CFD Mixing Analysis of Jets Injected from Straight and Slanted Slots into Confined Crossflow in Rectangular Ducts

A CFD study was performed to analyze the mixing potential of opposed rows of staggered jets injected into confined crossflow in a rectangular duct. Three jet configurations were numerically tested: (1) straight (0 deg) slots; (2) perpendicular slanted (45 deg) slots angled in opposite directions on top and bottom walls; and (3) parallel slanted (45 deg) slots angled in the same direction on top and bottom walls. All three configurations were tested at slot spacing-to-duct height ratios (S/H) of 0.5, 0.75, and 1.0; a jet-to-mainstream momentum flux ratio (J) of 100; and a jet-to-mainstream mass flow ratio of 0.383. Each configuration had its best mixing performance at S/H of 0.75. Asymmetric flow patterns were expected and predicted for all slanted slot configurations. The parallel slanted slot configuration was the best overall configuration at x/H of 1.0 for S/H of 0.75

CFD mixing analysis of axially opposed rows of jets injected into confined crossflow

A computational fluid dynamics (CFD) parametric study was performed to analyze axially opposed rows of jets mixing with crossflow in a rectangular duct. Isothermal analysis was conducted to determine the influence of lateral geometric arrangement on mixing. Two lateral arrangements were analyzed: (1) inline (jets' centerlines aligned with each other on top and bottom walls), and (2) staggered (jets' centerlines offset with each other on top and bottom walls). For a jet-to-mainstream mass flow ratio (MR) of 2.0, design parameters were systematically varied for jet-to-mainstream momentum-flux ratios (J) between 16 and 64 and orifice spacing-to-duct height ratios (S/H) between 0.125 and 1.5. Comparisons were made between geometries optimized for S/H at a specified J. Inline configurations had a unique spacing for best mixing at a specified J. In contrast, staggered configurations had two 'good mixing' spacings for each J, one corresponding to optimum inline spacing and the other corresponding to optimum non-impinging jet spacing. The inline configurations, due to their smaller orifice size at optimum S/H, produced better initial mixing characteristics. At downstream locations (e.g. x/H of 1.5), the optimum non-impinging staggered configuration produced better mixing than the optimum inline configuration for J of 64; the opposite results were observed for J of 16. Increasing J resulted in better mixing characteristics if each configuration was optimized with respect to orifice spacing. Mixing performance was shown to be similar to results from previous dilution jet mixing investigations (MR less than 0.5)

The state of agricultural credit in New Zealand

In this paper the subject of agricultural credit has been subdivided into three sections covering background, borrowing, and lending. The background covers some of the changes in the New Zealand economy and government policies which have affected both borrowers and lenders in the agricultural sector, and consequently the amount and form of credit used. The section on borrowing (Section 3) examines the present credit needs of farmers, in particular the apparent trends towards increased equity and greater difficulty in servicing debt. The lending section (Section 4) examines the roles of government and private lending institutions in the field of agricultural credit and changes in the amount and form of credit available

A review of agricultural credit in New Zealand

The following discussion of the agricultural credit market encompasses agriculture in its wider sense. Because most of the available information and data on agricultural credit is concerned with traditional forms of pastoral farming (sheep, beef and dairy) the discussion relates primarily to those sectors. However, the growing importance of other sectors such as horticulture, grain cropping and deer farming is recognised and where possible their credit situation is also considered. The purpose of the paper is to update previous research by the Agricultural Economics Research Unit into the financing of the agriculture industry. In the past the agricultural credit situation has been relatively stable. Because of its large contribution to exports, agriculture (pastoral agriculture in particular) received considerable support from Government in the form of policies aimed at maintaining a steady flow of investment. Credit assistance was one of the cornerstones of these policies. In 1982 the Government began to change its stance. In the Budget of that year interest payments and certain development ceased to be tax deductible where the farm property was sold within 10 years of purchase. Although this steadied inflation in land prices, long term investors particularly pastoral farm investors still enjoyed considerable advantages over investors wishing to borrow capital for diversification into or expansion of enterprises which were capable of better returns on investment. It was not until late 1984 that a wide range of policies were introduced to remove these advantages and promote greater equity between enterprises and industries requiring capital for restructuring or expansion. As a result some of the conclusions reached in Discussion Papers on agricultural and horticultural credit published by the Unit as recently as April and October 1984 have been quickly overtaken by economic events and need updating. This paper begins with a background of trends in the New Zealand economy and then in chronological order details recent changes in Government Policy. This is followed by a discussion of the implications of these changes for the financing of agriculture. Finally the present state of the agricultural credit market is discussed and some conclusions are drawn. The discussion is based on a variety of sources including MAF, Reserve Bank, Treasury, AERU and private economic reports and data. A considerable part of the material was also obtained from personal correspondence and interviews with people directly involved in the finance industry. The views expressed are, of course those of the authors

