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cylinders--shapes
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Transient analysis of falling cylinder in non-Newtonian fluids: further opportunity to employ the benefits of SPH method in fluid-structure problems
, Article Chemical Product and Process Modeling ; Volume 12, Issue 1 , 2017 ; 21946159 (ISSN) ; Ramazani Saadat Abadi, A ; Kamyabi, A ; Sharif University of Technology
Walter de Gruyter GmbH
2017
Abstract
Smoothed particle hydrodynamics (SPH) was applied to simulate the free falling of cylindrical bodies in three types of fluids including Newtonian, generalized-Newtonian and viscoelastic fluids. Renormalized derivation schemes were used because of their consistency in combination with the latest version of no slip boundary condition to improve the handling of moving fluid-structure interactions (FSIs). Verification of the method was performed through comparing the results of some benchmark examples for both single and two phase flows with the literature. The effects of some parameters such as the viscosity of the Newtonian fluid, the n index of the power-law fluid and the relaxation time of...
Theoretical and experimental studies of a magnetically actuated valveless micropump
, Article Journal of Micromechanics and Microengineering ; Volume 27, Issue 1 , 2017 ; 09601317 (ISSN) ; Shafii, M. B ; Moosavi, A ; Sharif University of Technology
Institute of Physics Publishing
2017
Abstract
This paper presents the prototype design, fabrication, and characterization of a magnetically actuated micropump. The pump body consists of three nozzle/diffuser elements and two pumping chambers connected to the ends of a flat-wall pumping cylinder. A cylindrical permanent magnet placed inside the pumping cylinder acts as a piston which reciprocates by using an external magnetic actuator driven by a motor. The magnetic piston is covered by a ferrofluid to provide self-sealing capability. A prototype composed of three bonded layers of polymethyl-methacrylate (PMMA) has been fabricated. Water has been successfully pumped at pressures of up to 750 Pa and flow rates of up to 700 μl min-1 while...
Optimization of the heat transfer coefficient and pressure drop of Taylor-Couette-Poiseuille flows between an inner rotating cylinder and an outer grooved stationary cylinder
, Article International Journal of Heat and Mass Transfer ; Volume 108 , 2017 , Pages 1449-1459 ; 00179310 (ISSN) ; Nakhchi, M. E ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
The aim of this study is to find optimum values of design parameters of annular flow with outer grooved cylinder and rotating inner cylinder in the presence of axial flow by using Response surface Method (RSM). This configuration is popular in cooling of electric generators and rotating machineries. Groove aspect ratio (0
Elastic-plastic behavior of sandwich cylindrical shell panels with a flexible core
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 231, Issue 2 , 2017 , Pages 223-241 ; 09544062 (ISSN) ; Fallah, F ; Naghdabadi, R ; Kargarnovin, M. H ; Sharif University of Technology
SAGE Publications Ltd
2017
Abstract
The linear static elastic-plastic behavior of sandwich cylindrical shell panels under a generally distributed loading with thick flexible core is studied. The core modeling is based on high-order theory of sandwich structures in which the in-plane stresses of the core are neglected. The faces are modeled based on Kirchhoff-Love shell theory. The materials of the faces and the core are assumed to be isotropic with linear work hardening behavior. The incremental Prandtl-Reuss plastic flow theory is used in this analysis. Using the principle of virtual displacements, the governing equations are derived and solved for any sort of boundary conditions based on elastic-plastic harmonic differential...
Heat transfer enhancement in annular flow with outer grooved cylinder and rotating inner cylinder: review and experiments
, Article Applied Thermal Engineering ; Volume 120 , 2017 , Pages 257-268 ; 13594311 (ISSN) ; Nakhchi, M. E ; Sharif University of Technology
Abstract
This experimental work is an attempt to identify the most significant parameters influencing heat transfer enhancement in annular flow with outer grooved cylinder and rotating inner cylinder. This type of flow known as Taylor-Couette flow has many industrial applications such as electrical power generators and rotating machineries. A comprehensive review of the previous works on flow regimes, heat transfer and pressure drop in grooved channels is provided. The experiments are conducted based on four different factors including Taylor number, 0
Decoupled stability equation for buckling analysis of FG and multilayered cylindrical shells based on the first-order shear deformation theory
, Article Composites Part B: Engineering ; Volume 154 , 2018 , Pages 225-241 ; 13598368 (ISSN) ; Taati, E ; Asghari, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Based on the first-order shear deformation and Donnell's shell theory with von Karman non-linearity, one decoupled stability equation for buckling analysis of functionally graded (FG) and multilayered cylindrical shells with transversely isotropic layers subjected to various cases of combined thermo-mechanical loadings is developed. To this end, the equilibrium equations are uncoupled in terms of the transverse deflection, the force function and a new potential function. Using the adjacent equilibrium method, one decoupled stability equation which is an eighth-order differential equation in terms of transverse deflection is obtained and conveniently solved to present analytical expressions...
