scholarly journals Experimental Study on Hydraulic Conductivity and Resistance in Silty Sediments

Water ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 75
Author(s):  
Wenlong Zhu ◽  
Minxi Zhang ◽  
Hui Sun ◽  
Guoliang Yu
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Hydraulic Conductivity ◽  
Friction Factor ◽  
Empirical Formula ◽  
Void Ratio ◽  
Particle Diameter ◽  
Median Particle Diameter ◽  
Median Particle ◽  
Silty Sediment

Hydraulic conductivity k as a function of void ratio e and particle diameter for silty sediment was experimentally investigated, and an empirical formula for the estimation of hydraulic conductivity was proposed. Seepage resistance for flow in silty sediment was deliberated. Based on the findings of the study, it was concluded that hydraulic conductivity k could be expressed as an exponential function of void ratio e and median particle diameter d50 {3.1 μm < d50 < 87 μm and 0.26 < e < 4}. It was further found that the formula of seepage resistance factor (?), a form of friction factor, varies linearly with Reynolds number (Re) for silty sediments. A family of such λ-Re curves for various particle diameter d50 is presented.

The intertidal macrofauna of Nigg Bay

1986 ◽  
Vol 91 ◽  
pp. 113-141
Author(s):  
D. Raffaelli ◽  
P. R. Boyle
Keyword(s):  
Particle Diameter ◽  
Detrended Correspondence Analysis ◽  
Distribution Patterns ◽  
Trophic Levels ◽  
Median Particle Diameter ◽  
Moray Firth ◽  
Median Particle ◽  
Biological Characters ◽  
Rich Fauna ◽  
Factor Governing

SynopsisSurveys of the intertidal macrofauna and sediment characters of Nigg Bay, Moray Firth, were carried out between 1981 and 1985. Permanent stations were located at the intersections of a half-kilometre grid covering the entire intertidal area and sampled for infauna, using replicate cores. Estimates were also made of mussel and lugworm densities from quadrats and cast counts respectively. The biomasses of selected species that constitute important resources for higher trophic levels were also estimated. The sediment for each station was analysed for median particle diameter and silt content.The infaunal data were analysed by Detrended Correspondence Analysis. This indicated that tidal height was the most important factor governing the distribution and abundance of the intertidal communities. Sediment characters were only poorly related to distribution patterns.The bay has a rich fauna and is biologically similar to other outer bays of the Moray Firth, which, like Nigg, are important areas for wildfowl and waders. Comparisons of survey data from different years indicate that there are natural cycles in some sediment and biological characters of Nigg Bay.

scholarly journals Validation of friction factor predictions in vertical slurry flows with coarse particles

2020 ◽  
Vol 68 (2) ◽  
pp. 119-127 ◽  
Author(s):  
Artur Bartosik
Keyword(s):  
Mathematical Model ◽  
Reynolds Number ◽  
Friction Factor ◽  
Particle Diameter ◽  
Solid Particles ◽  
Coarse Particles ◽  
Carrier Liquid ◽  
Different Types ◽  
Slurry Flows ◽  
The Mathematical Model

AbstractThe paper presents validation of a mathematical model describing the friction factor by comparing the predicted and measured results in a broad range of solid concentrations and mean particle diameters. Three different types of solids, surrounded by water as a carrier liquid, namely Canasphere, PVC, and Sand were used with solids density from 1045 to 2650 kg/m3, and in the range of solid concentrations by volume from 0.10 to 0.45. All solid particles were narrowly sized with mean particle diameters between 1.5 and 3.4 mm. It is presented that the model predicts the friction factor fairly well. The paper demonstrates that solid particle diameter plays a crucial role for the friction factor in a vertical slurry flow with coarse solid particles. The mathematical model is discussed in reference to damping of turbulence in such flows. As the friction factor is below the friction for water it is concluded that it is possible that the effect of damping of turbulence is included in the KB function, which depends on the Reynolds number.

