The chaotic phenomenon of parallel flow transition process in circle pipe which is nearby Critical Reynolds has been studied by numerical simulation. The present work is concentrated on coherent structure character observational explanation in lower Reynolds and critical value form laminar flow to turbulent. Simulated methods of power spectrum, space amplitude, Lyapunov and fractal dimension has been used to qualitative explain and quantitative describe the related structure that induced turbulent bursting. Power spectrum and space amplitude is relied methods to identify chaos( turbulent). The computation of Lyapunov and fractal dimension has based on phase space restructure of time sequence. This paper applied time drag delay construct which is used topology-embedded theory to recur the system dynamic character. It could be concluded that when Re=2657, flow field begin to be instability. Vortex roll as representative quasi-ordering structure appears. When Re=2683, flow field is in transient state. Paroxysm chaos emerges, vortex seldom appears, quasi-ordering structure of flow field is similar to that of flow field in global auto excitation vibration. When Re=2687, flow field is absolutely instable. Helical vortex structure appears. Dynamic system enters into chaos through RTN path. Correspond, flow in physics space transforming from laminar flow to turbulent. When Re=2700, annual and helical vortex structure emerges alone or with coupling form, quasi-ordering structure is diversity. But the system isn't wholly development turbulent. The calculation of fractal and lyapunov exponent shows: when Re is around 2687, parallel flow system appears chaos status, flow in the physical space change from laminar to turbulent; fractal dimension of strange attractors are 2.6.
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