Search for: hydraulics
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    Measurement of moisture and temperature profiles in different layers of soil

    , Article 3rd International Foundation Congress and Equipment Expo 2018: Case Histories and Lessons Learned, IFCEE 2018, 5 March 2018 through 10 March 2018 ; Volume 2018-March, Issue GSP 298 , 2018 , Pages 266-278 ; 08950563 (ISSN) Fazel Mojtahedi, F ; Ali, K ; Nazari, A ; Rezvani, S ; Khatami, A ; Ahmadi, N ; Deep Foundations Institute; International Association of Foundation Drilling; Pile Driving Contractors Association; The Geo-Institute (G-I) of the American Society of Civil Engineers (ASCE) ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2018
    Over past decades, extensive research has been performed on the measurement of land subsidence as a result of compaction of aquifer. This paper describes results from a new field-monitoring system to evaluate changes in matric suction and temperature profiles in soil layers over an extended time period. The monitoring system used in this study consists of inserting dielectric sensors into a 105 m borehole, drilled in a site in Ardabil Plain, The monitoring results from the site were used to calibrate predictions from HYDRUS-1D. The physical and hydraulic properties of the soil materials in different layers were obtained through performing some soil characteristics and filter paper tests... 

    Study of fast transient pressure drop in vver-1000 nuclear reactor using acoustic phenomenon

    , Article Science and Technology of Nuclear Installations ; Volume 2018 , 2018 ; 16876075 (ISSN) Heidari Sangestani, S ; Rahgoshay, M ; Vosoughi, N ; Athari Allaf, M ; Sharif University of Technology
    Hindawi Limited  2018
    This article aims to simulate the sudden and fast pressure drop of VVER-1000 reactor core coolant, regarding acoustic phenomenon. It is used to acquire a more accurate method in order to simulate the various accidents of reactor core. Neutronic equations should be solved concurrently by means of DRAGON 4 and DONJON 4 coupling codes. The results of the developed package are compared with WIMS/CITATION and final safety analysis report of Bushehr VVER-1000 reactor (FSAR). Afterwards, time dependent thermal-hydraulic equations are answered by employing Single Heated Channel by Sectionalized Compressible Fluid method. Then, the obtained results were validated by the same transient simulation in a... 

    Implementation of a dynamic Monte Carlo method for transients analysis with thermal-hydraulic feedbacks using MCNPX code

    , Article Annals of Nuclear Energy ; Volume 130 , 2019 , Pages 240-249 ; 03064549 (ISSN) Ghaderi Mazaher, M ; Salehi, A. A ; Vosoughi, N ; Sharif University of Technology
    Elsevier Ltd  2019
    Transient analysis which is vital in safety analysis requires a reliable calculation method. Most valid tools use diffusion theory with many approximations by now. However, the Monte Carlo method inherently overcomes these approximations and accurately calculates the parameters of a reactor. In this paper, a new time-dependent transport approach is described to simulate the nuclear reactor dynamic correctly using the MCNPX code. In this approach the fundamental parameters of a nuclear reactor like multiplication factor (K eff ) and mean generation time (t G ) are calculated using MCNPX code. They are then employed in the formulas to compute neutron population, proportional to K eff , during... 

    A numerical study on the effect of salinity on stability of an unsaturated railway embankment under rainfall

    , Article 4th European Conference on Unsaturated Soils, E-UNSAT 2020, 19 October 2020 through 21 October 2020 ; Volume 195 , 2020 Kolahdooz, A ; Sadeghi, H ; Ahmadi, M. M ; GDS; VJ Tech ; Sharif University of Technology
    EDP Sciences  2020
    Dispersive soils, as one of the main categories of problematic soils, can be found in some parts of the earth, such as the eastern-south of Iran, nearby the Gulf of Oman. One of the most important factors enhancing the dispersive potential is the existence of dissolved salts in the soil water. The main objective of this study is to explore the influence of water salinity on the instability of a railway embankment due to rainfall infiltration. In order to achieve this goal, the embankment resting on a dispersive stratum is numerically modeled and subjected to transient infiltration flow. The effect of dispersion is simplified through variations in the soil-water retention curve with salinity.... 

