Improving the performance of a numerical model to simulate the EHD interaction effect induced by dielectric barrier discharge

, Article International Journal of Heat and Fluid Flow ; Volume 67 , 2017 , Pages 79-94 ; 0142727X (ISSN) Omidi, J ; Mazaheri, K ; Sharif University of Technology

2017

Abstract

Over the past decade, there has been a growing interest in dielectric-barrier-discharge (DBD) plasma actuators. The lack of a general model to accurately simulate the related phenomena is one of the primary limitations in studying such type of actuators. One of the most frequently used models of this type was proposed by Suzen and Huang (S-H). Despite the numerous efforts made to improve this model, including a recent work of the authors, some deficiencies still exist. In this study, new modifications have been introduced to improve the performance and accuracy of the S-H phenomenological model. Here, a relation between the electrical-potential and charge-density equations has been made in...

Micro-plasma actuator mechanisms in interaction with fluid flow for wind energy applications: Physical parameters

, Article Physics of Fluids ; Volume 32, Issue 7 , 2020 Omidi, J ; Mazaheri, K ; Sharif University of Technology

American Institute of Physics Inc 2020

Abstract

Plasma actuator is a flow control device to improve the aerodynamic performance of wind turbine blades at low airspeeds. One of the most robust numerical models for simulation of plasma actuator interaction with the fluid flow is the electrostatic model. This model is improved recently and is extensively verified by the authors. Due to the high cost of performing experimental optimizations, the optimized geometrical dimensions and materials of a plasma actuator may be sought by this numerical model. The aim of the present study is the aerodynamic enhancement of a DU21 wind turbine blade airfoil in which the effect of geometric parameters and the dielectric material is examined separately....

Differential evolution algorithm for performance optimization of the micro plasma actuator as a microelectromechanical system

, Article Scientific Reports ; Volume 10, Issue 1 , 2020 Omidi, J ; Mazaheri, K ; Sharif University of Technology

Nature Research 2020

Abstract

Dielectric Discharge Barrier (DBD) plasma actuators are considered as one of the best active electro-hydrodynamic control devices, and are considered by many contemporary researchers. Here a simple electrostatic model, which is improved by authors, and uses the Maxwell’s and the Navier–Stokes equations, is proposed for massive optimization computations. This model is used to find the optimum solution for application of a dielectric discharge barrier on a curved surface of a DU25 wind turbine blade airfoil, in a range of 5–18 kV applied voltages, and 0.5 to 13 kHz frequency range. Design variables are selected as the dielectric thickness and material, and thickness and length of the...

Aerodynamic enhancement and improving the performance of a six-megawatt dowec wind turbine by micro-plasma actuator

, Article International Journal of Mechanical Sciences ; Volume 195 , 2021 ; 00207403 (ISSN) Omidi, J ; Mazaheri, K ; Sharif University of Technology

Elsevier Ltd 2021

Abstract

We have investigated the usage of a Dielectric Barrier Discharge (DBD) plasma actuator to improve the aerodynamic performance of an offshore 6 MW wind turbine. By controlling the aerodynamic load combined with pitch angles of 2, 5, and 10 degrees, we studied the plasma actuator effect on the overall harvested power. Actuators were installed in single and tandem configurations in different chord-wise locations to find the optimum design. The improved phenomenological model developed by authors was used in an analysis to simulate the interaction of the electrostatic field, the ionized particles and the fluid flow. A design software was used to estimate the harvested power of the real 3D blade....

Micro-plasma actuator mechanisms in interaction with fluid flow for wind energy applications: operational parameters

, Article Engineering with Computers ; 2022 ; 01770667 (ISSN) Omidi, J ; Mazaheri, K ; Sharif University of Technology

Springer Science and Business Media Deutschland GmbH 2022

Abstract

Plasma actuator is a flow control device which may be used to improve the performance of wind turbine blades at low airspeeds. One of the most robust numerical models to simulate the interaction of the plasma actuator with the fluid flow is the electrostatic model. This model is improved by the authors. Due to the high cost of performing experimental optimization, the optimization of plasma actuators may be investigated by this numerical model. To optimize the aerodynamic performance of a Delft University (DU) wind turbine airfoil in a full stall condition, we used the operational parameters (voltage, frequency and the waveform) applied to the plasma actuator as the main design variables. We...

