Search for: fluid-dynamics
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    Multiscale probability distribution of pressure fluctuations in fluidized beds

    , Article Journal of Statistical Mechanics: Theory and Experiment ; Volume 2012, Issue 7 , 2012 ; 17425468 (ISSN) Ghasemi, F ; Sahimi, M ; Rahimi Tabar, M. R ; Peinke, J ; Sharif University of Technology
    Analysis of flow in fluidized beds, a common chemical reactor, is of much current interest due to its fundamental as well as industrial importance. Experimental data for the successive increments of the pressure fluctuations time series in a fluidized bed are analyzed by computing a multiscale probability density function (PDF) of the increments. The results demonstrate the evolution of the shape of the PDF from the short to long time scales. The deformation of the PDF across time scales may be modeled by the log-normal cascade model. The results are also in contrast to the previously proposed PDFs for the pressure fluctuations that include a Gaussian distribution and a PDF with a power-law... 

    Hydrodynamic Analysis and Cake Erosion Properties of a Modified Water-Based Drilling Fluid by a Polyacrylamide/Silica Nanocomposite during Rotating-Disk Dynamic Filtration

    , Article ACS Omega ; Volume 7, Issue 48 , 2022 , Pages 44223-44240 ; 24701343 (ISSN) Movahedi, H ; Jamshidi, S ; Hajipour, M ; Sharif University of Technology
    American Chemical Society  2022
    In this study, the potential of using a polyacrylamide-silica nanocomposite (PAM-S) to control the filtration properties of bentonite water-based drilling muds under different salinity conditions was evaluated. Static filtration tests under low-pressure/low-temperature (LPLT) conditions accompanied by rheological measurements have been carried out to analyze the role of silica nanoparticles (NPs) and nanocomposites (NCs) in the base fluid properties. Moreover, high-pressure/high-temperature (HPHT) static filtration was also investigated to evaluate the thermal stability of PAM-S. Afterward, dynamic filtration has been conducted in a filtration cell equipped with an agitating system with a... 

    Experimental and numerical hydrodynamic modeling of an underwater manipulator

    , Article American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED ; Volume 256 , 2000 , Pages 291-296 ; 08888116 (ISSN) Khanicheh, A ; Tehranian, A ; Meghdari, A ; Sadeghipour, M. S ; Sharif University of Technology
    This paper presents the kinematics and dynamic modeling of a three-link (3-DOF) underwater manipulator where the effects of hydrodynamic forces are investigated. In our investigation, drag and added mass coefficients are not considered as constants. In contrast, the drag coefficient is a variable with respect to all relative parameters. Experiments were conducted to validate the hydrodynamic model for a one degree-of-freedom manipulator up to a three degrees-of-freedom manipulator. Finally, the numerical and experimental results are compared and thoroughly discussed  

    Rans simulation of hydrofoil effects on hydrodynamic coefficients of a planing catamaran

    , Article Brodogradnja ; Volume 67, Issue 1 , 2016 , Pages 43-66 ; 0007215X (ISSN) Najafi, A ; Seif, M. S ; Sharif University of Technology
    Brodarski Institute  2016
    Determination of high-speed crafts’ hydrodynamic coefficients will help to analyze the dynamics of these kinds of vessels and the factors affecting their dynamic stabilities. Also, it can be useful and effective in controlling the vessel instabilities. The main purpose of this study is to determine the coefficients of longitudinal motions of a planing catamaran with and without a hydrofoil using RANS method to evaluate the foil effects on them. Determination of hydrodynamic coefficients by experimental approach is costly, and requires meticulous laboratory equipment; therefore, utilizing numerical methods and developing a virtual laboratory seems highly efficient. In the present study, the... 

    Unsteady aerodynamic analysis of different multi-MW horizontal axis wind turbine blade profiles on SST K-ω model

    , Article Green Energy and Technology ; 2018 , Pages 17-30 ; 18653529 (ISSN) Radmanesh, A. R ; Abbaspour, M ; Soltani, M. R ; Sharif University of Technology
    Springer Verlag  2018
    In this study, in order to indicate the best airfoil profile for the different sections of a blade, five airfoils including S8xx, FFA, and AH series were studied. Among the most popular wind power blades for this application were selected, in order to find the optimum performance. Nowadays, modern wind turbines are using blades with multi-airfoils at different sections. On the large scale profile, SST K-ω model with different wind speed at large-scale profile was applied to the simulation of horizontal axis wind turbines (HAWT). The aerodynamic simulation was accomplished using the computational fluid dynamic (CFD) method based on the finite volume method. The governing equations applied in... 