    Economic evaluation of micro-turbines in Iranian electric industry

    , Article 2007 IEEE Lausanne POWERTECH, Lausanne, 1 July 2007 through 5 July 2007 ; 2007 , Pages 1776-1779 ; 9781424421909 (ISBN) Siahkali, H ; Sharif University of Technology
    Today the electric utility industry is being restructured from monopoly and regulated structure to competitive and deregulated structure. Changes in electricity markets, in technology, economics and regulatory structures have created a new interest in small-scale generation and efficiency resources, dispersed throughout the lower voltage networks. Many reasons have been developed and encouraged using DG (Distributed Generation) in different countries such as power system restructuring, DG technologies advances and price increases. The most important problems of many developing countries is the high cost of finance and limited access to financial resources because of the electric industry is... 

    B-Jump: Roller length, sequent depth, and relative energy loss using artificial neural networks

    , Article Journal of Hydraulic Research ; Volume 45, Issue 4 , 2007 , Pages 529-537 ; 00221686 (ISSN) Yazdandoost, F. Y ; Bateni, S. M ; Fazeli, M ; Sharif University of Technology
    International Association of Hydraulic Engineering Research  2007
    The phenomenon of the hydraulic jump is so complex that despite considerable laboratory and prototype studies, estimation of its main characteristics in a generalized and accurate form is still difficult. The Artificial Neural Network (ANN) approach aims at limiting the needs for costly and time-consuming experiments. In this study, two ANN models, multi-layer perceptron using back propagation algorithm (MLP/BP) and radial basis function using orthogonal least-squares algorithm (RBF/OLS), were used to predict the roller length, sequent depth, and the relative energy loss of the B-jump. Based on a pre-specified range of jump parameters, the input vectors include: upstream bed slope (tan θ),... 

    Experimental Study on Sediment Non-uniformity Effects on Local Scour Due to Hydraulic Jump Using Buried Plates

    , M.Sc. Thesis Sharif University of Technology Moftakhari Rostamkhani, Hamed (Author) ; Borghei, Mahmood (Supervisor)
    Local scour downstream of sluice gates in the erosive bed is one of the main concerns of hydraulic engineers, since it can cause serious damage to the structure. One of the ways to overcome this problem is the use of apron, or non-erosive bed. In order to shorten the apron or decrease the effect of the turbulence flow, different measures can be used. These approaches can be divided into two main branches, "Energy dissipating" and "bed reinforcement" measures. This study has investigated the scour phenomenon under the different conditions of the bed material gradation and bed reinforcement using vertical buried plates. The effect of sediment non-uniformity, unlike uniform sediment, has a... 

    Neutronic and Thermal-Hydraulic Coupling in time domain and Feasibility Study of its Application in Accident Prediction

    , M.Sc. Thesis Sharif University of Technology Abbasi Fashami, Sajjad (Author) ; Vosoughi, Naser (Supervisor)
    Analysis of neutronic and thermal-hydraulics fluctuations has various applications in calculation or measurement of the core dynamical parameters (temperature reactivity coefficients) furthermore it is applicable in thermal-hydraulics surveillance and diagnostics. Experience of the Fukushima Dai-ichi plant and the lessons learned from the European stress tests, demonstrated that alternative and various tools and methods are needed for the reactor's condition identification. In this paper the feasibility of development of an alternative accident monitoring via eminent coupling of neutron and thermal-hydraulics noise is proposed. and it is programming a simple simulator for calculating... 

    The Passive Design and Development of Digital Microfluidic Dynamic Memor

    , M.Sc. Thesis Sharif University of Technology Aminizadeh, Javad (Author) ; Moosavi, Ali (Supervisor)
    Microfluidics with the ability to control Nano-to-Pico meter volumes have caused the revolution in the systems of analytical biology and chemistry. However, the most Lab-On-Chip technologies (LOCs) depend on external control elements, so a lab is required to operate a chip. Bubble or drop logic through the bubble (drop) can control the flow internally and intrinsically digitally without utilizing of off-chip or moving components. Non-linearity is applied by using mutual drop-drop' effects on reversible linear flow in low Reynolds. for the proper exploitation of microfluidic systems, It is necessary to control droplet generation systems in one chip appropriately. The most crucial part of the... 

    Non-hydrostatic layered flows over a sill

    , Article Fluid Dynamics Research ; Volume 45, Issue 2 , February , 2013 ; 01695983 (ISSN) Jamali, M ; Sharif University of Technology
    This work takes a new approach to solving non-hydrostatic equations of layered flows over bottom topography. A perturbation technique is used to find explicit expressions for a flow for different regimes of single- and two-layer flows over a sill. Excellent agreement with previous solutions and experimental data is obtained, and more details of the non-hydrostatic flow over a sill are revealed. The proposed method is simple and compact and removes the need for complex numerical techniques to solve the non-hydrostatic equations. It is shown that in the approach-controlled regime of two-layer flow over a sill, the flow upstream and farther downstream the sill crest can be described by the... 

