Linear variations in conductivity and viscosity as particles’ basic profile for convective instability in nanofluids under various boundary conditions

Abstract

The present study investigates thermal sensitivity of a horizontal nanofluid layer which is subjected to conductivity and viscosity variations as linear functions of volume fraction of particles. A weak heterogeneous characteristic of the fluid is considered i.e. variations freeze as the basic profile of particles in the system. Further, the study undertakes various boundary conditions on the layer to analyse the convection process such as zero particle flux, equal, top and bottom heavy distribution of volume fraction of particles. The expression of Rayleigh number for nanofluid is found to be increased significantly due to conductivity and viscosity variation effects and has negligible impact in decreasing/increasing its value due to other nanofluid variables. Thus, a substantial enhancement in the stability of the system is established except for zero flux case where overall effects due to the presence of particles become almost negligible. The properties of base fluid and particles show conflicting roles in deciding the thermal sensitivity of the layer.