Much effort has been expended in recent decades in addressing the problem of heat transfer in Rayleigh-Bénard (RB) thermal convection cells. There is increasing agreement that in general there are no clean scaling laws for Nu(Ra, Pr) and Re(Ra, Pr), apart from asymptotic cases. One of these asymptotic cases has been doped the ultimate state of thermal convection, i.e. Ra → ∞, where the heat flu...

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...

A numerical investigation of forced convection in a channel with hot solid block inside a square porous block mounted on a bottom wall was carried out. The lattice Boltzmann method was applied for numerical simulations. The fluid flow in the porous media was simulated by Brinkman-Forchheimer model. The effects of parameters such as porosity and thermal conductivity ratio over flow pattern and t...

An asymptotic theory is presented to describe the possible mechanism for the excitation and maintenance of torsional oscillations in rotating convective stars and planets. It is demonstrated analytically that the torsional oscillations can be excited and sustained by global thermal convection. Subject headings: convection — hydrodynamics — stars: interiors

The falling and settling of solid particles in gases and liquids is a natural phenomenon happens in many industrial processes. This phenomenon has altered pure forced convection to a combination of heat conduction and heat convection in a flow over a plate. In this paper, the coupling of conduction (inside the plate) and forced convection of a non-homogeneous nanofluid flow (over a flat plate) ...

Turbulent convection is often present in liquids with a kinematic viscosity much smaller than the diffusivity of the temperature. Here we reveal why these convection flows obey a much stronger level of fluid turbulence than those in which kinematic viscosity and thermal diffusivity are the same; i.e., the Prandtl number Pr is unity. We compare turbulent convection in air at Pr=0.7 and in liquid...

A systematic study of the local convective heat transport in turbulent thermal convection is carried out in small-aspect-ratio cells filled with water. The local convective heat flux is obtained from the simultaneous velocity and temperature measurements over varying Rayleigh numbers and spatial positions across the entire convection cell. Large fluctuations of the local convective heat flux ar...

The influence of inertia and elasticity on the onset and stability of 3-D thermal convection is examined for highly elastic polymeric solutions with constant viscosity. These solutions are known as Boger fluids, and their rheology is approximated by the Oldroyd-B constitutive equation. The onset and the stability of steady convective patterns, namely rolls, hexagons and squares, are studied in ...

A two-dimensional (2D) lattice Boltzmann method (LBM)-cellular automaton model is presented to investigate the dendritic growth of binary alloys in the presence of natural convection. The kinetic-based LBM is adopted to calculate the transport phenomena by the evolution of distribution functions of moving pseudo-particles. To numerically solve natural convection thermal and solute transport sim...

We simulate the effects of an intrinsically dense boundary layer at the base of the mantle on the thermal structure of D and the dynamics of the lower mantle. Using a finite element model of thermo-chemical convection in 2-D with a Rayleigh number of 10, we investigate the dynamic consequences of varying the density and of increasing thermal diffusivity in the basal layer to simulate enrichment...