Late-Stage Transitional Boundary-Layer Structures. Direct Numerical Simulation and Experiment

Бородулин, В. И.; Gaponenko, V. R.; Kachanov, Y. S.; Meyer, D. G. W.; Rist, Ulrich; Qi, Lian; Lee, C.B.

doi:10.1007/s001620100054

Cited by 85 publications

(43 citation statements)

References 44 publications

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“…Although we cannot compare our DNS results with those given by Borodulin et al [4] quantitatively, we still can find that the shear layer structure are very similar in two DNS computations in Figure 9.…”

Section: Comparison With Other Dnscontrasting

confidence: 66%

“…After over a hundred years of study on flow transition, the linear and weakly non-linear stages of flow transition are pretty well understood [10,11]. However, for late non-linear transition stages, there are still many questions remaining for research [4,[12][13][14][15][16]. Adrian [17] described hairpin vortex organization in wall turbulence, but did not discuss the sweep and ejection events and the role of the shear layer instability.…”

Section: A Short Review Of Study On Late Boundary Layermentioning

confidence: 99%

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New Theories on Boundary Layer Transition and Turbulence Formation

Liu

Lü

Chen

et al. 2012

Modelling and Simulation in Engineering

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This paper is a short review of our recent DNS work on physics of late boundary layer transition and turbulence. Based on our DNS observation, we propose a new theory on boundary layer transition, which has five steps, that is, receptivity, linear instability, large vortex structure formation, small length scale generation, loss of symmetry and randomization to turbulence. For turbulence generation and sustenance, the classical theory, described with Richardson's energy cascade and Kolmogorov length scale, is not observed by our DNS. We proposed a new theory on turbulence generation that all small length scales are generated by "shear layer instability" through multiple level ejections and sweeps and consequent multiple level positive and negative spikes, but not by "vortex breakdown." We believe "shear layer instability" is the "mother of turbulence." The energy transferring from large vortices to small vortices is carried out by multiple level sweeps, but does not follow Kolmogorov's theory that large vortices pass energy to small ones through vortex stretch and breakdown. The loss of symmetry starts from the second level ring cycle in the middle of the flow field and spreads to the bottom of the boundary layer and then the whole flow field.

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Section: Comparison With Other Dnscontrasting

confidence: 66%

Section: A Short Review Of Study On Late Boundary Layermentioning

confidence: 99%

New Theories on Boundary Layer Transition and Turbulence Formation

Liu

Lü

Chen

et al. 2012

Modelling and Simulation in Engineering

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“…Crow theory [8] has been considered as the mechanism of multiple ring formation [2]. They pointed out that "the formation of a set of vortex rings from two counter-rotating vortices is usually called "Crow instability."…”

Section: Multiple Ring Formationmentioning

confidence: 99%

“…It is believed that the velocity in normal direction is almost zero in the inviscid zone and the ring stands almost perpendicularly. [8] has been considered as the mechanism of multiple ring formation [2]. Figure 13 shows a typical vortex chain formation by Crow theory.…”

Section: Mechanism Of First Ring Formationmentioning

confidence: 99%

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New Findings by High‐Order DNS for Late Flow Transition in a Boundary Layer

Liu

Lin

Lü

2011

Modelling and Simulation in Engineering

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This paper serves as a summary of new discoveries by DNS for late stages of flow transition in a boundary layer. The widely spread concept "vortex breakdown" is found theoretically impossible and never happened in practice. The ring-like vortex is found the only form existing inside the flow field. The ring-like vortex formation is the result of the interaction between two pairs of counterrotating primary and secondary streamwise vortices. Following the first Helmholtz vortex conservation law, the primary vortex tube rolls up and is stretched due to the velocity gradient. In order to maintain vorticity conservation, a bridge must be formed to link two Λ-vortex legs. The bridge finally develops as a new ring. This process keeps going on to form a multiple ring structure. The U-shaped vortices are not new but existing coherent vortex structure. Actually, the U-shaped vortex, which is a third level vortex, serves as a second neck to supply vorticity to the multiple rings. The small vortices can be found on the bottom of the boundary layer near the wall surface. It is believed that the small vortices, and thus turbulence, are generated by the interaction of positive spikes and other higher level vortices with the solid wall. The mechanism of formation of secondary vortex, second sweep, positive spike, high shear distribution, downdraft and updraft motion, and multiple ring-circle overlapping is also investigated.

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Structure Formation in Marginally Separated Aerodynamic and Related Boundary Layer Flows

Kluwick

Braun

2006

Solid Mechanics and Its Applications

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Late-Stage Transitional Boundary-Layer Structures. Direct Numerical Simulation and Experiment

Cited by 85 publications

References 44 publications

New Theories on Boundary Layer Transition and Turbulence Formation

New Theories on Boundary Layer Transition and Turbulence Formation

New Findings by High‐Order DNS for Late Flow Transition in a Boundary Layer

Structure Formation in Marginally Separated Aerodynamic and Related Boundary Layer Flows

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