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transient-behavior
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Monitoring and characterizing the finger patterns developed by miscible displacement in fractured heavy oil systems
, Article Industrial and Engineering Chemistry Research ; Volume 52, Issue 31 , July , 2013 , Pages 10853-10863 ; 08885885 (ISSN) ; Majidi, S. M. J ; Ghazanfari, M. H ; Sharif University of Technology
2013
Abstract
This work concerns experimentally quantifying finger behavior during miscible displacements in fractured porous media. A series of miscible tests were performed on five-spot fractured micromodels which were initially saturated with heavy crude oil, and the developed finger patterns were quantified using an image analysis technique. The results revealed that the numbers of macro fingers formed is well correlated with the square root of dimensionless time, while the rate of finger initiation is independent of fracture characteristics. The level of bypassed oil linearly decreases with dimensionless distance traveled by front precisely. The transient fractal dimension behavior experiences a...
Development of a Real Time System Identifier for Interconnected Systems
, M.Sc. Thesis Sharif University of Technology ; Bozorgmehri Boozarjomehri, Ramin (Supervisor)
Abstract
Access to a reduced and fast mathematical model that can predict the input-output behavior of interconnected systems with acceptable accuracy and in a short time is crucial. The purpose of this project is to provide an object-oriented platform for identifying a model based on input-output data of interconnected systems in real-time. On this basis, in the case of developing fast estimation algorithms and updating the model quickly (in case of extensive changes in the system), good predictions of the model can be used for various applications. In this research, machine learning and data analysis methods are used to extract useful features and relations from data. Then, taken advantage of this...
Effect of working fluid inventory and heat input on transient and steady state behavior of a thermosyphon
, Article Journal of Thermal Analysis and Calorimetry ; Volume 143, Issue 5 , 2021 , Pages 3825-3834 ; 13886150 (ISSN) ; Forootan, D ; Farajimoghaddam, F ; Sharif University of Technology
Springer Science and Business Media B.V
2021
Abstract
The effect of working fluid inventory and heat input on the performance of thermosyphon is investigated in this paper. First, a thermosyphon with diameter of 16 mm made of steel with toluene as working fluid and the length of the evaporator, adiabatic and condenser section 10, 23 and 17 cm was considered, respectively. The working fluid inventory was considered 0.1, 0.14, 0.18 and 0.24 of total volume of thermosyphon and in each case 54–235 W of heat input applied to the evaporator area also. In order to evaluate the transient behavior of the thermosyphon, in any amount of working fluid, 28 W of heat input was considered and temperature of the evaporator area were recorded at different...
Control over Fading Channels
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Alireza (Supervisor) ; Motahari, Abolfazl (Supervisor)
Abstract
As latency reduction is a key objective of upcoming mobile standards such as 5G, control applications over such channels have become of high interest in recent years. In this thesis, we will consider the problem of control over fading channels modeled by finite-state Markov chains. We will combine communication and control theory aspects of the problem and study stability of linear discrete-time plants which communicate with the controller over such fading channels. Two different scenarios are assumed for channel state information availability at encoder side, and the sufficient condition of almost sure asymptotic stabilizability is derived for each scenario. We will then examine the...
Transient behavior of fluid flow and heat transfer in vertical channels partially filled with porous medium: Effects of inertial term and viscous dissipation
, Article Energy Conversion and Management ; Volume 61 , September , 2012 , Pages 1-7 ; 01968904 (ISSN) ; Molaei Dehkordi, A ; Sharif University of Technology
Elsevier
2012
Abstract
In this article, transient hydrodynamic and heat-transfer behavior of Newtonian fluid flow in vertical parallel-plate channels partially filled with a porous medium has been investigated numerically. In this regard, the influences of macroscopic local inertial term and the viscous heating due to the viscous dissipation were taken into account in the momentum equations of porous region and the thermal energy equations, respectively. Moreover, Forchheimer-Brinkman extended Darcy model was used to model fluid flow in the porous region. In addition, an analytical solution was obtained in the case of negligible Brinkman and Forchheimer number values at the steady-state conditions. The predicted...
A transient model of vanadium redox flow battery
, Article Mechanics and Industry ; Volume 17, Issue 4 , 2016 ; 22577777 (ISSN) ; Elyasi, S ; Sharif University of Technology
EDP Sciences
2016
Abstract
It has been attempted to gain a new viewpoint in transient cell modeling of vanadium redox flow battery. This has been achieved by considering electrochemical relations along with conceptual electrical circuit of this kind of battery. The redox flow battery is one of the best rechargeable batteries because of its capability to average loads and output power sources. A model of transient behavior is presented in this paper. The transient features are considered as the most remarkable characteristics of the battery. The chemical reactions, fluid flow, and electrical circuit of the structure govern the dynamics. The transient behavior of the redox flow battery based on chemical reactions is...
