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    Analysis and Simulation Study of Energy Harvesting from Vortex shedding-induced Vibrations Using the Piezoelectric Materials

    , M.Sc. Thesis Sharif University of Technology Daraei, Aghil (Author) ; Tabeshpour, Mohammad Reza (Supervisor)
    Nowadays, energy harvesting from the sea is developing for a variety of applications, including small-scale technologies for the production of small amounts of energy, including the use of low-speed currents to power ocean floor sensors. Ocean floor sensors are currently working with batteries. The cost of replacing or recharging these batteries is high, and the technology of these conventional batteries does not keep up with the rapid development of these sensors. Using new energy harvesting technologies has made the ocean current harvesting system as an adequate replacement for the batteries. According to operating principles, energy harvester can be broadly classified into three general... 

    Harvesting of Aquatic Clean Energy from Vortex Induced Vibration Using Two Degree Of Freedom Cylindrical Oscillator and Piezoelectric

    , M.Sc. Thesis Sharif University of Technology Hassani Fakhrabadi, Pouria (Author) ; Raie, Mohammad (Supervisor)
    Vortex-induced vibration is a known phenomenon in fluids flow that is being studied in different fields of engineering and usually, we want to reduce the harmful effects of this phenomenon on the subjected structures. Also, it is possible to use this phenomenon for harvesting clean energy from fluids flow. Energy harvesting from vortex-induced vibrations is based on the maximizing of flow instead of its reduction, and the utilization of these vibrations instead of their suppression. Vortex induced vibrations occur in any ranges of Reynolds numbers. Only in three transient regions cause a reduction in vortex-induced vibrations; therefore, even in streams with a velocity less than 0.2 m/s, it... 

    Numerical Investigation of Nitrogen Condensation in a Two-phase Vortex Tube

    , M.Sc. Thesis Sharif University of Technology Mirjalili, Mohamad Reza (Author) ; Ghorbanian, Kaveh (Supervisor)
    The Ranque-Hilsch vortex tube (RHVT) has no moving parts through which a high-pressure fluid gains on rotational velocity by passing radially through the inlet nozzles and then enters the vortex chamber. Subsequently, the high-pressure fluid becomes divided into two relatively distinctive hot and cold axial flows. Today, while RHVT is of great industrial interest due to its simplicity in manufacturing and operation; however, the mechanism of energy dissociation, which is dominated by the complex coupled interaction of the viscous thermo-fluid characteristics and geometrical properties, is not fully understood and no clear theory has been proposed to explain the energy dissociation so far.... 

    Rotational regimes of freely suspended liquid crystal films under electric current in presence of an external electric field

    , Article Microfluidics and Nanofluidics ; Volume 13, Issue 1 , 2012 , Pages 83-89 ; 16134982 (ISSN) Shirsavar, R ; Amjadi, A ; Ejtehadi, M. R ; Mozaffari, M. R ; Feiz, M. S ; Sharif University of Technology
    The electrohydrodynamic (EHD) vortices produced by an electric current in freely suspended liquid crystal (LC) films of N-(4-methoxybenzylidene)-4- butylaniline (MBBA), convert to a pure rotation in the presence of external electric field (E ext) perpendicular to the current direction. Here, the direction and strength of the rotation are precisely under control by our self-made device called "liquid-film motor". In this paper, we present experimental observations of the EHD fluid flow when external electric field varies from zero to a value in which pure rotation on the liquid crystal (LC) film is observed. We also show experimentally that the presence of external electric field causes a... 

    Canard flow improvement in a split canard configuration

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 229, Issue 6 , 2015 , Pages 1076-1087 ; 09544100 (ISSN) Davari, A. R ; Askari, F ; Soltani, M. R ; Sharif University of Technology
    Extensive low-speed wind-tunnel tests are performed to study the flow field structure over a dual-surface canard, known as split canard, in comparison to the conventional configurations. Surface pressure for both steady deflections and unsteady oscillations of the canard are measured and compared for both canard-alone and split-canard cases. The split canard shows a superior advantage at high angles of attack, where a delay in the vortex breakdown phenomena on the canard surface is observed. For the split-canard configuration, the downwash of the front canard reduces the effective angle of attack at the inboard section of the rear element which postpones formation of the leading-edge vortex.... 