Micro-plasma actuator mechanisms in interaction with fluid flow for wind energy applications: operational parameters

, Article Engineering with Computers ; Volume 39, Issue 3 , 2023 , Pages 2187-2208 ; 01770667 (ISSN) Omidi, J ; Mazaheri, K ; Sharif University of Technology

Springer Science and Business Media Deutschland GmbH 2023

Abstract

Plasma actuator is a flow control device which may be used to improve the performance of wind turbine blades at low airspeeds. One of the most robust numerical models to simulate the interaction of the plasma actuator with the fluid flow is the electrostatic model. This model is improved by the authors. Due to the high cost of performing experimental optimization, the optimization of plasma actuators may be investigated by this numerical model. To optimize the aerodynamic performance of a Delft University (DU) wind turbine airfoil in a full stall condition, we used the operational parameters (voltage, frequency and the waveform) applied to the plasma actuator as the main design variables. We...

An Efficient Routing Method to Reduce Aging Effect in Reconfigurable Devices

, M.Sc. Thesis Sharif University of Technology Omidi, Behzad (Author) ; Asadi, Hossein (Supervisor)

Abstract

Signifcant downscaling of CMOS technology to provide high performance along with low power consumption has been accompanied by reliability degradations such as increased noise sensitivity and reliability concern due to aging phenomena (transient and permanent failuers). In this regard, with huge number of configuration bits, Field-Programmable Gate Arrays (FPGAs) are more susceptible to aging since aging not only degrades the performance, but also it may additionally result in corrupting the configuration cells and thus causing permanent circuit malfunctioning. While several works have investigated the aging effects in Look-Up Tables (LUTs), the routing fabric of these devices is seldom...

Numerical Simulation of DBD Plasma Actuator and Optimization for Separation Control

, M.Sc. Thesis Sharif University of Technology Omidi, Javad (Author) ; Mazaheri, Karim (Supervisor)

Abstract

Here we have used CFD to simulate the flow field around a DBD plasma active controller for flow control. Enhanced Electrostatic model is applied to model the plasma actuator, by solution of two elliptic equations to find electric field and charge density in whole flow field. So, it provided the body force by neglecting the magnetic forces in Lorentz equation. The body force is added to the momentum equation as a source term. A commercial software FLUENT is used for this simulation. To validate the algorithm, flow over a flat plate using DBD actuator is solved and results are compared with experimental and numerical results. Flow control around a cylinder with Reynolds number of 18,000 is...

The Study of Certain Evidence of Ooguri, Strominger, Vafa Conjecture for 4D Extremal Black Holes of Type and Heterotic Superstring Theories

, M.Sc. Thesis Sharif University of Technology Omidi, Farzad (Author) ; Arfaei, Hessamaddin (Supervisor)

Abstract

In 2004 Ooguri, Strominger, and Vafa could write the partition function of 4D N=2 extremal black holes in type IIA superstring theory as the square of the absolute value of the partition function of type A closed topological string theory, which had already been introduced by Edward Witten in 1990. In this study, T and S dualities were applied to the original conjecture of Ooguri, Strominger, and Vafa. By using T duality, we have verified that the conjecture holds for 4D N=2 extremal black holes of type IIB superstring theory to the one loop order in string coupling. In other words, one can write the partition function of these kinds of black holes as the square of the absolute value of...

