Presence Of Pipes Research Articles

Time Variations of Scour Below Submerged Skewed Pipelines

The presence of pipe across river initiates the piping effect combined with the stagnation eddy and vortex system in the vicinity of the pipeline. The main objective of the research is to investigate the physics of scour below skewed pipeline in river crossing as well as the time variations of the scour development. In this study, the experiments were conducted for four different angles of pipe (30°, 45°, 60° and 90°) across a channel and placed on the sediment bed with e/D = 0. The scour development for flow shallowness y/D = 3 and y/D = 4, initiated at downstream side of the pipe, where the bed sediment appeared to be ejected from the bed due to the piping effect process. At the initial stage, the scour process for 150mm flow depth enlarged rapidly. Whilst, the scour process for 200 mm flow depth slowly developed and after certain time, the sediment bed scoured rapidly. The scour depth increased considerably at development stage and the suspended load near the bed especially below the pipe decreased significantly compared to the initial stage. The rate of sediment eroded from the sediment bed decreased at the stabilization phase. The equilibrium phase of the scour depth considered achieved as the dimensions of the scour hole do not change significantly.

Characterization of Flow Within a Fuel Cell Manifold Subject to Asymmetric Inlet Conditions

Achievement of flow uniformity among cells of a fuel cell stack continues to be an issue in fuel cell design and can affect performance and longevity. While many studies have sought to examine the effects of manifold and cell geometries on stack pressure drops and current density, few have provided detailed mapping of the manifold flowfield or examined the effect of reactant supply pipe bends on this flow, as these bends can introduce flow asymmetries within the pipe downstream of the bend. A simplified scaled up model of a proton exchange membrane (PEM) fuel cell was fitted with different inlet flow configurations, including straight piping and piping containing a 90 deg bend and 180 deg bend prior to entering the manifold. Particle image velocimetry (PIV) was used to obtain mean and fluctuating velocity statistics within the manifold and in individual cells. These distributions were compared with previous results using a partially developed square inlet profile, as well as available experimental and computational data in the literature. The presence of pipe bends resulted in highly skewed flow within the manifold, which also affected the flow distribution among individual cells.

Procesos de piping en la región de Murcia (Sureste de España)

The processes of sub superficial erosion or piping have a wide development in semiarid environment when the suitable characteristics for it happen. In the Region of Murcia 67 areas have been located where the presence of piping concerns a notable surface and whose evolution degree is very advanced. These areas often coincide with neogene-quaternary basins, of marly lithologie, and whose predominant soil use are old dryness culture fields, terraced and abandon today. In all the areas detailed morphologic studies have been realized and in 15 of them, soil samples at two depths (surface and 100 cm depth) were taken. Physic- chemist analysis have been carried out with the aim to study their characteristics and to establish possible formation reasons. From the morphologic point of view, the terraced importance stands out on having generated a hydraulic gradient and as the pipes depth usually coincides with the low terrace height. The results of the realized analyses show as the piping presence, in the majority of the areas, is linked to changes in the structure and soils texture at different depths (thinner textures in depth and lacking structure soils), and high exchangeable sodium percentage (superior at deeper levels) what favours the soil dispersion and the appearance of these processes. As practices of soil conservation, in areas with these characteristics, the terraced fields would be totally inadvisable, especially with high terraces, and its later abandon.

Implications of natural soil piping for basin management in upland Britain

AbstractNatural soil pipes are a common feature in the British upland landscape, especially in podzolic and peat soils (spodosols and histosols). It is estimated that 30% of Britain (UK) is covered by soils susceptible to pipe development. Current re‐evaluation of the use of the uplands, including moves to preserve biodiversity, rehabilitate acidified surface waters, afforest, and recreate a ‘pre‐industrial’ landscape with aesthetic planting of previously native trees and shrubs, highlights the need to understand the key processes of hillslope hydrology that may affect the impact of any policy changes and the effectiveness of any rehabilitation programme.This paper reviews the evidence that soil piping can have a significant effect upon streamflow response, water quality and acidification, as well as creating diversity in plant communities and soil types, and initiating erosion features. Evidence from the University of Wales Experimental Catchment at Maesnant is compared with the results of observations elsewhere in the British uplands and with experience gained from research programmes in other countries. Some of the effects of piping, such as aggravation of the effects of acid rain and increases in the rate of floodflow response, may currently be regarded as negative. Conversely, its effects on landscape diversity are clearly positive. Piping is a natural process and should be regarded as an integral element in preserving and restoring a ‘natural’ landscape. Most importantly, the presence of piping can alter the ‘stormflow contributing area’ within a basin and significantly expand the area of catchment over which landuse change is likely to impact upon the hydrological and hydrochemical response of the catchment.The paper analyses the environmental impact of piping and considers the implications for basin management. Copyright © 2004 John Wiley & Sons, Ltd.

