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Numerical Simulation of DBD Plasma Actuator and Optimization for Separation Control
, M.Sc. Thesis Sharif University of Technology ; 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...
An Efficient Routing Method to Reduce Aging Effect in Reconfigurable Devices
, M.Sc. Thesis Sharif University of Technology ; 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...
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) ; 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 ; 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 ; 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) ; 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) ; 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) ; 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...
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 ; 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...
Multi-omic Single-cell Data Integration Using Deep Neural Networks
, M.Sc. Thesis Sharif University of Technology ; 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...
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 ; 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...
Effect of Surface Treatment on Bioactivity of Ti-6Al-4V Alloy
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
In this research Ti-6Al-4V samples were surface treated with acid, alkali and sandblasting treatment. Alkali treatment parameter was the NaOH concentration. The results of roughness measurement demonstrate that increase in NaOH Concentration results in rougher surface. Sandblasting produces rough surfaces in the scale of 1 to 10 micrometers. Acid treatment reduces initial roughness and the resultant roughness is in the under micrometer scale. After surface treatment, samples were soaked in simulated body fluid for invitro assessment. Results of this analysis indicate that sample with sandblasting+chemical treatment has the best invitro bioactivity. Chemical+sandblasting treated sample shows...
Effect of axially graded constraining layer on the free vibration properties of three layered sandwich beams with magnetorheological fluid core
, Article Composite Structures ; Volume 255 , 2021 ; 02638223 (ISSN) ; Asgari, M ; Haddadpour, H ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The free linear vibration of an adaptive sandwich beam consisting of a frequency and field-dependent magnetorheological fluid core and an axially functionally graded constraining layer is investigated. The Euler-Bernoulli and Timoshenko beam theories are utilized for defining the longitudinal and lateral deformation of the sandwich beam. The Rayleigh-Ritz method is used to derive the frequency-dependent eigenvalue problem through the kinetic and strain energy expressions of the sandwich beam. In order to deal with the frequency dependency of the core, the approached complex eigenmodes method is implemented. The validity of the formulation and solution method is confirmed through comparison...
On the dynamic behavior interpretation of sandwich beams with axially graded face sheets and magnetorheological core using modal strain energy approach
, Article Acta Mechanica ; Volume 234, Issue 7 , 2023 , Pages 2985-3008 ; 00015970 (ISSN) ; Asgari, M ; Haddadpour, H ; Sharif University of Technology
Springer
2023
Abstract
The free vibration properties of a sandwich beam with axially graded facings and a magnetorheological fluid core are studied. The facings and core are modeled using the Euler–Bernoulli and Timoshenko beam theories, respectively. The problem is discretized using the Rayleigh–Ritz method. The approached complex eigenmodes method is implemented for solving the resulting nonlinear eigenvalue problem numerically. The effects of multiple parameters, i.e., facings' material distribution, functionally graded material's gradient index, boundary conditions, constraining and core layers’ thickness, and magnetic field effect on the free vibration properties, are thoroughly studied. The obtained results...
Dynamic Response Analysis of a Three-Layered Circular Plate with Magnetorheological Fluid Core Under Low Velocity Impact Loading
, M.Sc. Thesis Sharif University of Technology ; Haddadpour, Hassan (Supervisor)
Abstract
Various public transportation types, e.g., Trains, Buses, and Airplanes, are susceptible to damages made by the impacts of the external objects, which are typically classified as low to medium velocity impacts. This problem reveals the significance of investigating the effects of impact on thin-walled structures, which are the main components of these vehicles' bodies. Owing to the controllable rheological properties of the Magnetorheological fluid with respect to the magnetic field, it can be utilized to control the structure exposed to impact adaptively and minimize the damages. Due to this purpose, sandwich structures such as sandwich beams and plates, thanks to their extended response...
A fuzzy random minimum cost network flow programming problem [electronic resource]
, Article Journal of Industrial and Systems Engineering (JISE)-Iranian Institute of Industrial Engineering ; Article 3, Volume 6, Issue 1, Spring 2012, Page 34-47 ; Eshghi, Kourosh ; Sharif University of Technology
Abstract
In this paper, a fuzzy random minimum cost flow problem is presented. In this problem, cost parameters and decision variables are fuzzy random variables and fuzzy numbers respectively. The object of the problem is to find optimal flows of a capacitated network. Then, two algorithms are developed to solve the problem based on Er-expected value of fuzzy random variables and chance-constrained programming. Furthermore, the results of two algorithms will be compared. An illustrative example is also provided to clarify the concept
Special classes of mathematical programming models with fuzzy random variables [electronic resource]
, Article Journal of Intelligent and Fuzzy Systems, Published In: IOS Press ; Volume 19, Number 2, 2008 ; Nematian, Javad ; Sharif University of Technology
Abstract
In this paper, we will discuss two special classes of mathematical programming models with fuzzy random variables. In the first model, a linear programming problem with fuzzy decision variables and fuzzy random coefficients is introduced. Then an algorithm is developed to solve the model based on fuzzy optimization method and fuzzy ranking method. In the second model, a fuzzy random quadratic spanning tree problem is presented. Then the proposed problem is formulated and solved by using the scalar expected value of fuzzy random variables. Furthermore, illustrative numerical examples are also given to clarify the methods discussed in this paper
A special class of fuzzy integer programming model with all different constraints [electronic resource]
, Article Scientia Iranica ; Vol. 16, No. 1, pp. 1-10, 2009 ; Nematian, Javad ; Sharif University Of Technology
Abstract
In this paper, a fuzzy approach is applied to special classes of integer programming problems with all diierent constraints. In the rst model, a fuzzy integer programming model is developed to represent the all-diierent constraints in mathematical programming. In order to solve the proposed model, a new branching scheme for the Branch and Bound algorithm is also presented. In the second model, a special class of large-scale multi-objective fuzzy integer programming problems with all-diierent constraints is introduced. A solution method for the proposed model is also developed by using the decomposition technique, weighting method and Branch and Bound algorithm. An illustrative numerical...
Fuzzy random minimum cost network problem [electronic resource]
, Article Journal of Industrial and Systems Engineering ; Vol. 6, No. 1, pp 34-47, 2012 ; Eshghi, Kourosh ; Sharif University of Technology
Abstract
In this paper, a fuzzy random minimum cost flow problem is presented. In this problem, cost parameters and decision variables are fuzzy random variables and fuzzy numbers respectively. The object of the problem is to find optimal flows of a capacitated network. Then, two algorithms are developed to solve the problem based on Er-expected value of fuzzy random variables and chance-constrained programming. Furthermore, the results of two algorithms will be compared. An illustrative example is also provided to clarify the concept
Study on the Behavior of Ship’s Bottom Structure under Grounding Phenomenon
, M.Sc. Thesis Sharif University of Technology ; Abbaspour, Majid (Supervisor) ; Omidvar, Mohammad Taghi (Co-Advisor)
Abstract
Whenever and wherever there is shipping, there exist risks of marine accidents. Subsequently, such accidents at sea may result in potential economic loss,environmental pollution and fatalities. In fact, ship grounding accident is a type of marine accident that involves the impact of a ship on seabed or waterway side. It may result in the damage of the submerged part of the ship’s hull and in particularly the bottom structure; potentially leading to water ingress, which may at the end compromise the ship's structural integrity, stability, and finally safety. An overall view on groundings categorizes the accidents in two major groups: Soft Grounding and Hard Grounding. A soft grounding does...