热射流拟序结构中混沌现象的实验研究  

THE EXPERIMENTAL STUDY OF THE CHAOTIC PHENOMENA OF HEATED JETS

作　　者：周慧良[1] 卢志明[2] 任逍涛 谢锡麟[1] 

机构地区：[1]复旦大学力学与工程科学系,上海200433 [2]上海大学上海市应用数学和力学研究所,上海200072

出　　处：《力学学报》1999年第5期603-610,共8页Chinese Journal of Theoretical and Applied Mechanics

摘　　要：就开放流体系统中的热射流拟序结构的混沌现象进行了实验研究．发现流场在绝对不稳定情况（S＜0.72）下，环涡模式控制了整个流场．此时相空间中对应的动力系统发生倍周期和Hopf分岔，说明动力系统可通过Feigenbaum和RTN途径进入混沌．相关维、相关熵和Lyapunov指数的计算表明：在一定Re数下，动力系统的时间渐近行为已呈混沌态，表现为奇异吸引子，相关维数D2约为3．80．The chaotic phenomena of the coherent structure in the open flow system of heated jetshave been studied by experiments. The present work is concentrated on the relationship betweentypes of the coherent structure in the physical space and asymptotic behaviors of the dynamicalsystem in the phase space.When S = 1 (cold jet), convective instability is everywhere in the flow field. Axisymmetricand belieal modes are the prevailing types of the coherent structure of the jets with two differentnozzle diameters.When S = 0.76, the flow field is in the transition status. In this circumstance, the coherentstructure is similar to that when the flow field is in global self-exciting status. According tochaos calculations, the strange attractors relating to axisymmetric and helical modes respectivelyhave different values and the latter are great than the former, but the values of different types ofaxiymmetric modes are approximately equal. It is need to point out that we calculate D2 relatingto belieal mode when S = 0.76 because of the limitation of our experiment facility, but accordingto stability analysis that belieal modes become absolute instability only when S≤ 0.35 so that itis worth and also need to further study.When S = 0.67, 0.60, the potential region of jets becomes absolute instability and the flowfield in global self-exciting status which is insensitive to external small amplitude disturbances.Only axisymmetric modes exist in all instances and belieal modes are completely inhibited. In aReceived 11 November 1997, revised 4 September 1998.certain range of Re number, the dynamical system in the phase space evolves into chaos statusand the flow field in the physical space correspondingly transits from laminar flow to 'turbulenceflow'--chaotic flow though Feigenbaum or RTN route. The calculations of correlation dimension, correlation entropy and Lyapunov exponent indicate that the asymptotic behaviors of thedynamical system are chaotic and the values of correlation dimension of strange attractors are thesame about 3.

关 键 词：热射流 拟序结构 动力系统 吸引子 混沌定量计算 

分 类 号：O358[理学—流体力学]