Standard and boundary layer perturbation approaches to predict nonlinear axisymmetric behavior of cylindrical shells
, Article Composite Structures ; Volume 204 , 2018 , Pages 855-881 ; 02638223 (ISSN) ; Taati, E ; Asghari, M ; Reddy, J. N ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
The feasibility and performance of standard and boundary layer perturbation techniques in nonlinear analyses of cylindrical shells are investigated. To this end, the nonlinear axisymmetric behavior of short and long functionally graded (FG) cylindrical shells is considered. The nonlinear governing equations of shell theory with first-order approximation and the von Karman nonlinearity are decoupled. This uncoupling makes it possible to present an analytical solution. A new boundary layer perturbation solution is presented by reducing the governing equations to a normalized form of boundary-layer type. Also, the uncoupled governing equations are solved using standard one-, two-, and...
Experimental study of convective heat transfer in the entrance region of an annulus with an external grooved surface
, Article Experimental Thermal and Fluid Science ; Volume 98 , 2018 , Pages 557-562 ; 08941777 (ISSN) ; Nakhchi, M. E ; Sharif University of Technology
Elsevier Inc
2018
Abstract
The aim of this experimental work is to study the effect of grooved surfaces in the entrance region of annular flows on local heat transfer. The outer stationary cylinder is grooved and the inner rotating cylinder is smooth. This configuration is applicable in industrial applications such as rotating heat pipes for cooling of superconducting machines or motors rotor, electrical generators where heat generates in the grooves containing wires, transient heating of axial compressor rotor drams, combustion chamber in turbojets, air-cooled axial-flux permanent-magnet machines. The experimental tests were performed based on aspect ratio of the groove, effective Reynolds number and Taylor number....
Towards an understanding of marine fouling effects on VIV of circular cylinders: Aggregation effects
, Article Ocean Engineering ; Volume 147 , 2018 , Pages 227-242 ; 00298018 (ISSN) ; Zeinoddini, M ; Soltanpour, M ; Zandi, A. P ; Seif, M. S ; Sharif University of Technology
Abstract
The current study is aimed at getting a further insight into the changes the fouling brings to the Vortex Induced Vibration (VIV) of circular cylinders. Instead of regular patterns considered in previous studies, using the Poisson Cluster Process, an aggregated spatial distribution was considered for the artificial marine fouling. This is believed to better simulate the natural settlement of the marine biofouling. Different coverage ratios and fouling shapes plus regular and aggregated distributions were considered. The towing tank VIV tests were conducted on elastically mounted rigid cylinders. The Reynolds number ranged from around 7.8 × 103 to 4.9 × 104. On the whole, the maximum...
Experimental and analytical study of telescopic lead yielding damper
, Article Journal of Constructional Steel Research ; Volume 150 , 2018 , Pages 371-383 ; 0143974X (ISSN) ; Pournamazian Najafabadi, E ; Sharif University of Technology
Abstract
In this study, a novel type of passive energy dissipation device called a Telescopic Lead Yielding Damper (TLYD) is proposed and analyzed. This device comprises co-axial steel cylinders and lead rings, such that these rings act as shear locks between the steel cylinders. TLYDs dissipate energy through the plastic shear deformation of lead metal. The telescopic mechanism used in TLYDs allows these small-sized dampers to tolerate large axial displacements with low fatigue. For each telescopic level, a yield plateau is added to the hysteresis behavior of TLYD devices. Each yield plateau resists a different performance level, namely design-based and maximum credible earthquakes. Seven...