Characteristics and controlling factors of bank gullies in two semi-arid mediterranean environments

Bank gullies are gullies that are formed due to a height drop caused by a terrace or a river bank, which develop by headward retreat in erodible hillslopes. This study aims (i) to investigate the morphology of actively eroding bank gullies, i.e., geometrical characteristics resulting from past erosion and active erosion processes shaping the gully, and, (ii), to find relationships with environmental site characteristics, such as topographical parameters, material properties and climate. The ultimate goal is to identify the most important controlling factors of past and present bank gully erosion. Fifty-five active bank gullies formed in different lithologies by various erosion processes have been selected in the Guadalentin basin and the surroundings of Guadix (Southeast Spain). For each bank gully site, geometrical and topographical parameters of both the channel and the drainage basin were measured. Erosion features indicating activity at the gully head, such as tension cracks, plunge pools, undercutting, fluting, piping and rill or sheet erosion on sloping side walls were mapped, and samples were taken from distinct lithological layers that were considered to influence the type and intensity of erosion processes. A relationship could be shown between the presence of piping and fluting and a number of material characteristics, including particle size distribution, dispersion behaviour and electrical conductivity. On the other hand, lithology appeared not to be a differentiating factor on gully development in the long run, as expressed by the total eroded volume ( V). This parameter was most strongly related to the drainage basin area in which the entire bank gully had been formed ( A o), explaining 66% of the variance. The relationship is V=1.75* A o 0.59. No significant difference was found between regression lines through sub-datasets of different soil textural classes. Finally, multiple regression was used to include both topographical parameters and material characteristics in an explanatory and/or predictive equation for the total eroded bank gully volume. The results of the analyses using the entire dataset, including the sites in the Guadalentin as well as in the Guadix area, have been compared with the results for the separate study areas. Differences are not only related to topographical and lithological characteristics, but may also be the consequence of a different climate in the two areas.

The influence of internal chills on the structure and properties of aluminium alloy castings

Many of the drawbacks associated with the production of conventionally cast ingots and castings, such as the presence of pipes, centre-line segregation and columnar grains, can be attributed to the manner and extent of cooling inside the mould cavity and the problems of heat transfer from the centre to the outside of the casting. These result in lowering of the average mechanical properties and the yield of the casting. In the past, the use of external chills to reduce the above defects has had limited effects. This is because the influence of external chills becomes marginal beyond a certain distance. One of the potential methods of overcoming such problems is to employ heat sinks in the form of internal chills. Despite reported work by Russian and Japanese investigators on the use of internal chills, in the form of powder or strip, in iron and steel castings, no detailed information on the use of such chills in aluminium or other non-ferrous alloys is available in the literature.This paper presents details and findings of an investigation carried out with Al-4.5% Cu (LM11) alloy using chills of cylindrical form of the same composition. The influence of such internal chills, placed centrally and non-centrally was assessed in terms of changes in solidification time, temperature gradient, percentage melting, microstructure, density, and the ultimate tensile strength of the castings.The investigation has shown that solidification time decreases linearly with the percentage volume of the chills. Progressive structural refinement, corresponding to this reduction in solidification time, has also been observed. Distribution of the chills is seen to play an important role. One centrally-placed chill is essential in the refinement of the structure of the central region of an ingot, as well as to reduce the size of the central open pipe. The use of microchills in the form of turnings and powder has also been found to refine the structure considerably. The density and ultimate tensile strength of castings has been found to increase up to the optimum volume of chill, i.e. 2.5% at 75–115 K and 0.63% at 35 K superheat, and then decrease.