The structure of causal sets

More often than not, recently popular structuralist interpretations of physical theories leave the central concept of a structure insufficiently precisified. The incipient causal sets approach to quantum gravity offers a paradigmatic case of a physical theory predestined to be interpreted in structuralist terms. It is shown how employing structuralism lends itself to a natural interpretation of the physical meaning of causal sets theory. Conversely, the conceptually exceptionally clear case of causal sets is used as a foil to illustrate how a mathematically informed rigorous conceptualization of structure serves to identify structures in physical theories. Furthermore, a number of technical issues infesting structuralist interpretations of physical theories such as difficulties with grounding the identity of the places of highly symmetrical physical structures in their relational profile and what may resolve these difficulties can be vividly illustrated with causal sets.Comment: 19 pages, 4 figure

Eyes on the bog. Long-term monitoring network for UK peatlands

Eyes on the Bog provides a scientifically robust, repeatable, low tech, long-term monitoring initiative. The standardised methodology enables individual peatland sites to be consistently monitored across the UK, creating a network of comparable sites. The initiative employs cheap, simple techniques and modern technology to enable useful monitoring information to be collected by peatland community employees or volunteers on: Peat subsidence and carbon loss Carbon capture Water table behaviour Peat soil condition Vegetation status, structure and composition Historical context of change and current trajectorie

Changes in union membership over time : a panel analysis for West Germany

Despite the apparent stability of the wage bargaining institutions in West Germany, aggregate union membership has been declining dramatically since the early 90's. However, aggregate gross membership numbers do not distinguish by employment status and it is impossible to disaggregate these sufficiently. This paper uses four waves of the German Socioeconomic Panel in 1985, 1989, 1993, and 1998 to perform a panel analysis of net union membership among employees. We estimate a correlated random effects probit model suggested in Chamberlain (1984) to take proper account of individual specfic effects. Our results suggest that at the individual level the propensity to be a union member has not changed considerably over time. Thus, the aggregate decline in membership is due to composition effects. We also use the estimates to predict net union density at the industry level based on the IAB employment subsample for the time period 1985 to 1997. JEL - Klassifikation: J

p-branes on the waves

We present a large family of simple, explicit ten-dimensional supergravity solutions describing extended extremal supersymmetric Ramond-Ramond p-branes embedded into time-dependent dilaton-gravity plane waves of an arbitrary (isotropic) profile, with the brane world-volume aligned parallel to the propagation direction of the wave. Generalizations to the non-extremal case are not analyzed explicitly, but can be pursued as indicated.Comment: 11 pages; v.2 minor notation changes, minor typos corrected (published version

Tapping Environmental History to Recreate America’s Colonial Hydrology

To properly remediate, improve, or predict how hydrological systems behave, it is vital to establish their histories. However, modern-style records, assembled from instrumental data and remote sensing platforms, hardly exist back more than a few decades. As centuries of data is preferable given multidecadal fluxes of both meteorology/climatology and demographics, building such a history requires resources traditionally considered only useful in the social sciences and humanities. In this Feature, Pastore et al. discuss how they have undertaken the synthesis of historical records and modern techniques to understand the hydrology of the Northeastern U.S. from Colonial times to modern day. Such approaches could aid studies in other regions that may require heavier reliance on qualitative narratives. Further, a better insight as to how historical changes unfolded could provide a “past is prologue” methodology to increase the accuracy of predictive environmental models