    Numerical investigation of a portable incinerator: A parametric study

    , Article Processes ; Volume 8, Issue 8 , 2020 Pour, M. S ; Hakkaki Fard, A ; Firoozabadi, B ; Sharif University of Technology
    MDPI AG  2020
    The application of incinerators for the municipal solid waste (MSW) is growing due to the ability of such instruments to produce energy and, more specifically, reduce waste volume. In this paper, a numerical simulation of the combustion process with the help of the computational fluid dynamics (CFD) inside a portable (mobile) incinerator has been proposed. Such work is done to investigate the most critical parameters for a reliable design of a domestic portable incinerator, which is suitable for the Iranian food and waste culture. An old design of a simple incinerator has been used to apply the natural gas (NG), one of the available cheap fossil fuels in Iran. After that, the waste height,... 

    Development of an integrated model for airflow in building spaces

    , Article Renewable Energy ; Volume 31, Issue 4 , 2006 , Pages 401-416 ; 09601481 (ISSN) Farhanieh, B ; Sattari, S ; Sharif University of Technology
    In building energy simulation, an integrated modelling of airflow in the building needed. Therefore, in this paper two approaches are used for building energy simulation: zonal network for modelling of the building segments and Computational Fluid Dynamics (CFD) for modelling of the airflow. It is noted that a synchronize solution process is needed for the building and the CFD equation-sets. For this purpose an iterative procedure is used to corresponding solution of these equations. © 2005 Elsevier Ltd. All rights reserved  

    Optimization of separator internals design using CFD modeling in the Joule-Thomson process

    , Article Journal of Natural Gas Science and Engineering ; Volume 89 , 2021 ; 18755100 (ISSN) Nabati Shoghl, S ; Naderifar, A ; Farhadi, F ; Pazuki, G ; Sharif University of Technology
    Elsevier B.V  2021
    In this work, gas dehydration and natural gas liquid (NGL) recovery by the Joule-Thomson (JT) process, were investigated using the computational fluid dynamics (CFD) modeling approach. Droplet behavior inside the separator was analyzed by particle tracing and moisture diffusion methods. The modified separator reduced the water content of natural gas from 0.008 to 0.0029 kg/m3. In addition, the separation efficiency was increased by addition of internal components. One of the added internal components was an inlet deflector. Among different inlet deflectors, the reversed type one exhibited the highest separation efficiency. The separation efficiency improved from 6 to 10% in the original... 

    Modeling Paramecium swimming in a capillary tube

    , Article Scientia Iranica ; Volume 23, Issue 2 , 2016 , Pages 658-667 ; 10263098 (ISSN) Sarvestani, A. N ; Shamloo, A ; Ahmadian, M. T ; Sharif University of Technology
    Sharif University of Technology 
    In certain types of biomimetic surgery systems, micro robots inspired by Paramecium are designed to swim in a capillary tube for gaining access to internal organs with minimal invasion. Gaining insight into the mechanics of Paramecium swimming in a capillary tube is vital for optimizing the design of such systems. There are two approaches to modeling the physics of micro swimming. In the envelope approach, which is widely accepted by researchers, Paramecium is approximated as a sphere, self-propelled by tangential and normal surface distortions. However, not only is this approach incapable of considering the specific geometry of Paramecium, but it also neglects short range hydrodynamic... 

    Numerical simulations of turbulent flow around side-by-side circular piles with different spacing ratios

    , Article International Journal of River Basin Management ; Volume 15, Issue 2 , 2017 , Pages 227-238 ; 15715124 (ISSN) Beheshti, A. A ; Ataie Ashtiani, B ; Dashtpeyma, H ; Sharif University of Technology
    Taylor and Francis Ltd  2017
    Numerical simulations of the turbulent flow around single and side-by-side piles at different spacing ratios (centre-to-centre distance to the pile diameter) with flow Reynolds number of 105 on the fixed flat-bed are presented. The calculations are performed using the computational fluid dynamics model, FLOW-3D, which solves the Navier–Stokes equations in three dimensions with a finite-volume method. The numerical results of time-averaged flow patterns around single and side-by-side piles are validated using the available experimental measurements. At the downstream of the single pile, dimensionless vortex shedding frequency (Strouhal number) is estimated as 0.22. The maximum values of bed... 

