有速度切变时,Lorenz系统中浑沌的特点
CHARACTERIZATION OF CHAOS OF THE LORENZ SYSTEM WITH VELOCITY SHEAR
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摘要: Lorenz方程中引进切变以后,对普朗特数为0.7的大气可以出现浑沌。速度切变在一定情况下起阻尼作用,有切变时比无切变时湍流发生的临界莱雷数要高。浑沌是一种非周期的现象,它在相空间中的轨迹是混乱的。通向湍流的道路有很多种。切变较小时为普通湍流形态;切变较大时是间歇湍流形态;切变适中时为短暂层流状态。有速度切变时的浑沌对大气湍流的研究有很大的实际意义。Abstract: The chaos motions may appear when the velocity shear damper is add into the Lorenz equation for the Prandtl number a=0.7. The critical Rayleigh number with velocity shear is larger than that without velocity shear. The chaos is aperiodic phenomena. The tra jectary of chaos motions is irregular in phase space. Roads to turbulence have many different kinds. The behaviour is general turbulence when shear is small. The behaviour is intermittent turbulence when shear is large. The behaviour is transient laminar when shear is moderate. The research of chaos motions with velocity shear is of significance for understanding atmospheric turbulence.
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