MHD Nanofluid Bioconvection over an Exponentially Stretching Sheet in the Presence of Gyrotactic Microorganisms and Thermal Radiation

摘要

Abstract In this paper, we have analyzed the effects of thermal radiation on heat transfer of water-based nanofluid containing motile gyrotactic microorganisms over an exponentially stretching sheet. The nanofluid bioconvection is due to the combined effects of magnetic field and buoyancy force on the interaction of motile gyrotactic microorganisms and nanoparticles in the base fluid. In order to stabilize the nanoparticles to suspend, microorganisms are imposed into the nanofluid. The governing partial differential equations are converted into a system of nonlinear ordinary differential equations by the use of similarity transformations which are then solved numerically using fifth order Runge-Kutta-Fehlberg integration scheme with shooting technique. Present results are compared with the previously published results in some limiting cases and the results are found to be in an excellent agreement. The effects of various thermophysical parameters and bioconvection parameters on nanofluid velocity, temperature, nanoparticles concentration, density of motile microorganisms, as well as on the local skin friction coefficient, local Nusselt number, and local Sherwood number are described in detail. It is found that the Lewis number tends to decelerate the concentration distributions of motile microorganisms in the presence of the magnetic field and thermal radiation. Also, it is observed that the effects of increase in the buoyancy ratio parameter and bioconvection Rayleigh number are to increase the nanoparticle concentration and the density of motile microorganisms.