Search for: flow-model
Total 99 records
A numerical comparison of 2-D inviscid and viscous approaches for flow through a stage of an axial compressor, Article Scientia Iranica ; Volume 11, Issue 1-2 , 2004 , Pages 128-137 ; 10263098 (ISSN) ; Amanifard, N ; Ghorbanian, K ; Sharif University of Technology
Sharif University of Technology 2004
In this paper, an unsteady, two-dimensional solver is developed, based on Van Leer's flux splitting algorithm, in conjunction with the "Monotonic Upstream Scheme for Conservation Laws (MUSCL)" limiters for improving the order of accuracy. For a minimum usage of computer memory and faster convergence, the two-layer Baldwin-Lomax turbulence model is implemented for a viscous solution. Three test cases are prepared to validate the solver. The computed results are compared with experimental data and the good agreement of the compared results validates the solver. Finally, the solver is used for the flow through a multi-blade stage of an axial compressor in its design condition. The solutions of...
Investigating Engineering Solutions to Preserve Goragan Bay:Dreding Ashouradeh Channel, M.Sc. Thesis Sharif University of Technology ; Raie, Mohammad
Gorgan Bay, registered as a biosphere reserve, has environmental value in the country and the world. The bay is separated from the Caspian Sea by sedimentation in the sandy spit of Miankaleh. Due to the declining water level of the Caspian Sea and the possibility of hydraulic connection disruption and closure of its openings, this water body may face many problems in the future. Main problems are the increase in water retention time and, consequently, the decrease in water quality and the problem of local access during the seasons when the water level drops. In this study, engineering solutions have been studied in proportional with the current conditions of the Gorgan Gulf, which include...
A new formulation for power system reliability assessment with AC constraints, Article International Journal of Electrical Power and Energy Systems ; Vol. 56, issue , March , 2014 , p. 298-306 ; ISSN: 1420615 ; Fotuhi-Firuzabad, M ; Aminifar, F ; Lehtonen, M ; Sharif University of Technology
Recent investigations have revealed the significant role of reactive power in blackout events. The associated disturbances frequently emerge in the form of voltage instability and collapse. Due to the computational complexity of modeling and analysis of enormous contingencies, DC approximation of the power flow, without accounting the role of reactive power, is usually used to evaluate the contingencies and to mitigate the associated probable violations. This paper, at first, presents a linear power flow model based on an approximated version of AC power flow formulation. The proposed model is then used to develop an efficient reliability assessment approach which is capable of taking both...
Performance prediction of twin-entry turbocharger turbines, Article Proceedings of the ASME Turbo Expo 2002; Aircraft Engine, Coal, Biomass and Alternative Fuels, Combustion and Fuels, Education, Electric Power, Vehicular and Small Turbomachines, Amsterdam, 3 June 2002 through 6 June 2002 ; Volume 1 , 2002 , Pages 1087-1095 ; Shirani, E ; Hajilouy Benisi, A ; The International Gas Turbine Institute ; Sharif University of Technology
In this paper, the performance of the twin-entry radial flow turbine under steady state and partial admission conditions is modeled. The method, which is developed here, is based on one-dimensional performance prediction. In one-dimensional modeling, the flow properties are assumed constant on a plane normal to the flow direction. This assumption is in contrast with the flow at the rotor entry of a twin-entry turbine under partial admission condition. In this study the one-dimensional performance prediction method for single-entry turbine is modified to analyze the twin-entry turbine. In particular, the loss coefficients due to friction, clearance and blade loading, which are already...
Extension of the Macroscopic Traffic Flow Model, Ph.D. Dissertation Sharif University of Technology ; Nassiri, Habibollah
Traffic flow modeling on different levels was always the topic of many studies. In this regard, many researchers have tried to eliminate traffic problems by developing precise models. Therefore, in this study and in its two major parts, we developed two models: one macroscopic and one microscopic. Like previous studies, the main purpose here was the development of traffic flow models that have better precision and give more information about the mechanism behind the traffic phenomena. Our focus was on the free spaces in front of drivers which were considered in a macroscopic traffic flow model and resulting microscopic traffic flow model.First part, addresses the first-order extension of the...
