Search for: flow-of-fluids
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    Dynamics and stability of conical/cylindrical shells conveying subsonic compressible fluid flows with general boundary conditions

    , Article International Journal of Mechanical Sciences ; Volume 120 , 2017 , Pages 42-61 ; 00207403 (ISSN) Rahmanian, M ; Firouz Abadi, R. D ; Cigeroglu, E ; Sharif University of Technology
    Elsevier Ltd  2017
    A fast and efficient reduced order formulation is presented for the first time to study dynamics and stability of conical/cylindrical shells with internal fluid flows. The structural and fluid formulations are developed based on general assumptions to avoid any deficiency due to modeling. Their respective solutions and the final solution to the coupled field problem are also developed in a way to be capable of capturing any desirable set of boundary conditions. In addition to the flexibility provided by the solution methodology and generalization provided by the formulation, current solution proposes an additional advantage over others which is the minimal computational cost due to the... 

    Experimental and analytical study of thermohydraulic performance of a novel loop heat pipe with an innovative active temperature control method

    , Article Applied Thermal Engineering ; Volume 143 , 2018 , Pages 964-976 ; 13594311 (ISSN) Khalili, M ; Mostafazade Abolmaali, A ; Shafii, M. B ; Sharif University of Technology
    In this study, a novel type of LHP is innovated, fabricated, and its performance is assessed by numerous experiments. Compared to conventional LHPs, this novel design has some modifications in its evaporator and reservoir configuration. This particular type has a simpler and less costly fabrication procedure compared to other LHPs and it yields acceptable performance. Additionally, a novel method is introduced to control the temperature distribution in the system. A steel ball is placed in the evaporator to actively control the operating temperature. The ball is moved by two magnets installed outside of the evaporator. Moreover, a steady-state one-dimensional mathematical model of the... 

    On the use of COMSOL Multiphysics for seawater intrusion in fractured coastal aquifers

    , Article 25th Salt Water Intrusion Meeting, SWIM 2018, 17 June 2018 through 22 June 2018 ; Volume 54 , 2018 ; 22671242 (ISSN) Mozafari, B ; Fahs, M ; Ataie Ashtiani, B ; Simmons, C. T ; Younes, R ; Sharif University of Technology
    EDP Sciences  2018
    COMSOL Multiphysics is a comprehensive simulation software environment for a wide range of applications. COMSOL has an interactive interface that facilitates the modeling procedure and allows an easy coupling of different physical processes. The Subsurface Flow module extends the COMSOL modeling environment to applications related to fluid flow in saturated and variably saturated porous media. COMSOL is increasingly used in the investigation of geophysical, hydrogeological and environmental phenomena. The main goal of this work is to explore the ability of COMSOL for simulating seawater intrusion (SWI) in fractured coastal aquifers. Numerical modeling of such a problem is of high interest as... 

    New correlative models to improve prediction of fracture permeability and inertial resistance coefficient

    , Article Transport in Porous Media ; Volume 121, Issue 3 , February , 2018 , Pages 557-584 ; 01693913 (ISSN) Foroughi, S ; Jamshidi, S ; Pishvaie, M. R ; Sharif University of Technology
    Springer Netherlands  2018
    Presence of fracture roughness and occurrence of nonlinear flow complicate fluid flow through rock fractures. This paper presents a qualitative and quantitative study on the effects of fracture wall surface roughness on flow behavior using direct flow simulation on artificial fractures. Previous studies have highlighted the importance of roughness on linear and nonlinear flow through rock fractures. Therefore, considering fracture roughness to propose models for the linear and nonlinear flow parameters seems to be necessary. In the current report, lattice Boltzmann method is used to numerically simulate fluid flow through different fracture realizations. Flow simulations are conducted over a... 

    Inertial microfluidics: a method for fast prediction of focusing pattern of particles in the cross section of the channel

    , Article Analytica Chimica Acta ; Volume 1083 , 2019 , Pages 137-149 ; 00032670 (ISSN) Mashhadian, A ; Shamloo, A ; Sharif University of Technology
    Elsevier B.V  2019
    Inertial microfluidics is utilized as a powerful passive method for particle and cell manipulation, which uses the hydrodynamic forces of the fluid in the channel to focus particles in specific equilibrium positions in the cross section of the channel. To achieve high performance manipulation, knowledge of focusing pattern of particles in the cross section of channel is essential. In this paper, we propose a method to address this important issue. To this end, firstly inertial microfluidics is analyzed in rectangular cross section channels. The results indicate that fluid flow velocity and channel's cross-sectional profiles have great impacts on the forces exerted on particles. Next, these... 