    Numerical study of soot nano-aerosol formation in a JP combustor embedded with a mini-scale air-distributor

    , Article 23rd AIAA Computational Fluid Dynamics Conference, 2017, 5 June 2017 through 9 June 2017 ; 2017 ; 9781624105067 (ISBN) Darbandi, M ; Ghafourizadeh, M ; Saidi, M. H ; Schneider, G. E ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc, AIAA  2017
    The main objective of this work is to investigate the effects of using a miniature or mini-scale air-distributor on the formation of soot nano-particles in a gas turbine combustor burning the jet propellant JP. To evaluate the achieved numerical predictions, it is necessary to choose a test case with available experimental data. It helps to compare the predicted flame structure with that of measurement. After the validation step, the chosen combustor configuration is modified to an inverse non-premixed flame configuration. This helps to split the incoming air between the primary and secondary air streams and to inject the primary air into the inverse flame via a primary air injector.... 

    , M.Sc. Thesis Sharif University of Technology Rasouli Pour, Sahand (Author) ; Abbsapour, Majid (Supervisor) ; Mozaffari, Ali Asghar (Supervisor)
    Unglazed Transpired Solar Collectors, recently called "Solar Wall", are known as the most efficient solar air heating system for the past two decades. The equator faced collector which is installed in this system has many tiny perforations to suck in the air with a fan and gain the absorbed heat by the collector. Convection and Radiation heat losses from the absorber to surrounding and other design factors have different influents to the heat gain of this system. In this study, Continuity, Momentum and Energy equations are written with proper boundary conditions, solved with computational fluid dynamics methods and validated in order to model Solar Wall system. Thus we could compare all... 

    Multi-objective trade-off analysis of an integrated cold gas propulsion system

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 227, Issue 8 , 2013 , Pages 1233-1250 ; 09544100 (ISSN) Banazadeh, A ; Gol, H. A ; Sharif University of Technology
    The overall design of cold gas propulsion systems is pretty complicated when considering the mission requirements, operating constraints and functional limitations imposed by the mechanical components. To address this complication, a precise design process is proposed, which attempts to optimize the cost of operation as well as to minimize the waste volume and weight by using multi-objective trade-off analysis. This analysis is based on a set of ordinary differential equations that are solved iteratively to describe the optimal behavior of the system. Therefore, a numerical code is being developed to give insight on the design sensitivity with respect to uncertainties on the design... 

    Characterization of interfacial hydrodynamics in a single cell of shaken microtiter plate bioreactors applying computational fluid dynamics technique

    , Article Procedia Engineering ; Volume 42 , 2012 , Pages 924-930 ; 18777058 (ISSN) Pouran, B ; Amoabediny, G ; Sadegh Saghafinia, M ; Haji Abbas, M. P ; Sharif University of Technology
    Development of orbital shaking technology for enhanced mixing with lower mechanical demand has been receiving significant attention since the advent of advanced mixing schemes. Amongst shaken bioreactors, microtiter plates play significant role both for research and industrial purposes due to their capability of handling tiny amount of liquid in parallel experimentations. Detailed understanding of complicated Flow hydrodynamics thus seems to be considered a continual effort, as it is responsible for efficient gas-liquid mass transfer. Computational fluid dynamics (CFD) technique is shown to be a suitable numerical method in particular for discovering concealed flow facts, which can reliably... 

    Retina-Choroid-Sclera Permeability for Ophthalmic Drugs in the Vitreous to Blood Direction: Quantitative Assessment

    , Article Pharmaceutical Research ; 2012 , Pages 1-19 ; 07248741 (ISSN) Haghjou, N ; Abdekhodaie, M. J ; Cheng, Y. L ; Sharif University of Technology
    Springer  2012
    Purpose: To determine the outward permeability of retina-choroid-sclera (RCS) layer for different ophthalmic drugs and to develop correlations between drug physicochemical properties and RCS permeability. Methods: A finite volume model was developed to simulate pharmacokinetics in the eye following drug administration by intravitreal injection. The RCS permeability was determined for 32 compounds by best fitting the drug concentration-time profile obtained by simulation with previously reported experimental data. Multiple linear regression was then used to develop correlations between best fit RCS permeability and drugs physicochemical properties. Results: The RCS drug permeabilities had... 

