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Numerical Simulation of Turbulent Flow in Annulus with Rotation of an Inner Cylinder in High Angular Speed
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor)
Abstract
In this thesis velocity and temperature fields of concentric cylinders with rotation of inner wall have been investigated numerically. Air enters the gap between cylinders and attains fully developed in both velocity and temperature fields after certain lengths. Adiabatic and constant heat flux boundary conditions have been applied and Nusselt number was calculated. In order to analyze the variations of velocity and temperature fields, different angular velocities at constant axial Reynolds number and different axial velocities at constant angular velocity have been investigated. The turbulent stresses were approximated with k ?? ...
Investigation of the Influence of Geometry and External Field on Fluid Flow Through Carbon Nanotubes by Molecular Dynamics Simulation
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
Water transportation through carbon nanotubes is key for designing nanodevices. The directed transport of water molecules through a rotating charged carbon nanotube (CNT) is investigated by molecular dynamics simulations. It is found that the net flux of continuous unidirectional water flow depended sensitively on the charge distribution, charge density and rotation of the CNT. we find that for a constant charge density, the water flux increases with the increase of the charge difference. Besides, we find that the water flux shows a nonlinear dependence on the angular velocity of the rotation. The rotation of the CNT with low angular velocities, can not generate a continuous water flux. The...
Vibration Analysis of Drill String under Inclined Drilling Including Stick-Slip Phenomenon
, M.Sc. Thesis Sharif University of Technology ; Ahmadiyan, Mohammad Taghi (Supervisor)
Abstract
Vibration is one of the most important factors in design, operation and lifetime of drill string. Evaluation of vibration in the drill string like other rotating machines is very important and according to the length of drill string, whirling is one of the issues discussed. The aim of this thesis is non-linear analysis of the oblique long drill string. By considering the effects of passing drill mud around drill as well as properties of the drilling mud and stick - slip effect in creating whirling. Therefore, the equations related to kinetic and potential energy of a rotating drill string by taking longitudinal and transverse vibrations are written and by using the Lagrange method, equations...
Identification and Control of Robot Manipulators using Cell Phone Sensors
, M.Sc. Thesis Sharif University of Technology ; Namvar, Mehrzad (Supervisor)
Abstract
The goal of controlling robot manipulators is to perform the mission intended for its end effector. Model-based control is a solution that can achieve the control goal with high speed and accuracy in the presence or absence of environmental obstacles by using the knowledge of the robot model. In this thesis, the Armtin 5 robot model parameters were identified in two steps. In the first step, the gravity and friction parameters and in the second step, the dynamic parameters were estimated. In the estimation of gravity and friction parameters, the non-linear behavior of friction causes the estimated parameters to be accompanied by a large amount of error. Estimation of the parameters was...
Coupled Vibration Analysis of Directional Drilling String Considering Effect of Drilling Mud
, M.Sc. Thesis Sharif University of Technology ; Ahmadian, Mohammad Taghi (Supervisor) ; Farrahi, Gholamhossein (Co-Advisor)
Abstract
Vibration is one of the most important factors in design, operation and lifetime of drill strings. There for, investigation of vibrations in drill string, like every other rotary machine, is very important. The main goal of this research is developing a nonlinear model for a drill string system dynamics in an inclined well. Effects of drilling mud flow rate, weight on bit, angular velocity along with viscous damping, on the stability and vibration of a drill string are studied. Dynamic equation of the model is developed considering axial displacement and lateral bending geometric nonlinear coupling. The effect of drilling mud flow is modeled using Paidoussis formulations. Equation of motion...
Modelling and Analysis of the Effect of Angular Velocity and Acceleration on Brain Strain Field in Traumatic Brain Injury
, M.Sc. Thesis Sharif University of Technology ; Ahmadiyan, Mohammad Tagh (Supervisor) ; Zohoor, Hassan (Supervisor)
Abstract
Traumatic brain injury (TBI) has long been known as one of the most anonymous reasons for death around the world. A presentation of a model of what happens in the process has been under study for many years; and yet it remains a question due to physiological, geometrical and computational complications. Although the modeling facilities for soft tissue modeling have improved, the precise CT-imaging of human head has revealed novel details of brain, skull and the interface (the meninges), a comprehensive FEM model of which is still being studied. This study aims to present an optimized model of human head after a comprehensive study of the previous models; which includes the brain, skull, and...