The evaluation of the confidence intervals for the state parameters of a DC power system, Article Journal of Engineering and Applied Sciences ; Volume 12, Issue 18 , 2017 , Pages 4544-4550 ; 1816949X (ISSN) ; Razalia, R ; Daud, H ; Norc, N. M ; Firuzabad, M. F ; Sharif University of Technology
State estimation in power engineering is used as a tool to find the unknown parameter values from the hypothesized model by utilizing the specified information available about the system. Due to random noises that are added from different sources, the exact value of the state vector cannot be found. This study is an effort to describe the simultaneous and individual confidence intervals for the state parameters in view of the heteroscedastic structure of the error terms. The performance of the constructed intervals in terms of coverage probability has been evaluated by using the Monte Carlo simulation study. The results of the study demonstrate that it is an effective method for practical...
Numerical Simulation of Oil Spill in Gheshm Channel, M.Sc. Thesis Sharif University of Technology ; Raie, Mohammad ; Ataie Ashtiani, Behzad
To meet the growing energy demand worldwide, oil and gas exploration and production activities have increased rapidly both in onshore and offshore areas. The produced oil from the ocean bed is transported onshore either by ship or pipeline. This has increased the risk of oil spill in the coastal areas. In order to prepare an emergency preparedness plan and to assess the magnitude of risk involved in transporting and offloading oil, oil spill simulation studies play an important role. This research describes a simulation of oil spill in coastal area of Persian Gulf, near Hormoz Strait which is called Gheshm Channel (Khouran Strait), using MIKE 21 model. The Gheshm Channel contains huge...
Red Tide Development Modelling by MIKE Software (in Persian Gulf), M.Sc. Thesis Sharif University of Technology ; Abasspour, Majid
Land sourced marine pollution, overexploitation of living marine resources, destruction of habitat and introduction of harmful aquatic organisms and pathogens to new environment had been identified as the four greatest threats to the world’s oceans. Since invasive species can not be cleaned or absorbed in the ocean so, their effects on the environment are irreversible. Red tide is one of the invasive spieces and is a colloquial term used to refer to one of a variety of natural phenomena known as algal bloom. This phenomenon occur in estuarine, marine, or fresh water and algae accumulate rapidly in the water column and resulting in coloration of the surface water, varying in colour normally...
Organizational secure knowledge flow model, Article 2015 7th Conference on Information and Knowledge Technology, IKT 2015, 26 May 2015 through 28 May 2015 ; May , 2015 , Page(s): 1 - 6 ; 9781467374859 (ISBN) ; Shalmani, M. T. M ; Habibi, J ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2015
With the advance and growth of knowledge management in the past two decades, currently knowledge is regarded as one of the most significant organizational assets. Today the success of businesses is dependent on the value that they give to knowledge and how they attempt to manage it. Hence, in such conditions, knowledge as a valuable asset of the organization must be well-protected. What is managed in knowledge management in organizations is actually not knowledge. What are managed are the knowledge-related processes thru which knowledge workers interact with each other. Hence, organizational knowledge protection does not mean protecting knowledge, but securing the management of knowledge and...
The development of a novel multi-objective optimization framework for non-vertical well placement based on a modified non-dominated sorting genetic algorithm-II, Article Computational Geosciences ; Volume 23, Issue 5 , 2019 , Pages 1065-1085 ; 14200597 (ISSN) ; Jamshidi, S ; Zirbes, E ; Sharif University of Technology
Springer International Publishing 2019
A single-objective well placement problem is one of the classical optimization problems in oilfield development and has been studied for many years, by researchers worldwide. However, the necessity to face practical applications and handle insufficient data in a single-objective optimization leads to the introduction of a multi-objective optimization framework, which consequently allows an engineer to manage more information. In this study, for the very first time, a multi-objective well placement optimization framework, based on a Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is utilized with a similarity-based mating scheme. To represent the power of this mating procedure, it is...
