scholarly journals Interactions of large-scale structures in the near field of round jets at high Reynolds numbers

2020 ◽  
Vol 888 ◽  
Author(s):  
Jahnavi Kantharaju ◽  
Romain Courtier ◽  
Benjamin Leclaire ◽  
Laurent Jacquin
Keyword(s):  
Large Scale ◽  
Near Field ◽  
Reynolds Numbers ◽  
Large Scale Structures ◽  
Round Jets ◽  
High Reynolds Numbers ◽  
Scale Structures ◽  
High Reynolds ◽  
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scholarly journals Large-scale structures in high-Reynolds-number rotating Waleffe flow

2019 ◽  
Vol 884 ◽  
Author(s):  
Shafqat Farooq ◽  
Martin Huarte-Espinosa ◽  
Rodolfo Ostilla-Mónico
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Large Scale ◽  
Large Scale Structures ◽  
Scale Structures ◽  
High Reynolds ◽  
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scholarly journals It is Not Easy to Replace Newtonian Gravitational Theory!

1988 ◽  
Vol 130 ◽  
pp. 602-603
Author(s):  
D. Gerbal ◽  
H. Siroussezia
Keyword(s):  
Large Scale ◽  
Gravitational Theory ◽  
Large Scale Structures ◽  
Newton's Law ◽  
Newton’S Law ◽  
Theory Of Gravitation ◽  
Scale Structures ◽  
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The great amount of unseen dynamical matter in large scale structures is derived from: the Newton's law of inertia and the theory of gravitation. But none of these law has been tested on scale larger than r > 10Kpc. It is then tempting to modify them following: where g(x) is a phenomenological function.

Three-dimensional conditional structure of a high-Reynolds-number turbulent boundary layer

2011 ◽  
Vol 673 ◽  
pp. 255-285 ◽  
Author(s):  
N. HUTCHINS ◽  
J. P. MONTY ◽  
B. GANAPATHISUBRAMANI ◽  
H. C. H. NG ◽  
I. MARUSIC
Keyword(s):  
Skin Friction ◽  
High Reynolds Number ◽  
Large Scale ◽  
Three Dimensional ◽  
Streamwise Velocity ◽  
Small Scale ◽  
Large Scale Structures ◽  
Local Mean ◽  
Scale Structures ◽  
High Reynolds

An array of surface hot-film shear-stress sensors together with a traversing hot-wire probe is used to identify the conditional structure associated with a large-scale skin-friction event in a high-Reynolds-number turbulent boundary layer. It is found that the large-scale skin-friction events convect at a velocity that is much faster than the local mean in the near-wall region (the convection velocity for large-scale skin-friction fluctuations is found to be close to the local mean at the midpoint of the logarithmic region). Instantaneous shear-stress data indicate the presence of large-scale structures at the wall that are comparable in scale and arrangement to the superstructure events that have been previously observed to populate the logarithmic regions of turbulent boundary layers. Conditional averages of streamwise velocity computed based on a low skin-friction footprint at the wall offer a wider three-dimensional view of the average superstructure event. These events consist of highly elongated forward-leaning low-speed structures, flanked on either side by high-speed events of similar general form. An analysis of small-scale energy associated with these large-scale events reveals that the small-scale velocity fluctuations are attenuated near the wall and upstream of a low skin-friction event, while downstream and above the low skin-friction event, the fluctuations are significantly amplified. In general, it is observed that the attenuation and amplification of the small-scale energy seems to approximately align with large-scale regions of streamwise acceleration and deceleration, respectively. Further conditional averaging based on streamwise skin-friction gradients confirms this observation. A conditioning scheme to detect the presence of meandering large-scale structures is also proposed. The large-scale meandering events are shown to be a possible source of the strong streamwise velocity gradients, and as such play a significant role in modulating the small-scale motions.

Dynamics of Large-Scale Structures for Jets in a Crossflow

1999 ◽  
Vol 121 (3) ◽  
pp. 577-587 ◽  
Author(s):  
F. Muldoon ◽  
S. Acharya
Keyword(s):  
Shear Layer ◽  
Large Scale ◽  
Computational Study ◽  
Near Field ◽  
Velocity Ratio ◽  
Leeward Side ◽  
Dynamic Features ◽  
Mean Velocity ◽  
Large Scale Structures ◽  
Scale Structures

Results of a three-dimensional unsteady computational study of a row of jets injected normal to a crossflow are presented with the aim of understanding the dynamics of the large-scale structures in the region near the jet. The jet to crossflow velocity ratio is 0.5. A modified version of the computer program (INS3D), which utilizes the method of artificial compressibility, is used for the computations. Results obtained clearly indicate that the near-field large-scale structures are extremely dynamic in nature, and undergo breakup and reconnection processes. The dynamic near-field structures identified include the counterrotating vortex pair (CVP), the horseshoe vortex, wake vortex, wall vortex, and shear layer vortex. The dynamic features of these vortices are presented in this paper. The CVP is observed to be a convoluted structure interacting with the wall and horseshoe vortices. The shear layer vortices are stripped by the crossflow, and undergo pairing and stretching events in the leeward side of the jet. The wall vortex is reoriented into the upright wake system. Comparison of the predictions with mean velocity measurements is made. Reasonable agreement is observed.

Large-scale structures in a developed flow over a wavy wall

2003 ◽  
Vol 478 ◽  
pp. 257-285 ◽  
Author(s):  
AXEL GÜNTHER ◽  
PHILIPP RUDOLF VON ROHR
Keyword(s):  
Velocity Field ◽  
Large Scale ◽  
Reynolds Shear Stress ◽  
Water Channel ◽  
Reynolds Numbers ◽  
Streamwise Velocity ◽  
Wavy Surface ◽  
Large Scale Structures ◽  
Stress Maximum ◽  
Scale Structures

We address – motivated in part by the findings of Gong et al. (1996) and Miller (1995) – the role of streamwise-oriented large-scale structures in a developed flow between a sinusoidal bottom wall and a flat top wall. Particle image velocimetry (PIV) is used to examine the spatial variation of the velocity in different planes of the flow through a water channel with an aspect ratio of 12:1. The wave amplitude is equal to one tenth of the wall wavelength, Λ, and Reynolds numbers between 500 and 7300, defined with the bulk velocity and the half-height of the channel, are considered. To examine streamwise-oriented structures, the spanwise variation of the velocity field is studied in a plane parallel to the top wall, and in one that intersects the wavy surface at an uphill location. From a proper orthogonal decomposition (POD) of the streamwise velocity fluctuations, we obtain the dominant eigenfunctions with a characteristic spanwise scale of O(1.5Λ), which agrees with the scale of perturbations for the streamwise velocity at laminar conditions. A decomposition of the turbulent velocity field close to the uphill section of the wavy surface reveals smaller structures at a location that coincides with the Reynolds shear stress maximum.

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