Low Frequency Unsteadyness of a Reattaching Turbulent Shear Layer

Eaton, John K.; Johnston, J. P.

doi:10.1007/978-3-642-95410-8_16

Cited by 101 publications

(94 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Within the oscillating recirculation bubble, the mean flow speed is one order of magnitude less than the mean main flow speed [26]. The large eddies move downstream and cause local flow reversal, as observed in [3,14,15,19,26]. Durst and Tropea [14] report that in the transitional regime, streamlines are wavy right after the step, and break into "vortex rolls" after 3-4 step heights downstream; as R .…”

Section: Bl Transitional and Turbulent Flow-experimental Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Validation study of vortex methods

Sethian

Ghoniem

1988

Journal of Computational Physics

View full text Add to dashboard Cite

Section: Bl Transitional and Turbulent Flow-experimental Resultsmentioning

confidence: 99%

“…Eaton and Johnson [15] characterize them as "large, turbulent, spanwise eddies" which effect large local flow reversal. These eddies are viewed as three-dimensional, responsible for dissipating structures and coupling together the various recirculation regions [3].…”

Section: Bl Transitional and Turbulent Flow-experimental Resultsmentioning

confidence: 99%

Validation study of vortex methods

Sethian

Ghoniem

1988

Journal of Computational Physics

View full text Add to dashboard Cite

“…This has been discussed in detail by Bradshaw and Wong (1972), Eaton and Johnston (1981), and by Cheun, Toy and Moss (1983), to cite but a few. For-this study, since we are not interested in the details of the separation/reattachment process, no attempt was made to modify the upstream flow so as to obtain a prescribed boundary layer state at the step.…”

Section: Onset and Equilibrium Boundary Layersmentioning

confidence: 95%

An experimental investigation of wall pressure fluctuations beneath non-equilibrium turbulent flows

Farabee¹

1988

The Journal of the Acoustical Society of America

View full text Add to dashboard Cite

“…In the backward-facing step, for instance, the dominant frequency was between St ' 0.06 (Le et al 1997) and 0.066 < St < 0.08 (Eaton & Johnston 1982). Aider & Danet (2006) found the flapping frequency as well as the shedding frequency at St = 0.064 and 0.102, respectively.…”

Section: Near-wall Turbulencementioning

confidence: 94%

“…Time series of pressure fluctuations are also shown in Figures 9(a,c). The spectra in the saddle plane have a low-frequency peak due to the flapping of the separated shear-layer, typical of the reattachment region of flows with separation, such as backward facing steps (Eaton & Johnston 1982;Driver et al 1987;Dejoan & Leschziner 2004;Aider & Danet 2006); St = 0.011 for the in-phase alignment, 0.021 for the staggered case. The state of the boundary layer approaching the crest may play a role in this di↵erence, in that in the staggered case, the boundary layer approaching the saddle plane is coming from the upstream lobe.…”

Section: Near-wall Turbulencementioning

confidence: 99%

Large-eddy simulation of three-dimensional dunes in a steady, unidirectional flow. Part 2. Flow structures

Omidyeganeh

Piomelli

2013

J. Fluid Mech.

View full text Add to dashboard Cite

This is the accepted version of the paper.This version of the publication may differ from the final published version. We performed large-eddy simulations of the flow over a series of three-dimensional (3D) dunes at laboratory scale. The bedform three-dimensionality was imposed by shifting a standard two-dimensional (2D) dune shape in the streamwise direction according to a sine wave. The turbulence statistics were discussed in Part 1 of this article [M. Omidyeganeh, U. Piomelli, J. Fluid Mech. 721, pp. 454-483, (2013)]. Coherent flow structures and their statistics are discussed concentrating on two cases with the same crestline amplitudes and wavelengths but di↵erent crestline alignments: in-phase and staggered. The present paper shows that the induced large-scale mean streamwise vortices are the primary factor that alters the features of the instantaneous flow structures. Wall turbulence is insensitive to the crestline alignment; alternating high-and low-speed streaks appear in the internal boundary layer developing on the stoss side, whereas over the node plane (the plane normal to the spanwise direction at the node of the crestline), they are inclined towards the lobe plane (the plane normal to the spanwise direction at the most downstream point of the crestline) due to the mean spanwise pressure gradient. Spanwise vortices (rollers) generated by Kelvin-Helmholtz instability in the separated shear-layer appear regularly over the lobe with much larger length scale than those over the saddle (the plane normal to the spanwise direction at the most upstream point of the crestline). Rollers over the lobe may extend to the saddle plane and a↵ect the reattachment features; their shedding is more frequent than in 2D geometries. Vortices shed from the separated shear-layer in the lobe plane undergo a three-dimensional instability while advected downstream, and rise toward the free surface. They develop into a horseshoe shape (similar to the 2D case) and a↵ect the whole channel depth, whereas those generated near the saddle are advected downstream and toward the bed. When the tip of such a horseshoe reaches the free surface, the ejection of flow at the surface causes "boils" (upwelling events on the surface). Strong boil events are observed on the surface of the lobe planes of 3D dunes more frequently than in the saddle planes. They also appear more frequently than in the corresponding 2D geometry. The crestline alignment of the dune alters the dynamics of the flow structures, in that they appear in the lobe plane and are advected towards the saddle plane of the next dune, where they are dissipated. Boil events occur at a higher frequency in the staggered alignment, but with less intensity than in the in-phase alignment. Permanent repository link

show abstract

Low Frequency Unsteadyness of a Reattaching Turbulent Shear Layer

Cited by 101 publications

References 8 publications

Validation study of vortex methods

Validation study of vortex methods

An experimental investigation of wall pressure fluctuations beneath non-equilibrium turbulent flows

Large-eddy simulation of three-dimensional dunes in a steady, unidirectional flow. Part 2. Flow structures

Contact Info

Product

Resources

About