格子Boltzmann方法分析加热尺寸和瑞利数对可变形开口腔内自然对流的影响  

Influence of Heating Size and Rayleigh Number on Natural Convection in a Deformable Open Cavity:Lattice Boltzmann Method

作　　者：唐古月 娄钦[1] 李凌[1] TANG Guyue;LOU Qin;LI Ling(School of Energy and Power Engineering,University of Shanghai for Science and Techonlogy,Shanghai 200093,China)

机构地区：[1]上海理工大学能源与动力工程学院,上海200093

出　　处：《计算物理》2020年第3期263-276,共14页Chinese Journal of Computational Physics

基　　金：国家自然科学基金(51476102,51736007)资助项目。

摘　　要：采用格子Boltzmann方法对可变形腔体内自然对流问题进行数值研究,给出平均努赛尔数的经验关系式.腔体左壁加热长度分为左壁面的整个区域(H)和左壁面的中间区域(0.5H)两种情况,右壁向外界环境开放,上下边界绝热且可以上下移动,以此调节右出口尺寸.主要研究瑞利数(10^4≤Ra≤10^6),右出口尺寸(1.0H≤L≤2.0H),左壁加热尺寸(Lh=0.5H或Lh=H)对腔体内等温线、流线、局部努塞尔数和平均努赛尔数的影响.结果表明:腔体内换热随着瑞利数的增大越来越强烈,表现为椭圆形准静止区域更加靠近上绝热壁,且热分层厚度逐渐变小,平均努赛尔数增加.而右出口尺寸的增加,对于两种加热尺寸下腔内的换热效果有不同程度影响,其中与加热尺寸为左壁面的全部区域Lh=H相比,加热尺寸为左壁面的中间情况Lh=0.5H时,右侧开口尺寸的增加对换热效果的影响不显著.此外,左壁加热尺寸为0.5H时显示出比加热尺寸为H时更高的平均传热效率.最后,针对不同的加热尺寸,提出加热面平均努赛尔数与Ra数及右壁面开口尺寸L^∗之间函数关系的经验预测,拟合效果满足工程实践与设计需要.Natural convection problem in a deformable outlet cavity is studied with lattice Boltzmann method.Heated size at left wall are set to two conditions:The whole wall(H)and the middle wall(0.5H).The right wall is open to external environment.The upper and lower boundaries are adiabatic and their right end can be moved up and down to adjust size of the right outlet.Effects of Rayleigh number(10^4≤Ra≤10^6),the right exit size(1.0H≤L≤2.0H),the left wall heating size(Lh=0.5H or Lh=H)on streamlines,isothermal lines,local Nusselt numbers and average Nusselt numbers are investigated.It shows that heat transfer in the cavity increases with the increase of Rayleigh number,which manifests as size of elliptical quasi-stationary region in the cavity increases and is closer to the upper and lower adiabatic boundaries.Thickness of thermal stratification is gradually reduced and average Nusselt number is increased.However,increase of the right outlet has a different degree of influence on heat transfer effect in the cavity.As the heating size is in the middle of the left wall surface,size of the right side opening does not significantly affect the heat exchange.In addition,at the left wall heating size of 0.5H it shows a higher average heat transfer efficiency.An empirical prediction of functional relation between average Nusselt number and control parameters is proposed.The fitting function satisfies practice and design in projects.

关 键 词：格子BOLTZMANN方法 自然对流 加热腔体 瑞利数 努赛尔数 

分 类 号：TK124[动力工程及工程热物理—工程热物理]