    Numerical investigation of different geometrical parameters of perforated conical rings on flow structure and heat transfer in heat exchangers

    , Article Applied Thermal Engineering ; Volume 156 , 2019 , Pages 494-505 ; 13594311 (ISSN) Erfanian Nakhchi, M ; Esfahani, J. A ; Sharif University of Technology
    Elsevier Ltd  2019
    A numerical study has been performed to investigate the flow and heat transfer characteristics of fluid flow through heat exchanger tubes fitted with perforated conical rings. The holes are circular, and the number of holes N is ranged from 0 to 10. The influences of perforated conical ring diameter ratios D2/D1=0.4,0.5and0.6 and the hole diameter ratios d/D=0.06,0.1and0.14 on average Nusselt number, friction factor and thermal performance factor are reported. This analysis is performed in the turbulent flow regime 4000⩽Re⩽14,000 and the governing equations are solved by using (RNG) k-∊ model. Due to strong turbulent intensity, perforated conical rings lead to more flow perturbation and... 

    Bidirectional water transport through non-straight carbon nanotubes

    , Article Journal of Molecular Liquids ; Volume 276 , 2019 , Pages 39-46 ; 01677322 (ISSN) Kargar, S ; Moosavi, A ; Sharif University of Technology
    Elsevier B.V  2019
    Natural nanochannels and those used for applied purposes are often several nanometers in diameter and have lengths up to micrometer scales. Since normally no pressure gradient, mechanical force or electrical field is exerted on fluids in these situations, the fluid flow within them is not single-file and can be bidirectional. For this reason, studying the behavior of bidirectional flows in the channels is of paramount importance. In this study, a comprehensive investigation on the straight and non-straight bidirectional water transfer through carbon nanotubes is conducted via extensive molecular dynamics simulations. The results indicate that by changing the length, the diameter and the... 

    Effect of active feather length on aerodynamic performance of airfoils at low reynolds number flow

    , Article AIAA AVIATION 2020 FORUM, 15 June 2020 through 19 June 2020 ; Volume 1 PartF , 2020 Esmaeili, A ; Darbandi, M ; Schneider, G. E ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc, AIAA  2020
    To increase the flight endurance of a Micro air vehicle (MAVs), which operates at low Reynolds number flow, one way is to harvest energy during its flight. By inspiring from the nature when all the birds use their feathers to control and distribute their power along the flying time, a solution might be design of a piezoelectric plate as feathers, which scavenges energy directly from the fluid flow. Cantilevered beam with piezo-ceramic layer undergoing vortex-induced vibrations can convert the mechanical energy available from the ambient environment to a usable electrical power. Since a flow-driven piezoelectric composite beam takes a form of natural three-way coupling of the turbulent fluid... 

    Antibody consumption reduction in lateral flow immunoassays within porous media

    , Article Chemical Engineering and Processing - Process Intensification ; Volume 147 , 2020 Gholami, A ; Shamloo, A ; Sharif University of Technology
    Elsevier B.V  2020
    In this study, the effect of the geometrical parameters of the Lateral Flow Immunoassay (LFI) membrane on the performance of the pregnancy kits is investigated. Consequently, a new geometry for LFI membrane is proposed based on some theoretical, numerical and experimental observations in order to improve the performance of the related kits. A pregnancy kit (for the detection of hCG in urine samples) is developed and the effect of the relocation of the test and the control lines over the membrane was studied based on the variation of the sample fluid velocity. Using Lattice-Boltzmann simulation of the lateral flow within the porous media and the experimental results, the fluid flow within the... 

    Micro-plasma actuator mechanisms in interaction with fluid flow for wind energy applications: Physical parameters

    , Article Physics of Fluids ; Volume 32, Issue 7 , 2020 Omidi, J ; Mazaheri, K ; Sharif University of Technology
    American Institute of Physics Inc  2020
    Plasma actuator is a flow control device to improve the aerodynamic performance of wind turbine blades at low airspeeds. One of the most robust numerical models for simulation of plasma actuator interaction with the fluid flow is the electrostatic model. This model is improved recently and is extensively verified by the authors. Due to the high cost of performing experimental optimizations, the optimized geometrical dimensions and materials of a plasma actuator may be sought by this numerical model. The aim of the present study is the aerodynamic enhancement of a DU21 wind turbine blade airfoil in which the effect of geometric parameters and the dielectric material is examined separately.... 

