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Total 82 records

    Development of a device for measuring air–water flow characteristics

    , Article International Journal of Civil Engineering ; Volume 15, Issue 2 , 2017 , Pages 195-203 ; 17350522 (ISSN) Fazel, Z ; Fazelian, M ; Sarkardeh, H ; Sharif University of Technology
    Springer International Publishing  2017
    Abstract
    Air–water flow is a complex and challenging subject in many engineering fields as well as hydraulic engineering; and discovery of its characteristics can help the engineers to predict and analyze a probable phenomenon. In the present paper, development of a device capable of measuring the flow velocity, air concentration, diameter and counts of bubbles in air–water flows is described. The heart of the present device is two resistive probes with a novel configuration. Being pressure and corrosion resistant and also having negligible resistivity in the flow are some of the unique features of the employed needles. Moreover, sampling frequency and time can be adjusted for the intended... 

    On molecular flow velocity meters

    , Article IEEE Transactions on Molecular, Biological, and Multi-Scale Communications ; Volume 7, Issue 4 , 2021 , Pages 224-238 ; 23327804 (ISSN) Farahnak Ghazani, M ; Mirmohseni, M ; Nasiri Kenari, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    Flow velocity is an important characteristic of the fluidic mediums. In this article, we introduce a molecular based flow velocity meter consisting of a molecule releasing node and a receiver that counts these molecules. We consider both flow velocity detection and estimation problems, which are employed in different applications. For the flow velocity detection, we obtain the maximum a posteriori (MAP) decision rule. To analyze the performance of the proposed flow velocity detector, we obtain the error probability, its Gaussian approximation and Chernoff information (CI) upper bound, and investigate the optimum and sub-optimum sampling times accordingly. We show that, for binary hypothesis,... 

    Analytical solution of turbulent problems using governing equation of cosserat continuum model

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 08888116 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Ghasvari Jahromi, H ; Atefi, Gh ; Moosaie, A ; Hormozi, S ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    Abstract
    In present paper the theory of the micropolar fluid based on a Cosserat continuum model has been applied for analysis of Couette flow and turbulent flow through rough pipes. The obtained results for the velocity field have been compared with known results from experiments done by Reichardt at Max Plank institute for fluids in Gottingen [1,2] and analytical solution of the problem from Gradient theory by alizadeh[3] for couette problem and with known results from experiments done by Nikuradse (1932).the boundary condition used here was the no slip one and Trostel's slip boundary condition[4].a good agreement between experimental results and the results of the problem for Reynolds near 18000... 

    Three-dimensional modeling of density current in confined and unconfined channels

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 08888116 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Aram, E ; Firoozabadi, B ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    Abstract
    Dense underflows are continuous currents which move down-slope due to the fact that their density is heavier than that ambient water. In this work, 2-D and 3-D density current in a channel were investigated by a set of experimental studies and the data were used to simulate the density current. The velocity components were measured using Acoustic Doppler Velocimetry (ADV). The height of density current (current's depth) was also measured. In this study, the density current with a uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. A low-Reynolds number turbulent model (Launder and Sharma, 1974) has been applied to... 

    Experimental characterization of response of lean premixed low-swirl flames to acoustic excitations

    , Article International Journal of Spray and Combustion Dynamics ; Volume 5, Issue 4 , 2013 , Pages 309-328 ; 17568277 (ISSN) Bagheri Sadeghi, N ; Shahsavari, M ; Farshchi, M ; Sharif University of Technology
    2013
    Abstract
    Acoustically excited lean premixed low-swirl flames were experimentally investigated to gain a better understanding of detrimental thermoacoustic couplings which can occur in applications like low-NOx gas turbines. Propane-air flames were imaged and analyzed at equivalence ratios of 0.6 to 0.8, mean flow velocities of 3.5 to 5.5 m/s and excitation frequencies of 135 Hz to 555 Hz. It was observed that with increasing excitation frequency, mean flame shape gradually became wider up to a Strouhal number of about 2.5 and then slowly reverted back to the unexcited flame shape. Such large changes in mean flame shape and possibly flow field under acoustic excitations can significantly affect flame... 