Simulation of rarefied micro to nano gas flows using improved slip flow models, Article 37th AIAA Fluid Dynamics Conference, Miami, FL, 25 June 2007 through 28 June 2007 ; Volume 1 , 2007 , Pages 576-583 ; 1563478978 (ISBN); 9781563478970 (ISBN) ; Rikhtegar, F ; Schneider, G. E ; Sharif University of Technology
If the hydrodynamic diameter of a channel is comparable with the mean free path of the gas molecules moving inside the channel, the fluid can no longer be considered to be in thermodynamic equilibrium and a variety of non-continuum or rarefaction effects can occur. To avoid enormous complexity and extensive numerical cost encountered in modeling of nonlinear Boltzmann equations, the Navier-Stokes equations can be solved considering the concepts of slip flow regime and applying slip velocity boundary conditions at the solid walls. The high-order slip models can, in some cases, extend the range of applicability of the Navier-Stokes equations beyond Kn = 0.1, where the accuracy of first-order...
A mass conservative scheme for simulating shallow flows over variable topographies using unstructured grid, Article Advances in Water Resources ; Volume 28, Issue 5 , 2005 , Pages 523-539 ; 03091708 (ISSN) ; Le Roux, D. Y ; Tajrishi, M ; Mazaheri, K ; Sharif University of Technology
Most available numerical methods face problems, in the presence of variable topographies, due to the imbalance between the source and flux terms. Treatments for this problem generally work well for structured grids, but most of them are not directly applicable for unstructured grids. On the other hand, despite of their good performance for discontinuous flows, most available numerical schemes (such as HLL flux and ENO schemes) induce a high level of numerical diffusion in simulating recirculating flows. A numerical method for simulating shallow recirculating flows over a variable topography on unstructured grids is presented. This mass conservative approach can simulate different flow...
Inviscid compressible flow computations on 3D unstructured grids, Article Scientia Iranica ; Volume 12, Issue 2 , 2005 , Pages 207-216 ; 10263098 (ISSN) ; Sharif University of Technology
Sharif University of Technology 2005
In this paper, an explicit finite element based numerical procedure is presented for simulating three-dimensional inviscid compressible flow problems. The implementation of the first-order upwind method and a higher-order artificial dissipation technique on unstructured grids, using tetrahedral elements, is described. Both schemes use a multi-stage Runge-Kutta time-stepping method for time integration. The use of an edge-based data structure in the finite element formulation and its computational merits are also elaborated. Furthermore, the performance of the two schemes in solving a benchmark problem involving transonic flow about an ONERA M6 wing is compared and detailed solutions are...
A coupled wellbore-reservoir flowmodel for numerical pressure transient analysis in vertically heterogeneous reservoirs, Article Journal of Porous Media ; Volume 16, Issue 5 , 2013 , Pages 395-400 ; 1091028X (ISSN) ; Soltanieh, M ; Farhadpour, F. A ; Sharif University of Technology
Pressure transient analysis in vertically heterogeneous reservoirs is examined. The inclusion of a separate model for the free fluid flow in the wellbore is essential to allow for hydraulic communication and mixing of the fluid issuing from different reservoir layers. A two-dimensional model coupling Darcy flow in the reservoir with Navier-Stokes flow in the wellbore is developed and solved by the finite element technique. The coupled wellbore-reservoir flow model is used to analyze a layered reservoir with an abrupt change in permeability and a thick formation showing a gradual change in permeability with depth. Contrary to conventional reservoir models, this new model is able to capture...
A non-iterative approach for AC state estimation using line flow based model, Article International Journal of Electrical Power and Energy Systems ; Volume 43, Issue 1 , 2012 , pages 1413-1420 ; 1420615 (ISSN) ; Fotuhi Firuzabad, M ; Aminifar, F ; Sharif University of Technology
One of the underlying requirements in the present energy management systems (EMSs) is to have a complete understanding of the system status. This feature is realized via state estimation (SE) engine. This paper presents a new and efficient SE approach which leads to a desirable outcome using a non-iterative calculation. The proposed model is based on a new AC power flow formulation designated as the line flow based (LFB) model. The objective function is to minimize the weighted least square of measurement residuals. The developed method adopts the line flows and square of voltage magnitudes as the problem state variables and incorporates both active and reactive power quantities. The...
