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Using experiment rain attenuation data at different rain rate, the correlation entropy and residue error of the system is obtained by system identification method.


On the basis of correlation entropy and residue error, we can determine the order of the predication system.


Using experiment rain attenuation data at different rain rate, the correlation entropy and residue error of the system is obtained by system identification method.


On the basis of correlation entropy and residue error, we can determine the order of the predication system.




 he time series of instantaneous velocity in the flows are obtained by the hotwire technique and data sampling.Based on the data,power spectra,correlation dimension and correlation entropy along the lateral direction are computed,chaos indicators are analysed and the information of flows along the lateral direction is given.  用热线风速仪和数据采样技术得到混合层中瞬时速度时间序列。计算了给定流向位置处，沿垂直于混合层的方向（横向）上不同点的流速功率谱、相关维数和相关熵；分析了流场的混沌特征；给出了流场横向变化特点。  The free cross mixing layer flow is measured by hot  wire technique. Based on the sampling data, the probability density distribution, correlation dimentsion, correlation entropy are calculated. The results show that there exist threedimension small coherent structures in the flow, these structures form in the location with some distance from exit and have no significant effects on the mixing layer.  本文用X型探头热线风速仪测量了斜向自由剪切层气流场,首次对该流场的测量数据进行能谱、相关维数、相关熵的计算,说明该流场存在三维涡结构,这些结构在距出口一定的位置上形成,具有螺旋状,不存在结构间配对合并等作用,因而剪切层厚度增长较慢。  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... 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 selfexciting 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 selfexciting 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 3.80. It is worth to state that some chaotic autopower spectrums show frequencybandwidth enlarged at basic frequency and its harmonics positions and are similar to those ofvortex shedding of two dimensional cylinder studied by Wei Zhonglei etc. (1991). This kind ofautopower chaotic spectrum implies that dynamical systems of open flow systems maybe containnew routes to chaos.  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．  
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