    Effect of entrance position on particle dispersion in the vortex engine

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 12 November 2010 through 18 November 2010 ; Volume 7, Issue PARTS A AND B , 2010 , Pages 1103-1110 ; 9780791844441 (ISBN) Dehghani, S. R ; Saidi, M. H ; Mozafari, A. A ; Ghafourian, A ; Sharif University of Technology
    Particle dispersion in the vortex flow has been one of the most interesting subjects in recent years. Bidirectional vortex flow field is an industrial sample of the rotating flow which is used to obtain advantages of better mixing and combustion. In this work penetration and dispersion quality of the particles which are entering from various positions on the vortex engine walls have been numerically predicted. Head side, end side, and sidewall are considered as the entering positions. The particle has been assumed to be a rigid sphere. Initial velocity, diameter, and density of entering the particles are assumed to be known. If the particle length scale is considered not to be comparable... 

    Dynamics of magnetic nano-flake vortices in Newtonian fluids

    , Article Journal of Magnetism and Magnetic Materials ; Volume 419 , 2016 , Pages 547-552 ; 03048853 (ISSN) Bazazzadeh, N ; Mohseni, S. M ; Khavasi, A ; Zibaii, M. I ; Movahed, S. M. S ; Jafari, G. R ; Sharif University of Technology
    We study the rotational motion of nano-flake ferromagnetic disks suspended in a Newtonian fluid, as a potential material owing the vortex-like magnetic configuration. Using analytical expressions for hydrodynamic, magnetic and Brownian torques, the stochastic angular momentum equation is determined in the dilute limit conditions under applied magnetic field. Results are compared against experimental ones and excellent agreement is observed. We also estimate the uncertainty in the orientation of the disks due to the Brownian torque when an external magnetic field aligns them. Interestingly, this uncertainty is roughly proportional to the ratio of thermal energy of fluid to the magnetic energy... 

    Geometric parameters and response surface methodology on cooling performance of vortex tubes

    , Article International Journal of Sustainable Energy ; 2016 , Pages 1-15 ; 14786451 (ISSN) Nouri borujerdi, A ; Bovand, M ; Rashidi, S ; Dincer, K ; Sharif University of Technology
    Taylor and Francis Ltd 
    This research has investigated the effect of certain geometric parameters on cooling performance of three vortex tubes. The influencing parameters include three length/diameter ratios L/D = 10, 25, 40, three nozzle cases and each case with number n = 2, 4, 6 nozzles, three cold orifice/diameter ratios β = 0.389, 0.5, 0.611 and three inlet pressures Pi = 2, 2.5 and 3 bar. The experiments are conducted based on three factors, two-level and central composite face-centred design with full factorial. The results are analysed according to the principle of response surface methodology. The goodness of fit of the regression model is inspected using the analysis of variance and F-ratio test. The... 

    Towards an understanding of the marine fouling effects on VIV of circular cylinders: Response of cylinders with regular pyramidal roughness

    , Article Applied Ocean Research ; Volume 59 , 2016 , Pages 378-394 ; 01411187 (ISSN) Zeinoddini, M ; Bakhtiari, A ; Ehteshami, M ; Seif, M. S ; Sharif University of Technology
    Elsevier Ltd  2016
    Underwater surface of man-made structures is quickly covered by unwanted aquatic organisms. They change the flow regime around the structure. Despite the important contributions of previous studies on the vortex induced vibration (VIV) of bluff bodies, the flow induced vibration of non-stationary cylinders covered by marine fouling appears not to have received due attentions in the literature. The current paper reports on an attempt for better understanding the marine fouling effects on the VIV of circular cylinders. A structured review of the literature related to the fluid structure interactions in marine fouled cylinders is first presented. Results of an experimental study on the VIV of... 

