Direct Numerical Simulation On Turbulent Convective Heat Transfer Of Viscoelastic-fluid-based Nanofluids

Nanofluids can dramatically enhance the convective heat transfer but increase flowresistance. On the contrary, viscoelastic fluid has ability of inducing drag reduction andheat transfer reduction in its turbulent flow. We wonder if the combination of nanofuidsand viscoelastic fuid has the characteristics of not only drag reduction but also heattransfer enhancement.Direct numerical simulation of turbulent heat transfer in a channel flow with aGiesekus model have been carried out to investigate turbulent heat transfer mechanismof Newtonian-fluid-based and viscoelastic-fluid-based nanofluids flows. The fluid wasassumed as single phase and temperature was considered as a passive scalar. For thetime advancement, the Adams-Bashforth scheme was used for convective term anddiffusion term and implicit method was employed for the pressure term in the governingequations. Second-order finite difference scheme was adopted for spatial discretization.Stagger grid was used to avoid zigzag pressure field. Pressure and temperaturecomponents located at the center of cell while velocity was stored at cell face.Statistical quantities such as mean and root-mean-square temperature and velocityfluctuations distributions, turbulent heat fluxes and their budget terms distributions,turbulent Prandtl number, drag reduction and Nusselt number were obtained. Comparedto the viscoelastic fluid base flow, the heat transfer enhancement for the viscoelasticfluid based nanofluids was also obtained. The extent of heat transfer enhancementincreased with the increase of volume fraction of nano-particles.