Analysis of in-plane vibration and critical speeds of the functionally graded rotating disks
, Article International Journal of Applied Mechanics ; Volume 11, Issue 2 , 2019 ; 17588251 (ISSN) ; Jahangiri, M ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2019
Abstract
In this paper, the in-plane free vibration analysis of the functionally graded rotating disks with variable thickness is presented utilizing DQM. It is assumed that the rotational velocity of the disk is constant and the thickness and material properties including modulus of elasticity and density vary along the radial coordinate. The distribution of the forward and backward traveling waves versus the angular velocity is demonstrated for several modal circles and nodal diameters with respect to the fixed and rotating coordinate systems. After presenting the accuracy and convergence of the numerical method, the derived formulation and the solution method are validated by comparing the results...
Wave propagation analysis of a spinning porous graphene nanoplatelet-reinforced nanoshell
, Article Waves in Random and Complex Media ; Volume 31, Issue 6 , 2021 , Pages 1655-1681 ; 17455030 (ISSN) ; Mohammadi, K ; Barouti, M. M ; Habibi, M ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
In this article, wave propagation behavior of a size-dependent spinning graphene nanoplatelet-reinforced composite (GNPRC) cylindrical nanoshell with porosity is presented. The effects of small scale are analyzed based on nonlocal strain gradient theory (NSGT), this accurate theory employs exact length scale parameter and nonlocal constant. The governing equations of GNPRC cylindrical nanoshell coupled with piezoelectric actuator (PIAC) are evolved by minimum potential energy principle and solved by the analytical method. For the first time in the current study, wave propagation-porosity behavior of a GNPRC cylindrical nanoshell coupled with PIAC is examined based on NSGT. The results show...
An analytical investigation of elastic-plastic deformation of FGM hollow rotors under a high centrifugal effect
, Article International Journal of Mechanical and Materials Engineering ; Volume 14, Issue 1 , 2019 ; 18230334 (ISSN) ; Aghajani, S ; Hemati, M ; Sharif University of Technology
Springer
2019
Abstract
Functionally graded material shafts are the main part of many modern rotary machines such as turbines and electric motors. The purpose of this study is to present an analytical solution of the elastic-plastic deformation of functionally graded material hollow rotor under a high centrifugal effect and finally determine the maximum allowed angular velocity of a hollow functionally graded material rotating shaft. Introducing non-dimensional parameters, the equilibrium equation has been analytically solved. The results for variable material properties are compared with the homogeneous rotor and the case in which Young’s modulus is the only variable while density and yield stress are considered...
Small-scale oriented elasticity modeling of functionally graded rotating micro-disks with varying angular velocity in the context of the strain gradient theory
, Article Acta Mechanica ; Volume 232, Issue 6 , 2021 , Pages 2395-2416 ; 00015970 (ISSN) ; Asghari, M ; Kargarzadeh, A ; Badiee, M ; Sharif University of Technology
Springer
2021
Abstract
During the varying angular speed timespans of the start or shutdown of rotating machinery, the machinery components may be subjected to intense mechanical loadings which should be taken into account by its fabricator in the designing processes. In the microscale rotating systems, where the angular velocity is typically very high, the importance of this issue is much higher. In this paper, a comprehensive strain-gradient elasticity formulation is presented for functionally graded rotating micro-disks under the effects of varying angular velocity. The gradation of the constituent material along the radial direction can be a helpful option to mitigate the stresses in rotating micro-disks under...
The size-dependent electromechanical instability of double-sided and paddle-type actuators in centrifugal and Casimir force fields
, Article Scientia Iranica ; Volume 24, Issue 3 , 2017 , Pages 1077-1090 ; 10263098 (ISSN) ; Farahani, M ; Kanani, A ; Rach, R ; Keivani, M ; Abadyan, M ; Sharif University of Technology
Sharif University of Technology
2017
Abstract
The present research is devoted to theoretical study of the pull-in performance of double-sided and paddle-type NEMS actuators fabricated from cylindrical nanowire operating in the Casimir regime and in the presence of the centrifugal force. D'Alembert's principle was used to transform the angular velocity into an equivalent static, centrifugal force. Using the couple stress theory, the constitutive equations of the actuators were derived. The equivalent boundary condition technique was applied to obtain the governing equation of the paddle-type actuator. Three distinct approaches, the Duan-Adomian Method (DAM), Finite Difference Method (FDM), and Lumped Parameter Model (LPM), were applied...
