Loading...
Search for:
hydraulics
0.012 seconds
Total 337 records
An enriched-finite element technique for numerical simulation of hydro-fracture evolution in naturally-layered formations
, Article 6th ECCOMAS European Conference on Computational Mechanics: Solids, Structures and Coupled Problems, ECCM 2018 and 7th ECCOMAS European Conference on Computational Fluid Dynamics, ECFD 2018, 11 June 2018 through 15 June 2018 ; 2020 , Pages 1685-1696 ; Akhondzadeh, S. H ; Khoei, A. R ; Khalili, N ; Sharif University of Technology
International Centre for Numerical Methods in Engineering, CIMNE
2020
Abstract
In this paper, a computational model is developed for the simulation of hydro-fracture growth in naturally layered impervious media using the extended finite element method (X-FEM). The equilibrium equation of the bulk is solved in conjunction with the hydro-fracture inflow and continuity equations using the staggered Newton method. The hydro-fracture inflow is modeled by using the lubrication theory, where the permeability of the fracture is incorporated by taking advantage of the cubic law. The Eigen-function expansion method is utilized in order to develop enrichment functions suited for the asymptotic stress field in the vicinity of the singular points. An energy release rate-based...
A hybrid pole climbing and manipulating robot with minimum DOFs for construction and service applications
, Article Industrial Robot ; Volume 32, Issue 2 , 2005 , Pages 171-178 ; 0143991X (ISSN) ; Zakerzadeh, M. R ; Vossoughi, G. R ; Bagheri, S ; Sharif University of Technology
2005
Abstract
Purpose - Aims to describe design, prototyping and characteristics of a pole climbing/manipulating robot with ability of passing bends and branches of the pole. Design/methodology/approach - Introducing a hybrid (parallel/serial) four degree of freedom (DOF) mechanism as the main part of the robot and also introduces a unique gripper design for pole climbing robots. Findings - Finds that a robot, with the ability of climbing and manipulating on poles with bends and branches, needs at least 4 DOFs. Also an electrical cylinder is a good option for climbing robots and has some advantages over pneumatic or hydraulic cylinders. Research limitations/implications - The robot is semi-industrial...
Shock wave sintering of Al/SiC metal matrix nano-composites: A molecular dynamics study
, Article Computational Materials Science ; Volume 125 , 2016 , Pages 255-262 ; 09270256 (ISSN) ; Mahnama, M ; Naghdabadi, R ; Sharif University of Technology
Elsevier
2016
Abstract
Mechanical properties of nano-composites produced by shock wave sintering of aluminum and silicon carbide nano-powders are investigated using Molecular Dynamics (MD) simulations. In this regard, the shock wave response of aluminum and silicon carbide nano-particles, arranged in a BCC super-lattice, is studied via the NPHug Hugoniostat method. Moreover, the effect of the initial hydrostatic compaction of powders as well as the cooling rate of the shocked material on the mechanical properties of the shock-sintered nano-composites is investigated. Employing the Hugoniot curves corresponding to the powders, it is concluded that an initial hydrostatic pressure, leads to a less temperature rise...
Thermal-hydraulic analysis of HPLWR fuel assembly cluster
, Article Journal of Supercritical Fluids ; Volume 77 , May , 2013 , Pages 91-99 ; 08968446 (ISSN) ; Salehi, A. A ; Jahanfarnia, G ; Sharif University of Technology
2013
Abstract
The High-Performance Light Water Reactor (HPLWR) is the European version of the Supercritical-pressure Water Cooled Reactor (SCWR). Light water reactors at supercritical pressure, being currently under design, are the new generation of nuclear reactors. The present article is a thermal-hydraulic analysis of the HPLWR fuel assembly cluster. The existing thermal hydraulic codes are not capable of analyzing and designing the HPLWR fuel assembly. It is necessary to introduce a new thermal-hydraulic code that can incorporate the parameters and specifications of the HPLWR fuel assembly. The governing equations include energy, mass and momentum equations beside thermal-hydraulic equations are...
