Scaling approaches to steady wall-induced turbulence

The problem of discerning key features of steady turbulent flow adjacent to a wall has drawn the attention of some of the most noted fluid dynamicists of all time. Standard examples of such features are found in the mean velocity profiles of turbulent flow in channels, pipes or boundary layers. The aim of this review article is to expound the essence of some elementary theoretical efforts in this regard. Possibly the best known of them, and certainly the simplest, is the argument (obtained independently) by Izakson (1937) and Millikan (1939). They showed that if an inner scaling and an outer scaling for the profile are valid near the wall and near the center of the flow (or the edge of the boundary layer), respectively, and if there is an overlap region where both scalings are valid, then the profile must be logarithmic in that common region. That theoretical justification has been used and expanded upon by innumerable authors for over 60 years, and at the present time is still rightly enjoying popularity. Although background discussions of several related topics are included in the present article, for example the classical ideas of Prandtl and von Karman, the main foci will be on (i) a careful examination of the Izakson-Millikan argument, together with a presentation of a better mathematical justification for its conclusion; and (ii) a detailed clarification of a newer approach to gaining theoretical understanding of the mean velocity and Reynolds stress profiles based on the search for scaling patches. The two approaches share common goals, they are both heavily involved with scaling concepts, and many results are similar, but the logical trains of thought are entirely different. The first, as mentioned, dates back to the 30's and the second was introduced in a series of recent papers by Fife, Wei and Klewicki et al.Comment: 41 pages, 4 figures. The article is submitted posthumously by Dr. Tie Wei, with the permission of Dr. Paul Fife's children: John Fife, Kit Barker, and Richard Fif

Consumer trust and confidence: Some recent ideas in the literature

This is a post-print version of the article. The official published version can be accessed from the link below - © IWA Publishing 2008This paper reflects on two recent debates in the consumer literature on trust that have implications for consumer relations in the water industry. The first concerns an important yet seldom made distinction between trust and confidence. The second concerns when and how trust is related to acceptance of, for example, new tariffs or new technologies, and it challenges the conventional view that trust is usually a precursor of acceptance. New conceptual models addressing these debates are described and their implications for future water-related consumer research are discussed as are potential implications for industry relationships with consumers

Bionomics of the Clover Leaf Weevil, Hypera Punctata (Fabr.), in Utah

The clover leaf weevil, Hypera punctata (Fabr.), is a foreign pest introduced from Europe into New York, which first became noticeable in 1881. The insect has rapidly spread westward reaching Utah at least by 1912. Since this time several outbreaks have occured. In 1927 the injury to alfalfa, Medicago sativa, was severe in limited areas in Hooper, Weber County, and in 1927 and 1928 the infestation was very pronounced in certain parts of Salt Lake City

Comparison of consumer attitudes between Cyprus and Latvia: An evaluation of effect of setting on consumer preferences in the water industry

This is the post-print version of the article. The official published version can be obtained from th link below - Copyright @ SpringerModels approaching consumer expectations of their water supplier from a risk perspective suggest that consumers primarily and overwhelmingly want safe drinking water supply. In this study consumer preferences in the water sector are investigated in two contrasting case studies: Cyprus, where there have been significant quantity and continuity of supply issues, and Riga, where there have been water quality issues. While water quality is undoubtedly the main priority of water consumers in Riga, in Cyprus consumers indicate that they prioritise a more reliable service even though many are sufficiently dissatisfied with water quality that they do not drink the tap water. The analysis of consumer attitudes in the two case studies suggests that when water supply is unreliable, reliability takes precedence; once it is reliable quality issues come to the fore.This research was carried out as part of Work Area 6 of the TECHNEAU project, an integrated project funded under FP6 of the European Commission, grant number: 018320

Multiscale analysis of heat transfer in fully developed turbulent channel flow

ManuscriptAn analysis is given for fully developed thermal transport through a wall-bounded turbulent fluid with constant heat flux supplied at the boundary. The analysis proceeds from the aver-aged heat equation and utilizes, as principal tools, various scaling considerations. The paper first provides an accounting of the relative dominance of the three terms in that averaged equation, based on existing DNS data. The results show a clear decomposition of the turbulent layer into zones, each with its characteristic transport mechanisms. There follows a theoretical treatment which justifies and greatly extends these empirical results. The main hypothesis in this development is the monotone and limiting dependence of the difference between the specially scaled centerline and wall temperatures on the Prandtl number, a fact well corroborated by DNS data. A fairly complete qualitative and order-of-magnitude quantitative picture emerges for a complete range in Prandtl numbers. It agrees with known empirical information. In a manner similar to previous analyses of turbulent fluid flow in a channel, conditions for the existence or nonexistence of logarithmic-like profiles are found

Properties of the mean momentum balance in turbulent boundary layer, pipe and channel flows

Journal ArticleThe properties of the mean momentum balance in turbulent boundary layer, pipe and channel flows are explored both experimentally and theoretically. Available high-quality data reveal a dynamically relevant four-layer description that is a departure from the mean profile four-layer description traditionally and nearly universally ascribed to turbulent wall flows. Each of the four layers is characterized by a predominance of two of the three terms in the governing equations, and thus the mean dynamics of these four layers are unambiguously defined

Stress gradient balance layers and scale hierarchies in wall-bounded turbulent flows

Journal ArticleSteady Couette and pressure-driven turbulent channel flows have large regions in which the gradients of the viscous and Reynolds stresses are approximately in balance (stress gradient balance regions). In the case of Couette flow, this region occupies the entire channel. Moreover, the relevant features of pressure-driven channel flow throughout the channel can be obtained from those of Couette flow by a simple transformation. It is shown that stress gradient balance regions are characterized by an intrinsic hierarchy of "scaling layers" (analogous to the inner and outer domains), filling out the stress gradient balance region except for locations near the wall. The spatial extent of each scaling layer is found asymptotically to be proportional to its distance from the wall

Mal De Debarquement Syndrome

Summary Mal de d

Kink Localization under Asymmetric Double-Well Potential

We study diffuse phase interfaces under asymmetric double-well potential energies with degenerate minima and demonstrate that the limiting sharp profile, for small interface energy cost, on a finite space interval is in general not symmetric and its position depends exclusively on the second derivatives of the potential energy at the two minima (phases). We discuss an application of the general result to porous media in the regime of solid-fluid segregation under an applied pressure and describe the interface between a fluid-rich and a fluid-poor phase. Asymmetric double-well potential energies are also relevant in a very different field of physics as that of Brownian motors. An intriguing analogy between our result and the direction of the dc soliton current in asymmetric substrate driven Brownian motors is pointed out