Effect of working fluid inventory and heat input on transient and steady state behavior of a thermosyphon
, Article Journal of Thermal Analysis and Calorimetry ; 2020 ; Forootan, D ; Farajimoghaddam, F ; Sharif University of Technology
Springer Netherlands
2020
Abstract
The effect of working fluid inventory and heat input on the performance of thermosyphon is investigated in this paper. First, a thermosyphon with diameter of 16 mm made of steel with toluene as working fluid and the length of the evaporator, adiabatic and condenser section 10, 23 and 17 cm was considered, respectively. The working fluid inventory was considered 0.1, 0.14, 0.18 and 0.24 of total volume of thermosyphon and in each case 54–235 W of heat input applied to the evaporator area also. In order to evaluate the transient behavior of the thermosyphon, in any amount of working fluid, 28 W of heat input was considered and temperature of the evaporator area were recorded at different...
Analysis of evaporating liquid bridge in horizontal fractures
, Article Journal of Petroleum Science and Engineering ; Volume 202 , 2021 ; 09204105 (ISSN) ; Ghazanfari, M.H ; Masihi, M ; Sharif University of Technology
Elsevier B.V
2021
Abstract
The formation of liquid bridge is pertinent to many fields including seepage into underground fractured rocks as an environmental issue and capillary continuity between matrix blocks which controls oil recovery in fractured reservoirs. Evaporation from the surface of liquid bridge into the surrounding gas could affect the stability of liquid bridge and fracture capillary pressure, which is not well discussed in the available literatures. In this research, by the aid of analogy between the diffusive flux and electrostatic potential, a new model for predicting evaporation rate from a liquid bridge inside a horizontal fracture is presented. The proposed model is then coupled with Young-Laplace...
Dynamic behavior analysis of doubly-fed induction generator wind turbines - The influence of rotor and speed controller parameters
, Article International Journal of Electrical Power and Energy Systems ; Volume 32, Issue 5 , June , 2010 , Pages 464-477 ; 01420615 (ISSN) ; Parniani, M ; Sharif University of Technology
2010
Abstract
This paper analytically investigates the effects of system and controller parameters and operating conditions on the dynamic and transient behavior of wind turbines (WTs) with doubly-fed induction generators (DFIGs) under voltage dips and wind speed fluctuations. Also, it deals with the design considerations regarding rotor and speed controllers. The poorly damped electrical and mechanical modes of the system are identified, and the effects of system parameters, and speed/rotor controllers on these modes are investigated by modal and sensitivity analyses. The results of theoretical studies are verified by time domain simulations. It is found that the dynamic behavior of the DFIG-based WT...
Investigation of membrane fouling in cross flow microfiltration of non-alcoholic beer and modeling of tubular membrane flow
, Article Desalination ; Volume 251, Issue 1-3 , 2010 , Pages 20-28 ; 00119164 (ISSN) ; Soltanieh, M ; Yazdanshenas, M ; Sharif University of Technology
2010
Abstract
In the present work, numerical simulation of cross flow microfiltration of non-alcoholic beer in a tubular membrane has been studied theoretically and verified experimentally. Finite element method was used as a powerful tool for simulation. The feed stream, which flows mainly tangentially to the porous membrane surface, is modeled by the Navier-Stokes equations whereas the porous wall conditions are described by the Darcy equation that relates the pressure gradient within a flow stream to the flow rate through the permeable wall. A new model that considers transient behavior of the membrane due to fouling was used to estimate the permeate flux reduction. A pilot-scale cross flow membrane...
Transient forced convection with viscous dissipation to power-law fluids in thermal entrance region of circular ducts with constant wall heat flux
, Article Energy Conversion and Management ; Volume 50, Issue 4 , 2009 , Pages 1062-1068 ; 01968904 (ISSN) ; Mohammadi, A. A ; Sharif University of Technology
2009
Abstract
A numerical investigation was conducted on the transient behavior of a hydrodynamically, fully developed, laminar flow of power-law fluids in the thermally developing entrance region of circular ducts taking into account the effect of viscous dissipation but neglecting the effect of axial conduction. In this regard, the unsteady state thermal energy equation was solved by using a finite difference method, whereas the steady state thermal energy equation without wall heat flux was solved analytically as the initial condition of the former. The effects of the power-law index and wall heat flux on the local Nusselt number and thermal entrance length were investigated. Moreover, the local...
Dynamic behavior of electric field in the microrings in the presence of Kerr and two-photon absorption
, Article Proceedings of SPIE - The International Society for Optical Engineering, 7 April 2008 through 10 April 2008, Strasbourg ; Volume 6996 , 2008 ; 0277786X (ISSN) ; 9780819471949 (ISBN) ; Karvar, M ; Bahrampour, A ; Sharif University of Technology
2008
Abstract
This paper a simple semi-analytical model for calculation of the time evolution and spatial variation of the electric field in microring resonators in the presence of The Kerr effect and two-photon absorption (TPA) is presented. The theoretical analysis is based on the delayed feedback model, which is well known in microring theory. The model is applied to the Chalcogenide glass and AlGaAs microrings to study the Kerr and TPA effects on the spatial and temporal variation of electric field respectively across the microring. The effects of microring parameters and input signal shapes on the transient behavior are taken into consideration. It is shown that, the results are in good agreement...