On the viscous modes of instability of a trailing line vortex

1991 ◽  
Vol 225 ◽  
pp. 197-212 ◽  
Author(s):  
Mehdi R. Khorrami
Keyword(s):  
Maximum Growth ◽  
Asymmetric Mode ◽  
Axisymmetric Mode ◽  
Viscous Forces ◽  
Viscous Instability ◽  
Long Wave ◽  
Instability Modes ◽  
Chebyshev Spectral Collocation ◽  
Collocation Technique

A viscous linear stability analysis of a trailing line (Batchelor) vortex is presented. Employing a staggered Chebyshev spectral collocation technique, very accurate results were obtained. The destabilising role of viscous forces has been shown to produce two types of viscous instability modes. These viscous disturbances consist of an axisymmetric mode and an asymmetric mode. Both disturbances are long-wave instabilities with maximum growth rates which are orders of magnitude smaller than the inviscid modes which have been found by others. Comparison with experimental results and condensation trail observations are found to be in good qualitative agreement with the present study.

World Economic Crisis as a Process of Substitution of Technological Modes

2009 ◽  
pp. 26-38 ◽  
Author(s):  
S. Glaziev
Keyword(s):  
Economic Crisis ◽  
Economic Activity ◽  
Sharp Increase ◽  
Energy Resources ◽  
Long Wave ◽  
The World ◽  
World Economic ◽  
Technological Mode ◽  
World Economic Crisis

The article analyzes fundamental reasons for the world economic crisis in the light of global technological shifts. It proves that it is caused by the substitution of technological modes. It is shown that sharp increase and slump in stock indices and prices for energy resources are typical of the process of technological substitution which occurs regularly according to the rhythm of long-wave fluctuations of the world economic activity. The article rationalizes a package of anti-crisis measures aimed at stimulating the new technological mode. Its structure and role of the locomotive factor of the new long wave of economic growth are revealed.

scholarly journals Is the ultraviolet waveband a special communication channel in avian mate choice?

2001 ◽  
Vol 204 (14) ◽  
pp. 2499-2507 ◽  
Author(s):  
Sarah Hunt ◽  
Innes C. Cuthill ◽  
Andrew T. D. Bennett ◽  
Stuart C. Church ◽  
Julian C. Partridge
Keyword(s):  
Mate Choice ◽  
Communication Channel ◽  
Visible Spectrum ◽  
Short Wave ◽  
Zebra Finches ◽  
Long Wave ◽  
Single Cone ◽  
Coloured Filters ◽  
Uv Reflection

SUMMARYThere is growing evidence that ultraviolet (UV) wavelengths play an important role in avian mate choice. One of the first experiments to support this idea showed that female zebra finches (Taeniopygia guttata) prefer UV-reflecting males to males whose ultraviolet reflection has been removed. The effect was very strong despite little or no UV reflection from several plumage areas. However, it is not clear how the importance of the UV waveband compares to other regions of the bird-visible spectrum. We tested whether the response of female zebra finches to the removal of male UV reflection is greater than to the removal of other wavebands. We presented females with a choice of males whose appearance was manipulated using coloured filters. The filters removed single blocks of the avian visible spectrum corresponding closely to the spectral sensitivities of each of the zebra finch’s single cone classes. This resulted in males that effectively had no UV (UV−), no short-wave (SW−), no medium-wave (MW−) or no long-wave (LW−) plumage reflection. Females preferred UV− and SW− males. LW− and MW− males were least preferred, suggesting that female zebra finches show the greatest response to the removal of longer wavelengths. Quantal catches of the single cone types viewing body areas of the male zebra finch are presented for each treatment. Our study suggests it is important to consider the role of the UV waveband in avian mate choice in conjunction with the rest of the avian visible spectrum.

The role of long-wave longitudinal phonons in kinetics of insulators

1997 ◽  
Vol 23 (2) ◽  
pp. 171-173
Author(s):  
R. N. Gurzhi ◽  
A. V. Yanovskiı̆
Keyword(s):  
Long Wave ◽  
Kinetics Of

Customer reciprocity in greening: the role of service quality

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Debarati Basu ◽  
Kamalika Chakraborty ◽  
Shabana Mitra ◽  
Nishant Kumar Verma
Keyword(s):  
Service Quality ◽  
Price Competition ◽  
Emerging Market ◽  
Maximum Growth ◽  
Customer Engagement ◽  
Content Type ◽  
Key Stakeholders ◽  
Business To Consumer ◽  
Operational Processes

