Lagrangian coherent structures and their heat-transport mechanism in the turbulent Rayleigh-Bénard convection

作     者：CHENG Hang SHEN Jie ZHANG YiZhao ZHOU Quan CHONG Kai Leong LIU YuLu LU ZhiMing CHENG Hang;SHEN Jie;ZHANG YiZhao;ZHOU Quan;CHONG Kai Leong;LIU YuLu;LU ZhiMing

作者机构：Shanghai Institute of Applied Mathematics and MechanicsShanghai Key Laboratory of Mechanics in Energy Engineering and School of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China The School of SciencesShanghai Institute of TechnologyShanghai 200072China 

出 版 物：《Science China(Technological Sciences)》 (中国科学（技术科学英文版）)

年 卷 期：2022年第65卷第4期

页      面：966-976页

核心收录：

学科分类：080701[工学-工程热物理] 080704[工学-流体机械及工程] 080103[工学-流体力学] 08[工学] 0807[工学-动力工程及工程热物理] 0801[工学-力学（可授工学、理学学位）] 

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 11732010  92052201  12072185  91952102  12032016) 

主　　题：Rayleigh-Bénard convection finite-time Lyapunov exponent Lagrangian coherent structures 

摘      要：In this paper,we investigate the Lagrangian coherent structures(LCSs)and their heat-transport mechanism in turbulent Rayleigh-Bénard(RB)*** numerical simulations(DNS)are performed in a closed square cell with Rayleigh numbers(Ra)ranging from 10^(6) to 10^(9) and Prandtl(Pr)number fixed at Pr=***,our results show the power-law relationship between Nusselt number(Nu)and Ra,Nu=0.99Ra^(0.30±0.02),confirming the results from previous *** gain insights into the material transport,LCSs are extracted using the finite-time Lyapunov exponent(FTLE)***,lobe structures are widely present,and we elucidate their role in transporting heat from the corner rolls to large-scale ***,the relationships between LCSs and thermal plumes are examined,and we identify two behaviors of thermal plumes:first,most plumes transport along the LCSs;second,few plumes are exposed to the bulk and subsequently mix with the turbulent ***,we quantify the heat flux along the LCSs,which contributes to about 85%of the total flux regardless of *** suggests that LCSs play a significant role in heat ***,the viscous(thermal)dissipation rate along the LCSs is quantified,which is larger than 80%(60%)of the total value,suggesting that LCSs are responsible for the large viscous and thermal dissipations.