Transient Analysis of Third-Grade Viscoelastic Nanofluid Flow External to a Heated Cylinder with Buoyancy Effects

Abstract

Nanotechnology is rapidly embracing numerous areas of manufacturing and process engineering. New types of nanomaterials are being exploited to improve, for example, coating integrity, anti-corrosion characteristics and other features of fabricated components. Motivated by these developments, in the current study a mathematical model is developed for unsteady free-convective laminar flow of third-grade viscoelastic fluid (doped with nanoparticles) from a semi-infinite vertical isothermal cylinder, as a model of thermal coating flow of a pipe geometry. Non-Newtonian behavior is simulated with the thermodynamically robust third-grade Reiner–Rivlin model which accurately represents polymer fluids. Nanoscale effects are analyzed with the Buongiorno two-component nanofluid model. The governing equations comprise a set of highly coupled, nonlinear, multi-degree partial differential equations featuring viscoelastic and nanofluid parameters. An implicit Crank–Nicolson numerical scheme is implemented to solve the emerging nonlinear problem with appropriate initial and boundary conditions. Detailed graphical plots for velocity, temperature and nanoparticle volume fraction are presented for a range of different parameters (i.e., third-grade fluid parameter, Brownian motion parameter, thermophoretic parameter, buoyancy ratio parameter, Lewis number). Additionally, distributions of the heat transfer coefficient, skin friction and Sherwood number at the cylinder surface are visualized. Furthermore, streamlines, isotherms and nanoparticle volume fraction contour plots are included for variation of the third-grade parameter. Contour plots for the third-grade nanofluid flow are found to deviate significantly from those corresponding to Newtonian nanofluids. Validation of the numerical solutions with earlier studies is also included.