Search results for: hydraulic diameter

Authors: Tahani Farah, Hanène Souli, Jean-Marie Fleureau, Guillaume Kermouche, Jean-Jacques Fry, Benjamin Girard, Denis Aelbrecht

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In this work, the bio-clogging of two soils with different granulometries is presented. The durability of the clogging is also studied under cycles of hydraulic head and under cycles of desaturation- restauration. The studied materials present continuous grain size distributions. The first one corresponding to the "material 1", presents grain sizes between 0.4 and 4 mm. The second material called "material 2" is composed of grains with size varying between 1 and 10 mm. The results show that clogging occurs very quickly after the injection of nutrition and an outlet flow near to 0 is observed. The critical hydraulic head is equal to 0.76 for "material 1", and 0.076 for "material 2". The durability tests show a good resistance to unclogging under cycles of hydraulic head and desaturation-restauration for the "material 1". Indeed, the flow after the cycles is very low. In contrast, "material 2", shows a very bad resistance, especially under the hydraulic head cycles. The resistance under the cycles of desaturation-resaturation is better but an important increase of the flow is observed. The difference of behavior is due to the granulometry of the materials. Indeed, the large grain size contributes to the reduction of the efficiency of the bio-clogging treatment in this material.

Keywords: bio-clogging, granulometry, permeability, nutrition

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Authors: C. Agrawal, R. Kumar, A. Gupta, B. Chatterjee

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An experimental investigation has been carried out to study the cooling of a hot horizontal Stainless Steel surface of 3 mm thickness, which has 800±10 °C initial temperature. A round water jet of 22 ± 1 °C temperature was injected over the hot surface through straight tube type nozzles of 2.5-4.8 mm diameter and 250 mm length. The experiments were performed for the jet exit to target surface spacing of 4 times of jet diameter and jet Reynolds number of 5000-24000. The effect of change in jet Reynolds number on the surface quenching has been investigated form the stagnation point to 16 mm spatial location.

Keywords: hot-surface, jet impingement, quenching, stagnation point

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Authors: Qudratullah Muradi

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Geothermal energy is a renewable energy source that can be found in abundance on our planet. Only a small fraction of it is currently converted to electrical power, though in recent years installed geothermal capacity has increased considerably all over the world. In this paper, we assumed a model for designing of Enhanced Geothermal System, EGS. We used computer modeling group, CMG reservoir simulation software to create the typical Hot Dry Rock, HDR reservoir. In this research two wells, one injection of cold water and one production of hot water are included in the model. There are some hydraulic fractures created by the mentioned software. And cold water is injected in order to produce energy from the reservoir. The result of injecting cold water to the reservoir and extracting geothermal energy is defined by some graphs at the end of this research. The production of energy is quantified in a period of 10 years.

Keywords: geothermal energy, EGS, HDR, hydraulic fracturing

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Authors: Ashraf Mohammed M. Eid, Hossam El Badry

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The bored pile friction resistance may be affected by many factors such as the method of construction, pile length and diameter, the soil properties, as well as the depth below ground level. These factors can be represented analytically to study the influence of diameter on the unit skin friction. In this research, the Egyptian Code of soil mechanics is used to assess the skin friction capacity for either the ordinary pile diameter as well as for the large pile diameter. The later is presented in the code and through the work of some researchers based on the results of investigations adopted for a sufficient number of field tests. The comparative results of these researchers with respect to the Egyptian Code are used to check the adequacy of both methods. Based on the results of this study, the traditional static formula adopted for piles of diameter less than 60 cm may be continually used for larger piles by correlating the analyzed formulae. Accordingly, the corresponding modified angle of internal friction is concluded demonstrating a reduction of shear strength due to soil disturbance along the pile shaft. Based on this research the difference between driven piles and bored piles constructed in same soil can be assessed and a better understanding can be evaluated for the effect of different factors on pile skin friction capacity.

