches the traveling-wave branch and is observed at negative values of the separation ratio in uid mixtures, but not in a pure uid. We show that this transition may be understood in ...

Very large eddy simulations of high-aspect-ratio unbounded Rayleigh-Bénard convection for Pr=0.71 over a 10-decade range of Rayleigh numbers (Ra=10(5)-10(15)) reveal a consolidation and dramatic thinning of the wall boundary layer with an increase in the Ra number. The fingerlike plumes between planform structures become also thinner, more distant, but much more vigorous. The Ra exponent in the...

Experimental and numerical data for the heat transfer as a function of the Rayleigh, Prandtl, and Rossby numbers in turbulent rotating Rayleigh-Bénard convection are presented. For relatively small Ra approximately 10(8) and large Pr modest rotation can enhance the heat transfer by up to 30%. At larger Ra there is less heat-transfer enhancement, and at small Pr less, similar 0.7 there is no hea...

The linear stability theory of Taylor-Couette flows (unbounded in z) is described including magnetic fields, Hall effect or a density stratification in order to prepare laboratory experiments to probe the stability of differential rotation in astrophysics. If an axial field is present then the magnetorotational instability (MRI) is investigated also for small magnetic Prandtl numbers. For rotat...

This paper illustrates the phenomenon of the critical speed in the range 100300 km/h. A real explanation and a precise calculation of the critical speed seems to rest an unresolved problem in many cases. Some authors, analogous to “Mach effect”, have attributed this phenomenon to the reaching the Rayleigh wave speed of substructure by trains. But this explanation can’t be thorough in many cases...

We consider a horizontal fluid layer between two rigid boundaries, maintained in a stationary thermal nonequilibrium state below the convective Rayleigh-Bénard instability. We derive an explicit expression for the nonequilibrium structure factor in a first-order Galerkin approximation valid for negative and positive Rayleigh numbers R up to the critical Rayleigh number R(c) associated with the ...

A numerical study of the onset of convection in rotating, internally heated, selfgravitating fluid spheres is presented. The exploration of the stability of the conduction state versus the Taylor and the Prandtl numbers supplies a detailed idea of the laws that fulfil the four types of solutions obtained at low Prandtl numbers. The main result found is that axisymmetric (torsional) modes of con...

We analyze low field hysteresis close to the demagnetized state in disordered ferromagnets using the zero temperature random-field Ising model. We solve the demagnetization process exactly in one dimension and derive the Rayleigh law of hysteresis. The initial susceptibility a and the hysteretic coefficient b display a peak as a function of the disorder width. This behavior is confirmed by nume...

Horizontal convection in a rectangular enclosure driven by a linear temperature profile along the bottom boundary is investigated numerically using a high-resolution spectralelement discretization in space and a third-order time integration scheme for velocity and temperature fields. A Boussinesq approximation is employed to model buoyancy. The emphasis of this study is on the scaling of Nussel...

Utilizing the Boussinesq approximation, a double-population incompressible thermal lattice Boltzmann method (LBM) for forced and natural convection in two and three space dimensions is developed and validated. A block-structured dynamic adaptive mesh refinement (AMR) procedure tailored for the LBM is applied to enable computationally efficient simulations of moderate to high Rayleigh number flo...