Wake interference of two identical oscillating cylinders in tandem: An experimental study
, Article Ocean Engineering ; Volume 166 , 2018 , Pages 311-323 ; 00298018 (ISSN) ; Khorasanchi, M ; Day, S ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
This study aims to assess the impact of the spacing between cylinders on their dynamic behaviour. Observations during this experiment have helped to identify the effect of spacing on excitation mechanism of each cylinder as well as establishing the relationship between cylinders response and the spacing between them. Arrays of cylindrical Structures in close proximity are common in variety of engineering structures, particularly in the offshore industry. If the cylinders are flexible, and are subject to excitation from fluid flow, then the dynamics is influenced by complex interactions between the cylinders, dependent on a variety of parameters. Two cylinders were flexibly mounted in tandem...
Free vibration analysis of functionally graded stiffened micro-cylinder based on the modified couple stress theory
, Article Scientia Iranica ; Volume 25, Issue 5B , 2018 , Pages 2598-2615 ; 10263098 (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
Sharif University of Technology
2018
Abstract
In this paper, free vibration of the micro-cylinder made by functionally graded material stiffened in circumferential direction was investigated based on modified couple stress and first-order shear deformation theories. Modified Couple Stress Theory (MCST) was used to catch size effects in micro scales. By using first-order shear deformation theory and Hamilton's principle, the general equations of motion and corresponding boundary conditions were derived. Free vibration of the structure was investigated by implementing simply-supported boundary condition as a common case. The effects of different parameters, such as dimensionless length scale parameter, distribution of FGM properties,...
Sloshing effects on supersonic flutter characteristics of a circular cylindrical shell partially filled with liquid
, Article International Journal for Numerical Methods in Engineering ; 2018 ; 00295981 (ISSN) ; Ovesy, H. R ; Dehghani Firouz Abadi, R ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
This paper aims to revisit the effect of sloshing on the flutter characteristics of a partially liquid-filled cylinder. A computational fluid-structure interaction model within the framework of the finite element method is developed to capture fluid-structure interactions arising from the sloshing of the internal fluid and the flexibility of its containing structure exposed to an external supersonic airflow. The internal liquid sloshing is represented by a more sophisticated model, referred to as the liquid sloshing model, and the shell structure is modeled by Sanders' shell theory. The aerodynamic pressure loading is approximated by the first-order piston theory. The initial geometric...
Effect of multiphase fluid and functionally graded density fluid on the stability of spinning partially-filled shells
, Article International Journal of Mechanical Sciences ; Volume 140 , 2018 , Pages 109-118 ; 00207403 (ISSN) ; Nikkhah Bahrami, M ; Dehghani Firouz Abadi, R ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
The effect of a multiphase fluid, including an arbitrary number of liquid phases, and a functionally graded density fluid on the stability of rotating partially-filled cylindrical shells is investigated. The first-order shear shell theory is used for modeling the structural dynamics of the shell and a 2D model is introduced based on the Navier–Stokes equations, for fluid motion. The multiphase and the functionally graded density fluids are arranged according to the mass density in a steady state condition due to centrifugal forces. Using the boundary conditions between liquid phases and the boundary conditions of the fluid on the cylinder wall, the coupled fluid-structure system model is...
Elastic collapse of thin long cylindrical shells under external pressure
, Article Thin-Walled Structures ; Volume 124 , 2018 , Pages 81-87 ; 02638231 (ISSN) ; Fallah, F ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
This paper investigates local elastic buckling of thin long cylindrical shells under external pressure. Based on Donnell's and Sanders’ theories of thin shells and von Karman nonlinearity assumptions, the potential energy is derived. The buckling load and curves of the static equilibrium path are obtained using the Ritz method. The results are validated with the existing ones in the literature. Furthermore, the case where the pressure is perpendicular to the deformed state is compared with a dead loading. It is demonstrated that the former yields a lower critical pressure in both shell theories. © 2017 Elsevier Ltd
DOA error estimation in 3D cylindrical dipole array geometries including the mutual coupling effect
, Article AEU - International Journal of Electronics and Communications ; Volume 84 , February , 2018 , Pages 321-330 ; 14348411 (ISSN) ; Sasan Nia, Z ; Farzaneh, F ; Sharif University of Technology
Elsevier GmbH
2018
Abstract
The direction of arrival (DOA) error in dipole 3D arrays is estimated through Monte-Carlo simulations using the standard MUSIC algorithm. Novel 3D geometries are implemented which demonstrate better precision given the same lateral area. The mutual coupling effect is included by changing the search vector in the MUSIC DOA algorithm for the novel 3D geometries. A simple straight forward method is used which does not need complex electromagnetic computations. Simulations show that the proposed method can successfully account for the mutual coupling effects in two dimensional direction finding (both azimuth and elevation angle) with novel 3D array geometries. Reduced DOA estimation error is...