Keywords: large piles, static formula, friction piles, sandy soils

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Authors: T. S. Ijimdiya, K. J. Osinubi

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This study examines the influence of compactive efforts on hydraulic conductivity behaviour of compacted black cotton soil treated with bagasse ash which is necessary in assessing the performance of the soil - bagasse ash mixture for use as a suitable barrier material in waste containment application. Black cotton soil treated with up to 12% bagasse ash (obtained from burning the fibrous residue from the extraction of sugar juice from sugarcane) by dry weight of soil for use in waste containment application. The natural soil classifies as A-7-6 or CH in accordance with the AASHTO and the Unified Soil Classification System, respectively. The treated soil samples were prepared at molding water contents of -2, 0, +2, and +4 % of optimum moisture contents and compacted using four compactive efforts of Reduced British Standard Light (RBSL), British Standard light (BSL), West African Standard (WAS) and British Standard Heavy (BSH). The results obtained show that hydraulic conductivity decreased with increase in bagasse ash content, moulding water content and compaction energy.

Keywords: bagasse ash treatment, black cotton soil, hydraulic conductivity, moulding water contents, compactive efforts

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Authors: C. Milind Caspar, Valtonia Octavio Massingue, K. Maneesh Reddy, K. V. Ramesh

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Gas holdup data were obtained from measured pressure drop values in a gas-liquid upflow bubble column in the presence of string of hemispheres promoter internal. The parameters that influenced the gas holdup are gas velocity, liquid velocity, promoter rod diameter, pitch and base diameter of hemisphere. Tap water was used as liquid phase and nitrogen as gas phase. About 26 percent in gas holdup was obtained due to the insertion of promoter in in the present study in comparison with empty conduit. Pitch and rod diameter have not shown any influence on gas holdup whereas gas holdup was strongly influenced by gas velocity, liquid velocity and hemisphere base diameter. Correlation equation was obtained for the prediction of gas holdup by least squares regression analysis.

Keywords: bubble column, gas-holdup, two-phase flow, turbulent promoter

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Authors: A. H. Alenezi

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Cooling by impingement jet is known to have a significant high local and average heat transfer coefficient which make it widely used in industrial cooling systems. The heat transfer characteristics of an impinging jet on rib-roughened flat plate has been investigated numerically. This paper was set out to investigate the effect of rib height on the heat transfer rate. Since the flow needs to have enough spacing after passing the rib to allow reattachment especially for high Reynolds numbers, this study focuses on finding the optimum rib height which would be the best to maximize the heat transfer rate downstream the plate. This investigation employs a round nozzle with hydraulic diameter (Dh) of 13.5 mm, Jet-to-target distance of (H/D) of 4, rib location=1.5D and and finally jet angels of 45˚ and 90˚ under the influence of Re =10,000.

Keywords: jet impingement, CFD, turbulence model, heat transfer

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Authors: Natia Tabatadze

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The research aim is to study the physical - mechanical characteristics of structural materials, in particular, hydraulic concrete in the surface active environment and receiving of high strength concrete, low-deformable, resistant to aggressive environment concrete due application of nano technologies. The obtained concrete with additives will by possible to apply in hydraulic structures. We used cement (compressive strength R28=39,42 mPa), sand (0- 5 mm), gravel (5-10 mm, 10-20 mm), admixture CHRYSO® Fuge B 1,5% dosage of cement. CHRYSO® Fuge B renders mortar and concrete highly resistant to capillary action and reduces, or even eliminates infiltration of water under pressure. The fine particles that CHRYSO® Fuge B contains combine with the lime in the cement to form water repellent particles. These obstruct the capillary action within concrete. CHRYSO® Fuge B does not significantly modify the characteristics of the fresh concrete and mortar, nor the compressive strength. As result of research, the alkali-silica reaction was improved (relative elongation 0,122 % of admixture instead of 0,126 % of basic concrete after 14 days). The aggressive environment impact on the strength of heavy concrete, fabricated on the basis of the hydraulic admixture with the penetrating waterproof additives also was improved (strength on compression R28=47,5 mPa of admixture instead of R28=35,8 mPa), as well as the mass water absorption (W=3,37 % of admixture instead of W=1,41 %), volume water absorption (W=1,41 % of admixture instead of W=0,59 %), water tightness (R14=37,9 mPa instead R14=28,7 mPa) and water-resistance (B=18 instead B=12). The basic parameters of concrete with admixture was improved in comparison with basic concrete.