    Investigation of a centrifugal compressor and study of the area ratio and TIP clearance effects on performance

    , Article Journal of Thermal Science ; Volume 17, Issue 4 , December , 2008 , Pages 314-323 ; 10032169 (ISSN) Nili Ahmadabadi, M ; Hajilouy Benisi, A ; Durali, M ; Ghadak, F ; Sharif University of Technology
    In this research, the centrifugal compressor of a turbocharger is investigated experimentally and numerically. Performance characteristics of the compressor were obtained experimentally by measurements of rotor speed and flow parameters at the inlet and outlet of the compressor. Three dimensional flow field in the impeller and diffuser was analyzed numerically using a full Navier-Stokes program with SST turbulence model. The performance characteristics of the compressor were obtained numerically, which were then compared with the experimental results. The comparison shows good agreement. Furthermore, the effect of area ratio and tip clearance on the performance parameters and flow field was... 

    Particle trajectory study in submerged flows with baffles using v 2̄ - f and k -ε turbulence models

    , Article 46th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, 7 January 2008 through 10 January 2008 ; 2008 ; 9781563479373 (ISBN) Mehdizadeh Momen, A ; Sherif, A ; Firoozabadi, B ; Sharif University of Technology
    In this paper, the structure of a wall jet deflected by a baffle along with the trajectory of particles has been studied. This baffle is used to produce a stable deflected surface jet, thereby deflecting the high-velocity supercritical stream away from the bed to the surface. An elliptic relaxation turbulence model (v2̄ - f model) has been used to simulate this submerged flow. During the last few years, the v2̄ - f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. In addition, it has been proven that the v2̄ - f model is superior to other RANS methods in many fluid flows where complex flow features are... 

    3-D simulation of sedimentation in turbidity currents

    , Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 8 , 2007 , Pages 503-517 ; 0791843025 (ISBN) Hormozi, S ; Firoozabadi, B ; Ghasvari Jahromi, H ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2007
    The gravity currents on the inclined boundaries are formed when the inflow fluid has a density difference with the ambient fluid and a tangential component of gravity becomes the driving force. If the density difference arises from the suspended particles, the currents are known as particle-laden density currents, or turbidity currents in which the local density depends on the concentration of particles. A low Reynolds k- Turbulent model is used to simulate three dimensional turbidity currents. Also some laboratory tests were conducted to study the 3D flow resulting from the release of particle laden density currents on a sloping surface in a channel of freshwater via a sluice gate. Kaolin... 

    Multiscale modeling of fluid turbulence and flocculation in fiber suspensions

    , Article Journal of Applied Physics ; Volume 100, Issue 3 , 2006 ; 00218979 (ISSN) Jafari, A ; Zamankhan, P ; Mousavi, S. M ; Henttinen, K ; Sharif University of Technology
    A mathematically rigorous, multiscale modeling methodology capable of coupling behaviors from the Kolmogorov turbulence scale through the full scale system in which a fiber suspension is flowing is presented. Here the key aspect is adaptive hierarchical modeling. Numerical results are presented focus of which are on fiber floe formation and destruction by hydrodynamic forces in turbulent flows. Specific consideration was given to molecular-dynamics simulations of viscoelastic fibers in which the fluid flow is predicted by a method which is a hybrid between direct numerical simulations and large eddy simulation techniques, and fluid fibrous structure interactions were taken into account. The... 

    Stagnation-point flow of upper-convected maxwell fluids

    , Article International Journal of Non-Linear Mechanics ; Volume 41, Issue 10 , 2006 , Pages 1242-1247 ; 00207462 (ISSN) Sadeghy, K ; Hajibeygi, H ; Taghavi, M ; Sharif University of Technology
    Two-dimensional stagnation-point flow of viscoelastic fluids is studied theoretically assuming that the fluid obeys the upper-convected Maxwell (UCM) model. Boundary-layer theory is used to simplify the equations of motion which are further reduced to a single non-linear third-order ODE using the concept of stream function coupled with the technique of the similarity solution. The equation so obtained was solved using Chebyshev pseudo-spectral collocation-point method. Based on the results obtained in the present work, it is concluded that the well-established but controversial prediction that in stagnation-point flows of viscoelastic fluids the velocity inside the boundary layer may exceed... 

