Loading...
Search for: flow-control
0.005 seconds
Total 83 records

    Sulfide stress corrosion cracking and hydrogen induced cracking of A216-WCC wellhead flow control valve body

    , Article Case Studies in Engineering Failure Analysis ; Volume 1, Issue 3 , 2013 , Pages 223-234 ; 22132902 (ISSN) Ziaei, S. M. R ; Kokabi, A. H ; Nasr Esfehani, M ; Sharif University of Technology
    2013
    Abstract
    The wellhead flow control valve bodies which are the focal point of this failure case study were installed in some of the upstream facilities of Khangiran's sour gas wells. These valve bodies have been operating satisfactorily for 3 years in wet H2S environment before some pits and cracks were detected in all of them during the periodical technical inspections. One failed valve body was investigated by chemical and microstructural analytical techniques to find out the failure cause and provide preventive measures. The valve body alloy was A216-WCC cast carbon steel. During investigation many cracks were observed on the inner surface of the valve body grown from the surface pits. The results... 

    Analysis of separation control authority of DBD plasma actuator using hot-film sensor array

    , Article Journal of Applied Fluid Mechanics ; Volume 14, Issue 5 , 2021 , Pages 1421-1435 ; 17353572 (ISSN) Daliri, A ; Maghrebi, M. J ; Soltani, M. R ; Sharif University of Technology
    Isfahan University of Technology  2021
    Abstract
    The boundary-layer control authority of a DBD plasma actuator using surface mounted hot-film sensors is evaluated. Wind tunnel experiments on a wind-turbine blade section were established at a Reynolds number of 0.27 x 106. Aerodynamic performance of the wind-turbine blade section for both plasma-ON and plasma-OFF modes are evaluated using measurements made by both surface pressure and wake survey behind the model. Two distinct boundary-layer states are recognized. A state which occurs at the onset and in proximity of the deep stall, which is affected by the low-frequency instabilities of the separated flow. In this case, the steady actuation of plasma imparts local momentum on the nearby... 

    Failure analysis: Sulfide stress corrosion cracking and hydrogen-induced cracking of A216-WCC wellhead flow control valve body

    , Article Journal of Failure Analysis and Prevention ; Vol. 14, issue. 3 , 2014 , p. 376-383 Ziaei, S. M. R ; Kokabi A.H ; Mostowfi J ; Sharif University of Technology
    Abstract
    The wellhead flow control valve bodies which are the focal point of this failure case study were installed in some of the upstream facilities of Khangiran's sour gas wells. These valve bodies have been operating satisfactorily for 3 years in wet H2S environment before some pits and cracks were detected in all of them during the periodical technical inspections. One failed valve body was investigated by chemical and microstructural analytical techniques to find out the failure cause and provide preventive measures. The valve body alloy was A216-WCC cast carbon steel. During investigation many cracks were observed on the inner surface of the valve body grown from the surface pits. The results... 

    Optimization of bump and blowing to control the flow through a transonic compressor blade cascade

    , Article Shock Waves ; 2017 , Pages 1-13 ; 09381287 (ISSN) Mazaheri, K ; Khatibirad, S ; Sharif University of Technology
    Springer New York LLC  2017
    Abstract
    Shock control bump (SCB) and blowing are two flow control methods, used here to improve the aerodynamic performance of transonic compressors. Both methods are applied to a NASA rotor 67 blade section and are optimized to minimize the total pressure loss. A continuous adjoint algorithm is used for multi-point optimization of a SCB to improve the aerodynamic performance of the rotor blade section, for a range of operational conditions around its design point. A multi-point and two single-point optimizations are performed in the design and off-design conditions. It is shown that the single-point optimized shapes have the best performance for their respective operating conditions, but the... 

    Cavitation passive control on immersed bodies

    , Article Journal of Marine Science and Application ; Volume 16, Issue 1 , 2017 , Pages 33-41 ; 16719433 (ISSN) Javadi, K ; Dorostkar, M. M ; Katal, A ; Sharif University of Technology
    Harbin Engineering University  2017
    Abstract
    This paper introduces a new idea of controlling cavitation around a hydrofoil through a passive cavitation controller called artificial cavitation bubble generator (ACG). Cyclic processes, namely, growth and implosion of bubbles around an immersed body, are the main reasons for the destruction and erosion of the said body. This paper aims to create a condition in which the cavitation bubbles reach a steady-state situation and prevent the occurrence of the cyclic processes. For this purpose, the ACG is placed on the surface of an immersed body, in particular, the suction surface of a 2D hydrofoil. A simulation was performed with an implicit finite volume scheme based on a SIMPLE algorithm... 

