Research On Rayleigh-Benard Convection Pattern In Binary Fluid Mixtures By Numerical Simuation

Thermal convection is a common phenomenon occurring in nature and in many engineering applications.Rayleigh-Benard convection,which is one of the typical models for the research of these phenomena,is that,in one close channel,the top surface keeps steady temperature and the bottom keeps heated,the difference temperature will cause the fluid convection in the channel.It is also one of typical models for investigating the stability, spatio-temporal structure and nonlinear dynamics of convection,because Rayleigh-Benard convection experiment is easy to control and the equation for this system is clear.More and more research has concentrated in Rayleigh-Benard convection pattern in binary fluid mixtures since 1980's,which has revealed that it implicats rich spatio-temproal pattern formations.With the rapid development of computer technology,there are new progresses in the numerical simulation of Rayleigh-Beuard convection.In this thesis,our main interest focuses on simulateing flow,temperature and concentration field of the binary fluid mixture in long and narrow cells by solving the basic equations of fluid mechanics,and investigating pattern formations and nonlinear characteristics.Author mainly simulates bifurcation diagramcoms and gains many interesting convection patterns along these curves,including the localized traveling wave state with defect,the traveling wave state with two defects and counter propagating wave state with defect source immobilizing which have not been seen before,in the rectangular cellΓ=12 andΓ=20 for separation ratioψ=-0.6,-0.4 and -0.2.The thesis describes convection characteristic and pattern form of these especial traveling waves in detail,studies the ranges,the spatiotemporal structures,and the stability of all the traveling wave states,and tries to gain the mechanism of localized traveling wave state by calculating the mean concentration current in this state.At the end,Author summarizes the dependence of the convection pattern appearancance and its characteristics on the different aspect ratio and separation ratio,expecting to offer the theoretical basis and experiences for the future research of Rayleigh-Benard convection.