    Dynamics of drops - Formation, growth, oscillation, detachment, and coalescence

    , Article Advances in Colloid and Interface Science ; Volume 222 , 2015 , Pages 413-424 ; 00018686 (ISSN) Karbaschi, M ; Taeibi Rahni, M ; Javadi, A ; Cronan, C. L ; Schano, K. H ; Faraji, S ; Won, J. Y ; Ferri, J. K ; Krägel, J ; Miller, R ; Sharif University of Technology
    Elsevier  2015
    Single drops or bubbles are frequently used for the characterization of liquid- fluid interfaces. Their advantage is the small volume and the various protocols of their formation. Thus, several important methods are based on single drops and bubbles, such as capillary pressure and profile analysis tensiometry. However, these methods are often applied under dynamic conditions, although their principles are defined under equilibrium conditions. Thus, specific attention has to be paid when these methods are used beyond certain limits. In many cases, computational fluid dynamics (CFD) simulations have allowed researchers, to extend these limits and to gain important information on the... 

    Numerical aerodynamic evaluation and noise investigation of a Bladeless fan

    , Article Journal of Applied Fluid Mechanics ; Volume 8, Issue 1 , January , 2015 , Pages 133-142 ; 17353572 (ISSN) Jafari, M ; Afshin, H ; Farhanieh, B ; Bozorgasareh, H ; Sharif University of Technology
    Isfahan University of Technology  2015
    Bladeless fan is a novel fan type that has no observable impeller, usually used for domestic applications. Numerical investigation of a Bladeless fan via Finite Volume Method was carried out in this study. The fan was placed in center of a 4×2×2m room and 473 Eppler airfoil profile was used as cross section of the fan. Performance and noise level of the fan by solving continuity and momentum equations as well as noise equations of Broadband Noise Source (BNS) and Ffowcs Williams and Hawkings (FW-H) in both steady state and unsteady conditions were studied. Flow increase ratio of the fan was captured. Furthermore, BNS method could find outlet slit of the air as the main source of the noise... 

    Experimental and numerical investigation of a 60cm diameter bladeless fan

    , Article Journal of Applied Fluid Mechanics ; Volume 9, Issue 2 , 2016 , Pages 935-944 ; 17353572 (ISSN) Jafari, M ; Afshin, H ; Farhanieh, B ; Bozorgasareh, H ; Sharif University of Technology
    Isfahan University of Technology 
    Bladeless fan is a novel type of fan with an unusual geometry and unique characteristics. This type of fan has been recently developed for domestic applications in sizes typically up to 30cm diameter. In the present study, a Bladeless fan with a diameter of 60cm was designed and constructed, in order to investigate feasibility of its usage in various industries with large dimensions. Firstly, flow field passed through this fan was studied by 3D modeling. Aerodynamic and aeroacoustic performance of the fan were considered via solving the conservation of mass and momentum equations in their unsteady form. To validate the acoustic code, NACA 0012 airfoil was simulated in a two dimension domain... 

    Effect of vortex generators on hydrodynamic behavior of an underwater axisymmetric hull at high angles of attack

    , Article Journal of Visualization ; Volume 20, Issue 3 , 2017 , Pages 559-579 ; 13438875 (ISSN) Dehghan Manshadi, M ; Hejranfar, K ; Farajollahi, A. H ; Sharif University of Technology
    Springer Verlag  2017
    Abstract: Underwater vehicles when yawed to free stream flow, like submarines in a turning maneuver, produce large vortical separated regions. This vortical flow affects acoustic, body drag, control effectiveness and maneuverability. A suitable way to reduce the effects of this separated flow is to use vortex generators. The main goal of this study is to investigate the effect of the vortex generator on the flow field around a standard underwater model employing the vortex generators by using the oil flow visualization method in wind tunnel only in yaw direction (0° ≤ β ≤ 30° angles of attack, due to the experimental cost) and the CFD method in the pitch direction (0° ≤ α ≤ 30° angles of... 

    Hydrodynamic analysis of trimaran vessels

    , Article Polish Maritime Research ; Volume 15, Issue 1 , June , 2008 , Pages 11-18 ; 12332585 (ISSN) Javanmardi, M ; Jahanbakhsh, E ; Seif, M ; Sayyaadi, H ; Sharif University of Technology
    Trimaran vessels are developed for different applications and hydrodynamic behavior of such vessels is different than usual mono-hulls. In this paper hydrodynamic resistance and maneuvering of a trimaran with Wigley body form are investigated. The effects of outriggers position in four different longitudinal and two transverse locations are studied. For hydrodynamic simulations a CFD code has been developed and used. This code is capable for simulating three dimensional, time dependent, two phases, viscous flow coupled with rigid body motion. Formulation and solution algorithm are described in detail. Different case studies have been performance and numerical results have shown good...