Extended self-similar scaling law of multi-scale eddy structure in wall turbulence

2000 ◽  
Vol 21 (9) ◽  
pp. 1016-1023
Author(s):  
Jiang Nan ◽  
Wang Zhen-dong ◽  
Shu Wei
Keyword(s):  
Scaling Law ◽  
Wall Turbulence ◽  
Extended Self ◽  
Eddy Structure ◽  
Multi Scale ◽  
Self Similar

scholarly journals Minimal multi-scale dynamics of near-wall turbulence

2021 ◽  
Vol 913 ◽  
Author(s):  
Patrick Doohan ◽  
Ashley P. Willis ◽  
Yongyun Hwang
Keyword(s):  
Wall Turbulence ◽  
Multi Scale ◽  
Near Wall Turbulence ◽  
Near Wall

Abstract

Wall turbulence eddy structure control by a group of heating wires

2002 ◽  
Author(s):  
N. Jiang ◽  
Y. Lian ◽  
Wei Shu ◽  
Zhi Wang
Keyword(s):  
Wall Turbulence ◽  
Structure Control ◽  
Eddy Structure

Enhancement of Turbulent Shear Stress and Mass Transfer in Wall Turbulence Accompanied With Wall Blowing

2016 ◽  
Author(s):  
Yushi Okamura ◽  
Hideaki Sugioka ◽  
Yasuo Kawaguchi
Keyword(s):  
Mass Transfer ◽  
Shear Stress ◽  
Spatial Distribution ◽  
Solid Wall ◽  
Structural Parameters ◽  
Wall Turbulence ◽  
Experimental Result ◽  
Turbulent Shear ◽  
Eddy Structure ◽  
Turbulent Schmidt Number

Spatial distribution of velocity and mass concentration fluctuation in turbulent channel flow with wall blowing were simultaneously measured by PIV/PLIF. The recorded pictures were analyzed to clarify the turbulent momentum and mass transfer from statistical view point and from spatial evolution of coherent eddy structure. Experimental result revealed that the Reynold shear stress and turbulent intensity are enhanced as the blowing rate increasing. On the other hand, structural parameters based on local turbulence such as turbulent Schmidt number and a degree of turbulent anisotropy is not affected by wall blowing. In comparison without wall blowing, we found that the turbulent eddy structure locates apart from the wall. Besides, energy spectrum and swirling strength is also enhanced by wall blowing. It is associated with increase of resistance by wall blowing. Generally in wall turbulence, fluctuation motions are restricted by the presence of solid wall. But for the blowing from the wall relaxes this restriction and Reynolds shear stress is enhanced, which leads to enhancement of turbulent mass flux. Moreover, from results of spatial distribution of instantaneous fields, wall-blowing helps development of hairpin vortexes. It is concluded that development of hairpins leads to enhancement of turbulent mass transfer.

Gravity currents with residual trapping

2008 ◽  
Vol 611 ◽  
pp. 35-60 ◽  
Author(s):  
M. A. HESSE ◽  
F. M. ORR ◽  
H. A. TCHELEPI
Keyword(s):  
Scaling Law ◽  
Leading Edge ◽  
Power Laws ◽  
Gravity Currents ◽  
Sharp Interface Model ◽  
Current Volume ◽  
Residual Trapping ◽  
Self Similar ◽  
Loss Term ◽  
Structural Closure

Motivated by geological carbon dioxide (CO2) storage, we present a vertical-equilibrium sharp-interface model for the migration of immiscible gravity currents with constant residual trapping in a two-dimensional confined aquifer. The residual acts as a loss term that reduces the current volume continuously. In the limit of a horizontal aquifer, the interface shape is self-similar at early and at late times. The spreading of the current and the decay of its volume are governed by power-laws. At early times the exponent of the scaling law is independent of the residual, but at late times it decreases with increasing loss. Owing to the self-similar nature of the current the volume does not become zero, and the current continues to spread. In the hyperbolic limit, the leading edge of the current is given by a rarefaction and the trailing edge by a shock. In the presence of residual trapping, the current volume is reduced to zero in finite time. Expressions for the up-dip migration distance and the final migration time are obtained. Comparison with numerical results shows that the hyperbolic limit is a good approximation for currents with large mobility ratios even far from the hyperbolic limit. In gently sloping aquifers, the current evolution is divided into an initial near-parabolic stage, with power-law decrease of volume, and a later near-hyperbolic stage, characterized by a rapid decay of the plume volume. Our results suggest that the efficient residual trapping in dipping aquifers may allow CO2 storage in aquifers lacking structural closure, if CO2 is injected far enough from the outcrop of the aquifer.