    Optimization of bump and blowing to control the flow through a transonic compressor blade cascade

    , Article Shock Waves ; Volume 28, Issue 2 , 2018 , Pages 285-297 ; 09381287 (ISSN) Mazaheri, K ; Khatibirad, S ; Sharif University of Technology
    Springer New York LLC  2018
    Abstract
    Shock control bump (SCB) and blowing are two flow control methods, used here to improve the aerodynamic performance of transonic compressors. Both methods are applied to a NASA rotor 67 blade section and are optimized to minimize the total pressure loss. A continuous adjoint algorithm is used for multi-point optimization of a SCB to improve the aerodynamic performance of the rotor blade section, for a range of operational conditions around its design point. A multi-point and two single-point optimizations are performed in the design and off-design conditions. It is shown that the single-point optimized shapes have the best performance for their respective operating conditions, but the... 

    Flow control in a cavity with tiny-obstacles on the walls for mixing enhancement part I: Flow physics

    , Article Journal of Applied Fluid Mechanics ; Volume 12, Issue 1 , 2019 , Pages 11-23 ; 17353572 (ISSN) Maneshian, B ; Javadi, K ; Taeibi Rahni, M ; Sharif University of Technology
    Isfahan University of Technology  2019
    Abstract
    This paper seeks to make a study on flow control in two-dimensional square cavities having obstacles on their walls. The goal of using these passive controllers is to enhance mixing in an enclosed space. Lattice Boltzmann method is used to simulate the problem. Results are presented for various Reynolds numbers, 400≤Re≤4000 and different arrangements of tiny-obstacles with different heights. To give a perspective on the physics of this problem, time evolution of the flow is studied at Re= 1000. Then, the flow structure is studied for different Reynolds numbers. Findings show that the interaction of the main vortex with the tiny-obstacles inserted on the wall cavity changes the flow pattern... 

    Flow control in a cavity with tiny-obstacles on the walls for mixing enhancement part I: Flow physics

    , Article Journal of Applied Fluid Mechanics ; Volume 12, Issue 1 , 2019 , Pages 11-23 ; 17353572 (ISSN) Maneshian, B ; Javadi, K ; Taeibi Rahni, M ; Sharif University of Technology
    Isfahan University of Technology  2019
    Abstract
    This paper seeks to make a study on flow control in two-dimensional square cavities having obstacles on their walls. The goal of using these passive controllers is to enhance mixing in an enclosed space. Lattice Boltzmann method is used to simulate the problem. Results are presented for various Reynolds numbers, 400≤Re≤4000 and different arrangements of tiny-obstacles with different heights. To give a perspective on the physics of this problem, time evolution of the flow is studied at Re= 1000. Then, the flow structure is studied for different Reynolds numbers. Findings show that the interaction of the main vortex with the tiny-obstacles inserted on the wall cavity changes the flow pattern... 

    Optimal unified power flow controller application to enhance total transfer capability

    , Article IET Generation, Transmission and Distribution ; Volume 9, Issue 4 , 2015 , Pages 358-368 ; 17518687 (ISSN) Rajabi Ghahnavieh, A ; Fotuhi Firuzabad, M ; Othman, M ; Sharif University of Technology
    Institution of Engineering and Technology  2015
    Abstract
    For a power transfer path, total transfer capability (TTC) represents maximum power that can be transferred over the transmission system. Unified power flow controller (UPFC) is a device that can be used to increase in TTC. This study presents a new method for optimal UPFC application to minimise power loss while enhancing TTC. Based on UPFC injection model, the solution region of UPFC parameters is first found using the proposed method to maximise TTC. It then searches the solution region to find optimal UPFC control mode and setting to minimise system power loss. The proposed method is applied to the IEEE-Reliability Test System and the UPFC application impact are evaluated. Comparative... 

    A surrogate optimization-based mechanism for resource allocation and routing in networks with strategic agents

    , Article IEEE Transactions on Automatic Control ; Volume 64, Issue 2 , 2019 , Pages 464-479 ; 00189286 (ISSN) Farhadi, F ; Golestani, S. J ; Teneketzis, D ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    We consider a mechanism design problem for the joint flow control and multipath routing in informationally decentralized networks with strategic agents. Based on a surrogate optimization approach, we propose an incentive mechanism that strongly implements the social-welfare maximizing outcome in Nash equilibria. This mechanism possesses several other desirable properties, including individual rationality and budget balance at equilibrium. More importantly, in contrast to the existing literature on the network resource allocation mechanisms, the proposed mechanism is dynamically stable, meaning that the Nash equilibrium (NE) of the game induced by the mechanism can be learned by the agents in... 