Effect of operating conditions on the performance of a PEM fuel cell, Article International Journal of Heat and Mass Transfer ; Volume 144 , 2019 ; 00179310 (ISSN) ; Sharif University of Technology
Elsevier Ltd 2019
In this study, a two-phase flow model based on species transport, energy, and electrochemical equations was developed for polymer electrolyte membrane fuel cell (PEMFC). The influences of heat sources and sinks, and water transport inside the fuel cell were also taken into account. In this regard, the effect of the operating conditions including cell temperature and pressure, anode and cathode inlet humidity, and anode and cathode stoichiometric ratios on the fuel cell performance was investigated. The simulation results show that inlet humidity and stoichiometric ratio of the anode side, cell pressure and temperature, and distribution of the heat sources and sinks are crucial factors...
Theoretical comparative assessment of single- and two-phase models for natural convection heat transfer of Fe3O4/ethylene glycol nanofluid in the presence of electric field, Article Journal of Thermal Analysis and Calorimetry ; 2020 ; Tavakoli, S ; Pishvaie, M. R ; Sharif University of Technology
Springer Netherlands 2020
Natural convective heat transfer of Fe3O4/ethylene glycol nanofluids around the platinum wire as a heater in the absence and presence of the high electric field was investigated, numerically. The control volume finite element method was employed for the numerical simulation. Effects of the flow model, the volume fraction of nanoparticles, Rayleigh number, and the electric field intensity on the natural heat transfer coefficient (NHTC) of nanofluid were studied. Simulation results of single-phase and two-phase flow models showed that the two-phase model could better predict experimental data than the single-phase model due to take into account the velocity of each phase in the mixture. The...
Prediction of waterflood performance using a modified capacitance-resistance model: A proxy with a time-correlated model error, Article Journal of Petroleum Science and Engineering ; Volume 198 , 2021 ; 09204105 (ISSN) ; Aminshahidy, B ; Bazargan, H ; Sharif University of Technology
Elsevier B.V 2021
Capacitance-Resistive Model (CRM), as a fast yet efficient proxy model, suffers from some limitations in modeling relatively complex reservoirs. Some current improvements on this proxy made it a more powerful simulator with updating parameters over time. However, the model's intrinsic uncertainty arisen from simplifying fluid-flow modeling by some limited number of constant parameters is not addressed yet. In this study, this structural limitation of CRM has been addressed by introducing a time-correlated model error, including stochastic and non-stochastic parameters, embedded into this proxy's formulation. The error term's non-stochastic parameters have been tuned to be used in forecasting...
Experimental and CFD simulation of slurry flow in the annular flow path using two-fluid model, Article Journal of Petroleum Science and Engineering ; Volume 198 , 2021 ; 09204105 (ISSN) ; Jamshidi, S ; Sharif University of Technology
Elsevier B.V 2021
The current study is allocated to experimental evaluation of the multiphase flow of fine solid particles (FSPs) as well as comprehensive numerical study in an annular space under static, laminar, and turbulent flow conditions with consideration of the inner pipe eccentricity and rotation. The experimental investigation was carried out using an annular pipe flow loop. The numerical modeling and simulation of the multiphase flow in the annular space have been performed using the Euler-Euler approach. The unsteady-state multiphase model based on the kinetic theory of granular flow (KTGF) is developed to investigate the particulate flow characteristics in the annular space. Moreover, Standard...
Simulation of Advection and Diffusion of Hazardous Noxious Substances (HNS) in Sea, Case Study: Oil Derivations in Caspian Sea, M.Sc. Thesis Sharif University of Technology ; Raie, Mohammad
Hazardous Noxious Substances (HNS) are chemicals. Due to population increase and as a result, increased demand, HNS transportation by sea has been raised. Gasoline and diesel are two kinds of HNS which have the largest transported amount via northern ports of Iran especially Anzali port. So, HNS spill from tankers is an imminent event and threat for environment of Caspian Sea. Organizations that are concern about the health of coasts and seas water always try to use the softwares to simulate the currents and waves to define the hydrocarbon slick transport. Therfore in this study, a 2D hydrodynamic/oil spill model has been developed to predict the transportation of diesel and gasoline slick...