A Scaling Law for the Urban Heat Island Phenomenon: Deductions From Field Measurements and Comparisons With Existing Results From Laboratory Experiments

2014 ◽  
Author(s):  
Marina K.-A. Neophytou ◽  
Harindra J. S. Fernando ◽  
Ekaterina Batchvarova ◽  
Mats Sandberg ◽  
Jos Lelieveld ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Laboratory Experiments ◽  
Scaling Law ◽  
Field Measurements ◽  
Capital City ◽  
Mitigation Measures ◽  
Heat Island ◽  
Multi Scale ◽  
Urban Heat ◽  
The Impact

We report results from a multi-scale field experiment conducted in Cyprus in July 2010 in order to investigate the Urban Heat Island (UHI) in Nicosia capital city and its interaction with multi-scale meteorological phenomena taking place in the broader region. Specifically, the results are analysed and interpreted in terms of a non-dimensional/scaling parameter dictating the urban heat island circulation reported from laboratory experiments (Fernando et al, 2010). We find that the field measurements obey the same scaling law during the day, in the absence of any other flow phenomena apart from the urban heating. During the night we find that the deduced non-dimensional value reduces to half (compared to that during the day); this is due to the presence of katabatic winds from Troodos mountains into the urban center of Nicosia and their cooling effect superimposed on diurnal urban heating. Based on this deduction, the impact of various proposed heat island mitigation measures in urban planning can be evaluated.

Extended Self-Similarity in Drag-Reduced Turbulent Flow of Viscoelastic Fluid

2010 ◽  
Author(s):  
Feng-Chen Li ◽  
Hong-Na Zhang ◽  
Wei-Hua Cai ◽  
Juan-Cheng Yang
Keyword(s):  
Channel Flow ◽  
Viscoelastic Fluid ◽  
Isotropic Turbulence ◽  
Scaling Law ◽  
Viscoelastic Fluids ◽  
Turbulent Channel Flow ◽  
Elastic Model ◽  
Homogeneous Isotropic Turbulence ◽  
Self Similarity ◽  
Extended Self

Direct numerical simulations (DNS) have been performed for drag-reduced turbulent channel flow with surfactant additives and forced homogeneous isotropic turbulence with polymer additives. Giesekus constitutive equation and finite extensible nonlinear elastic model with Peterlin closure were used to describe the elastic stress tensor for both cases, respectively. For comparison, DNS of water flows for both cases were also performed. Based on the DNS data, the extended self-similarity (ESS) of turbulence scaling law is investigated for water and viscoelastic fluids in turbulent channel flow and forced homogeneous isotropic turbulence. It is obtained that ESS still holds for drag-reduced turbulent flows of viscoelastic fluids. In viscoelastic fluid flows, the regions at which δu(r)∝r and Sp(r)∝S3(r)ζ(p) with ζ(p) = p/3, where r is the scale length, δu(r) is the longitudinal velocity difference along r and Sp(r) is the pth-order moment of velocity increments, in the K41 (Kolmogorov theory)-fashioned plots and ESS-fashioned plots, respectively, are all broadened to larger scale for all the investigated cases.

scholarly journals Computational Design and Analysis of a Magic Snake

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Zilong Li ◽  
Songming Hou ◽  
Thomas C. Bishop
Keyword(s):  
3D Structure ◽  
Three Dimensional ◽  
Computational Design ◽  
Space Curve ◽  
One Dimensional ◽  
3D Structures ◽  
Multi Scale ◽  
3D Space ◽  
Slender Bodies ◽  
Self Similar

Abstract The Magic Snake (Rubik’s Snake) is a toy that was invented decades ago. It draws much less attention than Rubik’s Cube, which was invented by the same professor, Erno Rubik. The number of configurations of a Magic Snake, determined by the number of discrete rotations about the elementary wedges in a typical snake, is far less than the possible configurations of a typical cube. However, a cube has only a single three-dimensional (3D) structure while the number of sterically allowed 3D conformations of the snake is unknown. Here, we demonstrate how to represent a Magic Snake as a one-dimensional (1D) sequence that can be converted into a 3D structure. We then provide two strategies for designing Magic Snakes to have specified 3D structures. The first enables the folding of a Magic Snake onto any 3D space curve. The second introduces the idea of “embedding” to expand an existing Magic Snake into a longer, more complex, self-similar Magic Snake. Collectively, these ideas allow us to rapidly list and then compute all possible 3D conformations of a Magic Snake. They also form the basis for multidimensional, multi-scale representations of chain-like structures and other slender bodies including certain types of robots, polymers, proteins, and DNA.

scholarly journals Optimizing our patient’s entropy production as therapy? Hypotheses originating from the physics of physiology

2020 ◽  
Author(s):  
Andrew Ervine Seely
Keyword(s):  
Entropy Production ◽  
Treatment Strategies ◽  
Maximal Entropy ◽  
Multi Scale ◽  
Spontaneous Formation ◽  
Emergent Order ◽  
Self Similar ◽  
Physical Laws ◽  
Over Time ◽  
Improve Health

Abstract Physical laws dictate that energy is preserved; yet energy gradients irreversibly dissipate, thus producing entropy. As living complex non-equilibrium systems, humans must produce entropy continuously over time to create healthy internal emergent order. Entropy production is measured by heat production divided by temperature. Several hypotheses are presented. First, human entropy production is due to both metabolism and consciousness, dissipating energy and information gradients. Second, the physical drive for maximal entropy production is responsible for spontaneous formation of fractal multi-scale self-similar structures in time and space, ubiquitous and essential for health. Third, the evolutionary drive for enhanced function and adaptability selects states with both robust basal and maximal entropy production (i.e. the capacity to augment it when required). Last, targeted focus on optimizing our patients’ entropy production will improve health and clinical outcomes. These hypotheses have implications for understanding health, metabolism and consciousness, and offer novel clinical treatment strategies.

Sign in / Sign up

Export Citation Format

Share Document