The Intrusion of Fine Sediments into a Stable Gravel Bed

1979 ◽  
Vol 36 (2) ◽  
pp. 204-210 ◽  
Author(s):  
Robert L. Beschta ◽  
William L. Jackson
Keyword(s):  
Sediment Transport ◽  
Pore Space ◽  
Particle Diameter ◽  
Experimental Tests ◽  
Gravel Bed ◽  
Fine Sediments ◽  
Median Particle Diameter ◽  
Key Words Sediment ◽  
Median Particle ◽  
Flow Variables

A rectangular flume was used to study variables affecting the intrusion of fine sands into a stable gravel streambed. The amount of intrusion by sand (median particle diameter 0.5 mm) was determined under varied conditions of discharge, depth, velocity, flume slope, and rates of sediment transport. During all experimental tests, sand particles were trapped in voids within the upper 10 cm of an initially clean gravel bed (median particle diameter 15 mm), forming a barrier to further intrusion. An analysis of flow variables showed that flow conditions, as indexed by Froude number, significantly (90% confidence level) affected intrusion amounts, possibly by influencing the rate and depth of formation of the sand seal. Intrusion amounts, expressed as a percent of total volume, varied from 2 to 8%. Two replications used a finer grade sand (median particle diameter 0.2 mm) that intruded more and, in one case, completely filled the gravel pore space (25% by volume), further indicating that particle size, and not hydraulic variables, may have a more important influence on the total amount of intrusion. Key words: sediment transport, intrusion, streambed, substrates, riffles, sedimentation

An expert system with radial basis function neural network based on decision trees for predicting sediment transport in sewers

2016 ◽  
Vol 74 (1) ◽  
pp. 176-183 ◽  
Author(s):  
Isa Ebtehaj ◽  
Hossein Bonakdari ◽  
Amir Hossein Zaji
Keyword(s):  
Neural Network ◽  
Expert System ◽  
Sediment Transport ◽  
Radial Basis Function ◽  
Decision Trees ◽  
Basis Function ◽  
Particle Diameter ◽  
Median Particle Diameter ◽  
Radial Basis ◽  
Median Particle

In this study, an expert system with a radial basis function neural network (RBF-NN) based on decision trees (DT) is designed to predict sediment transport in sewer pipes at the limit of deposition. First, sensitivity analysis is carried out to investigate the effect of each parameter on predicting the densimetric Froude number (Fr). The results indicate that utilizing the ratio of the median particle diameter to pipe diameter (d/D), ratio of median particle diameter to hydraulic radius (d/R) and volumetric sediment concentration (CV) as the input combination leads to the best Fr prediction. Subsequently, the new hybrid DT-RBF method is presented. The results of DT-RBF are compared with RBF and RBF-particle swarm optimization (PSO), which uses PSO for RBF training. It appears that DT-RBF is more accurate (R2 = 0.934, MARE = 0.103, RMSE = 0.527, SI = 0.13, BIAS = −0.071) than the two other RBF methods. Moreover, the proposed DT-RBF model offers explicit expressions for use by practicing engineers.

Effect of Reaction Temperature in the Alumina Preparation by Combustion in a Muffle Furnace

2014 ◽  
Vol 775-776 ◽  
pp. 687-691 ◽  
Author(s):  
Mirele Costa da Silva ◽  
Ana Cristina F. Melo Costa ◽  
Hélio Lucena Lira ◽  
Normanda Lino de Freitas
Keyword(s):  
Size Distribution ◽  
Particle Diameter ◽  
Synthesis Temperature ◽  
Effect Of Temperature ◽  
X Ray Diffraction ◽  
Muffle Furnace ◽  
X Ray ◽  
Median Particle Diameter ◽  
Particles Size Distribution ◽  
Median Particle

The aim of this study is to evaluate the effect of temperature during the synthesis of alumina by combustion in a muffle furnace. The alumina was characterized by X-ray diffraction, particles size distribution and scanning electron microscopy. The results showed that the synthesis temperature of the alumina can affect the structure of the produced samples. The size distribution of the median particle diameter reached higher value for the alumina synthesized at 500°C with 16.07 μm, the range of the total distribution of particles is introduced to the large alumina synthesized 500 and 600°C and close synthesized when 700 and 800°C. The phase of the alumina was identified only after the synthesized sample at 800°C with crystallite size of 22.16 and 6.75 μm synthesized samples 800 and 900°C, respectively. With respect to morphology, increased synthesis temperature was not enough to significantly change.