Effects of linear acceleration in a harmonically excited proof mass MEMS rate gyroscope
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 232, Issue 19 , 2018 , Pages 3551-3563 ; 09544062 (ISSN) ; Salarieh, H ; Sharif University of Technology
SAGE Publications Ltd
2018
Abstract
MEMS rate gyroscopes are prone to different errors because of environmental conditions and manufacturing errors. These errors can result to mismatch between the fabricated gyros and the designed ones. Different environmental conditions and disturbances can change the parameters and specifications of a gyro, and its sensitivity may deteriorate, since the parameters are different from the optimal ones. External linear acceleration is one of the main environmental disturbances that may change the behavior of an MEMS rate gyro that its effect on the accuracy of an MEMS proof mass gyroscope is found here. This is done by finding the equations of motion of gyroscope in presence of acceleration and...
Magnetic field effect on free vibration of smart rotary functionally graded nano/microplates: a comparative study on modified couple stress theory and nonlocal elasticity theory
, Article Journal of Intelligent Material Systems and Structures ; Volume 29, Issue 11 , 2018 , Pages 2492-2507 ; 1045389X (ISSN) ; Saeidi Googarchin, H ; Mahinzare, M ; Eftekhari, S. A ; Sharif University of Technology
SAGE Publications Ltd
2018
Abstract
In this article, free vibration behavior of a rotating nano/microcircular plate constructed from functionally graded magneto-elastic material is simulated with the first-order shear deformation theory. For the sake of comparison, the nonlocal elasticity theory and the modified couple stress theory are employed to implement the small size effect in the natural frequencies behavior of the nano/microcircular plate. The governing equations of motion for functionally graded magneto-elastic material nano/microcircular plates are derived based on Hamilton’s principle; comparing the obtained results with those in the literature, they are in a good agreement. Finally, the governing equations are...
Influence of system parameters on buckling and frequency analysis of a spinning cantilever cylindrical 3D shell coupled with piezoelectric actuator
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 234, Issue 2 , 2020 , Pages 512-529 ; Safarpour, H ; Habibi, M ; Sharif University of Technology
SAGE Publications Ltd
2020
Abstract
In this research, buckling and vibrational characteristics of a spinning cylindrical moderately thick shell covered with piezoelectric actuator carrying spring-mass systems are performed. This structure rotates about axial direction and the formulations include the Coriolis and centrifugal effects. In addition, various cases of thermal (uniform, linear, and nonlinear) distributions are studied. The modeled cylindrical moderately thick shell covered with piezoelectric actuator, its equations of motion, and boundary conditions are derived by the Hamilton's principle and based on a moderately cylindrical thick shell theory. For the first time in the present study, attached mass-spring systems...
Influence of spring-mass systems on frequency behavior and critical voltage of a high-speed rotating cantilever cylindrical three-dimensional shell coupled with piezoelectric actuator
, Article JVC/Journal of Vibration and Control ; Volume 25, Issue 9 , 2019 , Pages 1543-1557 ; 10775463 (ISSN) ; Pourghader, J ; Habibi, M ; Sharif University of Technology
SAGE Publications Inc
2019
Abstract
In this article, vibrational behavior and critical voltage of a spinning cylindrical thick shell covered with piezoelectric actuator (PIAC) carrying spring-mass systems are investigated. It should be noted that, the installed sensors on the proposed systems are considered as a tip mass. This structure rotates about axial direction and the formulations include the Coriolis and centrifugal effects. In addition, various cases of thermal (uniform, linear, and nonlinear) distributions are studied. The modeled cylindrical thick shell covered with PIAC, its equations of motion, and boundary conditions are derived by the principle of minimum total potential energy and based on a new...