Purpose Firms are increasingly making customers key stakeholders in their greening processes, requiring them to voluntarily use their resources to benefit the firm. In this context, this paper develops a new construct – tangible customer citizenship behaviour (CCB), i.e. voluntary participation of customer in operational processes of the company beyond normal requirements of exchange. This requires more involvement than the already documented intangible CCB. The purpose of the paper is to then explore whether service quality (SQ) (online and offline) influences such voluntary customer reciprocity in greening. Design/methodology/approach This study used a virtual survey among 400 customers of e-commerce firms that have adopted greening practices requiring customer engagement and regressions were used to test the hypotheses. Findings The authors find that both online and offline SQ positively impact intangible CCB but have no impact on customer greening reciprocity (tangible CCB). Additionally, the authors find that offline SQ positively impacts customer greening awareness. However, in spite of the presence of greening awareness and display of intangible CCB, SQ does not have any impact on greening reciprocity. Originality/value This study introduces to literature a more tangible form of voluntary behaviour on the part of the customer, i.e. tangible CCB or reciprocity. To the best of the authors’ knowledge, it is also one of the first to study the customer as an important stakeholder and participant in a business-to-consumer firm’s operating processes, particularly in greening which has no direct impact on the firm’s core offering. The focus on greening in the Indian context is also novel given the greening costs and requirements and the price competition are very different in emerging market contexts where e-commerce firms are experiencing the maximum growth.

The role of barbituric acid in the nutrition of Bacillus popilliae

1970 ◽  
Vol 16 (9) ◽  
pp. 801-807 ◽  
Author(s):  
Wilson H. Coulter ◽  
Ralph N. Costilow
Keyword(s):  
Barbituric Acid ◽  
Deoxyribonucleic Acid ◽  
Synthetic Medium ◽  
Maximum Growth ◽  
General Distribution ◽  
Significant Stimulation ◽  
Cell Components ◽  
Bacillus Popilliae ◽  
And Control

Barbituric acid is required at a level of 0.1% for maximum growth of Bacillus popilliae in a synthetic medium. However, only a trace amount of that added (~2%) disappeared from the medium during growth. A general distribution of the 14C from 2-14C-barbituric acid among cell components was observed, but a small amount of the radioactivity from this isotope was consistently associated with both ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). The 14C found in RNA was uniformly distributed throughout the 4 S, 16 S, and 23 S RNA fractions, and control experiments indicated that the association of 14C from 2-14C-barbituric acid with the nucleic acids may occur by nonspecific absorption. The presence of barbituric acid resulted in very significant stimulation of both nucleic acid and protein synthesis. The mechanism of this stimulation is unresolved.

Long-wave instability of a helical vortex

2015 ◽  
Vol 780 ◽  
pp. 687-716 ◽  
Author(s):  
Hugo Umberto Quaranta ◽  
Hadrien Bolnot ◽  
Thomas Leweke
Keyword(s):  
Growth Rate ◽  
Water Channel ◽  
Vortex Filament ◽  
Linear Stability Theory ◽  
Wave Instability ◽  
Characteristic Distance ◽  
Long Wave ◽  
Instability Modes ◽  
Small Pitch ◽  
Helical Vortex

We investigate the instability of a single helical vortex filament of small pitch with respect to displacement perturbations whose wavelength is large compared to the vortex core size. We first revisit previous theoretical analyses concerning infinite Rankine vortices, and consider in addition the more realistic case of vortices with Gausssian vorticity distributions and axial core flow. We show that the various instability modes are related to the local pairing of successive helix turns through mutual induction, and that the growth rate curve can be qualitatively and quantitatively predicted from the classical pairing of an array of point vortices. We then present results from an experimental study of a helical vortex filament generated in a water channel by a single-bladed rotor under carefully controlled conditions. Various modes of displacement perturbations could be triggered by suitable modulation of the blade rotation. Dye visualisations and particle image velocimetry allowed a detailed characterisation of the vortex geometry and the determination of the growth rate of the long-wave instability modes, showing good agreement with theoretical predictions for the experimental base flow. The long-term (downstream) development of the pairing instability leads to a grouping and swapping of helix loops. Despite the resulting complicated three-dimensional structure, the vortex filaments surprisingly remain mostly intact in our observation interval. The characteristic distance of evolution of the helical wake behind the rotor decreases with increasing initial amplitude of the perturbations; this can be predicted from the linear stability theory.

scholarly journals On the origin of the circular hydraulic jump in a thin liquid film

2018 ◽  
Vol 851 ◽  
Author(s):  
Rajesh K. Bhagat ◽  
N. K. Jha ◽  
P. F. Linden ◽  
D. Ian Wilson
Keyword(s):  
Thin Film ◽  
Surface Tension ◽  
Liquid Film ◽  
Thin Liquid Film ◽  
Capillary Waves ◽  
Hydraulic Jumps ◽  
Planar Surface ◽  
Normal Impact ◽  
Viscous Forces

This study explores the formation of circular thin-film hydraulic jumps caused by the normal impact of a jet on an infinite planar surface. For more than a century, it has been believed that all hydraulic jumps are created due to gravity. However, we show that these thin-film hydraulic jumps result from energy loss due to surface tension and viscous forces alone. We show that, at the jump, surface tension and viscous forces balance the momentum in the liquid film and gravity plays no significant role. Experiments show no dependence on the orientation of the surface and a scaling relation balancing viscous forces and surface tension collapses the experimental data. A theoretical analysis shows that the downstream transport of surface energy is the previously neglected critical ingredient in these flows, and that capillary waves play the role of gravity waves in a traditional jump in demarcating the transition from the supercritical to subcritical flow associated with these jumps.

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