Development of Conductive and Anticorrosive Paint Dispersed with Carbon Particles for Metal Separators of PEFC

2007 ◽  
Vol 534-536 ◽  
pp. 1433-1436
Author(s):  
Masahiro Okahara ◽  
Zenzo Ishijima ◽  
Minoru Shirahige
Keyword(s):  
Electricity Generation ◽  
Particle Diameter ◽  
Conductive Filler ◽  
Polymer Electrolyte Fuel Cells ◽  
Passive State ◽  
Severe Reaction ◽  
Mixed Powder ◽  
Carbon Particles ◽  
Median Particle Diameter ◽  
Median Particle

A resin paint dispersed with carbon particles was developed for the purpose of good conductivity and corrosion resistance for metal separators used in Polymer Electrolyte Fuel Cells (PEFC). The use of metal separators, especially Ti separators is a technology which has received much attention for its practical application as it allows for much greater compact stacking, since it is superior in both productivity and strength, in comparison with that of carbon molding separators. However, if pure Ti separators are used in a severe reaction of electricity generation, there is a deterioration in conductivity, because of the formation of a passive film, which subsequently causes electricity generation difficulties after a few hours of use. Through examining the type of resin used for the purpose of controlling the passive state, the grain size of the conductive filler (graphite (Gr) + carbon black (CB)) and the composition combination for the purpose of secure conductivity, it was found that the combination of a scaly graphite-furnaced black mixed powder with a median particle diameter of 4μm and VDF-10%HFP copolymer resin was optimal. As a result of performing a single cell electricity generation evaluation of the Ti separator, which had the above mentioned coating material, the life of 22,000 or more hours was confirmed and an electricity generation evaluation is now being undertaken.

The ecology of Bathyporeia pilosa (Amphipoda: Haustoriidae) in the Tay Estuary. I. Factors influencing the distribution on Tayport and Tentsmuir beaches

1980 ◽  
Vol 78 (3-4) ◽  
pp. s109-s119 ◽  
Author(s):  
N. H. Khayrallah ◽  
A. M. Jones
Keyword(s):  
Particle Diameter ◽  
Clay Content ◽  
Sedimentary Characteristics ◽  
Median Particle Diameter ◽  
Median Particle ◽  
Distribution Studies ◽  
Chemical Characters ◽  
Physical And Chemical ◽  
Sediment Preference

SynopsisThe distribution of Bathyporeia pilosa is discussed in relation to variations in a number of physical and chemical characters of the sediment on eight transects. Relationships were found between density and median particle diameter, silt content, and water content of the sediment, but stability of the beach appeared to be the main parameter influencing B. pilosa distribution. Sediment preference experiments showed that sediments varied in attractiveness, medium and fine grade sands being preferred: coarse sands and muds were avoided as were sediments with a high silt and clay content. Attractiveness in laboratory conditions was not correlated with observed field densities in some cases, indicating that other parameters were important in determining the distribution. Studies of swimming behaviour demonstrated the importance of current speed during the pelagic phase and it is concluded that hydrological conditions may be as important as sedimentary characteristics in the determination of the distribution of this species.

An Experimental Study of Heat Transfer and Pressure Drop on the Bend Surface of a U-Duct

2010 ◽  
Author(s):  
Tareq Salameh ◽  
Bengt Sunden
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Cross Section ◽  
Outer Wall ◽  
Cross Section Area ◽  
Section Area ◽  
The Cross

