DNS Study on Vortex and Vorticity in Late Boundary Layer Transition

Wang, Yiqian; Yang, Yong; Yang, Guang; Liu, Chaoqun

doi:10.4208/cicp.oa-2016-0183

Cited by 61 publications

(15 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In 1989, Robinson [11,12] pointed out that the association between regions of strong vorticity and actual vortices can be rather weak in the turbulent boundary layer, especially in the near wall region. Similar conclusions were obtained by Wang et al [13] a vortex is not necessarily the congregation of vorticity lines, but a dispersion in most three dimensional cases, which means the vorticity in a vortex is not necessarily larger than the surrounding area in many 3D cases.…”

supporting

confidence: 87%

Study on vorticity structures in late flow transition

Dong

Liu

2018

Physics of Fluids

Self Cite

View full text Add to dashboard Cite

Vorticity and vortex are two different but related concepts. This paper focuses on the investigation of vorticity generation and development, and vorticity structure inside/ outside the vortex. Vortex is a region where the vorticity overtakes deformation. Vortex cannot be directly represented by the vorticity. Except for those vorticity lines which come from and end at side boundaries, another type of vorticity, self-closed vorticity lines named vorticity rings, is numerouslygenerated inside the domain during flow transition. These new vorticity rings are found around the hairpin vortex heads and legs. The generation and growth of vorticity rings are produced by the buildup of the vortices according to the vorticity transport equation. On the other hand, vortex buildup is a consequence of vorticity line stretching, tilting and twisting. Both new vorticity and new vortices are generated during the flow transition. According to the Helmholtz vorticity flux conservation law, vorticity line cannot be interrupted, started, or ended inside the flow field, the newly produced vorticity has only one form which is the vorticity rings. In addition, an interesting finding is that a single hairpin vortex consists of several types of vorticity lines which could come from the side boundaries, whole vorticity rings and part of vorticity rings. Nomenclature M∞ = Mach number Rein = Reynolds number δin = inflow displacement thickness ∞  Corresponding author. Email address: cliu@uta.edu xin = distance between leading edge of flat plate and upstream boundary of computational domain Subscript in = inflow w = wall ∞ = free stream

show abstract

supporting

confidence: 87%

Study on vorticity structures in late flow transition

Dong

Liu

2018

Physics of Fluids

Self Cite

View full text Add to dashboard Cite

show abstract

“…Y. Wang et al (2017) found in the direct numerical simulation results that not only the vorticity and the direction of the vorticity were completely separated from the darts, but there was also a region with strong rotation but small vorticity, and the vorticity was large in the non-rotating area.…”

Section: Contact Zhengren Wu Zhengren_wu@163commentioning

confidence: 97%

Analysis of the influence of transverse groove structure on the flow of a flat-plate surface based on Liutex parameters

Yang

Liu

et al. 2021

Engineering Applications of Computational Fluid Mechanics

View full text Add to dashboard Cite

Research on turbulent drag reduction has been limited owing to the limitations of existing parameters used for the identification of vortex structures. As a new and more suitable vortex parameter, Liutex provides a novel research method for turbulence control. We used a channel with a transverse groove structure as the research model and employed large-eddy simulation method based on Liutex to study the influence and mechanism of the transverse groove structure on the watershed. The analysis revealed that the transverse groove structure significantly inhibited the vortex intensity, and this effect diminished with the increase of the normal height. Moreover, the transverse groove structure could maintain the stability of the flow vortex and restrain the hairpin vortex. The fundamental action mechanism of the groove structure pertained to slip condition of the bottom surface along the flow direction, which was essential for conveying the bottom fluid. Furthermore, the transverse groove structure could significantly reduce the overall increase in the vortex intensity in the transition layer, and the fluctuation of the vortex intensity in the logarithmic layer was lower under the action of the groove structure. This case can guide the application of the new vortex identification method in turbulence drag reduction.

show abstract

“…However, Green [6] gave more detailed and different exposition, the early transition constitutes an event where vorticity is abruptly focused and ejected in a concentrated plume out of the surface layer; then it can be described as comprising a reorganization and local concentration of the existing vorticity field in a transition state. There are also other voices, vortex is not necessarily congregation of vorticity lines, but dispersion in most three dimensional cases [7], which means the vorticity in a vortex is not necessarily larger than the surrounding area in 3D cases. [8] defined vortices by using vortex tubes which has been proved to be inaccurate by many researchers [5,[9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…Until now, many researchers track vortex by high concentration of vorticity. That is why some researchers hold the view that the transition is a process with vorticity increase while others believe the total vorticity is constant during the transition process [6,12,13]. So what is the true symbol of vortex generation and growth in the transition from laminar flow to turbulence?…”

Section: Introductionmentioning

confidence: 99%

Correlation analysis on volume vorticity and vortex in late boundary layer transition

2018

Self Cite

View full text Add to dashboard Cite

In this paper, two functions are introduced to describe turbulence generation in late flow transition. One is called the volume Omega Bar (volume Ω), which represents the flow rotation or vortex strength. The other is called the volume vorticity, which shows the flow statistical fluctuations. Although they have very different definitions, one for fluctuation and the other for rotation, volume Ω and volume vorticity are found very highly correlated with a correlation factor greater than 0.9, which means there is a very close relation between flow fluctuation and flow rotation (vortex). While the vorticity flux keeps constant in the late flow transition through the integration over any sections either parallel or perpendicular to the flow direction, the volume Ω is fast increased along the flow direction and fast increased as the time marching during the flow transition process. This means the vortex structure is fast built up and rotation becomes more and more dominant. On the other hand, the total volume vorticity is also quickly increased, which shows the fluctuation is stronger. The flow transition is a process with significant volume vorticity increase, which was contributed by two

show abstract

DNS Study on Vortex and Vorticity in Late Boundary Layer Transition

Cited by 61 publications

References 28 publications

Study on vorticity structures in late flow transition

Study on vorticity structures in late flow transition

Analysis of the influence of transverse groove structure on the flow of a flat-plate surface based on Liutex parameters

Correlation analysis on volume vorticity and vortex in late boundary layer transition

Contact Info

Product

Resources

About