    A steady-state saturation model to determine the subsurface travel time (STT) in complex hillslopes

    , Article Hydrology and Earth System Sciences ; Volume 14, Issue 6 , Jun , 2010 , Pages 891-900 ; 10275606 (ISSN) Sabzevari, T ; Talebi, A ; Ardakanian, R ; Shamsai, A ; Sharif University of Technology
    2010
    Abstract
    The travel time of subsurface flow in complex hillslopes (hillslopes with different plan shape and profile curvature) is an important parameter in predicting the subsurface flow in catchments. This time depends on the hillslopes geometry (plan shape and profile curvature), soil properties and climate conditions. The saturation capacity of hillslopes affect the travel time of subsurface flow. The saturation capacity, and subsurface travel time of compound hillslopes depend on parameters such as soil depth, porosity, soil hydraulic conductivity, plan shape (convergent, parallel or divergent), hillslope length, profile curvature (concave, straight or convex) and recharge rate to the groundwater... 

    Analysis of threshold and incipient conditions for sediment movement

    , Article Coastal Engineering ; Volume 55, Issue 5 , 2008 , Pages 423-430 ; 03783839 (ISSN) Beheshti, A. A ; Ataie Ashtiani, B ; Sharif University of Technology
    2008
    Abstract
    Prediction of threshold conditions and incipient motion is the essential issue for the study of sediment transport. This work compares existing empirical threshold curves proposed for Shields diagram, a method based on the concept of probability of sediment movement, and an empirical method based on movability number. These methods are used to predict the incipient motion conditions for experimental runs taken from various studies. Most of the experimental data, used in this work, have not been used before in derivation of alternative formulations for Shields diagram and other methods. The empirical threshold curves based on the Shields entrainment function was the least successful at... 

    Experimental investigation of the effects of surfactants on the mass transfer in liquid-liquid extraction equipment

    , Article 2007 5th Joint ASME/JSME Fluids Engineering Summer Conference, FEDSM 2007, San Diego, CA, 30 July 2007 through 2 August 2007 ; Volume 2 FORA, Issue PART A , 2007 , Pages 239-244 ; 0791842886 (ISBN); 9780791842881 (ISBN) Haghdoost, A ; Shah Alami, M ; Mansouri, H ; Sharif University of Technology
    2007
    Abstract
    Mass transfer rates to the drops in liquid-liquid extraction equipment are often likely to be reduced by the presence of surface active contaminants. This reduction in mass transfer is said to be due to a reduction in terminal velocity, and to changes in pattern of internal circulation. A single-drop extraction apparatus was used to investigate the dependency of mass transfer coefficient on the amount of surfactant added in a system of n-butanol/succinic acid/water. Three types of surfactants, SDS, DTMAC and Triton X-100, were used to study their effects on the inhibition of mass transfer in liquid-liquid extraction. The effect of surfactants concentration on extraction percentage, overall... 

    Simulation of rarefied micro to nano gas flows using improved slip flow models

    , Article 37th AIAA Fluid Dynamics Conference, Miami, FL, 25 June 2007 through 28 June 2007 ; Volume 1 , 2007 , Pages 576-583 ; 1563478978 (ISBN); 9781563478970 (ISBN) Darbandi, M ; Rikhtegar, F ; Schneider, G. E ; Sharif University of Technology
    2007
    Abstract
    If the hydrodynamic diameter of a channel is comparable with the mean free path of the gas molecules moving inside the channel, the fluid can no longer be considered to be in thermodynamic equilibrium and a variety of non-continuum or rarefaction effects can occur. To avoid enormous complexity and extensive numerical cost encountered in modeling of nonlinear Boltzmann equations, the Navier-Stokes equations can be solved considering the concepts of slip flow regime and applying slip velocity boundary conditions at the solid walls. The high-order slip models can, in some cases, extend the range of applicability of the Navier-Stokes equations beyond Kn = 0.1, where the accuracy of first-order... 

    Neural network and neuro-fuzzy assessments for scour depth around bridge piers

    , Article Engineering Applications of Artificial Intelligence ; Volume 20, Issue 3 , 2007 , Pages 401-414 ; 09521976 (ISSN) Bateni, S. M ; Borghei, S. M ; Jeng, D. S ; Sharif University of Technology
    2007
    Abstract
    The mechanism of flow around a pier structure is so complicated that it is difficult to establish a general empirical model to provide accurate estimation for scour. Interestingly, each of the proposed empirical formula yields good results for a particular data set. Hence, in this study, alternative approaches, artificial neural networks (ANNs) and adaptive neuro-fuzzy inference system (ANFIS), are proposed to estimate the equilibrium and time-dependent scour depth with numerous reliable data base. Two ANN models, multi-layer perception using back-propagation algorithm (MLP/BP) and radial basis using orthogonal least-squares algorithm (RBF/OLS), were used. The equilibrium scour depth was... 

