Search for: hydraulics
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    Analysis of accumulators configuration in LB-LOCA for Bushehr NPP

    , Article Annals of Nuclear Energy ; Volume 92 , 2016 , Pages 96-106 ; 03064549 (ISSN) Shoushtari, M. M ; Jafari, J ; Aghaie, M ; Vosoughi, N ; Nemati, M ; Sharif University of Technology
    Elsevier Ltd 
    This research focuses on a sensitivity analysis of accumulators configuration in a Large Break Loss of Coolant Accident (LB-LOCA) in Bushehr Nuclear Power Plant (BNPP). In this way, primary and secondary side components are modeled using RELAP5/MOD3.3 code. Having modeled the BNPP in a steady state hot full power operation, the thermal hydraulic consequences of a LB-LOCA in the reactor inlet is considered and sensitivity analysis for four major different configurations of accumulators are studied in detail. It is shown that any arrangement of accumulators in the Reactor Pressure Chamber (RPC) or Reactor Collection Chambers (RCC) leads to variation of fuel and clad temperatures during the... 

    Experimental Study of Geotextile's Drainage and Filtration Properties in Dams under Different Hydraulic Gradients and Boundary Conditions

    , M.Sc. Thesis Sharif University of Technology Zahmatkesh, Zahra (Author) ; Pak, Ali (Supervisor)
    Geotextiles are one of the most widely used materials in filtration and drainage applications. Since geotextiles are exposed to different stresses and hydraulic gradients, thier hydraulic behavior in real situations is of great importance. In this study, filtration and drainage of several nonwoven needle-punched geotextiles with different properties and unit masses per area of 200g/m2, 400g/m2, 500g/m2 and 800g/m2 under various confined stresses and hydraulic gradients are investigated. To get to these aims, permittivity and transmissivity apparatuses were designed and built in the course of this investigation. Then samples which were emerged for at least 24 hours were tested under different... 

    Hydraulic and Sediment Simulation of effect of structures On Urban Rivers In HEC-RAS (Case study :Kan River)

    , M.Sc. Thesis Sharif University of Technology Abhari Rasht Abadi, Maryam (Author) ; Agha Mohammad Hossein Tajrishi, Massoud (Supervisor) ; Torabi, Oveis ($item.subfieldsMap.e)
    Construction of some structures including parks, bridges and leading walls conducted on the rivers in urbanization leads to the change in the form of the rivers and consequently the change in the hydraulic.The response of river to these changes which are in the form of changes in morphologic features seems to pose some threats such as flood, damage to the buildings located on the route, weakening the bridge of highways and aggradation and degradation of the ecosystem. Kan river, one of the biggest urban rivers in the mega city of tehran, has had some changes such as resort purposes, canalization, the change of slip and roughness and intersection with different bridges during recent... 

    The effect of water-cement ratio in compressive and abrasion strength of the nano silica concretes

    , Article World Applied Sciences Journal ; Volume 17, Issue 4 , 2012 , Pages 540-545 ; 18184952 (ISSN) Shamsai, A ; Rahmani, K ; Peroti, S ; Rahemi, L ; Sharif University of Technology
    Development and construction of hydraulic structures like dams, the concrete durability in these kinds of structures has gained special attention. One of the crucial factor in concrete technology is it durability in hydraulic structures. Concrete has to resist against abrasion due to the crash of particles carried by water. To enhance the abrasion resistance of concrete different methods have been offered. In the present stud, the role of water-cement ratio in compressive and abrasion strength of nano silica concrete was investigated. The constructed concrete samples with 3% nano silica and water-cement ratios of 0.33, 0.36, 0.40, 0.44 and 0.50 were experimented. Other design features... 

    Effect of hydraulic hysteresis and degree of saturation of infill materials on the behavior of an infilled rock fracture

    , Article International Journal of Rock Mechanics and Mining Sciences ; Volume 88 , 2016 , Pages 105-114 ; 13651609 (ISSN) Khosravi, A ; Dadashi Serej, A ; Mousavi, S. M ; Haeri, S. M ; Sharif University of Technology
    Elsevier Ltd 

    Design of a mechanically closed-loop test rig for testing aviation industry’s gearboxes

