Coherent structures

These data indicate that thermal losses during unsteady flame-wall interactions constitute an intense source of combustion noise. This is exemplified in other cases where extinctions result from large coherent structures impacting on solid boundaries, or when a turbulent flame is stabilized close to a wall and impinges on the boundary. However, in many cases, the flame is stabilized away from the boundaries and this mechanism may not be operational. 

DNS results are usually considered as references providing the same level of accuracy as experimental data. The maximum attainable Reynolds number (Re) in a DNS is, however, too low to duplicate most practical turbulent reacting flows, and hence, the use of DNS is neither to replace experiments nor for direct comparisons— not yet at least. However, DNS results can be used to investigate three-dimensional (3D) features of the flow (coherent structures, Reynolds stresses, etc.) that are extremely difficult, and sometimes impossible, to measure. One example of such achievement for nonreacting... 

The concept of ionic crosslinking is in accord with the idea that a gel must possess a coherent structure. However, although crosslinking may be essential to gel formation it does not necessarily have to be a simple ionic salt bridge. 

Fig. 6.5. Coherent structure function S(q) in absolute units in comparison to amorphous cell simulations [194] and neutron scattering data [185]...

The coherent structure factor of the Zimm model can be calculated [34] following the lines outlined in detail in connection with the Rouse model. As the incoherent structure factor (83), it is also a function of the scaling variable ( fz(Q)t)2/3 and has the form... 

The equilibrium population is said to have a structure when a substantial fraction of the molecules adopts similar conformations. But the phrase lacking structure does not imply that individual molecules comprising the ensemble lack a conformation rather, the population is too heterogeneous to be readily characterized using a coherent, structure-based descriptor. The unfolded state resists ready characterization because it is so diverse. Typical biophysical methods report ensemble-... 

Determination of protein secondary structure has long been a major application of optical spectroscopic studies of biopolymers (Fasman, 1996 Havel, 1996 Mantsch and Chapman, 1996). These efforts have primarily sought to determine the average fractional amount of overall secondary structure, typically represented as helix and sheet contributions, which comprise the extended, coherent structural elements in well-structured proteins. In some cases further interpretations in terms of turns and specific helix and sheet segment types have developed. Only more limited applications of optical spectra to determination of tertiary structure have appeared, and these normally have used fluorescence or near-UV electronic circular dichroism (ECD) of aromatic residues to sense a change in the fold (Haas, 1995 Woody and Dunker, 1996). 

This part of the turbulent boundary layer is rich in coherent structures, ie the flow exhibits features that are not random. Flow visualization studies [Kline et al (1967), Praturi and Brodkey (1978), Rashidi and Banerjee (1990)] have revealed a fascinating picture. The first observations indicated the occurrence of fluid motions called inrushes and eruptions or bursts in the fluid very close to the wall. During eruptions, fluid... 

Praturi, A.K. and Brodkey, R.S., A stereoscopic visual study of coherent structures in turbulent shear flow, Journal of Fluid Mechanics, 89, pp. 251-72 (1978). 

TNC.26. 1. Prigogine and A. Babloyantz, Coherent structures and thermodynamic stability, in Chemical Evolution and the Origin of Life, 1, R. Buvet and C. Ponnamperuma, eds.. North Holland, Amsterdam, 1971. 

Zaman, K. B. M. Q. 1996. Axis switching and spreading of an asymmetric jet The role of coherent structure dynamics. J. Fluid Mechanics 316 1-27. 

Grinstein, F.F., and C. R. DeVore. 1996. Dynamics of coherent structures and transition to turbulence in free square jets. J. Physics Fluids 8 1237-51. 

Husain, H. S., and F. Hussain. 1993. Elliptic jets. Part 3. Dynamics of preferred mode coherent structure. J. Fluid Mechanics 248 315-61. 

Velocity measurements showed an increase in mean flow with forcing implying a strong radial air entrainment caused by the coherent structures. 

As the relative velocity difference is increased, however, coherent structure development is suppressed by compressibility effect [7, 8] and thus the effect on mixing by coherent structures diminishes. The compressibility effect can be quantified in terms of the convective Mach number, which is defined as the... 

Yu, K. H., and K. C. Schadow. 1997. Role of large coherent structures in turbulent compressible mixing. J. Experimental Thermal Fluid Science 14 75-84. 

R. M. Kiehn, Torsion-Helicity and Spin as Topological Coherent Structures in Plasmas, available at www.un.edu/rkiehn/car/carhomep.htm. 

FIG. 9.17 Illustrations of LEED spots and coherent structures formed by adsorbed species, (a) indexing of the LEED spots of W(100) pattern in Figure 9.16a as described in Example 9.7 (b) side view of coherent structures formed by adsorbed (open circles) species on metal surface (c) unit mesh for W(100) with adsorbed oxygen (open circles) (d) unit mesh for W(100) with adsorbed hydrogen (open circles). 

In this regard, Melander and Hussain [10] have made significant advances in casting fresh light on the perplexing problems of vortex core dynamics and the coupling between large scales and fine scales in the vicinity of a coherent structure. Essentially, they postulated that the dynamics of coherent structures is... 

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