    Effect of surface roughness on an airfoil in pitching motion

    , Article 36th AIAA Fluid Dynamics Confernce, San Francisco, CA, 5 June 2006 through 8 June 2006 ; Volume 4 , 2006 , Pages 2785-2792 ; 1563478102 (ISBN); 9781563478109 (ISBN) Seddighi, M ; Soltani, M. R ; Sharif University of Technology
    2006
    Abstract
    Extensive experimental tests have been conducted to examine the roughness effects on the aerodynamic performance of a model in an oscillatory motion. All tests were carried out in a 0.8×0.8 m 2 low-speed wind tunnel. The model had 0.25m chord and was pitched about its quarter-chord. Data were acquired at various Reynolds number and reduced frequencies. Surface roughness was applied at two different locations of the model upper surface, leading edge and the point of maximum thickness. Furthermore, tunnel turbulent was varied and all tests were repeated. The results indicate that the width of the hysteresis loop, position of the figure eight shape, slope of the normal force coefficient curve,... 

    Computational analysis of injection-velocity effects on dynamic parameters of unconfined fuel-vapor clouds

    , Article Combustion, Explosion and Shock Waves ; Volume 41, Issue 5 , 2005 , Pages 510-520 ; 00105082 (ISSN) Doustdar, M. M ; Mazaheri, K ; Hosseinalipour, M ; Sharif University of Technology
    2005
    Abstract
    A computational investigation is performed to study the effects of injection velocity on the main dynamic parameters of the fuel cloud released into the open atmosphere. The volume, shape, and growth rate of the cloud, turbulence intensity, as well as the distribution of fuel concentration, temperature gradient, and self-ignition induction time are the most important parameters determining the mode of combustion that propagates through the cloud. A modified KIVA-based program is employed to fulfill the calculations. Systems of equations are solved by a finite-volume method. The k-ε model and discrete droplet model are applied for modeling gas-phase turbulence and liquid spray, respectively.... 

    The effect of influent COD and upward flow velocity on the behaviour of sulphate-reducing bacteria

    , Article Process Biochemistry ; Volume 40, Issue 7 , 2005 , Pages 2305-2310 ; 13595113 (ISSN) Shayegan, J ; Ghavipanjeh, F ; Mirjafari, P ; Sharif University of Technology
    2005
    Abstract
    The effect of up velocity and influent COD concentration on the activity of sulphate-reducing bacteria (SRB) in UASB reactors is discussed. To study these effects, four UASB reactors were built and utilized in parallel. Examinations were carried out in two different concentrations of molasses (500 mg COD/l and 1000 mg COD/l) and four different upward flow velocities. It was observed that at velocities greater than 1 m/h, SRB bacteria were easily washed out from the reactors due to lower density and lack of ability to form dense and firm granules. It was found that in low-strength wastewaters with a COD to sulphate ratio of 2, an upward velocity in the range of 1.5-2.5 m/h could be... 

    Simulation of turbulent swirling flow in convergent nozzles

    , Article Scientia Iranica ; Volume 19, Issue 2 , 2012 , Pages 258-265 ; 10263098 (ISSN) Nouri-Borujerdi, A ; Kebriaee, A ; Sharif University of Technology
    Abstract
    This work simulates the turbulent boundary layer of an incompressible viscous swirling flow through a conical chamber. To model the pressure gradient normal to the wall, the radial and tangential velocity components across the boundary layer have been calculated by both the integral and numerical methods. The numerical solution is accomplished by finite difference, based on the finite volume method. The results show that the radial and tangential boundary layer thicknesses depend on the velocity ratios, Reynolds number and nozzle angle. The peak of radial and tangential boundary layer thicknesses are located at zL≈0.2 and zL≈0.8 from the nozzle inlet, respectively. Due to the short length of... 

    Relative and interactive effects of fluid's physicochemical characteristics on the incipient motion of a granular particle under laminar flow condition

    , Article Journal of Hydraulic Engineering ; Volume 144, Issue 5 , 2018 ; 07339429 (ISSN) Xiao, M ; Gholizadeh Vayghan, A ; Adams, B. T ; Rajabipour, F ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2018
    Abstract
    This paper presents an experimental research for studying the relative and interactive effects of three physicochemical fluid characteristics (viscosity, pH, and ionic strength) on the incipient motion of a granular particle under laminar flow condition. Critical flow velocity for particle's incipient motion, an important factor for evaluating flow-induced soil erosion, was used to quantify the relative erosive capacity of the test fluids. Response surface methodology (RSM), a statistical design of experiments, was used to design and implement 20 test fluids with various levels of the three fluid characteristics. Incipient motion of a highly spherical glass bead positioned atop a specially... 

