Pneumatic Transport of Fine Granular Material

1969 ◽  
Vol 91 (2) ◽  
pp. 315-322
Author(s):  
G. Broersma
Keyword(s):  
Boundary Layer ◽  
Capital Investment ◽  
Production Efficiency ◽  
Vertical Plane ◽  
Pneumatic Transport ◽  
Sand Transport ◽  
Actual Case ◽  
Moulding Sand ◽  
Stationary Laminar ◽  
Fine Granular Material

Investigations show that production efficiency of foundries is influenced strongly by the nature and the use of means of transport. An important aspect of foundry transport is that of moulding sand. Impressive gains in space, as well as a decrease in capital investment may be had by applying pneumatic transport of moulding sand. The paper presents a basic approach to the nature of pneumatic transport of sand in a horizontal and circular tube, and indicates an approach to the calculation of the pressure gradient to be overcome. Although the analysis of the transport in a stationary laminar flow is interesting, it appears that sand is carried through a narrow sector of the tube, symmetrical to the vertical plane, and below the horizontal plane [1]. In the actual case of sand transport in a turbulent air current through a tube with a rough inner wall, sand is carried through the boundary layer at the complete circumference of the tube. It is easily seen how to generalize the approach for sand transport in a turbulent air current through a tube at an inclination to the horizontal, up to the vertical, and how to increase sand transport by injecting air which increases the turbulence of the boundary layer carrying the sand. After the various parameters for the stationary transport have been deduced, it appears to be possible to analyze the introduction of the sand grains into the air current as well as their acceleration to stationary motion [1].

Dynamics of Aeolian Sand Streamers and Airflow Turbulence over a Beach Surface

2021 ◽  
Author(s):  
Andreas Baas
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Temporal Variability ◽  
Large Scale ◽  
Sonic Anemometer ◽  
Dynamic Structure ◽  
Sand Transport ◽  
Video Imagery ◽  
Spatio Temporal ◽  
The Impact

<p>Sand transport by wind over granular beds displays dynamic structure and organisation in the form of streamers (aka ‘sand snakes’) that appear, meander and intertwine, and then dissipate as they are advected downwind. These patterns of saltating grain populations are thought to be initiated and controlled by coherent flow structures in the turbulent boundary layer wind that scrape over the bed surface raking up sand into entrainment. Streamer behaviour is thus fundamental to understanding sand transport dynamics, in particular its strong spatio-temporal variability, and is equally relevant to granular transport in other geophysical flows (fluvial, submarine).</p><p>This paper presents findings on streamer dynamics and associated wind turbulence observed in a field experiment on a beach, with measurements from 30Hz video-imagery using Large-Scale Particle Image Velocimetry (LS-PIV), combined with 50Hz wind measurements from 3D sonic anemometry and co-located sand transport rate monitoring using an array of laser particle counters (‘Wenglors’), all taking place over an area of ~10 m<sup>2</sup> and over periods of several minutes. The video imagery was used to identify when and where streamers advected past the sonic anemometer and laser sensors so that relationships could be detected between the passage of turbulence structures in the airflow and the length- and time-scales, propagation speeds, and sand transport intensities of associated streamers. The findings form the basis for a phenomenological model of streamer dynamics under turbulent boundary layer flows that predicts the impact of spatio-temporal variability on local measurement of sand transport.</p>

Recent Developments in the Ironfounding Industry

1972 ◽  
Vol 186 (1) ◽  
pp. 149-168
Author(s):  
H. Morrogh
Keyword(s):  
Capital Investment ◽  
Production Efficiency ◽  
Cumulative Effect ◽  
Spheroidal Graphite ◽  
Mechanical Equipment ◽  
Cast Irons ◽  
Delivery Times ◽  
Iron Castings ◽  
Wide Range ◽  
Recent Developments

Iron castings are in extensive use throughout engineering construction and are available in a wide range of properties, casting size and complexity. Ironfounding is in part associated with a particular industry—the ironfounding industry—and is in part a production engineering technique adopted by firms, their designers and engineers, on the basis of its process and product merits compared with those of other techniques. The changing pattern of manufacture and competition from other techniques is having important influences on the structure and capacity of industry producing iron castings. Additionally, the repeated cycles of business recession may result in the disappearance of the facilities for the production of certain types of foundry product. Although most recent developments in ironfounding are a continuation of trends which could be discerned or forecast a long time ago, the cumulative effect of these changes has been to revolutionize completely some aspects of the process of iron casting. The range of cast irons has been somewhat increased in recent years by addition to the variety of spheroidal graphite (s.g.) irons, malleable irons and alloy cast irons available. Most of the recent developments in ironfounding have, however, been concerned with improving production efficiency and the introduction of new melting, moulding and coremaking processes, enabling the ironfounder to provide the engineer and designer with a better service—maintaining prices at low level, improving dimensional accuracy and casting soundness with reduced delivery times. This has been achieved by the increased use of scrap made possible by developments in melting furnaces and molten metal treatment, by the introduction of new and improved moulding machinery and by the adoption of new methods of bonding sand used for moulds and cores, replacing many traditional techniques. These changes have had their influence equally in the large, highly mechanized mass-production foundries and in the jobbing foundries catering for short run work. An ironfoundry is an extremely exacting environment for mechanical equipment and for all control engineering. For this reason automatic moulding and other foundry plant need special design and robust construction. Most mechanized foundry plant of an automatic character represents a high capital investment which must run for long periods without breakdown, requiring long orders and work of a repetitive character.