    Experimental Investigation of Leading Edge Flow Control for a Rigid Flapping Wing Using Plasma Actuator

    , M.Sc. Thesis Sharif University of Technology Taheri, Benyamin (Author) ; Ebrahimi, Abbas (Supervisor)
    Abstract
    Using flapping motions, birds produce aerodynamic forces required to fly. Flapping wing aerodynamics is one of the most complicated problems in unsteady aerodynamic field. Experimental study on the structure, the way of production and growth and the feasibility of controlling the leading edge vortex are the main goals of this research in order to improve the aerodynamic performance of flapping wings. Since leading edge vortex structure appears in both upstroke and downstroke of a complete storke in flapping motion, controlling the structure in one of the half-storkes can provide the possibility of having a better aerodynamic performance. In this research, the wing is designed and... 

    Experimental Investigation of Aerodynamic Performance Enhancement by Trailing Edge Active Flow Control Using Plasma Actuator

    , M.Sc. Thesis Sharif University of Technology Mohaghegh Kojidi, Mohammad Javad (Author) ; Ebrahimi, Abbas (Supervisor)
    Abstract
    Flow control means changing the optimal flow behavior of the fluid in accordance with the desired targets, such as decreasing drag force, increasing the lift force or lift to drag ration, as well as manipulating the separation of the flow from the surface. So far, little research has been done on increasing the airflow performance through the active control of the trailing edge flow. Gurney flap is a great tool, and its experimental results show a significant increase lift force in the airfoil. In this study, it is possible experimentally to use plasma actuators to create microtap and garney flap artificial for enhancing the aerodynamic performance of airfoil by controlling the flow field at... 

    Design and Making of Piezoelectric-based Micro-airpump for Flow Control Application

    , M.Sc. Thesis Sharif University of Technology Valizadeh, Ali (Author) ; Ebrahimi, Abbas (Supervisor)
    Abstract
    The importance of creating a fluid flow with accurate and controllable flow in many industries is undeniable. There are several ways to create this type of flow, and a variety of pumps can be used to create such a flow. The presence of noise, limitations in reducing the flow rate (sometimes in some pumps the flow rate can not be reduced to a minimum), depreciation costs and many other limitations, reduce the attractiveness of using conventional pumps in some applications. The subject of this project is the design and construction of piezoelectric based micro-pumps to solve the above problems. In many applications, the need for fluid flow with very low flow and high quality and accuracy is... 

    Quasi-radial wall jets as a new concept in boundary layer flow control

    , Article Journal of Turbulence ; Volume 19, Issue 1 , 2018 , Pages 25-48 ; 14685248 (ISSN) Javadi, K ; Hajipour, M ; Sharif University of Technology
    Taylor and Francis Ltd  2018
    Abstract
    This work aims to introduce a novel concept of wall jets wherein the flow is radially injected into a medium through a sector of a cylinder, called quasi-radial (QR) wall jets. The results revealed that fluid dynamics of the QR wall jet flow differs from that of conventional wall jets. Indeed, lateral and normal propagations of a conventional three-dimensional wall jet are via shear stresses. While, lateral propagation of a QR wall jet is due to mean lateral component of the velocity field. Moreover, discharged Arrays of conventional three-dimensional wall jets in quiescent air lead to formation of a combined wall jet at large distant from the nozzles, while QR wall jet immediately spread in... 

    Power improvement of NREL 5-MW wind turbine using multi-DBD plasma actuators

    , Article Energy Conversion and Management ; Volume 146 , 2017 , Pages 96-106 ; 01968904 (ISSN) Ebrahimi, A ; Movahhedi, M ; Sharif University of Technology
    Elsevier Ltd  2017
    Abstract
    The present study numerically investigates the feasibility of using multiple dielectric barrier discharge (multi-DBD) plasma actuators as a novel approach for active flow control over a large horizontal axis wind turbine rotor. The National Renewable Energy Laboratory 5 MW offshore wind turbine is used as the baseline case. This turbine uses pitch control system to adjust the generated power above its rated wind speeds, but at lower speeds, this system remains inactive. In this paper, the operational condition speed is considered lower than the rated wind speed. The mathematical electro-static model is implemented to simulate the effects of plasma actuator on the external flow and the... 