Neutronic analysis of HPLWR fuel assembly cluster
, Article Annals of Nuclear Energy ; Volume 50 , December , 2012 , Pages 38-43 ; 03064549 (ISSN) ; Salehi, A. A ; Jahanfarnia, G ; Abbaspour Tehrani Fard, A ; Sharif University of Technology
2012
Abstract
In the present study the neutronic analysis of fuel assembly cluster of the HPLWR is discussed. Neutronic calculations are performed using WIMS-D4 and CITATION codes. Thermal-hydraulic code containing the properties and specifications of the fuel assembly of HPLWR is utilized. The calculated axial power in each selected control volume is used in the thermal-hydraulic code to get the properties of the fluid and fuel needed for further neutronic analysis. The process of coupling continues until convergence is achieved. Finally, the obtained neutronic results including axial power distribution, neutron flux, and power peaking factors are discussed in the present article
Experimental study of small and medium break LOCA in the TTL-2 thermo-hydraulic test loop and its modeling with RELAP5/MOD3.2 code
, Article Scientia Iranica ; Volume 17, Issue 6 B , NOVEMBER-DECEMBER , 2010 , Pages 492-501 ; 10263098 (ISSN) ; Jafari, J ; Vosoughi, N ; Arabnezhad, H ; Sharif University of Technology
2010
Abstract
Small and medium break LOCA accidents at low pressure and under low velocity conditions have been studied in the TTL-2 Thermo-hydraulic Test Loop, experimentally. TTL-2 is a thermal hydraulic test facility which is designed and constructed in NSTRI to study thermal hydraulic parameters under normal operational and accident conditions of nuclear research reactors. A nodalization has been developed for the TTL-2 and experimental results have been compared with RELAP5/MOD3.2 results. The considered accidents are a 25% and 50% cold leg break without emergency core cooling systems. Results show good agreement between experiments and RELAP5/MOD3.2 results. This research provides experimental data...
Comparison of finite difference schemes for water flow in unsaturated soils
, Article World Academy of Science, Engineering and Technology ; Volume 40 , 2009 , Pages 21-25 ; 2010376X (ISSN) ; Ataie Ashtiani, B ; Sharif University of Technology
2009
Abstract
Flow movement in unsaturated soil can be expressed by a partial differential equation, named Richards equation. The objective of this study is the finding of an appropriate implicit numerical solution for head based Richards equation. Some of the well known finite difference schemes (fully implicit, Crank Nicolson and Runge-Kutta) have been utilized in this study. In addition, the effects of different approximations of moisture capacity function, convergence criteria and time stepping methods were evaluated. Two different infiltration problems were solved to investigate the performance of different schemes. These problems include of vertical water flow in a wet and very dry soils. The...
Optimized fuzzy control strategy for a spa hybrid truck
, Article International Journal of Automotive Technology ; Volume 13, Issue 5 , August , 2012 , Pages 817-824 ; 12299138 (ISSN) ; Foumani, M. S ; Sharif University of Technology
2012
Abstract
In this paper, an optimized control strategy is proposed for a split parallel hydraulic hybrid truck. The model of the vehicle was simulated in Simulink. According to a global optimization technique, a fuzzy control strategy is developed for the vehicle. This strategy shows flexibility for different drive cycles and a desirable fuel consumption reduction, especially for a low speed drive cycle, which is extracted according to an urban utility vehicle mission
Implementation of an optimal control strategy for a hydraulic hybrid vehicle using CMAC and RBF networks
, Article Scientia Iranica ; Volume 19, Issue 2 , 2012 , Pages 327-334 ; 10263098 (ISSN) ; Foumani, M. S ; Boroushaki, M ; Sharif University of Technology
2012
Abstract
A control strategy on a hybrid vehicle can be implemented through different methods. In this paper, the Cerebellar Model Articulation Controller (CMAC) and Radial Basis Function (RBF) neural networks were applied to develop an optimal control strategy for a split parallel hydraulic hybrid vehicle. These networks contain a nonlinear mapping, and, also, the fast learning procedure has made them desirable for online control. The RBF network was constructed with the use of the K-mean clustering method, and the CMAC network was investigated for different association factors. Results show that the binary CMAC has better performance over the RBF network. Also, the hybridization of the vehicle...