Adaptation of the near-surface wind to the development of sand transport

1993 ◽  
Vol 252 ◽  
pp. 99-115 ◽  
Author(s):  
Ian K. Mcewan ◽  
Brian B. Willetts
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Surface Wind ◽  
Internal Boundary Layer ◽  
Internal Boundary ◽  
Sand Transport ◽  
Temporal Response ◽  
Near Surface ◽  
Spatial Response ◽  
Aerodynamic Roughness

A model of wind-blown sand transport is described with particular emphasis on the feedback between the grain cloud and the near-surface wind. The results from this model are used to develop Owen's (1964) hypothesis that ‘the grain layer behaves, so far as the flow outside it is concerned, as increased aerodynamic roughness whose height is proportional to the thickness of the layer’. The hypothesis is developed to show the influence this dynamic roughness has on the turbulent boundary layer above the saltation layer. Two processes are identified which influence the path of the system towards equilibrium. The first is the feedback between the near-surface wind and the grain cloud in which the quantity of sand transported is limited by the carrying capacity of the wind. The second is due to the temporal development of an internal boundary layer in response to the additional roughness imposed on the flow above the grain layer by the grain cloud. A similarity is noted between the temporal response of a turbulent boundary layer to sand transport and the spatial response of a turbulent boundary layer downstream of a step increase in surface roughness. Finally it is noted that the work may have important implications for transport rate prediction in unsteady winds.

scholarly journals Turbulent Natural Convection from a Vertical Plane Surface

1968 ◽  
Vol 90 (1) ◽  
pp. 1-6 ◽  
Author(s):  
R. Cheesewright
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Natural Convection ◽  
Vertical Plane ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Convection Boundary Layer ◽  
Transfer Coefficients ◽  
Turbulent Natural Convection ◽  
Heat Transfer Coefficients

The paper reports the results of an experimental investigation which was intended to clarify the present uncertain position with regard to the distributions of mean temperature and mean velocity in a turbulent natural-convection boundary layer. Data reported for the turbulent boundary layer for Grashof numbers between 1010 and 1011 include local heat transfer coefficients as well as temperatures and velocities. Local heat transfer coefficients and temperature distributions are also reported for the laminar and transitional boundary-layer regions. Results are compared with other experimental data and with theoretical predictions.

scholarly journals Business Profile of Australian Nurseries

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 456E-456
Author(s):  
Robin G. Brumfield ◽  
Peter F. McSweeney
Keyword(s):  
Capital Investment ◽  
Production Management ◽  
Production Efficiency ◽  
Cash Flows ◽  
Marketing Strategies ◽  
Labor Costs ◽  
Increase Production Efficiency ◽  
Chain Stores ◽  
General Terms ◽  
The U.S

We surveyed 22 Australian nurseries in 1995 to: 1) develop a profile of Australian nurseries from a production, management, and profitability perspective; 2) compare the data to relevant U.S. benchmarks; and 3) identify trends and potential areas of improvement in the management of Australian nursery enterprises. The study confirmed that Australian nurseries incur high labor costs (38.8% of sales) that are comparable to United States nurseries, while costs of materials and supplies were lower than their U.S. counterparts. Overall, the costs of the surveyed nurseries appeared lower than their U.S. counterparts. Concerns of managers were directed towards recruiting and keeping labor and marketing rather than increasing capital investment to increase production efficiency. Capital expenditures tended to be funded from internal cash flows rather than external borrowings. Many of the nursery managers used relatively simple performance indicators and most business objectives were stated in general terms. Australian nurseries carried more diverse product ranges than the U.S. nurseries. Many of the nurseries adopted quite vigorous marketing strategies with a stronger emphasis on marketing than in those in the U.S. Concerns about the viability of the industry included oversupply, the growth in chain stores business, factors eroding the demand for nursery products and greater regulation.

scholarly journals SAND TRANSPORT BY SURFACE WAVES: CAN STREAMING EXPLAIN THE ONSHORE TRANSPORT?

