Bioconvection in rotating system immersed in nanofluid with temperature dependent viscosity and thermal conductivity

This paper investigates the bioconvection in rotating system between two rotating plates immersed in a nanofluid with temperature dependent viscosity and thermal conductivity. The passively controlled model is introduced to characterize the nanoparticle concentration on the upper plate. By means of the similarity transformation, the proposed governing equations are reduced to a class of coupled ODEs with boundary conditions and then the numerical solutions are obtained by the Matlab bvp4c ODE solver. Some important characteristics of velocity, temperature, nanoparticle concentration and density of the motile microorganisms are displayed graphically and discussed in detail. Results show that the viscosity variation parameter has remarkable influence on the local skin friction coefficient and Sherwood number, while local Nusselt number and wall motile microorganisms flux are more sensitive to the thermal conductivity variation parameter. Higher bioconvection Peclet number leads to the aggregation of the motile microorganisms in the middle of the two plates. Moreover, the aggregation of motile microorganisms is weakened by the intense Brownian motion, but improved by the thermophoresis effect. (C) 2017 Elsevier Ltd. All rights reserved.