Nonlinear power balance control of a SPA hydraulic hybrid truck
, Article 2009 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM 2009, Singapore, 14 July 2009 through 17 July 2009 ; 2009 , Pages 805-810 ; 9781424428533 (ISBN) ; Alasty, A ; Saadat Foumani, M ; Sharif University of Technology
2009
Abstract
An integrated procedure for mathematical modeling and power control balance for a SPA (Split Parallel Architecture) hydraulic hybrid vehicle is presented in this paper. Dynamic mathematical model of the powertrain is constructed firstly, which includes five modules: diesel engine, traction motor, starter, loading pump and accumulator. Based on the mathematic model of control modes a stability analysis is done. For some control modes a Sliding Mode Control is designed, which uses full-states closed-loop feedback. The paper finally illustrates and discusses the results of simulation. The results show that the performance and stability of control modes are proper and a power control strategy...
Improvement of soil moisture and groundwater level estimations using a scale-consistent river parameterization for the coupled ParFlow-CLM hydrological model: A case study of the Upper Rhine Basin
, Article Journal of Hydrology ; Volume 610 , 2022 ; 00221694 (ISSN) ; Fahs, M ; Bitar, A. A ; Ataie Ashtiani, B ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Accurate implementation of river interactions with subsurface water is critical in large-scale hydrologic models with a constant horizontal grid resolution when models apply kinematic wave approximation for both hillslope and river channel flow. The size of rivers can vary greatly in the model domain, and the implemented grid resolution is too coarse to accurately account for river interactions. Consequently, the flow velocity is underestimated when the width of the rivers is much narrower than the selected grid size. This leads to inaccuracy and uncertainties in calculations of water quantities. In addition, the rate of exfiltration and infiltration between the river and the subsurface may...
Microbial leaching of a low-grade sphalerite ore using a draft tube fluidized bed bioreactor
, Article Hydrometallurgy ; Volume 99, Issue 3-4 , 2009 , Pages 131-136 ; 0304386X (ISSN) ; Hosseini, S ; Roostaazad, R ; Petersen, J ; Mousavi, M ; Kazemi Vasiri, A ; Sharif University of Technology
2009
Abstract
The use of a draft tube fluidized bed bioreactor (DTFBB) has been successfully demonstrated for the bioleaching of a chalcopyrite concentrate (Mousavi, et. al., 2005). In the present paper this technique was used for the bioleaching of zinc from a sphalerite bearing low-grade ore. A strain of the thermophilic bacterium, Sulfobacillus, has been isolated from the Kooshk lead and zinc mine near the city of Yazd (Iran) and is tested at temperatures 47 °C-72 °C. This is compared to leaching with a strain of the mesophile Acidithiobacillus ferrooxidans, which has been adapted to the high levels of zinc and the presence of the low-grade ore, and which was tested at temperatures 18 °C-42 °C. The...
Seepage through rockfill dams in narrow valleys
, Article Proceedings of From Research to Practice in Geotechnical Engineering Congress 2008 - From Research to Practice in Geotechnical Engineering, 9 March 2008 through 12 March 2008, New Orleans, LA ; Volume 325 , 2008 , Pages 522-539 ; 9780784409626 (ISBN) ; Jafarzadeh, F ; Sharif University of Technology
2008
Abstract
Seepage analysis serves as one of the most significant stages in the design process of an embankment dam. In two-dimensional (2D) seepage analysis of embankment dams, little or no attention is paid to the seepage through side abutments. Moreover the role of grout curtain extensions into the side abutments and abutment material properties are inevitably neglected when performing a 2D seepage analysis. In this paper, two and three-dimensional (3D) models of a rockfill dam during operation state are generated and several unsteady and steady state seepage analyses are performed using finite element method (FEM). The results obtained from 2D and 3D seepage analyses were compared with measurements...
New seepage-related design graphs for rock-fill dams
, Article International Symposium on Dams in the Societies of the 21st Century, ICOLD-SPANCOLD - Dams and Reservoirs, Societies and Environment in the 21st Century, Barcelona, 18 June 2006 through 18 June 2006 ; Volume 1 , 2006 , Pages 971-978 ; 0415404231 (ISBN); 9780415404235 (ISBN) ; Jafarzadeh, F ; Sharif University of Technology
Taylor and Francis/ Balkema
2006
Abstract
Seepage analysis serves as one of the most significant stages in the design process of an embankment dam. In two-dimensional (2D) seepage analysis of embankment dams, little or no attention is paid to the widthwise flows from side abutments. Moreover, the role of grout curtain extensions into the side abutments and abutment material properties are inevitably neglected when performing seepage analyses in 2D plane. In this paper, two and three-dimensional (3D) models of a rock-fill dam are generated and several unsteady and steady state seepage analyses are performed using finite element method (FEM). The results obtained from 2D and 3D seepage analyses were compared with measurements from the...
