Gravitational settling effect of nanoparticles on the onset of thermal convection in a rotating nanofluid layer
Journal
Mechanics Research Communications
Journal Volume
149
Start Page
104543
ISSN
00936413
Date Issued
2025-10
Author(s)
Abstract
This study investigates the stability of a rotating horizontal nanofluid layer confined between two rigid plates and uniformly heated from below. The mechanism of gravitational settling of nanoparticles is incorporated into the convective transport model to describe the relative slip motion of nanoparticles within the base fluid in addition to the effects of thermophoresis and Brownian motion. Aqueous aluminum oxide nanofluids with three representative nanoparticle diameters: 20, 40, and 60 nm, are examined to evaluate the influence of gravitational settling on instability behavior. A linear stability analysis is performed and the results reveal that rotation acts as a stabilizing mechanism. However, this stabilizing effect diminishes gradually with increasing nanoparticle volume fraction. Enhanced gravitational settling effect promotes the flow stability significantly, and its interplay with thermophoresis induces the onset of oscillatory mode at low Taylor number (Ta) condition. As Ta increases, the oscillatory mode is progressively suppressed and the onset of instability is eventually governed by the stationary mode with a higher critical wavenumber. Particularly, once the size of nanoparticles is large enough, a bimodal neutral curve is observed and the critical mode may shift from stationary to oscillatory mode with increasing the volume fraction of nanoparticles. These findings demonstrate that the instability characteristics in a rotating nanofluid layer deviate significantly from those observed in a classical rotating fluid layer, and reveal the pivotal role of gravitational settling in the nature and threshold of thermally driven instability in this flow system.
Subjects
Gravitational settling
Nanofluid
Rotation effect
Thermal instability
Publisher
Elsevier Ltd
Type
journal article