    A comprehensive study on the critical ventilation velocity in tunnels with different geometries

    , Article International Journal of Ventilation ; Volume 14, Issue 3 , Mar , 2015 , Pages 303-320 ; 14733315 (ISSN) Kazemipour, A ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
    VEETECH Ltd  2015
    Longitudinal ventilation is a common technique for smoke management during a fire accident within tunnels. In this paper, fire and smoke movement behaviour in longitudinally ventilated tunnels is investigated focusing on critical ventilation velocity. Firstly, critical velocity (VC) is evaluated for different heat release rates and results are compared and verified with model scale experimental data. Secondly, two fire scenarios inside tunnels with different cross sections are arranged and the reliability of some existing correlations for VC is explored. Results illustrate that using a combined geometric scale rather than the traditional single length-scale ones results in better estimation... 

    Numerical simulation of submerged flows with baffles uSING ν2̄ - F and k-ε turbulence models

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 08888116 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Mehdizadeh, A ; Firoozabadi, B ; Sherif, S. A ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    This paper introduces the concept of a submerged hydraulic jump being used for energy dissipation. A baffle wall is used to produce a stable deflected surface jet, thereby deflecting the high-velocity supercritical stream away from the bed to the surface. An elliptic relaxation turbulence model (v 2̄ - f model) has been used to simulate this submerged flow. During the last few years, the v2̄ - f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. In addition, it has been proved that the v̄2 - f model is superior to other RANS methods in many fluid flows where complex flow features are present. In this study,... 

    Physical and hydraulic properties of a new spring packing

    , Article CHISA 2006 - 17th International Congress of Chemical and Process Engineering, Prague, 27 August 2006 through 31 August 2006 ; 2006 ; 8086059456 (ISBN); 9788086059457 (ISBN) Mafi, M ; Yazdani, F ; Farhadi, F ; Deldari, H ; Sharif University of Technology
    Physical and hydraulic properties of new stainless steel spring packing are introduced. The measured hydraulic properties are: dry and wetted packed bed pressure drop, loading and flooding points and the liquid holdups. The appropriate coefficients for predicting the mentioned hydraulic properties from different correlations are also reported. Hydraulic properties for this packing are compared with available packings. In spite of small size, the dry and wetted packed bed pressure drops of spring packing are less than similar Raschig and Protruded rings. The total liquid holdup of this packing is greater than other commercial packings. The big total liquid holdup and physical surface area are... 

    A coupled hydro-mechanical analysis for prediction of hydraulic fracture propagation in saturated porous media using EFG mesh-less method

    , Article Computers and Geotechnics ; Vol. 55, issue , January , 2014 , p. 254-266 Oliaei, M. N ; Pak, A ; Soga, K ; Sharif University of Technology
    The details of the Element Free Galerkin (EFG) method are presented with the method being applied to a study on hydraulic fracturing initiation and propagation process in a saturated porous medium using coupled hydro-mechanical numerical modelling. In this EFG method, interpolation (approximation) is based on nodes without using elements and hence an arbitrary discrete fracture path can be modelled.The numerical approach is based upon solving two governing partial differential equations of equilibrium and continuity of pore water simultaneously. Displacement increment and pore water pressure increment are discretized using the same EFG shape functions. An incremental constrained Galerkin... 

    Field scale characterization of geological formations using percolation theory

    , Article Transport in Porous Media ; Volume 92, Issue 2 , 2012 , Pages 357-372 ; 01693913 (ISSN) Sadeghnejad, S ; Masihi, M ; Shojaei, A ; Pishvaie, M ; King, P. R ; Sharif University of Technology
    The connectivity of high conductivity pathways in geological formations depend on the spatial distribution of geological heterogeneities that may appear on various length scales. Appropriate modeling of this is crucial within in hydrology and petroleum systems. The approach taken in this study is to use percolation theory to quantify the connectivity, hydraulic conductivity, and breakthrough time behavior between an injector and a producer within such systems. In particular, a three-dimensional overlapping sandbody model is considered which assumes that the geological formation can be split into either conductive flow units (i. e., good sands) or non-conductive units (i. e., poor sands). The... 

