Nature of sweep and ejection events in transitional and turbulent boundary layers

Guo, Hao; Бородулин, В. И.; Kachanov, Y. S.; Pan, Chong; Wang, J. J.; Qi, Lian; Wang, S. F.

doi:10.1080/14685248.2010.498425

Cited by 49 publications

(46 citation statements)

References 33 publications

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“…Being different from Guo et el. [19], the Ushaped vortex is not a wave and is not induced by second sweeps and positive spikes. Actually, the U-shaped vortex is a tertiary (not secondary) vortex with same vorticity sign as the original ring legs (Figures 19 and 20).…”

Section: Observation and Analysis Done By Our Dnsmentioning

confidence: 94%

“…The important mechanism of boundary layer transition such as sweeps, ejections, and positive spikes cannot be found from that paper. Recently, Guo et al [19] conducted an experimental study for late boundary layer transition in more details. They concluded that the U-shaped vortex is a barrel-shaped head wave, secondary vortex, and is induced by second sweeps and positive spikes.…”

Section: A Short Review Of Study On Late Boundary Layermentioning

confidence: 99%

“…Figure 12(a) [19] represents an experimental investigation of the vortex structure including ring-like vortex and barrel-shaped head (U-shaped vortex). The vortex structures of the nonlinear evolution of T-S waves in the transition process are given by DNS in Figure 12(b).…”

Section: U-shaped Vortex In Comparison With Experimentalmentioning

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: Observation and Analysis Done By Our Dnsmentioning

confidence: 94%

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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“…(15) requiring that continuity (for the face velocities which are obtained by linear interpolation) should be satisfied on level n + 1, i.e., ∂u…”

Section: Direct Numerical Simulationsmentioning

confidence: 99%

“…Also in these studies vortex structures and streak formations are related. Horseshoe vortices which generate ring-like vortices are responsible for the appearance of streamwiseelongated streaks [15]. Kim [23] showed that the near-wall streamwise vortices are the single most important turbulent structure when studying drag reduction.…”

Section: Introductionmentioning

confidence: 99%

Direct numerical simulation analysis of spanwise oscillating Lorentz force in turbulent channel flow at low Reynolds number

Altıntaş

Davidson

2016

Acta Mech

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Direct numerical simulations of a turbulent channel flow at low Reynolds number (Re τ = 180, based on the driving pressure gradient and channel half width) are performed. Some results are also presented for Re τ = 400. In this work we apply an idealized spanwise Lorentz force near the lower wall of the channel and compare the results for the applied force and no-force cases in both the upper half and the lower half of the channel. We have studied two-point correlations to explain the effect of the Lorentz force on streamwise vortices and streaky structures. Despite the observation of clear stabilization of the streaky structures in the vicinity of the wall, the existence of the streamwise vortices is explained by the well-known turbulence regeneration cycle, which improves the understanding of streaky and streamwise vortex structure formation on turbulence generation. Spanwise oscillating Lorentz force effects on the Rankine vortex structures are investigated. Our results lead us to establish an explanation on the effect of sweep and ejection events on the mean vortex structures in the flow field. A mean vortex structure is defined by the time-averaged location of the local minimum and maximum of the streamwise r.m.s. vorticity. We also depict turbulence production rates for both cases and compared the lower and upper half of the channel.

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A revised WENO‐THINC scheme for the general structured mesh and applications in the direct numerical simulation of compressible turbulent flows

Liu

2023

Numerical Methods in Fluids

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The Tangent of Hyperbola for INterface Capturing (THINC) scheme allows a jump‐like reconstruction and brings about a significant improvement in resolving the discontinuous part of the numerical solutions. However, it is found that the original THINC scheme loses accuracy when working on the stretched, curvilinear or highly‐skewed grid. In this study, we propose a simple strategy to determine the jump thickness parameter in the THINC function, so as to effectively suppress the unphysical oscillation. A Boundary Variation Diminishing (BVD) guideline is introduced to make options between the Weighted Essentially Non‐Oscillatory (WENO) scheme and the modified THINC scheme, thus both the smooth and discontinuous solutions can be reconstructed properly avoiding distortion of grids. Numerical validations indicate that the improved WENO‐THINC‐BVD approach maintains high resolution and is more robust on various types of non‐uniform meshes. The present method is further extended to validate the low‐dissipation property in resolving higher wave numbers portions by simulating an isotropic turbulence decay problem. Finally, we perform the direct numerical simulation (DNS) of a spatially evolving adiabatic flat plate boundary‐layer flow problem at a supersonic Mach number (). Numerical results show the predicted mean flow variables and the normalized shear stress agree well with the experimental data, significant improvements are found in the resolution of the small‐scale vortices, especially in the transition process.

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Nature of sweep and ejection events in transitional and turbulent boundary layers

Cited by 49 publications

References 33 publications

New Theories on Boundary Layer Transition and Turbulence Formation

New Theories on Boundary Layer Transition and Turbulence Formation

Direct numerical simulation analysis of spanwise oscillating Lorentz force in turbulent channel flow at low Reynolds number

A revised WENO‐THINC scheme for the general structured mesh and applications in the direct numerical simulation of compressible turbulent flows

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