An analytical investigation of a 2d-ppms hollow infinite cylinder under Thermo-Electro-Mechanical (TEM) loadings
, Article Journal of Theoretical and Applied Mechanics (Poland) ; Volume 56, Issue 1 , 2018 , Pages 107-122 ; 14292955 (ISSN) ; Firoozbakhsh, K ; Jabbari, M ; Selkghafari, A ; Sharif University of Technology
Polish Society of Theoretical and Allied Mechanics
2018
Abstract
The analytical solution of steady-state asymmetric thermo-electro-mechanical loads of a hollow thick infinite cylinder made of porous piezoelectric materials (2D-PPMs) based on two-dimensional equations of thermoelasticity is considered. The general form of thermal and mechanical boundary conditions is considered on the inside and outside surfaces. A direct method is used to solve the heat conduction equation and the non-homogenous system of partial differential Navier equations using the complex Fourier series and the power-exponential law functions method. The material properties are assumed to depend on the radial and circumferential variable and are expressed as power-exponential law...
Numerical and experimental study of a jet impinging with axial symmetry with a set of heat exchanger tubes
, Article Mechanics and Industry ; Volume 19, Issue 1 , 2018 ; 22577777 (ISSN) ; Alayi, R ; Kasaeian, A ; Kasaeian, F ; Ahmadi, M. H ; Sharif University of Technology
EDP Sciences
2018
Abstract
The main purpose of this research is to predict the flow field of impinging turbulent jet with cylinder in a 3-d state. Nowadays, shear stress has multiple uses in the industry. The study has been conducted in both compressible and incompressible states with output velocities between 100 and 150 m/s, in different eccentricities of jet with respect to the first cylinder, and in various nozzle outlet orifice distances from front edge of the first cylinder. Pressure distribution and shear stress on cylinder surfaces have been determined and efficiency of jet in cleaning the heat exchangers pipes has been analyzed. Also, an experimental investigation has been conducted in order to verify the...
Effects of after-body on the FIV of a right-angle triangular cylinder in comparison to circular, square, and diamond cross-sections
, Article Ships and Offshore Structures ; 2018 ; 17445302 (ISSN) ; Naeeni, T. O ; Zeinoddini, M ; Seif, M. S ; Dolatshahi Pirooz, M ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
This in-water experimental study deals with the effects of the after-body on the FIV response of round and sharp edge cylinders. Different circular, square, diamond, and right-angle isosceles triangular cross-sections are investigated. The triangular cylinder is examined in four different symmetrical and unsymmetrical configurations with respect to the incident flow. The current towing tank experiments form a basis for the feasibility study of the isosceles triangular cylinders for FIV energy converters. The results indicate that the cylinders with a flat side perpendicular to the flow have a galloping type of response. In contrast, the cylinders with a sharp vertex pointing the flow show a...
Flexural instability of viscoelastic spinning cylinders partially filled with liquid
, Article International Journal of Structural Stability and Dynamics ; Volume 9, Issue 1 , 2009 , Pages 45-60 ; 02194554 (ISSN) ; Haddadpour, H ; Sharif University of Technology
2009
Abstract
This paper deals with the determination of free vibration characteristics and instability conditions of flexible spinning cylinders partially filled with fluid. Using the linearized Navier-Stokes equations for the incompressible, inviscid flow, a 2D model is developed for fluid motion at each section of the cylinder. The forces exerted on the cylinder wall as a result of the fluid motion are calculated as functions of lateral acceleration of the cylinder axis in the Laplace domain. Applying the Hamilton principle, the governing equations of flexural motion of the cylinder are derived and then combined with the equations describing the fluid forces to obtain the coupled field equations of the...