    Effect of interline power flow controller (IPFC) on interconnected power systems adequacy

    , Article 2008 IEEE 2nd International Power and Energy Conference, PECon 2008, Johor Baharu, 1 December 2008 through 3 December 2008 ; 2008 , Pages 1358-1363 ; 9781424424054 (ISBN) Aminifar, F ; Fotuhi Firuzabad, M ; Nasiri, R ; Khodaei, A ; Sharif University of Technology
    2008
    Abstract
    This paper probes the impact of utilizing an IPFC on the reliability indices of interconnected power systems. First, a concise presentation of IPFC and its structure are provided and the reliability model of two unequally-rated parallel transmission lines equipped with IPFC is then extracted. The assumed IPFC is composed from two parallel converting bridges associated with each line. Afterwards, based-on equivalent assisting unit approach, different commonly-used adequacy indices including the loss of load expectation (LOLE), loss of energy expectation (LOEE) and system minutes (SM) are calculated. A set of numerical analyses are conducted to illustrate the sensitivity of these indices with... 

    Active flow control of a wing section in stall flutter by dielectric barrier discharge plasma actuators

    , Article Physics of Fluids ; Volume 34, Issue 7 , 2022 ; 10706631 (ISSN) Hajipour, M ; Ebrahimi, A ; Amandolese, X ; Sharif University of Technology
    American Institute of Physics Inc  2022
    Abstract
    This paper investigates the potential of using an active flow control technique to modify stall flutter oscillations of a NACA (National Advisory Committee for Aeronautics) 0015 wing section. Wind tunnel experiments have been performed with a test-rig that provides the elastic degree of freedom in pitch. Measurements of the clean airfoil are taken at preset angles of θ 0 = 6 ° - 12 °, and for Reynolds numbers of R e c = 6.2 × 10 4 - 1.25 × 10 5, which reveal the dependency of the stall flutter oscillations to Rec and θ0. Then, flow control experiments are carried out at θ 0 = 10 ° and R e c = 1.04 × 10 5. Two dielectric barrier discharge plasma actuators have been employed simultaneously to... 

    UPFC for enhancing power system reliability

    , Article IEEE Transactions on Power Delivery ; Volume 25, Issue 4 , 2010 , Pages 2881-2890 ; 08858977 (ISSN) Rajabi Ghahnavieh, A ; Fotuhi Firuzabad, M ; Shahidehpour, M ; Feuillet, R ; Sharif University of Technology
    2010
    Abstract
    This paper discusses various aspects of unified power flow controller (UPFC) control modes and settings and evaluates their impacts on the power system reliability. UPFC is the most versatile flexible ac transmission system device ever applied to improve the power system operation and delivery. It can control various power system parameters, such as bus voltages and line flows. The impact of UPFC control modes and settings on the power system reliability has not been addressed sufficiently yet. A power injection model is used to represent UPFC and a comprehensive method is proposed to select the optimal UPFC control mode and settings. The proposed method applies the results of a contingency... 

    Central Difference Finite Volume Lattice Boltzmann Method for Simulation of Incompressible Electro-Magneto-Hydrodanamic Flows

    , M.Sc. Thesis Sharif University of Technology Taheri, Sina (Author) ; Hejranfar, Kazem (Supervisor)
    Abstract
    In the present study, the simulation of incompressible Electro-Magneto-hydrodynamic flows is performed using a finite volume lattice Boltzmann method (FVLBM). The Boltzmann transport equation is solved using a cell-centered finite volume method on structured meshes. A central difference scheme is used to discretize the spatial derivatives and the fourth-order numerical dissipation term is added to stabilize the solution. To discretize the temporal derivative, the fourth-order Runge-Kutta time stepping scheme is applied. The standard collision-streaming lattice Boltzmann method has been used to simulate EMHD flows in the literature, however, it has several deficiencies such as the... 

    Aerodynamic Control of Flow Around a Rigid Wing in Flapping Motion Using Geometry Modification Methods

    , M.Sc. Thesis Sharif University of Technology Mohammadi, Mohammad Hossein (Author) ; Ebrahimi, Abbas (Supervisor) ; Farahani, Mohammad (Supervisor)
    Abstract
    The physics of the flow around the wing in the oscillatory motion of the wing has various patterns, including the leading edge vortex, the tip vortex and trailing edge vortex escape. The interaction of these vortices forms a complex flow structure around the wing, which will have a direct effect on the aerodynamic performance of the wing. Therefore, controlling these structures can be considered as a way to improve the performance of the flapping wing. One of the passive flow control techniques that has recently been taken into consideration is a leading-edge protuberance method. Another type of passive flow control is geometric correction, using corrugation method. According to studies, two...