Keywords: structural materials, hydraulic concrete, low-deformable, water absorption for mass, water absorption for volume

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Authors: Manwendra Kumar Tripathi, Subhas Ganguly

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A few glass forming ability expressions in terms of characteristic temperatures have been proposed in the literature. Attempts have been made to correlate the expression with the critical diameter of the bulk metallic glass composition. However, with the advent of new alloys, many exceptions have been noted and reported. In the present approach, a genetic programming based code which generates an expression in terms of input variables, i.e., three characteristic temperatures viz. glass transition temperature (Tg), onset crystallization temperature (Tx) and offset temperature of melting (Tl) with maximum correlation with a critical diameter (Dmax). The expression evolved shows improved correlation with the critical diameter. In addition, the expression can be explained on the basis of time-temperature transformation curve.

Keywords: glass forming ability, genetic programming, bulk metallic glass, critical diameter

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Authors: Xiyue Wang, Shaoning Yan

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Cities in China today is faced with an increasingly serious river ecological crisis accompanying with the development of urbanization: waterlogging on account of the fragmented urban natural hydrological system; the limited ecological function of the hydrological system caused by a destruction of water system and waterfront ecological environment. Additionally, the eco-hydrological processes of rivers are affected by various environmental factors, which are more complex in the context of urban environment. Therefore, efficient hydrological monitoring and analysis tools, accurate and visual hydrological and hydraulic models are becoming more important basis for decision-makers and an important way for landscape architects to solve urban hydrological problems, formulating sustainable and forward-looking schemes. The study mainly introduces the river and flood analysis model based on the platform of Autodesk Civil 3D. Taking the Luanhe River in Qian'an City of Hebei Province as an example, the 3D models of the landform, river, embankment, shoal, pond, underground stream and other land features were initially built, with which the water transfer simulation analysis, river floodplain analysis, and river ecology analysis were carried out, ultimately the real-time visualized simulation and analysis of rivers in various hypothetical scenarios were realized. Through the establishment of digital hydrological and hydraulic model, the hydraulic data can be accurately and intuitively simulated, which provides basis for rational water system and benign urban ecological system design. Though, the hydrological and hydraulic model based on Autodesk Civil3D own its boundedness: the interaction between the model and other data and software is unfavorable; the huge amount of 3D data and the lack of basic data restrict the accuracy and application range. The hydrological and hydraulic model based on Autodesk Civil3D platform provides more possibility to access convenient and intelligent tool for urban planning and monitoring, a solid basis for further urban research and design.

Keywords: visualization, hydrological and hydraulic model, Autodesk Civil 3D, urban river

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Authors: Moses. O. Eyankware, Benard I. Odoh, Omoleomo O. Omo-Irabor, Alex O. I. Selemo

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Knowledge of hydraulic conductivity and transmissivity is essential for the determination of natural water flow through an aquifer. These parameters are commonly estimated from the analysis of electrical conductivity, soil properties and fluid flow data. In order to achieve a faster and cost effective analysis of aquifer parameters in Ochudo City in Abakaliki, this study relied on non-invasive geophysical methods. As part of this approach, Vertical Electrical Sounding (VES) was conducted at 20 sites in the study area for the identification of the vertical variation in subsurface lithology and for the characterization of the groundwater system. The area variously consists of between five to seven geoelectric layers of different thicknesses. Depth to aquifer ranges from 9.94 m-134.0 m while the thickness of the identified aquifer varies between 8.43 m and 44.31 m. Based on the electrical conductivity values of water samples collected from two boreholes and two hand-dug wells within the study area, the hydraulic conductivity was determined to range from 0.10 to 0.433 m/day. The estimated thickness of the aquifer and calculated hydraulic conductivity were used to derive the aquifer transmissivity. The results indicate that this parameter ranges from 1.58-7.56 m²/day with a formation factor of between 0.31-3.6.

Keywords: Asu river group, transmissivity, hydraulic conductivity, abakaliki, vertical electrical sounding (VES)

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Authors: J. Kloypayan, W. Pimpakan

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The pipe taper thread measurement and uncertainty normally used the four-wire probe according to the JIS B 0262. Besides, according to the EA-10/10 standard, the pipe thread could be measured using the three-wire probe. This research proposed to use the three-wire probe measuring the pitch diameter of the pipe taper thread. The measuring accessory component was designed and made, then, assembled to one side of the ULM 828 CiM machine. Therefore, this machine could be used to measure and calibrate both the pipe thread and the pipe taper thread. The equations and the expanded uncertainty for pitch diameter measurement were formulated. After the experiment, the results showed that the pipe taper thread had the pitch diameter equal to 19.165 mm and the expanded uncertainty equal to 1.88µm. Then, the experiment results were compared to the results from the National Institute of Metrology Thailand. The equivalence ratio from the comparison showed that both results were related. Thus, the proposed method of using the three-wire probe measured the pitch diameter of the pipe taper thread was acceptable.