    , Article Aviation ; Volume 21, Issue 4 , 2017 , Pages 132-142 ; 16487788 (ISSN) Mozafari, S ; Rezazadeh Mohamadi, M ; Dolatkhah Takloo, S ; Mardani, M ; Sharif University of Technology
    Due to the wide usage of rotary equipment and the necessity of their testing for maintenance and repair, test rigs have become necessary. The mechanical closed-loop test rig developed in Sharif University of Technology branch of ACECR (Academic Centre of Education, Culture and Research) is a test rig with low energy losses that is suitable for testing high power gearboxes such as aerospace or wind turbine gearboxes. It can be loaded up to 489Hp at a maximum speed of 3000 rpm, and the test components can be tested in different testing conditions including a variety of torques and speeds. This paper describes the preliminary, conceptual, and detailed design, steps including frame work design,... 

    Effects of permeability and cementation on the pattern of hydraulically induced fractures in oil sands

    , Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Volume 31, Issue 2 , 2009 , Pages 149-162 ; 15567036 (ISSN) Pak, A ; Chan, D. H ; Sharif University of Technology
    It is generally accepted that a hydraulically induced fracture in the reservoir is approximately a plane fracture perpendicular to the direction of the in situ minor principal stress. However, field observations, in some cases, do not support the above traditional assumption. This is especially true when hydraulic fracturing technique is applied to the uncemented porous materials such as oil sands. In this article, the pattern of hydraulically induced fractures in oil sands and other geomaterials is discussed. Field observations and experimental investigation results are combined with the outcomes of the numerical simulations of hydro-fracturing in oil sands conducted by the authors to... 

    Analysis of the effect of kevlar fibers on abrasion resistance, flexural strength and hydraulic conductivity coefficient of silica fume concretes

    , Article Iranian Journal of Science and Technology - Transactions of Civil Engineering ; Volume 44, Issue 2 , 2020 , Pages 669-674 Rahmani, K ; Piroti, S ; Ghameian, M ; Sharif University of Technology
    Springer  2020
    Reinforcing fiber and silica fume of concrete can be considered as one of the most widely used additives. In this study, with a review of the history and advantages of using silica fume and polypropylene fibers in concrete, 380 concrete laboratory samples were constructed, of which 25 mixing designs with water–cement ratio of 0.35 and fiber content of 0.2, 0.3, 0.4 and 0.5 of concrete volume and 7% silica fume were prepared according to the ACI standard in their manufacturing. In the present research, samples of Kevlar fiber containing silica fume were tested under flexural strength, abrasion resistance and hydraulic conductivity coefficient. According to achieved results, the optimum amount... 

    Modeling and direction control of a 2 D.O.F. Heavy launching bed on a moving car using a full suspension model

    , Article 2003 ASME Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Chicago, IL, 2 September 2003 through 6 September 2003 ; Volume 5 B , 2003 , Pages 1677-1685 Durali, M ; Afsharzadeh, A ; ASME ; Sharif University of Technology
    American Society of Mechanical Engineers  2003
    In this paper dynamic modeling and direction control of a launching bed (L.B.) with 2 D.O.F. rotation around vertical and lateral axes, mounted on a vehicle moving on a rough road is investigated. The purpose of direction control is to bring the L.B. from any initial angle to a desired angle with respect to the reference frame and to keep it there. The vehicle model is a full car with bounce, yaw, roll and pitch degrees of freedom. The suspension system of the vehicle is considered to have passive elements and unsprung masses. The stiffness of the tires is also included in the model. To control the position of the launching bed, a servo-hydraulic system comprising of hydro-motors, gearboxes,... 

    A finite volume central differencing scheme for simulation of the shut down procedure of a hydraulic system

    , Article International Journal of Fluid Power ; Volume 3, Issue 2 , 2002 , Pages 17-27 ; 14399776 (ISSN) Mazaheri, K ; Farahani, R. H ; Sharif University of Technology
    A new central differencing finite volume scheme is investigated for solution of unsteady hydraulic problems as water hammer in pipe systems. Special time stepping procedure similar to Runge-Kutta algorithm is used to stabilize this second order scheme. It is monotonized by adding dissipative terms including second and fourth derivatives of the conserved variables, with coefficients proportional to derivatives of pressure or volumetric flow, which keeps the second order of accuracy in smooth flow regions. The one-dimensional unsteady incompressible equations are solved for a water hammer situation, and results are compared to existing analytical solutions. Results are also compared with... 