Monitoring temperature changes in a hypersaline lake using MODIS-derived water temperatures (the case of Urmia Lake, Iran)
, Article 6th International Symposium on Environmental Hydraulics, Athens, 23 June 2010 through 25 June 2010 ; Volume 2 , 2010 , Pages 881-886 ; 9780415595469 (ISBN) ; Tajrishy, M ; Sharif University of Technology
2010
Abstract
Lake surface temperature is an important indicator of the lake state and a driver of regional weather and climate near large lakes. The objective of this study is to use thermal imagery from the MODIS on board the Earth Observing System Terra and Aqua platforms to assess the spatial and temporal variations in Urmia lake temperature. Urmia Lake, located in northwestern Iran is one of the largest permanent hypersaline lakes in the world. The surface temperature of Urmia Lake is examined between 2008 and 2009, as dry years. MODIS-derived lake SWT then was calibrated with monthly observations. MODIS-derived lake SWT exhibits a cool bias (-0.72°C) relative to in situ temperature observations in...
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) ; Sharif University of Technology
2007
Abstract
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...
Analysis of accumulators configuration in LB-LOCA for Bushehr NPP
, Article Annals of Nuclear Energy ; Volume 92 , 2016 , Pages 96-106 ; 03064549 (ISSN) ; Jafari, J ; Aghaie, M ; Vosoughi, N ; Nemati, M ; Sharif University of Technology
Elsevier Ltd
Abstract
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...
Influence of lakebed sediment deposit on the interaction of hypersaline lake and groundwater: A simplified case of lake Urmia, Iran
, Article Journal of Hydrology ; Volume 588 , 2020 ; Ataie Ashtiani, B ; Safaie, A ; Simmons, C. T ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Lake Urmia, which was once the second-largest saline lake in the world, has been shrinking dramatically. Moreover, Lake Urmia has become supersaturated with total salinity averaging more than 350 g/l. Salt precipitation and dissolved materials brought by inflowing rivers have formed a layer of sediment with low hydraulic conductivity on the lakebed. Considering the flat bathymetry of Lake Urmia, we conducted a series of numerical simulation scenarios to study the groundwater flow pattern in the vicinity of the hypersaline Lake Urmia using COMSOL Multiphysics®. In the first step, we performed the simulations in steady-state conditions. Secondly, we simulated the lake level fall in 10 years at...
The effect of influent COD and upward flow velocity on the behaviour of sulphate-reducing bacteria
, Article Process Biochemistry ; Volume 40, Issue 7 , 2005 , Pages 2305-2310 ; 13595113 (ISSN) ; Ghavipanjeh, F ; Mirjafari, P ; Sharif University of Technology
2005
Abstract
The effect of up velocity and influent COD concentration on the activity of sulphate-reducing bacteria (SRB) in UASB reactors is discussed. To study these effects, four UASB reactors were built and utilized in parallel. Examinations were carried out in two different concentrations of molasses (500 mg COD/l and 1000 mg COD/l) and four different upward flow velocities. It was observed that at velocities greater than 1 m/h, SRB bacteria were easily washed out from the reactors due to lower density and lack of ability to form dense and firm granules. It was found that in low-strength wastewaters with a COD to sulphate ratio of 2, an upward velocity in the range of 1.5-2.5 m/h could be...
Dynamic simulation of the biped normal and amputee human gait
, Article Mobile Robotics: Solutions and Challenges - Proceedings of the 12th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, CLAWAR 2009, 9 September 2009 through 11 September 2009, Istanbul ; 2010 , Pages 1113-1120 ; 9814291269 (ISBN) ; 9789814291262 (ISBN) ; Farahmand, F ; Zohour, H ; Sharif University of Technology
2010
Abstract
A two-dimensional seven link biped dynamic model was developed to investigate the mechanical characteristics of the normal and amputee locomotion during the complete gait cycle. The foot-ground contact was simulated using a five-point penetration contact model. The equations of motion were derived using Lagrange method. Optimization of the normal human walking model provided constant coefficients for the driving torque equations that could reasonably reproduce the normal kinematical pattern. The resulting torques were then applied to the intact joints of the amputee model with a prosthetic leg equipped with a kinematical driver controller for the ankle and either a hydraulic, elastic or...