Unsteady flow over an expanding cylinder in a nanofluid containing gyrotactic microorganisms

In this paper, an analysis is made for the unsteady flow due to an expanding cylinder in a nanofluid which contains both nanoparticles and gyrotactic microoganisms with suction. The nonlinear system of partial differential equations is transformed to high order non-linear and ordinary differential equations by similarity transformations and then solved numerically using a shooting method with fourth-fifth-order Runge-Kutta integration technique. Besides, the influences of significant physical parameters on the distributions of the velocity, temperature, nanoparticle volume fraction, as well as the density of motile microorganisms are graphically presented and discussed in detail. It is found that dual solutions exist for both stretching and shrinking cases and the range of dual solutions increases with the strength of the expansion. The results also indicate that larger bioconvection Peclet number and smaller Schmidt number lead to higher the concentrate of microorganisms and thicker boundary layer thickness.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author