scholarly journals Large Scale Vortex Structure and Sand Waves in River Confluence

1992 ◽  
Vol 36 ◽  
pp. 373-378
Author(s):  
Terunori OHMOTO ◽  
Muneo HIRANO ◽  
Mituho AMANO ◽  
Makoto Matsuo
Keyword(s):  
Vortex Structure ◽  
Large Scale ◽  
Sand Waves ◽  
River Confluence ◽  
Large Scale Vortex ◽  
Large Scale Vortex Structure

Numerical simulation of large-scale vortex-structure formation in shear flow of the atmosphere

2009 ◽  
Vol 54 (11) ◽  
pp. 494-498
Author(s):  
O. M. Belotserkovskiĭ ◽  
A. V. Konyukhov ◽  
A. M. Oparin ◽  
V. M. Chechetkin
Keyword(s):  
Numerical Simulation ◽  
Shear Flow ◽  
Structure Formation ◽  
Vortex Structure ◽  
Large Scale ◽  
Large Scale Vortex ◽  
Large Scale Vortex Structure

Numerical Simulation of Quasi Periodic Large Scale Vortices in Rod Bundles With Non-Uniform Wall Roughness

2013 ◽  
Author(s):  
Gaojie Hu ◽  
Lei Yu ◽  
Yangwei Zhang ◽  
Binghuo Yan
Keyword(s):  
Heat Transfer ◽  
Vortex Structure ◽  
Large Scale ◽  
Wall Roughness ◽  
Rod Bundles ◽  
Flow And Heat Transfer ◽  
Large Scale Vortex ◽  
Uniform Wall ◽  
Tight Lattice ◽  
Large Scale Vortex Structure

The flow and heat transfer in rod bundles are of vital importance in the reactor design. Studies on the turbulent flow in tight lattice have presented the quasi periodic large scale vortex structure is highly accounted for the local flow and heat transfer and turbulent mixing in rod bundles. In this work, the Unsteady Reynolds Averaged Navier–Stokes (URANS) simulation with the Reynolds Stress Model (RSM) is adopted to simulate the flow and vortex structure in rod bundles. The vortex structure in sparse lattice with nonuniform wall roughness is also investigated and compared with that in tight lattice. The results indicate that the quasi periodic large scale vortex structure and flow pulsation are available in both tight lattice and the sparse lattice with non-uniform wall roughness. Due to the existence of the vortex structure, the heat transfer in spare lattice is enhanced.

The turbulent mixing layer: geometry of large vortices

1985 ◽  
Vol 158 ◽  
pp. 489-509 ◽  
Author(s):  
F. K. Browand ◽  
T. R. Troutt
Keyword(s):  
Vortex Structure ◽  
Turbulent Mixing ◽  
Large Scale ◽  
Mixing Layer ◽  
Speed Ratio ◽  
Hot Wire ◽  
Turbulent Mixing Layer ◽  
Correlation Lengths ◽  
Large Scale Vortex ◽  
Large Scale Vortex Structure

Several means for visualizing large-scale vortex structure in a turbulent mixing layer are proposed. Most of the observations are recorded along the low-speed side of the mixing layer, external to the rotational portion of the flow. Conventional correlation measurements in both the streamwise and spanwise directions indicate that the vortex structure becomes independent of the downstream coordinate in a non-dimensional distance of order λx/θi = 300–400, where $\lambda = \Delta U/2\overline{U}$ is the speed ratio and θi is the initial integral thickness. Simultaneous hot-wire measurements at 12 spanwise positions allow computer reconstruction of the velocity field as a function of span and time. These visualizations show the vortex structures to be primarily aligned across the span of the flow, but to contain irregularities. Spanwise correlation lengths are of the order of 3–5δω (δω is the local vorticity thickness). However, the large vortices typically have lengths of order 20δω when the irregularities along the span are ignored.

Structure of a turbulent separation bubble

1983 ◽  
Vol 137 ◽  
pp. 83-113 ◽  
Author(s):  
Masaru Kiya ◽  
Kyuro Sasaki
Keyword(s):  
Surface Pressure ◽  
Vortex Structure ◽  
Large Scale ◽  
Separation Bubble ◽  
Pressure Fluctuations ◽  
Velocity Fluctuations ◽  
Turbulent Separation ◽  
Large Scale Vortex ◽  
Cross Correlations ◽  
The Cross

Flow in the separation bubble formed along the sides of a blunt flat plate with right-angled corners has been studied in terms of extensive single- and two-point measurements of velocity and surface-pressure fluctuations. The cross-correlations between the surface-pressure and velocity fluctuations are found to be useful for the study of large-scale vortex structure in the bubble. Large-scale vortices are shed downstream from the separation bubble with a frequency of about 0.6U∞/xR, where U∞ is the approaching velocity and xR is the time-mean length of the bubble. On top of this regular vortex shedding, there exists a large-scale unsteadiness in the bubble. Vortices which are much larger than the regular vortices are shed with frequencies less than about 0.2U∞/xR. The large-scale unsteadiness is accompanied by enlargement and shrinkage of the bubble and also by a flapping motion of the shear layer near the separation line. The intermittent nature of the flow in the bubble is clarified in some detail. The distributions of the cross-correlations between the pressure and velocity fluctuations demonstrate the vortex structure in the reattaching zone. The longitudinal distance between the vortices is estimated to be (0.7–0.8) xR and their convection velocity is about 0.5U∞ near the reattachment line. The cross-correlations also suggest the existence of a longitudinal counter-rotating system in the bubble. The distance between the axes of the rotation is of the order of 0.6xR. Variations of timescales, lengthscales and phase velocities of the vortices are presented and discussed.

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