Keywords: pipe taper thread, three-wire probe, measure and calibration, the universal length measuring machine

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Authors: Young Man Cho, Sang Hyun Kim

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Even though various management practices such as sediment dredging were attempted to improve water quality of Dongcheon located in Busan, the environmental condition of this stream was deteriorated. Therefore, Busan metropolitan city had pumped and diverted sea water to upstream of Dongcheon for several years. This study explored hydraulic characteristics of Dongcheon to configure the best management practice for ecological restoration and water quality improvement of a man-made urban stream. Intensive field investigation indicates that average flow velocities at depths of 20% and 80% from the water surface ranged 5 to 10 cm/s and 2 to 5 cm/s, respectively. Concentrations of dissolved oxygen for all depths were less than 0.25 mg/l during low tidal period. Even though density difference can be found along stream depth, density current seems rarely generated in Dongcheon. Short period of high tidal portion and shallow depths are responsible for well-mixing nature of Doncheon.

Keywords: hydraulic, tidal river, density current, sea water

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Authors: Hossain Samani, Mohammad Ehteram

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In this paper, we consider finite volume method (FVM) in water hammer. We will simulate these techniques on a looped network with complex boundary conditions. After comparing methods, we see the FVM method as the best method. We compare the results of FVM with experimental data. Finite volume using staggered grid is applied for solving water hammer equations.

Keywords: hydraulic transient, water hammer, interpolation, non-liner interpolation

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Authors: Malinda Sabrina, F. Andree Yohanes, Khoerul Anwar

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There are many sources that cause noise in a car, one of them is noise from radiator cooling fan. This part is used to control engine temperature by ensuring adequate airflow through radiator. Radiator cooling fan noise is a very important matter especially for vehicle manufacturers. This can affect brand image of the car and their customer satisfaction. Therefore, some experiments to measure noise level of the fan are required. Sound pressure level measurements for two axial fans with different diameter have been investigated in a hemi-anechoic chamber based on standard JIS-B8346, focusing on aerodynamic noise. Both fans have the same profile and shape with diameter respectively 43 cm and 49 cm. The measurement was performed in hemi-anechoic chamber in order to obtain a background noise at measuring point as low as possible. Noise characterizations of these radiator cooling fans were measured in five different rotating speed and the results were compared. The measurement result shows that the sound pressure level increases with increasing rotational speed of the fan. In comparison with a smaller diameter, it is shown that fan with larger diameter produces higher noise level at the same rotational speed.

Keywords: aerodynamics noise, hemi-anechoic chamber, radiator cooling fan, sound pressure level

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Authors: Kenechi Kurtis Onochie

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This paper shows the use of filter paper technique in the measurement of matric suction of unsaturated expansive soil around the Haspolat region of Lefkosa, North Cyprus in other to establish the soil water characteristics curve (SWCC) or soil water retention curve (SWRC). The dry filter paper approach which is standardized by ASTM, 2003, D 5298-03 in which the filter paper is initially dry was adopted. The whatman No. 42 filter paper was used in the matric suction measurement. The maximum dry density of the soil was obtained as 2.66kg/cm³ and the optimum moisture content as 21%. The soil was discovered to have high air entry value of 1847.46KPa indicating finer particles and 25% hydraulic capacity using filter paper technique. The filter paper technique proved to be very useful for measuring the hydraulic capacity of unsaturated expansive soil.

