Eur. Phys. J. Spec. Top. (2021) 230: 1415-1425
https://doi.org/10.1140/epjs/s11734-021-00036-w

Regular Article

Individual effects of sinusoidal and non-sinusoidal gravity modulation on Rayleigh-Bénard convection in a ferromagnetic liquid and in a nanoliquid with couple stress

Department of Mathematics, CHRIST (Deemed to be University), Bangalore, India

^a meghana.j@res.christuniversity.in

Received: 30 October 2020
Accepted: 31 January 2021
Published online: 6 May 2021

Abstract

The effects of sinusoidal (sine wave) and non-sinusoidal (square wave, triangular wave, and sawtooth wave) forms of gravity modulation on Rayleigh-Bénard Convection (RBC) in a ferromagnetic liquid and a nanoliquid with couple stress is examined using linear and non-linear stability analyses. From the linear analysis, the stability of the system is investigated by calculating the correction Rayleigh number using the Venezian method. The heat transfer coefficient is obtained by solving the non-autonomous Lorenz equation. T he influence of various non-dimensional parameters on the onset of convection and heat transfer is analyzed. It is observed that the couple stress parameter stabilizes the system and decreases the heat transfer. It is found that the square type of gravity modulation facilitates more heat transport compared to other types of gravity modulation. The ferromagnetic parameters are shown to have their known influence on the onset of convection and heat transport. The results of the single-phase ferromagnetic nanoliquid with couple stress are extracted from the results of the ferromagnetic liquid with couple stress. Advancement of onset due to nanoparticle presence and thereby enhanced heat transfer is discussed. The higher concentration of alumina is shown to be preferable to the rather expensive copper nanoparticles in obtaining the same quantity of heat transfer.