    Separation control using quasi-radial wall jets

    , Article Aerospace Science and Technology ; Volume 68 , 2017 , Pages 240-251 ; 12709638 (ISSN) Javadi, K ; Hajipour, M ; Sharif University of Technology
    Elsevier Masson SAS  2017
    In this paper, flow separation control over a NACA 4415 wing section using arrays of discrete quasi-radial wall jets is numerically investigated. This novel flow control method is studied under conditions which the wing section angle of attack is α=18 degrees and Reynolds number based on chord length is Rec=550000. Contours of mean streamwise velocity indicated that quasi-radial wall jets cover wing surface rapidly. Therefore, arranging them in a spanwise row can be an effective way in adding momentum to the near wall fluid particles. According to the results, if blowing parameters of the jets be chosen correctly, arrays of quasi-radial wall jets would lead to considerable decrease in wake... 

    LPG mass separation by vortex tube cascade and its economics

    , Article Applied Thermal Engineering ; Volume 148 , 2019 , Pages 1139-1147 ; 13594311 (ISSN) Majidi, D ; Alighardashi, H ; Farhadi, F ; Sharif University of Technology
    Elsevier Ltd  2019
    In the present experimental study, the effect of operating parameters such as inlet and outlet pressure as well as inlet temperature on the mass separation capability of vortex tubes (VTs) for a gas mixture is investigated. Specifically, concentrating heavier components of a gas mixture in the hot outlet stream is considered. Proposing a semi-empirical index from the experimental study, the simulation of different arrangements of VTs, and the effect of recycling a portion of the hot outlet stream on its mass separation performance are investigated. Moreover, the proposed separation method by VTs is economically compared with commonly used methods by distillation columns and two-phase... 

    Analytical and numerical biaxial bending analysis of deepwater riser due to vortex-induced vibration

    , Article Journal of Marine Science and Technology (Japan) ; 2021 ; 09484280 (ISSN) Tabeshpour, M. R ; Komachi, Y ; Sharif University of Technology
    Springer Japan  2021
    Previous studies of analysis and prediction of marine risers responses usually focus on vortex-induced vibration (VIV) of cross-flow (CF) direction rather than in-line (IL). Recent studies show that responses of IL direction tend to dominate in some cases. Responses of long riser due to biaxial bending of IL and CF VIV are investigated. Closed-form formulas are derived for estimating maximum normal stress due to the biaxial moment of CF/IL VIV and relations for estimating biaxial stress using CF values are presented. Analytical results are compared with numerical results of the time domain model and a good correlation is observed. It is shown that for tension and bending-controlled modes of... 

    The Study of Wind Aerodynamics Effects on Degrading the Dry Cooling Tower Performance; Using Experimental and CFD Tools

    , M.Sc. Thesis Sharif University of Technology Bagheri, Amir Hossein (Author) ; Darbandi, Massoud (Supervisor)
    A power plant cooling tower is like a tower, which needs to be studied very carefully from the aerodynamics point of view. Both the aerodynamics forces on the plume and intake stram are affected by the local winds and the performance of cooling tower decreases. There is a symmetric turbulent flow through the cooling tower if there is no. Wind blowing creates different vorticies, which appear in the lower section of the tower. Their periodic and wuick movments causes deficiency in towers performance and efficiency. Additionally there is wind effect on the plane of cooling tower and this causes a chocked plume which is named Wind Cover. The objective of this study is to decrease the adverse... 

    Influence of Tail on the Wing Pressure Distribution of a Model at Different Conditions

    , M.Sc. Thesis Sharif University of Technology Bahman Jahromi, Iman (Author) ; Soltani, Mohammad Reza (Supervisor) ; Ghorbanian, Kaveh (Supervisor)
    Control surfaces are used in combat aircrafts to control the pitching moment and to help the aircraft perform high angle of attack manoeuvres. For delta wing configuration, the flow characteristics around the horizontal tail depend on the wing and tail flow field and their interactions. The flow over delta wing is mainly characterised by strong vortices. These vortices move downstream and affect the tail flow field making the problem more complicated. The goal of this research is to study the effect of tail up wash on the horizontal wing-body- tail configurations in subsonic flow. For this purpose a series of wind tunnel tests were conducted on a model containing a moveable horizontal tail... 