Keywords: SWCC, matric suction, filter paper, expansive soil

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Authors: A. Brahma

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Drying is a phenomenon that accompanies the hardening of hydraulic materials. It can, if it is not prevented, lead to significant spontaneous dimensional variations, which the cracking is one of events. In this context, cracking promotes the transport of aggressive agents in the material, which can affect the durability of concrete structures. Drying shrinkage develops over a long period almost 30 years although most occurred during the first three years. Drying shrinkage stabilizes when the material is water balance with the external environment. The drying shrinkage of cementitious materials is due to the formation of capillary tensions in the pores of the material, which has the consequences of bringing the solid walls of each other. Knowledge of the shrinkage characteristics of concrete is a necessary starting point in the design of structures for crack control. Such knowledge will enable the designer to estimate the probable shrinkage movement in reinforced or prestressed concrete and the appropriate steps can be taken in design to accommodate this movement. This study is concerned the modelling of drying shrinkage of the hydraulic materials and the prediction of the rate of spontaneous deformations of hydraulic materials during hardening. The model developed takes in consideration the main factors affecting drying shrinkage. There was agreement between drying shrinkage predicted by the developed model and experimental results. In last we show that developed model describe the evolution of the drying shrinkage of high performances concretes correctly.

Keywords: drying, hydraulic concretes, shrinkage, modeling, prediction

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Authors: Zhanat Umarova

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Until the present time, modeling of the pores form influence on the hydraulic resistance of membranes and their permeability has not been analyzed. The aim of the given work is the theoretical consideration of the issue on the productivity of polymer membranes with the profile pores and determination of the optimum form of pores.

Keywords: modeling, polymer membranes, permeability, pore’s density

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Authors: A. Ghafouri, N. Pourmahmoud, I. Mirzaee

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In this numerical study, effects of using Al2O3-water nanofluid on the rate of heat transfer have been investigated numerically. The physical model is a square enclosure with insulated top and bottom horizontal walls while the vertical walls are kept at different constant temperatures. Two appropriate models are used to evaluate the viscosity and thermal conductivity of nanofluid. The governing stream-vorticity equations are solved using a second order central finite difference scheme, coupled to the conservation of mass and energy. The study has been carried out for the nanoparticle diameter 30, 60, and 90 nm and the solid volume fraction 0 to 0.04. Results are presented by average Nusselt number and normalized Nusselt number in the different range of φ and D for mixed convection dominated regime. It is found that different heat transfer rate is predicted when the effect of nanoparticle diameter is taken into account.

Keywords: nanofluid, nanoparticle diameter, heat transfer enhancement, square enclosure, Nusselt number

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Authors: Evgeny Obraztsov, Ilya Kremnev, Vitaly Sokolov, Maksim Gavrilov, Evgeny Tretyakov, Vladimir Kukhtevich, Vladimir Bezlepkin

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Over the last decade, a specific set of connected software tools and calculation codes has been gradually developed. It allows simulating I&C systems, thermal-hydraulic, neutron-physical and electrical processes in elements and systems at the Unit of NPP (initially with WWER (pressurized water reactor)). In 2012 it was called a complex simulation suite “Virtual Unit of NPP” (or CSS “VEB” for short). Proper application of this complex tool should result in a complex coupled mathematical computational model. And for a specific design of NPP, it is called the Virtual Power Unit (or VPU for short). VPU can be used for comprehensive modelling of a power unit operation, checking operator's functions on a virtual main control room, and modelling complicated scenarios for normal modes and accidents. In addition, CSS “VEB” contains a combination of thermal hydraulic codes: the best-estimate (two-liquid) calculation codes KORSAR and CORTES and a homogenous calculation code TPP. So to analyze a specific technological system one can build thermal-hydraulic simulation models with different detalization levels up to a nodalization scheme with real geometry. And the result at some points is similar to the notion “engineering/testing simulator” described by the European utility requirements (EUR) for LWR nuclear power plants. The paper is dedicated to description of the tools mentioned above and an example of the application of the engineering thermal-hydraulic simulator in analysis of the boron acid concentration in the primary coolant (changed by the make-up and boron control system).