    Evaluation of hydraulic fracturing pressure in a porous medium by using the finite element method

    , Article Energy Sources ; Volume 24, Issue 8 , 2002 , Pages 715-724 ; 00908312 (ISSN) Nouri, A ; Panah, A. K ; Pak, A ; Vaziri, H ; Islam, M. R ; Sharif University of Technology
    Hydraulic fracturing is a complicated phenomenon in which deformation of the porous medium and fluid leak-off to the surrounding area take place simultaneously. Their interaction therefore must not be overlooked. Modeling of this phenomenon in isothermal conditions requires analysis of soil deformation and crack and pore fluid pressure interaction. In this paper, a numerical scheme is presented for analysis of soil stresses and deformations and fluid flow in a coupled manner. This scheme is also used to detect the fracture in the medium. Our model was used in simulating a set of hydraulic fracturing experiments. These experiments were performed on compacted hollow cylindrical specimens under... 

    Specific surface and porosity relationship for sandstones for prediction of permeability

    , Article International Journal of Rock Mechanics and Mining Sciences ; Vol. 71, issue , October , 2014 , p. 25-32 Rabbani, A ; Jamshidi, S ; Sharif University of Technology
    Porosity and specific surface are two prominent factors in describing the hydraulic properties of porous media. Determination of these two important parameters leads to identify the capability of porous media to conduct the fluids. In the present study, a new relationship between porosity and specific surface of sandstones has been developed. Micro-CT data from 10 types of sandstones has been utilized in order to present a porosity-specific surface correlation. This correlation also contains the average grain radius of each rock obtained by image processing algorithms. Finally, the correlation is tested on the provided data to evaluate its precision. The simplicity and applicability of the... 

    The effect of step on the hydraulic characteristics of the subcritical free surface flow in conveyance tunnel

    , Article Tunnelling and Underground Space Technology ; Volume 28, Issue 1 , 2012 , Pages 212-217 ; 08867798 (ISSN) Najafi, M. R ; Nabipour, M ; Sharif University of Technology
    Due to the water scarcity and uneven distribution of water resources, conveyance systems are designed to carry water through basins. For this purpose conveyance tunnels which carry supper/subcritical flows are commonly constructed. The occurrence of steps in the tunnels created by segment off-sets during the TBM operations would cause significant local head losses. As a result, the flow discharge may reduce. In this study subcritical free surface flow in conveyance tunnel is simulated using the one-dimensional HEC-RAS model. Impact of the invert segment off-set on the discharge rate is then estimated. Similarly a two-dimensional numerical model based on the Volume of Fluid (VOF) scheme is... 

    A new and applicable method to calculate mass and heat transfer coefficients and efficiency of industrial distillation columns containing structured packings

    , Article Energy ; Volume 36, Issue 3 , 2011 , Pages 1415-1423 ; 03605442 (ISSN) Sadeghifar, H ; Safe Kordi, A. A ; Sharif University of Technology
    Most of the methods developed for efficiency estimation of distillation columns were based on the empirical mass transfer and hydraulic relations correlated to laboratory data. Therefore, these methods cannot estimate efficiency of industrial columns with sufficient accuracy. In this paper, a new and applicable method was developed for calculation of efficiency (and mass and heat transfer coefficients) of distillation columns containing structured packings. This method has potential advantages; e.g., it can calculate efficiency without using any empirical mass transfer and hydraulic correlations and models, and without the need to estimate the operational and hydraulic parameters of column.... 

    Calculation and analysis of thermal-hydraulics fluctuations in pressurized water reactors

    , Article Annals of Nuclear Energy ; Volume 76 , 2015 , Pages 75-84 ; 03064549 (ISSN) Malmir, H ; Vosoughi, N ; Sharif University of Technology
    Elsevier Ltd  2015
    Analysis of thermal-hydraulics fluctuations in pressurized water reactors (e.g., local and global temperature or density fluctuations, as well as primary and charging pumps fluctuations) has various applications in calculation or measurement of the core dynamical parameters (temperature or density reactivity coefficients) in addition to thermal-hydraulics surveillance and diagnostics. In this paper, the thermal-hydraulics fluctuations in PWRs are investigated. At first, the single-phase thermal-hydraulics noise equations (in the frequency domain) are originally derived, without any simplifying assumptions. The fluctuations of all the coolant parameters, as well as the radial distribution of... 