    Regulator and tracking system design for a single-rod hydraulic actuator via pole-placement approach

    , Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011, 11 November 2011 through 17 November 2011 ; Volume 7, Issue PARTS A AND B , November , 2011 , Pages 173-181 ; 9780791854938 (ISBN) Moradi, H ; Hajikolaei, K. H ; Bakhtiari Nejad, F ; Sharif University of Technology
    Due to the nonlinear dynamics of hydraulic systems, applying high performance closed-loop controllers is complicated. In this paper, a single-rod hydraulic actuator is considered in which load displacement (for positioning purposes) is controlled via manipulation of the input voltage to the servo-valve. Dynamics of the servo-valve is described by first and second order transfer functions (named as Models 1 and 2). Through linearization of the system around its operating points, dynamics of the hydraulic actuator is represented in the state space. A full-order observer is designed for on-line states estimation. Then, feedback control system is designed for both regulation and tracking... 

    Prediction of hydraulic efficiency of primary rectangular settling tanks using the non-linear k - ε turbulence model

    , Article Scientia Iranica ; Volume 17, Issue 3 B , 2010 , Pages 167-178 ; 10263098 (ISSN) Firoozabadi, B ; Ashjari, M. A ; Sharif University of Technology
    Circulation is created in some parts of settling tanks. It can increase the mixing level, decrease the effective settling, and create a short circuiting from the inlet to the outlet. All above-mentioned phenomena act in such a way to decrease the tank's hydraulic efficiency, which quantitatively shows how flow within the tank is uniform and quiet. So, the main objective of the tank design process is to avoid forming the circulation zone, which is known as the dead zone. Prediction of the flow field and size of the recirculation zone is the first step in the design of settling tanks. In the present paper, the non-linear k - ε turbulence model is used for predicting the length of the... 

    Discharge coefficient of triangular and asymmetric labyrinth side weirs using the nonlinear PLS method

    , Article Journal of Irrigation and Drainage Engineering ; Volume 142, Issue 11 , 2016 ; 07339437 (ISSN) Parvaneh, A ; Kabiri Samani, A ; Nekooie, M. A ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2016
    Side weirs are hydraulic control structures widely used in irrigation and drainage systems as well as wastewater treatment plants. These structures also serve as adjusting/diverting flow structures with a minimum head loss. In the present study, by applying experimental data of more than 400 laboratory tests and using the multivariable nonlinear partial least-squares (PLS) method, three nonlinear equations are proposed for discharge coefficient, CM, of triangular and asymmetric labyrinth side weirs. These equations relate the discharge coefficient to the relevant geometrical and hydraulic dimensionless characteristics of flow. Results indicate that the new proposed equations are more... 

    Determination of discharge coefficient of triangular labyrinth side weirs with one and two cycles using the nonlinear PLS method

    , Article Sustainable Hydraulics in the Era of Global Change - Proceedings of the 4th European Congress of the International Association of Hydroenvironment engineering and Research, IAHR 2016, 27 July 2016 through 29 July 2016 ; 2016 , Pages 653-657 ; 9781138029774 (ISBN) Nekooie, M. A ; Parvaneh, A ; Kabiri Samani, A ; Sharif University of Technology
    CRC Press/Balkema  2016
    Side weirs are hydraulic control structures widely used in irrigation, drainage networks and waste water treatment plants. These structures can be used for adjusting and diverting of flow with minimum energy loss. In spite of many studies were carried out on rectangular side weirs, the studies on oblique and labyrinth side weirs are scarce. In this study, based on the experimental data from more than 210 laboratory tests and through using the multivariable nonlinear partial least square (PLS) method, two nonlinear equations are presented for discharge coefficient CM of triangular labyrinth side weirs with one and two cycles. The obtained empirical equations relating CM with the relevant... 

    Estimating the drainage rate from surface soil moisture drydowns: application of DfD model to in situ soil moisture data

    , Article Journal of Hydrology ; Volume 565 , 2018 , Pages 489-501 ; 00221694 (ISSN) Jalilvand, E ; Tajrishy, M ; Brocca, L ; Massari, C ; Ghazi Zadeh Hashemi, S ; Ciabatta, L ; Sharif University of Technology
    The large heterogeneity in soil surface conditions makes it impracticable to obtain reliable estimates of soil hydraulic parameters for areas larger than few squared kilometers. However, identifying these parameters on a global scale is essential for many hydrological and climatic applications. In this study, a new approach named Drainage from Drydown (DfD) is proposed to estimate the coefficients of drainage using soil moisture observations. DfD firstly selects multiple drydown events when surface runoff and evapotranspiration rates are negligible compared to the drainage rate. Secondly, by inverting the soil water balance equation, the drainage coefficients are obtained. Synthetic...