Keywords: best-estimate code, complex simulation suite, engineering simulator, power plant, thermal hydraulic, VEB, virtual power unit

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Authors: Abdelmalk Brahma

Abstract:

Drying is a phenomenon that accompanies the hardening of hydraulic materials. It can, if it is not prevented, lead to significant spontaneous dimensional variations, which the cracking is one of events. In this context, cracking promotes the transport of aggressive agents in the material, which can affect the durability of concrete structures. Drying shrinkage develops over a long period almost 30 years although most occurred during the first three years. Drying shrinkage stabilizes when the material is water balance with the external environment. The drying shrinkage of cementitious materials is due to the formation of capillary tensions in the pores of the material, which has the consequences of bringing the solid walls of each other. Knowledge of the shrinkage characteristics of concrete is a necessary starting point in the design of structures for crack control. Such knowledge will enable the designer to estimate the probable shrinkage movement in reinforced or prestressed concrete and the appropriate steps can be taken in design to accommodate this movement. This study is concerned the modelling of drying shrinkage of the hydraulic materials and the prediction of the rate of spontaneous deformations of hydraulic materials during hardening. The model developed takes in consideration the main factors affecting drying shrinkage. There was agreement between drying shrinkage predicted by the developed model and experimental results. In last we show that developed model describe the evolution of the drying shrinkage of high performances concretes correctly.

Keywords: drying, hydraulic concretes, shrinkage, modeling, prediction

Procedia PDF Downloads 236

Authors: Kiurski S. Jelena, Ranogajec G. Jonjaua, Kecić S. Vesna, Oros B. Ivana

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The present study investigates the effectiveness of newly designed clayey pellets (fired clay pellets diameter sizes of 5 and 8 mm, and unfired clay pellets with the diameter size of 15 mm) as the beds in the column adsorption process. The adsorption experiments in the batch mode were performed before the column experiment with the purpose to determine the order of adsorbent package in the column which was to be designed in the investigation. The column experiment was performed by using a known mass of the clayey beds and the volume of the waste printing developer, which was purified. The column was filled in the following order: fired clay pellets of the diameter size of 5 mm, fired clay pellets of the diameter size of 8 mm, and unfired clay pellets of the diameter size of 15 mm. The selected order of the adsorbents showed a high removal efficiency for zinc (97.8%) and copper (81.5%) ions. These efficiencies were better than those in the case of the already existing mode adsorption. The obtained experimental data present a good basis for the selection of an appropriate column fill, but further testing is necessary in order to obtain more accurate results.

Keywords: clay materials, fix bed adsorption column, metal ions, printing developer

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Authors: G. Adelian, A. Mirzaii, S. S. Yasrobi

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This paper represents data of an extensive experimental laboratory testing program for the measurement of the water coefficient of permeability of clayey sand in different hydraulic and mechanical boundary conditions. A novel permeameter was designed and constructed for the experimental testing program, suitable for the study of flow in unsaturated soils in different hydraulic and mechanical loading conditions. In this work, the effect of hydraulic hysteresis, net isotropic confining stress, water flow condition, and sample dimensions are evaluated on the water coefficient of permeability of understudying soil. The experimental results showed a hysteretic variation for the water coefficient of permeability versus matrix suction and degree of saturation, with higher values in drying portions of the SWCC. The measurement of the water permeability in different applied net isotropic stress also signified that the water coefficient of permeability increased within the increment of net isotropic consolidation stress. The water coefficient of permeability also appeared to be independent of different applied flow heads, water flow condition, and sample dimensions.

Keywords: water permeability, unsaturated soils, hydraulic hysteresis, void ratio, matrix suction, degree of saturation

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Authors: Altayeb Qasem, Mousa Bani Baker, Amani Nawafleh

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The complexity of the sand-bentonite liner barrier system calls for an adequate model that reflects the conditions depending on the barrier materials and the characteristics of the permeates which lead to hydraulic conductivity changes when liners infiltrated with polar, no-polar, miscible and immiscible liquids. This paper is dedicated to developing a model for evaluating the hydraulic conductivity in the form of a simple indicator for the compatibility of the liner versus leachate. Based on two liner compositions (95% sand: 5% bentonite; and 90% sand: 10% bentonite), two pressures (40 kPa and 100 kPa), and three leachates: water, ethanol and biofuel. Two characteristics of the leacahtes were used: viscosity of permeate and its octanol-water partitioning coefficient (Kow). Three characteristics of the liners mixtures were evaluated which had impact on the hydraulic conductivity of the liner system: the initial content of bentonite (%), the free swelling index, and the shrinkage limit of the initial liner’s mixture. Engineers can use this modest tool to predict a potential liner failure in sand-bentonite barriers.