An Energy-saving Control Strategy for Multi-zone Demand Controlled VAV Systems with Optimal Control of air Handling Unit

, M.Sc. Thesis Sharif University of Technology Omidi Jeze, Hossein (Author) ; Moradi, Hamed (Supervisor)

Abstract

Nowadays, due to the increasing use of Air Handling Units (AHU) in buildings, reducing energy consumption and improving the performance of these devices is one of the most important goals of researchers in the field of heating, ventilation and air conditioning (HVAC) technology. The purpose of this project is to design an optimal control system in different parts of the Air Handling Unit in order to provide standard ambient and breathing conditions for the people. Therefore, the mathematical model of the multi-zone space and the equipment of the Air Handling Unit are studied as separate subsystems based on the laws of thermodynamics and heat transfer. The obtained equations provide a...

Multi-omic Single-cell Data Integration Using Deep Neural Networks

, M.Sc. Thesis Sharif University of Technology Omidi, Alireza (Author) ; Sharifi Zarchi, Ali (Supervisor)

Abstract

The advent and advance of single-cell technologies have enabled us to measure the cell function and identity by using different assays and viewing it by different technologies. Nowadays, we are able to measure multiple feature vectors from same- single cells from multiple abstract molecular levels (genome, transcriptome, proteome, ...) simultaneously. Hence, the analysts can view the cell from different yet correlated angles and study their behaviours. Such progress in joint single-cell assessments plus the development and spread of more common single-cell assays - that measure one feature vector per cell - caused the growing need for computational tools to integrate these datasets in order...

Direct Torque Control of Permanent Magnet Synchronous Machine Using Nonlinear Flux Observer

, M.Sc. Thesis Sharif University of Technology Yaghoubi, Mokhtar (Author) ; Tahami, Farzad (Supervisor)

Abstract

Direct Torque Control (DTC) is one of the vector methods to control Permanent Magnet Synchronous Machines (PMSM). In order to achieve an appropriate control in vector control methods, an accurate estimation of flux is indispensable. Flux estimation should be fulfilled in a wide speed range without considerable dependence on motor parameters. Prevalent flux estimation methods are based on integration of stator voltage which is not feasible in low speed, or performed based on assumption of decoupled equations on d and q axis which is not precise for applications with fast dynamic. Different flux estimation methods are investigated in this thesis with the aim of improving the flux estimation in...

Design and Implementation of a Soft Switched Bidirectional Charger for Vehicle-to-grid (V2G) Applications

, M.Sc. Thesis Sharif University of Technology Akbari, Rasoul (Author) ; Tahami, farzad (Supervisor)

Abstract

Due to the growing oil price and environmental considerations, tendency to use local and environmentally friendly energy sources has increased.Bidirectional transmission can be one of the key features of the smart grid,so the use of car battery connected to the grid as local energy sources makes sense. This can provide network stability, especially during peak load times. Vehicles connected to grid (V2G) is an electric vehicle or a plug-in hybrid electric vehicles can delivered the electricity to the grid. These systems require either two separate power electronic converters can be used for transmission in either directions or a two-way transfer charger. The aim of this project is to design...

Design and Implementation of a Soft-Switched Multiport Bidirectional Converter

, M.Sc. Thesis Sharif University of Technology Mirzahosseini, Ramin (Author) ; Tahami, Farzad (Supervisor)

Abstract

In recent years, multiport bidirectional converters have been a center of attention in renewable energy systems. This research focuses on three-port bidirectional converters. First, series resonant bidirectional converter is precisely analyzed. This analysis includes sinusoidal, exact state space and small signal analysis through phasor concept. This converter can work in higher switching frequencies and higher power ratings in comparison with common DAB bidirectional converter due to its inductor impedance cancellation. To increase power rating a three-phase version is proposed which has reduced output filter capacitance. Then, three-port bidirectional resonant converter is proposed and...

Direct Speed Control of Permenant Magnet Synchronous Machine

, M.Sc. Thesis Sharif University of Technology Dana, Shekoofe (Author) ; Tahami, Farzad (Supervisor)

Abstract

Accurate and fast position controlling is an important issue in today’s industrial needs. Drives used for position control require fast dynamics on speed control. Cascade linear controllers have sluggish response due to bandwidth limitations on speed and current loop. These structures limit the dynamics above all in high power applications where the switching frequency is low. In this thesis, deadbeat direct speed control is proposed, which overcomes limitations by cascade loops resulting in high-speed control dynamics. This approach uses a model of the plant to generate the control signals. According to measured speed and currents, the controller specifies the best voltage vector in order...