    Careful parameter study to enhance the effect of injecting heavy fuel oil into a crossflow using numerical approaches

    , Article ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting, FEDSM 2018, 15 July 2018 through 20 July 2018 ; Volume 2 , July , 2018 ; 08888116 (ISSN) ; 9780791851562 (ISBN) Darbandi, M ; Fatin, A ; Schneider, G.E ; Fluids Engineering Division ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2018
    Abstract
    The flow and spray parameters can have noticeable roles in heavy fuel oil (HFO) spray finesse. As known, the interaction between droplets and cross flow should be considered carefully in many different industrial applications such as the process burners and gas turbine combustors. So, it would be so important to investigate the effect of injecting HFO into a crossflow more subtly. In this work, the effects of various flow and spray parameters on the droplet breakup and dispersion parameters are investigated numerically using the finite-volume-element method. The numerical method consists of a number of different models to predict the droplets breakup and their dispersion into a cross flow... 

    An efficient system identification approach to estimate unsteady loads on cavitator plates

    , Article Ocean Engineering ; Volume 207 , 2020 Tehrani, M. A ; Dehghani Firouz Abadi, R ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    A new and efficient model for calculation of the unsteady hydrodynamic loads on an oscillating plate in two-dimensional flow is proposed. In order to compute the hydrodynamic loads, an unsteady hydrodynamic model is derived using the boundary-element method along with the potential flow assumption. To this aim, the steady boundary of cavity is determined by a full-nonlinear iterative procedure. Thereafter, assuming that amplitude and frequency of oscillations are so that the length of cavity in unsteady flow remains intact, simulation of the unsteady hydrodynamic flow is performed by imposing some velocity perturbations over the steady cavity solutions. Consequently, based on this... 

    Nanofluidic transport inside carbon nanotubes

    , Article Journal of Physics D: Applied Physics ; Volume 47, Issue 6 , 12 February , 2014 ; ISSN: 00223727 Moghimi Kheirabadi, A ; Moosavi, A ; Akbarzadeh, A. M ; Sharif University of Technology
    Abstract
    Using non-equilibrium molecular dynamics simulations, we investigate the effects of nanotube size, mean flow velocity, ion concentration and temperature of an electrolyte water solution on shearing stress and nominal viscosity. It is shown that the distributed electric field arising from the electrolyte water solution has significant influences on fluid properties. Also, the temperature of the solution, which causes thermal movement, affects nanofluidic transport in nanoenvironments. The nominal viscosity and shearing stress increases as the tube diameter increases. When the temperature of solution increases or ion concentration decreases, the shearing stress and nominal viscosity increase.... 

    Nonlinear vibration analysis of a micro beam exposed to an external flow

    , Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 ; Volume 7, Issue PARTS A AND B , 2011 , Pages 643-646 ; 9780791854938 (ISBN) Mazaheri, H ; Hosseinzadeh, A ; Ahmadian, M. T ; Barari, A ; Sharif University of Technology
    2011
    Abstract
    In this paper, nonlinear vibration of a micro cantilever exposed to a constant velocity flow is studied. In order to obtain vibration frequency and time response of the micro beam the variational iteration method is used as a novel tool for solving nonlinear differential equations. Results of the analytical solution are compared with those obtained by Runge-Kutta method which shows very good agreement between them. Results confirm that frequency of vibration depends on the flow velocity. Also, the high sensitivity of the vibration frequency to the flow velocity means that it can be an effective indicator of velocity  

    Induced soap-film flow by non-uniform alternating electric field

    , Article Journal of Electrostatics ; Volume 73 , February , 2015 , Pages 112-116 ; 03043886 (ISSN) Shirsavar, R ; Ramos, A ; Amjadi, A ; Taherinia, J ; Mashhadi, M ; Nejati, A ; Sharif University of Technology
    Elsevier  2015
    Abstract
    Fluid flows generated on soap films by non-uniform alternating electric fields are studied. Two parallel metal rods subjected to an AC voltage are placed perpendicular to the soap film, which is anchored in a dielectric frame. The fluid flow is generated by electrohydrodynamic induction. At very low signal frequencies there is induced surface charge, but there is no tangential electric field at the surface, so there is no force and no flow. Fluid flow is observed increasing the frequency, when there are both surface charge and tangential electric field. The flow velocity increases with decreasing thickness of the soap film