2011 ◽  
Vol 1 (32) ◽  
pp. 11
Author(s):  
Wouter Kranenburg ◽  
Jan Ribberink ◽  
Rob Uittenbogaard
Keyword(s):  
Boundary Layer ◽  
Sediment Transport ◽  
Sediment Flux ◽  
Sand Transport ◽  
Current Profile ◽  
Fall Velocity ◽  
Full Explanation ◽  
Wave Induced ◽  
Further Development ◽  
Additional Current

In wave flumes an onshore boundary layer current is present that is not present in oscillating flow tunnels. We investigate numerically the hypothesis that this streaming explains the measured increase of onshore directed sediment transport in flumes over tunnels. In the formulation and validation of the model special attention has been given to the wave-generated net current profile. From model experiments we conclude that the additional current indeed contributes to onshore transport, but can not be the full explanation of the measured differences in transport rates. Other contributing mechanisms are the amplification/reduction of the fall velocity by vertical sediment advection (only relevant for fine grains) and the amplification/reduction of the concentration at maximum onshore/offshore velocity by intra-wave gradients in horizontal sediment flux. The latter contributes, for the investigated cases, to onshore transport with comparable order as the boundary layer current. These conclusions are relevant for further development of parameterizations of wave-induced sediment transport for morphodynamic models.

THE ECONOMIC COMPONENT EVALUATION OF AGRICULTURAL PRODUCTION SUSTAINABLE DEVELOPMENT IN CONDITIONS OF NATIONAL ECONOMY OPENNESS

2019 ◽  
Vol 4 (4) ◽  
pp. 265-281
Author(s):  
Nataliya LAGODIIENKO ◽  
Vladyslav LAGODIIENKO
Keyword(s):  
Sustainable Development ◽  
National Economy ◽  
Agricultural Production ◽  
Capital Investment ◽  
Production Efficiency ◽  
Agricultural Sector ◽  
Economic Life ◽  
Poultry Meat ◽  
Meat Production ◽  
The Real

Introduction. The article assesses the importance of economic efficiency of agricultural production sustainable development in the conditions of the national economy openness. It is noted that sustainable development as a new form of social dynamics, applies to all spheres of socio-economic life and requires scientific and methodological development of models and mechanisms for its implementation in the practice of management. The least developed aspects of it now remain the problem of assessing the economic component of the agricultural production sustainable development in the conditions of the national economy openness. The purpose of the article is to assess the economic component of sustainable development of agricultural production in the conditions of the national economy openness. Within the achieve-ment of the goal, the following tasks were identified: research into the dynamics of the main indicators of the agricultural production level; estimation of indicators of agricultural enterprises economic activity; research of the self-sufficiency level in Ukraine by the main types of food. Results. It has been researched that in the agricultural sector of agrarian production of Ukraine there are positive changes – yields of all included in the analysis crops tend to increase. However, the indicators of the stability level of such growth (coefficient of variation) show significant differentiation. Despite the low values of the variation coefficients in agricultural productivity (excluding the average daily growth of pigs), the current state of the domestic livestock industry cannot be called satisfactory – because the number of cattle and pigs that are not compensated for the growth of animals continues to decline. As a result, production of milk, beef and pork decreases. In livestock farming, the decrease in production can only be compensated by the increase in poultry meat production. Conclusions. There is an extremely unstable dynamics of agricultural production. In our opinion, the main reason for the sharp fluctuations in production downward was: 1) rapid devaluation of the hryvnia; 2) the loss of traditional markets. The real flow of investment into agriculture demonstrates extremely volatile dynamics. The real dynamics of capital investment in Ukraine’s agriculture, not distorted by inflationary influence, has a low level of stability. Keywords: agricultural production, sustainable development, social infrastructure, rural territories, food security, economic component of sustainable development, production efficiency.

scholarly journals The ventilated filling box containing a vertically distributed source of buoyancy

2010 ◽  
Vol 646 ◽  
pp. 39-58 ◽  
Author(s):  
PAUL COOPER ◽  
GARY R. HUNT
Keyword(s):  
Boundary Layer ◽  
Theoretical Analysis ◽  
Point Source ◽  
Single Point ◽  
Vertical Plane ◽  
Vertical Direction ◽  
General Situation ◽  
Uniform Density ◽  
Distributed Source ◽  
Naturally Ventilated Buildings

This paper describes the fluid mechanics within a box containing a vertical plane distributed source of buoyancy. A theoretical analysis is presented that models the development of plumes from such sources in an unconfined ambient of uniform density. Two extensions are considered. The first concerns a sealed box and the second involves the more general situation where the box is ventilated by openings at top and bottom. In the sealed box the stratification develops in much the same way as for a ‘filling box’ containing a single-point source of buoyancy on the floor. An initial front descends from the ceiling of the box and an asymptotic stratification eventually develops which is continuous in the vertical direction. In the case of the ventilated box it is found that a complex stratification develops where one or more horizontal intrusions are formed by detachment of the plume/boundary layer from the vertically distributed source where the buoyancy of the plume is less than, or equal to, that of the stratified ambient at a given height. Experimental results are presented to demonstrate the validity of the theory. The findings are relevant to both forced and naturally ventilated buildings containing non-adiabatic vertical surfaces.

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