Keywords: liner performance, sand-bentonite barriers, viscosity, free swelling index, shrinkage limit, octanol-water partitioning coefficient, hydraulic conductivity, theoretical modeling

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Authors: S. K. Verma, S. L. Sinha, D. K. Chandraker

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The Advanced Heavy Water Reactor (AHWR) is a vertical pressure tube type, heavy water moderated and boiling light water cooled natural circulation based reactor. The fuel bundle of AHWR contains 54 fuel rods arranged in three concentric rings of 12, 18 and 24 fuel rods. This fuel bundle is divided into a number of imaginary interacting flow passage called subchannels. Single phase flow condition exists in reactor rod bundle during startup condition and up to certain length of rod bundle when it is operating at full power. Prediction of the thermal margin of the reactor during startup condition has necessitated the determination of the turbulent mixing rate of coolant amongst these subchannels. Thus, it is vital to evaluate turbulent mixing between subchannels of AHWR rod bundle. With the remarkable progress in the computer processing power, the computational fluid dynamics (CFD) methodology can be useful for investigating the thermal–hydraulic characteristics phenomena in the nuclear fuel assembly. The present report covers the results of simulation of pressure drop, velocity variation and turbulence intensity on single rod bundle with 54 rods in circular arrays. In this investigation, 54-rod assemblies are simulated with ANSYS Fluent 15 using steady simulations with an ANSYS Workbench meshing. The simulations have been carried out with water for Reynolds number 9861.83. The rod bundle has a mean flow area of 4853.0584 mm2 in the bare region with the hydraulic diameter of 8.105 mm. In present investigation, a benchmark k-ε model has been used as a turbulence model and the symmetry condition is set as boundary conditions. Simulation are carried out to determine the turbulent mixing rate in the simulated subchannels of the reactor. The size of rod and the pitch in the test has been same as that of actual rod bundle in the prototype. Water has been used as the working fluid and the turbulent mixing tests have been carried out at atmospheric condition without heat addition. The mean velocity in the subchannel has been varied from 0-1.2 m/s. The flow conditions are found to be closer to the actual reactor condition.

Keywords: AHWR, CFD, single-phase turbulent mixing rate, thermal–hydraulic

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Authors: M. Ezzat, Y. Zaghloul, T. Sorour, A. Hefny, M. Eid

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Ultimate capacity of large diameter bored piles is usually determined from pile loading tests as recommended by several international codes and foundation design standards. However, loading of this type of piles till achieving apparent failure is practically seldom. In this paper, numerical analyses are carried out to simulate load test of a large diameter bored pile performed at the location of Alzey highway bridge project (Germany). Test results of pile load settlement relationship till failure as well as results of the base and shaft resistances are available. Apparent failure was indicated in this test by the significant increase of the induced settlement during the last load increment applied on the pile head. Measurements of this pile load test are used to assess the quality of the numerical models investigated. Three different material soil models are implemented in the analyses: Mohr coulomb (MC), Soft soil (SS), and Modified Mohr coulomb (MMC). Very good agreement is obtained between the field measured settlement and the calculated settlement using the MMC model. Results of analysis showed also that the MMC constitutive model is superior to MC, and SS models in predicting the ultimate base and shaft resistances of the large diameter bored pile. After calibrating the numerical model, behavior of large diameter bored piles under axial loads is discussed and the formation of the plastic zone around the pile is explored. Results obtained showed that the plastic zone below the base of the pile at failure extended laterally to about four times the pile diameter and vertically to about three times the pile diameter.

Keywords: ultimate capacity, large diameter bored piles, plastic zone, failure, pile load test

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Authors: Ahmed Ramadhan Al-Obaidi, Jassim Alhamid

Abstract:

In this investigation, the flow pattern, characteristics of thermal-hydraulic, and improvement of heat transfer performance are evaluated using a numerical technique in three dimensions corrugated pipe heat exchanger. The modification was made under different corrugated pipe geometrical parameters, including corrugated ring angle (CRA), distance between corrugated ring (DBCR), and corrugated diameter (CD), the range of Re number from 2000 to 12000. The numerical results are validated with available experimental data. The numerical outcomes reveal that there is an important change in flow field behaviour and a significant increase in friction factor and improvement in heat transfer performance owing to the use of the corrugated shape in the heat exchanger pipe as compared to the conventional smooth pipe. Using corrugated pipe with different configurations makes the flow more turbulence, flow separation, boundary layer distribution, flow mixing, and that leads to augmenting the performance of heat transfer. Moreover, the value of pressure drop, and the Nusselt number increases as the corrugated pipe geometrical parameters increase. Furthermore, the corrugation configuration shapes have an important influence on the thermal evaluation performance factor, and the maximum value was more than 1.3. Numerical simulation can be performed to predict the various geometrical configurations effects on fluid flow, thermal performance, and heat transfer enhancement.

