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Double-diffusive and vibrational convection with the Soret effect is considered in a cubic rigid cell filled with water ͑90%͒ and isopropanol ͑10%͒, subjected to a temperature difference between opposite lateral walls. Numerical simulations are carried out for g-jitter induced flow. The direction of g-jitter is the same as the residual gravity vector, which is perpendicular to the applied temperature gradient. Along with various combinations of static and oscillatory components, vibrations with two different frequencies are examined: ͑a͒ when the period of oscillations is smaller than any characteristic time ͑viscous, thermal, and diffusion͒, f = 0.2 Hz; ͑b͒ when the period of oscillations is comparable with viscous time, f = 0.01 Hz. Component separation due to the Soret effect under these driving actions is analyzed. The concept of time-averaged models is applied for the explanation of the high-frequency results. The interplay between the mean and fluctuating motions is discussed. Three research groups performed a benchmark of numerical solutions of three-dimensional Navier-Stokes, energy, and concentration equations using the true physical parameters for a future Space experiment. The objective of this paper is twofold: ͑i͒ to carry out an accurate study of heat and mass transfer in a binary liquid with the Soret effect in the presence of steady residual gravity and its oscillatory component; ͑ii͒ to carry out a benchmark of numerical solutions.

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Purpose This paper aims to investigate numerically the free convective heat transfer efficiency inside a rectotrapezoidal enclosure filled with Al2O3–Cu/water hybrid fluid. The bottom wall of the cavity is uniformly heated, the upper horizontal wall is insulated, and the remaining walls are considered cold. A new thermophysical relation determining the thermal conductivity of the hybrid nanofluid has been established, which produced results those match with experimental ones. Design/methodology/approach The governing partial differential equations are solved using the finite element method of Galerkin type. The simulated results in terms of streamlines, heat lines and isotherms are displayed for various values of the model parameters, which govern the flow. Findings The Nusselt number, friction factor and the thermal efficiency index are also determined for the pertinent parameters varying different ratios of the hybrid nanoparticles. The simulated results showed that thermal buoyancy significantly controls the heat transfer, friction factor and thermal efficiency index. The highest thermal efficiency is obtained for the lowest Rayleigh number. Practical implications This theoretical study is significantly relevant to the applications of the hybrid nanofluids electronic devices cooled by fans, manufacturing process, renewable energies, nuclear reactors, electronic cooling, lubrication, refrigeration, combustion, medicine, thermal storage, etc. Originality/value The results showed that nanoparticle loading intensified the rate of heat transfer and thermal efficiency index at the expense of the higher friction factor or higher pumping power. The results further show that the heat transmission in Al2O3–Cu/water hybrid nanofluid at a fixed value of intensified $\phi_{hnf}$ compared to the Al2O3/water nanofluid when an amount of higher conductivity nanoparticles (Cu) added to it. Besides, the rate of heat transfer in Cu/water nanofluid declines when the lower thermal conductivity Al2O3 nanoparticles are added to the mixture.

This paper describes the measurement of the Soret coefficient of a hydrocarbon binary liquid mixture at different orientations to the gravity vector. The working fluid in the experiment was composed of 1,2,3,4‐tetrahydronaphtalene (THN) and dodecane (C12) at mass fractions of 0.50/0.50 and a temperature of 298.15 K. The experimental technique used in this study was an optical digital interferometry method using a Mach‐Zehnder Interferometer. A fast Fourier transform method was used for image processing. The experimental approach was supplemented with a numerical solution using the finite volume method. Experimental and numerical results both confirmed that cell inclination during the thermodiffusion process had a tremendous effect on the measurement of the Soret coefficient.