Rotation induced by uniform and non-uniform magnetic fields in a conducting fluid carrying an electric current
, Article RSC Advances ; Volume 6, Issue 113 , 2016 , Pages 112641-112645 ; 20462069 (ISSN) ; Nasiri, M ; Amjadi, A ; Nejati, A ; Sobhani, S.O ; Habibi, M ; Sharif University of Technology
Royal Society of Chemistry
2016
Abstract
We study the dynamics of a conducting fluid carrying (i) a uniform current in the presence of a non-uniform magnetic field or (ii) carrying a non-uniform current in the presence of a uniform magnetic field, using particle image velocimetry (PIV). Our results show that the average angular velocity of the induced rotation has a power-law dependence on the electric current passing through the fluid with an exponent ≈2/3, in excellent agreement with our simulation results, for the same system. To explain the experimental observations we explore all possibilities for inducing rotation in a fluid carrying an electric current. Our theoretical discussion indicates two scenarios wherein applying...
Design and simulation of an integrated centrifugal microfluidic device for CTCs separation and cell lysis
, Article Micromachines ; Volume 11, Issue 7 , July , 2020 ; Shamloo, A ; Akbari, J ; Tebon, P ; Dokmeci, M. R ; Ahadian, S ; Sharif University of Technology
MDPI AG
2020
Abstract
Separation of circulating tumor cells (CTCs) from blood samples and subsequent DNA extraction from these cells play a crucial role in cancer research and drug discovery. Microfluidics is a versatile technology that has been applied to create niche solutions to biomedical applications, such as cell separation and mixing, droplet generation, bioprinting, and organs on a chip. Centrifugal microfluidic biochips created on compact disks show great potential in processing biological samples for point of care diagnostics. This study investigates the design and numerical simulation of an integrated microfluidic device, including a cell separation unit for isolating CTCs from a blood sample and a...
Hardware implementation of an ADRC controller on a gimbal mechanism
, Article IEEE Transactions on Control Systems Technology ; Volume 26, Issue 6 , 2018 , Pages 2268-2275 ; 10636536 (ISSN) ; Nobakhti, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Active disturbance rejection control (ADRC) is applied to a one-axis gimbal mechanism. The dynamic model of the system is derived and validated from mathematical modeling and practical experiments. Disturbances acting on the complete model of the gimbal mechanism are introduced via base lateral acceleration and angular motion. The ADRC is designed by utilizing an extended state observer for observing and suppressing the effects of external disturbances and internal parameter uncertainties. A PID controller is used to form a basis of comparison for set-point tracking and disturbance rejection performance. The effects of identification errors and observer bandwidth are experimentally...
Rotation rate estimation in parametrically excited micro gyroscopes
, Article Mechatronics ; Volume 31 , October , 2015 , Pages 264-275 ; 09574158 (ISSN) ; Salarieh, H ; Alasty, A ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
This paper reports the estimation of angular velocity in micro gyroscopes with parametric excitation. The identification procedure is done into two consecutive steps: In the first step, the physical parameters of the gyroscope (stiffness, damping, and actuator parameters) are estimated via continuous time Extended and Unscented Kalman filter. In the second step, a separate Kalman filter is dedicated to estimate the time varying rotation rate, using the output of the first step. Using numerical simulations, it is found that by introducing an artificial noise in the observer equations and tuning its variance, arbitrary temporal variation of angular velocity can be well tracked by the proposed...
Closed-form solution for free vibration of variable-thickness cylindrical shells rotating with a constant angular velocity
, Article Thin-Walled Structures ; Volume 166 , 2021 ; 02638231 (ISSN) ; Fallah, F ; Ahmadian, M. T ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Based on the classical Donnell's and Love's shell theories, free vibration behavior of variable-thickness thin cylindrical shells rotating with a constant angular velocity is analyzed. The equations of motion and corresponding boundary conditions of rotating homogenous cylindrical shells with axisymmetric variation of thickness are derived using Hamilton's principle. This formulation includes effects of initial hoop tension due to the centrifugal force as well as Coriolis and centrifugal accelerations. Considering the variation of stiffness coefficients in axial direction, the classical Love's theory results in a coupled system of two second-order and one fourth-order partial differential...