Keywords: corrugated ring angle, corrugated diameter, Nusselt number, heat transfer

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Authors: L. Achou, A. Doghmane

Abstract:

Elastic performances, as an essential property of nanowires (NWs), play a significant role in the design and fabrication of modern nanodevices. In this paper, our interest is focused on ZnO NWs to investigate wire diameter (D_wire ≤ 400 nm) effects on elastic properties. The plotted data reveal that a strong size dependence of the elastic constants exists when the wire diameter is smaller than ~ 100 nm. For larger diameters (D_wire > 100 nm), these ones approach their corresponding bulk values. To enrich this study, we make use of the scanning acoustic microscopy simulation technique. The calculation methodology consists of several steps: determination of longitudinal and transverse wave velocities, calculation of refection coefficients, calculation of acoustic signatures and Rayleigh velocity determination. Quantitatively, it was found that changes in ZnO diameters over the ranges 1 nm ≤ D_wire ≤ 100 nm lead to similar exponential variations, for all elastic parameters, of the from: A = a + b exp(-D_wire/c) where a, b, and c are characteristic constants of a given parameter. The developed relation can be used to predict elastic properties of such NW by just knowing its diameter and vice versa.

Keywords: elastic properties, nanowires, semiconductors, theoretical model, ZnO

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Authors: Arya Pirooz

Abstract:

Air and fuel must be mixed correctly so that there is perfect combustion, which calls for fuel atomization by injection. In this study, the effects of different parameters such as number of orifices, length and diameter of orifices, diameter of nozzle sac and the angle of needle seat in injectors were investigated with the use of rate of injection and sac pressure. The unit pump of the OM-457 diesel engine was modelled on Avl-Hydsim. The results illustrate that the sac pressure decreased by 46% when the number of holes were doubled, although the rate of injection had an immense change. Also, the sac pressure increased up to 60% when the diameter of orifices decreased by 40% in spite of the semi-constant injection rate.

Keywords: injection, OM-457 engine, nozzle geometry, atomization

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Authors: Jean-Jacques Randrianarimanana, Nassim Sebaibi, Mohamed Boutouil

Abstract:

In order to solve problems associated with stormwater runoff in urban areas and their effects on natural and artificial water bodies, the integration of new technical solutions to the rainwater drainage becomes even more essential. Permeable pavement systems are one of the most widely used techniques. This paper presents a laboratory analysis of stormwater runoff hydraulic and pollutant removal performance of permeable pavement system using pervious pavements based on seashell products. The laboratory prototype is a square column of 25 cm of side and consists of the surface in pervious concrete, a bedding of 3 cm in height, a geotextile and a subbase layer of 50 cm in height. A series of constant simulated rain events using semi-synthetic runoff which varied in intensity and duration were carried out. The initial vertical saturated hydraulic conductivity of the entire pervious pavement system was 0.25 cm/s (148 L/m²/min). The hydraulic functioning was influenced by both the inlet flow rate value and the test duration. The total water losses including evaporation ranged between 9% to 20% for all hydraulic experiments. The temporal and vertical variability of the pollutant removal efficiency (PRE) of the system were studied for total suspended solids (TSS). The results showed that the PRE along the vertical profile was influenced by the size of the suspended solids, and the pervious paver has the highest capacity to trap pollutant than the other porous layers of the permeable pavement system after the geotextile. The TSS removal efficiency was about 80% for the entire system. The first-flush effect of TSS was observed, but it appeared only at the beginning (2 to 6 min) of the experiments. It has been shown that the PPS can capture first-flush. The project in which this study is integrated aims to contribute to both the valorization of shellfish waste and the sustainable management of rainwater.

Keywords: hydraulic, pervious concrete, pollutant removal efficiency, seashell by-products, stormwater runoff

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