Design and Implementation of High Efficient Charger for Plug-in Hybrid Vehicles with Power Factor Correction Feature

, M.Sc. Thesis Sharif University of Technology Yazdani, Farzad (Author) ; Tahami, Farzad (Supervisor)

Abstract

In this project the novel zero-voltage-switching topology for power factor correction bridgeless boost rectifier is proposed. By employing an improved ZVS pulse-width-modulation (PWM) switch cell, ZVS of all the main switches is achieved without additional current or voltage stress of main switches. Also for the auxiliary switch the zero-current-switching is provided. In all modes of opretion of this converter, the power path is provided by maximum two semiconductor so the conduction loss of converter is low as in conventional converter. With this features the efficiency of proposed converter is very high

Hybrid Modeling and Control of DC-DC Series Resonant Converters for Applications of Wide Range Power

, Ph.D. Dissertation Sharif University of Technology Afshang, Hamid (Author) ; Tahami, Farzad (Supervisor)

Abstract

The subject of control and stabilization of dc-dc series resonant converter (SRC) is still a challenge in power electronics. The conventional controller design and stability analysis for this converter are based on the model which is derived using the sinusoidal approximation and averaging followed by linearization about an operating point. This model is not applicable to a SRC that operates below resonance especially in discontinuous conduction mode (DCM) because the sinusoidal approximation is no longer acceptable. However, a SRC may be purposely designed to operate in DCM. Therefore, it is essential to investigate the stability analysis and controller design using a more sophisticated...

Control of Quasi-Resonant Converters Using Model Predictive Control

, M.Sc. Thesis Sharif University of Technology Ebad, Mehdi (Author) ; Tahami, Farzad (Supervisor)

Abstract

DC-DC switching convertors are power electronic circuits that have various applications nowadays. Quasi-resonant convertors are a kind of these convertors that are of great interest due to their simple structure and soft switching. The goal of controlling these convertors is to achieve constant output voltage while varying the input voltage and the load by choosing a proper switching frequency. Classic controllers show drawbacks in the case of high input voltage and load tolerance, and this nonlinear behavior of the systems results in some practical challenges. In this thesis, nonlinear predictive controller for quasi-resonant Buck convertors is designed. Having designed the linear...

Control of Quasi-Resonant Converters Using Multiple Model Fusion

, M.Sc. Thesis Sharif University of Technology Nejadpak, Aarsh (Author) ; Tahami, Farzad (Supervisor)

Abstract

Nowadays, power electronics converters with pulse width modulation (PWM) are widely used in different power circuits. Operation of semi-conductive switches during on and off conditions causes switching dissipation and consequently decreases the efficiency of the PWMs. Recently, by increasing the required power for power electronics applications, quasi-resonant converters attract attentions. Quasi-resonant converters, by adding resonant circuits to the PWM converters causes the soft switching operation (switching with zero current or voltage) and decreases the energy loss. In conventional control methods of these converters, the nonlinear average circuit model is linearized around the...

Design of Electrical Drive for Steer-by-Wire Systems

, M.Sc. Thesis Sharif University of Technology Afshang, Hamid (Author) ; Tahami, Farzad (Supervisor)

Abstract

Hydraulic steering technology has been used in vehicles for decades. Recently, a trend has been seen towards the use of electronic steer-by-wire systems that provide greater design flexibility by customizing the connection between the steering wheel and the steering mechanism. Steer-by-Wire systems (SbW) offer the potential to enhance steering functionality by enabling features such as automatic lane keeping, park assist, variable steer ratio, and advanced vehicle dynamics control. The lack of a steering intermediate shaft significantly enhances vehicle architectural flexibility. The task of a SbW system is two-fold: turning the steered wheels by tracking the hand wheel (HW) rotation and...