This work concerns an experimental study of pressure drop and heat transfer for turbulent flow inside a U-duct. Such duct geometries can be found in many engineering applications where cooling air extracts heat from hot internal walls of the duct, e.g., passage cooling inside gas turbine blades. Both friction factors and convective heat transfer coefficients were measured inside a U-duct for three different cases, namely (a) the smooth straight part, (b) the smooth bend (turn) part, and (c) a rough (ribbed) bend (turn) part. The details of the duct geometry were as follows: the cross section area of the straight part was 50×50 mm2, the inside length of the bend part 240 mm, the cross section area of the rib was 5×5 mm2 and the rib height-to-hydraulic diameter ratio, e/Dh, was 0.1. The Reynolds number was varied from 8,000 to 20,000. The test rig has been built in such a way that various experimental setups can be handled as the bend (turn) part of the U-duct can easily be removed and the rib configuration can be changed. Both the U-duct and the rib were made from plexiglass material to allow optical access for measuring the surface temperature by using a high-resolution measurement technique based on narrow band thermochromic liquid crystals (TLC R35C5W) and a CCD camera placed facing the bend (turn) part of the U-duct. The calibration of the TLC is based on the hue-based color decomposition system using an in-house designed calibration box. The rib was placed transversely to the direction of the main flow at the outer wall of the bend (turn) part where the wall was heated by an electrical heater. The friction factor ratio and the heat transfer enhancement ratio for case (c) at a Reynolds number of 20,000 were 48.75 and 2.66, respectively. It is found that the presence of the rib increases the heat transfer coefficient on the outer wall of the bend part (tip of side U-duct). The uncertainties were 3% and 6% for the Nusselt number and friction factor, respectively.

Influences of Microemulsion Cross-linking Reaction and Ball-milling on Particle Size Characteristics of Potato and Maize Starches

2006 ◽  
Vol 2 (4) ◽  
Author(s):  
Yu-guang Zhou ◽  
Dong Li ◽  
Li-jun Wang ◽  
Necati Özkan ◽  
Xiao Dong Chen ◽  
...  
Keyword(s):  
Particle Size ◽  
Ball Milling ◽  
Surface Area ◽  
Potato Starch ◽  
Particle Diameter ◽  
Cross Linking ◽  
Maize Starch ◽  
Median Particle Diameter ◽  
Mean Diameter ◽  
Median Particle

In this study, microemulsion cross-linking treatment was used on food grade potato and maize starches for preparing micro starch particles. Laser diffraction technique was introduced to measure the particle size characteristics, including the median particle diameter (d 50), surface area mean diameter D [3, 2], volume mean diameter D [4, 3] and specific surface area of micro potato and maize starch particles. The volume distributions and number distributions were also analyzed using Mastersizer 2000 Software. The d 50, D [3, 2], D [4, 3] of the potato starch granules were reduced significantly (p < 0.05) after the microemulsion cross-linking reaction and ball-milling treatment. However, the microemulsion cross-linking treatment did not produce significant changes in the particle size characteristics of the maize starch samples.

scholarly journals Natural Ventilation Characterization in a Classroom under Different Scenarios

2021 ◽  
Vol 18 (10) ◽  
pp. 5425
Author(s):  
Sergio A. Chillon ◽  
Mikel Millan ◽  
Iñigo Aramendia ◽  
Unai Fernandez-Gamiz ◽  
Ekaitz Zulueta ◽  
...  
Keyword(s):  
Particle Size ◽  
Relative Humidity ◽  
Natural Ventilation ◽  
Particle Diameter ◽  
Co2 Concentration ◽  
Median Particle Diameter ◽  
Surgical Masks ◽  
Computer Classroom ◽  
Median Particle ◽  
Carbon Dioxide Co2

The COVID-19 pandemic has pointed to the need to increase our knowledge in fields related to human breathing. In the present study, temperature, relative humidity, carbon dioxide (CO2) concentration, and median particle size diameter measurements were taken into account. These parameters were analyzed in a computer classroom with 15 subjects during a normal 90-minute class; all the subjects wore surgical masks. For measurements, Arduino YUN, Arduino UNO, and APS-3321 devices were used. Natural ventilation efficiency was checked in two different ventilation scenarios: only windows open and windows and doors open. The results show how ventilation affects the temperature, CO2 concentration, and median particle diameter size parameters. By contrast, the relative humidity depends more on the outdoor meteorological conditions. Both ventilation scenarios tend to create the same room conditions in terms of temperature, humidity, CO2 concentration, and particle size. Additionally, the evolution of CO2 concentration as well as the particle size distribution along the time was studied. Finally, the particulate matter (PM2.5) was investigated together with particle concentration. Both parameters showed a similar trend during the time of the experiments.

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