Fluidization pipes in volcaniclastic mass flows, Volcan Hudson, Southern Chile

ABSTRACTThe presence of fluidization pipes within pyroclastic sediments has been proposed as a criterion for differentiating these volcaniclastic deposits from those of epiclastic mass flows. Observations of pipe structures within low‐temperature epiclastic mudflows produced by the 1971 eruption of Volcan Hudson, Southern Chile, demonstrate that this assumption is invalid and that the presence of pipes may only be utilized to interpret the precise mechanics of the fluidization process itself.

The adsorption and reaction of adenine nucleotides on montmorillonite.

The binding of AMP to Zn(2+)-montmorillonite was investigated in the presence of buffers and salts. Good's buffers, piperazine-N,N'-bis(2-ethanesulfonate) [PIPES] and morpholine-N-2-ethanesulfonate [MES], perturbed the exchangeable cations to a lesser extent (only 9% of Zn2+ displaced by 0.2 M buffer) than was observed with imidazole and lutidine buffers or NaCl and KCl salts (up to 80% of Zn2+ displaced). AMP adsorption isotherms measured in the presence of 0.2 M PIPES, MES, or Na2SO4 exhibited normal Langmuir-type behavior. The adsorption coefficient, KL, is 3-fold greater in the presence of HEPES or PIPES than it is in the absence of buffers. Basal spacings measured by X-ray diffraction for Zn(2+)-montmorillonite are 13 and 15 angstroms in the presence of PIPES, while a value of 12.8 angstroms was determined in the absence of PIPES. These data are interpreted in a model in which the adsorption of AMP is mediated by a Zn2+ complex of PIPES in different orientations in the interlamellar region of the montmorillonite. The type of exchangeable cation does not affect the ability of the lattice-bound Fe3+ in the montmorillonite to oxidize diaminomaleonitrile (DAMN). Exchangeable Cu2+ oxidizes DAMN, but exchangeable Fe3+ is nearly ineffective as an oxidant. The addition of DISN to 3'-AMP bound to Zn(2+)-montmorillonite in the presence of 0.2 M PIPES resulted in a higher yield of 2',3'-cAMP than is observed with a comparable concentration of Zn2+, a result which inplicates surface catalysis by the montmorillonite.

Improved hydrogen ion buffering of media for the culture of freshwater algae

Six hydrogen ion buffers, piperazine-N, N′-bis (2-ethanesulphonic acid) (PIPES), N(-2-acetamido)-2-aminoethanesulphonic acid (ACES), N, N-bis (2-hydroxyethyl)-2-aminoethanesulphonic acid (BES), N-tris (hydroxymethyl)-methyl-2-aminoethanesulphonic acid (TES), N-2-hydroxyethylpiperazine-N′-2-ethanesulphonic acid (HEPES) and N-tris (hydroxymethyl) methylglycine (TRICINE), employed at 0·02 m concentration in freshwater media at their p K a values, were found to have no adverse effects on the growth rates of Oscillatoria redekei van Goor, Chlorella vulgaris Beij. and Pediastrum boryanum (Turp.) Menegh. The doubling times of Aphanizomenon flos-aquae fa. gracile (Ralfs) Lemm. and Anabaena flos-aquae Breb. were lengthened by the presence of PIPES and ACES but this was interpreted as an effect of their low p K a values. Further results with HEPES and Oscillatoria redekei during exponential growth showed that, with a 1% CO2-in-air gas phase, a pH variation of only 0·06 pH units was obtained compared with 2·77 units...

Soil Piping and Stream Channel Initiation

The hydrologic significance of soil piping has been generally ignored. Piping has been associated primarily with drylands, yet evidence of piping is available from a large range of climatic regions. In particular, soil piping is found to be widespread in the United Kingdom. Preferred locations for piping are either just above or within a horizon of low relative permeability and low aggregate stability. Chemical environment may range from acidic moorland soils to saline marshes. There are significant trends to lower aggregate stability and coarser grain size (particularly in the range above 250 μm) in the bed of a pipe than in the roof. Many pipes in the areas studied appear to be dormant or relatively inactive and may well be in approximate equilibrium with the soil pore and channel subsystems. However, when equilibrium is destroyed (e.g., by stream incision) pipes can form loci for channel extension. Studies of the spatial distribution of outlets show that to create normal channel networks, pipe clusters within the ensemble and, similarly, individual pipes within those clusters must be selected on an unequal basis. A low density random selection from pipes located on percolines would fulfill the requirements. The presence of piping may have a significant effect on the form of the hydrograph.