    Mass Transfer Modeling while Formation of Liquid Jet to another Liquid

    , M.Sc. Thesis Sharif University of Technology Safarirad, Mohammad Reza (Author) ; Bastani, Darioush (Supervisor)
    Liquid-liquid extraction is one of most important processes in chemical industries. So determination of operating condition effects is very critical. In this thesis we modeled concentration profile in the jet via mathematical equations and compare with experimental data. The major problem in concentration profile and solving equations is lack of knowledge in velocity profile within the jet was formed. Therefore, different flow models such as piston flow model, parabolic flow model, vortex flow model and a cone flow model was used and terminal concentrations inside the jet compared with laboratory values. Results shows the most accurate model to predict the flow concentration along the... 

    Aerodynamic Analysis and Design of a Propeller for Light Flying Objects

    , M.Sc. Thesis Sharif University of Technology Sardari, Ali (Author) ; Farhanieh, Bijan (Supervisor)
    One of the major concerns in the use of light flying objects is propulsion for cruise and take off from land. Creating propulsion force is important in such way that no excessive weight is introduced, especially in case of UAVs. A common trend for propulsion in light flying objects is using propellers. Propellers are commonly driven by an external motive force and due to this force and their geometry, they convert energy from this motive force into the momentum of fluid in which they are immersed as a result a lift force is generated.In the present work, trend of propeller design with optimum performance is introduced with use of vortex theory, optimum energy loss condition or Betz condition... 

    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)
    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... 

    Aerodynamic Analysis of Dual Rotors Using Potential Method and Free Wake Modeling

    , M.Sc. Thesis Sharif University of Technology Yeylaghi, Shahab (Author) ; Hejranfar, Kazem (Supervisor)
    Potential flow solvers simplify the mathematical formulation and achieve efficient solutions. The prediction of aerodynamic of dual rotor systems using computational fluid dynamic methods is difficult task due to the interference effects between the wakes shed from the rotors. In the present work, a free wake vortex lattice method is used to predict the vertical wake and blade loading of dual rotors in hover. In this approach the blades are modeled as flat plates with zero thickness and ring vortices are distributed on the surface of each blade. When the blades rotate, vortices are shed into the wake and freely move with a local velocity induced by the effects of the vortices on the blades... 

    Simulation of Vortex Induced Vibration and Limit Cycle Oscillation on Flexible tall towers and Suspended Cables

    , M.Sc. Thesis Sharif University of Technology Imaninejad, Ehsan (Author) ; Dehghani Firoozabadi, Rouhollah (Supervisor)
    Vibration of flexible slender structures under vortex induced vibrations is one of the important subjects in the different fields of engineering such as overhead electricity transmission cables, columns, tall towers and suspended bridges. During passes of flow around bluff bodies, in the certain range of velocity, the Von Karman vortices sheds unsynchronized from two sides of bluff bodies. When structure frequency closed to the vortex shedding frequency, resonant vibrations happen and one can observe vibrations with limited amplitude. Simulations of these phenomenons are so complicated and time consuming prosess, but there is an engineering method for simulating this phenomenon. The aim of... 

    Design and Manufacture of Energy Harvesting Set-up from Oscillating Airfoil in Stall Flutter Condition

    , M.Sc. Thesis Sharif University of Technology Roghani, Mostafa (Author) ; Ebrahimi, Abbas (Supervisor)
    Energy harvesting is a process in which energies in nature are recycled on a small scale and used to power equipment such as sensors, data recorders and transmitters, IoT monitoring and applications. Recently, energy harvesting from a new model based on movements caused by vortices of wind and water flow has been considered. The fall of unstable vortices behind the body induces aero-hydrodynamic forces into the body. If the body has degrees of freedom of movement, the vortex phenomenon can cause the body to rotate or rotate, resulting in energy extraction. Previous studies show that very little activity has been done so far on energy extraction from the Stall flutter phenomenon. The main...