on the onset of triple-diffusive convection in a horizontal layer of nanofluid heated from below and salted from above and below is studied both analytically and numerically. the effects of thermophoresis and brownian diffusion parameters are also introduced through buongiorno model in the governing equations. by using linear stability analysis based on perturbation theory and applying normal m...

Well-resolved direct numerical simulations of 2D Rayleigh-Bénard convection in a porous medium are presented for Rayleigh numbers Ra≤4×10(4) which reveal that, contrary to previous indications, the linear classical scaling for the Nusselt number, Nu~Ra, is attained asymptotically. The flow dynamics are analyzed, and the interior of the vigorously convecting system is shown to be increasingly we...

We investigate the effect of weak rotation on the large-scale circulation (LSC) of turbulent Rayleigh-Bénard convection, using the theory for cessations in a low-dimensional stochastic model of the flow previously studied. We determine the cessation frequency of the LSC as a function of rotation, and calculate the statistics of the amplitude and azimuthal velocity fluctuations of the LSC as a f...

[1] We derive a scaling law for the onset of convection in an incompressible fluid cooled from above with temperatureand depth-dependent viscosity, on the basis of 2-D numerical simulation. Rayleigh numbers up to 10 are considered. The activation energy is varied from 0 to 200 kJ mol , and a variation of up to 10 is considered in depth-dependent reference viscosity. Our scaling law is shown to ...

A lattice Boltzmann model is developed by coupling the density (D2Q9) and the temperature distribution functions with 9-speed to simulate the convection heat transfer utilizing Al2O3-water nanofluids in a square cavity. This model is validated by comparing numerical simulation and experimental results over a wide range of Rayleigh numbers. Numerical results show a satisfactory agreement between...

a lattice boltzmann method is applied to demonstrate the comparison results of simulating natural convection in an open end cavity using different hydrodynamic and thermal boundary conditions. the prandtl number in the present simulation is 0.71, rayleigh numbers are 104,105 and 106 and viscosities are selected 0.02 and 0.05. on-grid bounce-back method with first-order accuracy and non-slip met...

The mixing of pollutions and sediments in near shore regions of natural water bodies depends heavily on the characteristics such as the strength and frequency of flow instability. In the present paper, the instability of natural convection induced by absorption of solar radiation in littoral regions is considered. Spectral analysis is conducted on the quasi-steady state flow to reveal the power...

High resolution computer simulations of two-dimensional convection using the anelastic approximation are presented. These calculations span Rayleigh numbers from 10(8)-10(12) for Prandtl number equal to unity, with the fluid density decreasing by a factor of 12 from the bottom to the top of the convection region. This range covers several decades in the "hard" turbulent regime. While many studi...

Convection in a colloidal suspension with a large negative separation ratio psi is studied experimentally by heating from above. Shadowgraph observations at very large solutal Rayleigh numbers Rtilde; are reported as a function of time. Fast relaxation oscillations are reported for the root mean square value of the shadowgraph intensity. While pure fluids exhibit a transition to turbulent conve...

Thermal convection in a fluid layer confined between two horizontal rigid boundaries has been studied with the help of the Floquet theory. The temperature distribution consists of a steady part and an oscillatory time-dependent part. Disturbances are assumed to be infinitesimal. Numerical results for the critical Rayleigh numbers and wave numbers are obtained. It is found that the disturbances ...