    3D simulation of propagation of hydraulically driven fractures in oil reservoirs using EFG mesh-less method considering coupled hydro-mechanical effects

    , Article Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014, 22 September 2014 through 25 September 2014, Kyoto ; September , 2015 , Pages 1675-1680 ; 9781138001480 (ISBN) Pak, A ; Samimi, S ; Sharif University of Technology
    Taylor and Francis - Balkema  2015
    Creating hydraulically induced fractures in oil/gas reservoirs is one of the methods for Enhanced Oil Recovery (EOR) that has been applied extensively in petroleum industry in recent years. Despite its popularity, the design process of Hydraulic Fracture treatment is mostly empirical based on the previous experiences gained in the oil-rich formation. The reason lies in the complexities involved in the Hydraulic Fracture process including interacting effects of fluid(s) flowand solid deformations, injection of non-Newtonian fluids in the porous media, leak-off of the injected fluid into the formation, complex geometry of the induced fracture in the intact or naturally fractured rock,... 

    Impact of void ratio and state parameters on the small strain shear modulus of unsaturated soils

    , Article 15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability ; 2015 , Pages 241-246 Khosravi, A ; Gheibi, A ; Rahimi, M ; McCartney, J. S ; Haeri, S. M
    The unsaturated small strain shear modulus, Gmax, is a key reference value in predicting relationships between dynamic shear modulus and shear strain amplitude and is thus a key quantity to properly model the behavior of dynamically-loaded geotechnical systems such as pavements, rail beds, and machine foundations. From the interpretation of the experimental Gmax results for unsaturated soils, different definitions of trends between Gmax and the stress state of the unsaturated soils and material properties are proposed. However, in most of trends, the relationship between the stress state and void ratio is considered and the effect of void ratio on the unsaturated small strain shear modulus... 

    Simulation and experimental validation of flow-current characteristic of a sample hydraulic servo valve

    , Article Scientia Iranica ; Volume 17, Issue 5 B , 2010 , Pages 327-336 ; 10263098 (ISSN) Sadooghi, M. S ; Seifi, R ; Saadat Foumani, M ; Sharif University of Technology
    This paper presents a novel model to simulate the flow-current characteristic curve of an electro-hydraulic servo valve in steady state condition. This characteristic curve has three major zones: dead zone, linear zone and saturation zone. By using the presented approach, we can simulate the behavior of all types of valves including under lapped, critical center (zero lapped) and over lapped valves. A hydraulic tester has been designed and constructed for validation of the results. It can test the performance of flow-current and some other properties of the valve. Comparison of experimental and simulated curves describes that the model has an acceptable accuracy in determining the four... 

    An extended finite element method for hydraulic fracture propagation in deformable porous media with the cohesive crack model

    , Article Finite Elements in Analysis and Design ; Volume 73 , 2013 , Pages 77-95 ; 0168874X (ISSN) Mohammadnejad, T ; Khoei, A. R ; Sharif University of Technology
    In this paper, a fully coupled numerical model is developed for the modeling of the hydraulic fracture propagation in porous media using the extended finite element method in conjunction with the cohesive crack model. The governing equations, which account for the coupling between various physical phenomena, are derived within the framework of the generalized Biot theory. The fluid flow within the fracture is modeled using the Darcy law, in which the fracture permeability is assumed according to the well-known cubic law. By taking the advantage of the cohesive crack model, the nonlinear fracture processes developing along the fracture process zone are simulated. The spatial discretization... 

    Water hammer in a horizontal rectangular conduit containing air-water two-phase slug flow

    , Article Journal of Hydraulic Engineering ; Volume 142, Issue 3 , 2016 ; 07339429 (ISSN) Eyhavand Koohzadi, A ; Borghei, S. M ; Kabiri Samani, A ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2016
    The study of water hammer in air-water, two-phase flows in hydraulic structures such as pressurized pipelines and tunnels, siphons, culverts, and junctions is of great importance for design purposes. Water hammer if combined with a periodic slug flow would lead to severe periodic transient pressure fluctuations inside the conduit. Laboratory experiments have been conducted to investigate waterhammer pressure inside a horizontal rectangular conduit carrying a two-phase, air-water slug flow. Tests were performed in an experimental apparatus comprising a 6.8-m-long transparent pipeline 0.06 m wide and 0.1 m high. By rapidly closing a control gate at the end of the conduit, propagating pressure...