Soutenance de thèse : Xin ZHENG

Numerical Study on Viscoelastic Rayleigh-Bénard Convection

Doctorant :  Xin ZHENG

Laboratoire INSA : CETHIL

Ecole doctorale : ED162 : Mécanique, Energétique, Génie Civil, Acoustique de Lyon

Polymer additive (viscoelastic) in a liquid will bring enhancement of convective heat transfer and drag reduction effects in thermal convection and channel flow, compared to the Newtonian fluid flow as we know. A direct numerical simulation (DNS) solver of the viscoelastic Rayleigh-Bénard convection (VRBC) in 2D/3D rectangular enclosure cavity bases on finite difference method was developed using Fortran language. The solver considers a quasi-linear treatment to hyperbolic terms of governing equation system to avoid numerical instability at high Weissenberg number. The Phan-Thien-Tanner (PTT) constitutive model was chosen in the thesis as that is a nonlinear model and is more suitable for simulating real viscoelastic fluids. The contents of the thesis can be divided into three parts: (a) we focus on the VRBC in a 2:1 enclosure cavity and introduced a particular regular reverse convection phenomenon in detail. We studied the influence of different rheological parameters of viscoelastic on flow and heat transfer. We have also discovered, for the first time, the second critical Rayleigh number from reversal convection to stable convection. (b) We studied VRBC in the tilt enclosure cavity and checked the influence of the viscosity ratio and the elastic intensity on the convection structure and heat transfer. (c) Numerical study about 3D VRBC has also been started in this paper, a basic introduction was given.