Computational Analysis of the Dynamics of Generalized-Viscoelastic-Fluid-Based Nanofluids Subject to Exothermic-Reaction in Shear-Flow

Abstract

A novel problem that describes laminar simple shear-flow of generalized-viscoelastic-fluid-based nanofluids (GVFBN) containing spherical shaped nano-particles under non-isothermal conditions but with isothermal walltemperature boundary-conditions is investigated. The GVFBN model is an extension of the VFBN to include shear-rate dependent viscosity effects. The Generalized non-isothermal Giesekus constitutive model (which is reducible to generalized Oldroyd-B model) with essential modifications for thermodynamics is used to account for the viscoelastic effects. Spherical shaped nano-particles are homogeneously mixed to the viscoelastic base fluid. To characterize the shear-thinning-viscosity, a viscosity-constitutive-model of the Carreau-type is employed. A temperature-dependent thermal conductivity is also considered. Additionally, empirical models are employed to account for to the nano-particle effects on the thermal conductivity. We use an efficient, semi-implicit, numerical scheme, based on finite difference methods (FDM), to obtain the numerical solutions of the model equations. The numerical scheme is computationally implemented in MATLAB. Results are graphically presented in both a qualitative and quantitative sense with regards to the various embedded parameters. Specifically, the thermodynamic and fluid-dynamical impacts of variations in the volume fraction of nano-particles are explored. In summary, we notice enhanced thermal conductivity and hence also increased temperature with increasing nano-particle volume fraction. The GVFBN model accounts for all four nanofluid types, Generalized-Newtonian-fluid-based nanofluids (GNFBN), Newtonian-fluid-based nanofluids (NFBN), Generalized-viscoelastic-fluid-based nanofluids (GNFBN), and viscoelastic-fluid-based nanofluids (VFBN). The comparative thermal runaway susceptibility of the four nanofluid types is presented and we demonstrate that the order of susceptibility from the most to the least susceptible is GNFBN, NFBN, GVFBN, VFBN.