    Meshless solution of 2D fluid flow problems by subdomain variational method using MLPG method with radial basis functions (RBFS)

    , Article 2006 ASME Joint U.S.- European Fluids Engineering Division Summer Meeting, FEDSM2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 1 SYMPOSIA , 2006 , Pages 333-341 ; 0791847500 (ISBN); 9780791847503 (ISBN) Haji Mohammadi, M ; Shamsai, A ; Sharif University of Technology
    This paper deals with the solution of two-dimensional fluid flow problems using the truly meshless Local Petrov-Galerkin (MLPG) method. The present method is a truly meshless method based only on a number of randomly located nodes. Radial basis functions (RBF) are employed for constructing trial functions in the local weighted meshless local Petrov-Galerkin method for two-dimensional transient viscous fluid flow problems. No boundary integration is needed, no element matrix assembly is required and no special treatment is needed to impose the essential boundary conditions due to satisfaction of kronecker delta property in RBFs. Three different radial basis functions (RBFs), i.e.... 

    Numerical modeling of flow over a dam spillway

    , Article 2006 2nd ASME Joint U.S.-European Fluids Engineering Summer Meeting, FEDSM 2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2006 , 2006 ; 0791837831 (ISBN); 9780791837832 (ISBN) Saeedpanah, I ; Shayanfar, M ; Jabbari, E ; Haji Mohammadi, M ; Sharif University of Technology
    Free surface flows are frequently encountered in hydraulic engineering problems including water jets, weirs and around gates. An iterative solution to the incompressible two-dimensional vertical steady Navier-Stokes equations, comprising momentum and continuity equations, is used to solve for the priori unknown free surface, the velocity and the pressure fields. The entire water body is covered by a unstructured finite element grid which is locally refined. The dynamic boundary condition is imposed for the free surface where the pressure vanishes. This procedure is done continuously until the normal velocities components vanish. To overcome numerical errors and oscillations encountering in... 

    Coupled hydro-mechanical analysis of underground gas storage at Sarajeh field, Qom formation, Iran

    , Article Journal of Natural Gas Science and Engineering ; Volume 92 , 2021 ; 18755100 (ISSN) Bakhtiari, M ; Shad, S ; Zivar, D ; Razaghi, N ; Sharif University of Technology
    Elsevier B.V  2021
    Production or injection of fluids from/in an underground storage site causes variations of pore pressure and stress states. These fluctuations significantly affect implications for hydraulic fracturing, wellbore integrity, top surface subsidence and heave, fault-reactivation, and stability of reservoir and caprock. Therefore, in order to keep optimal conditions during the process of gas injection and production, it is of paramount importance to have accurate estimates of the pore pressure. In this investigation, coupled fluid flow and geomechanical simulations, as well as rock mechanical tests, are performed on the Sarajeh field, Iran to investigate the geomechanical behavior of the Sarajeh... 

    Design of a hybrid inertial and magnetophoretic microfluidic device for ctcs separation from blood

    , Article Micromachines ; Volume 12, Issue 8 , 2021 ; 2072666X (ISSN) Nasiri, R ; Shamloo, A ; Akbari, J ; Sharif University of Technology
    MDPI AG  2021
    Circulating tumor cells (CTCs) isolation from a blood sample plays an important role in cancer diagnosis and treatment. Microfluidics offers a great potential for cancer cell separation from the blood. Among the microfluidic-based methods for CTC separation, the inertial method as a passive method and magnetic method as an active method are two efficient well-established methods. Here, we investigated the combination of these two methods to separate CTCs from a blood sample in a single chip. Firstly, numerical simulations were performed to analyze the fluid flow within the proposed channel, and the particle trajectories within the inertial cell separation unit were investigated to... 

    Design of two Inertial-based microfluidic devices for cancer cell separation from Blood: A serpentine inertial device and an integrated inertial and magnetophoretic device

    , Article Chemical Engineering Science ; 2021 ; 00092509 (ISSN) Nasiri, R ; Shamloo, A ; Akbari, J ; Sharif University of Technology
    Elsevier Ltd  2021
    The separation of cancer cells from a heterogeneous biological sample such as blood plays a vital role in cancer study and future treatments. In this paper, we designed and investigated two microfluidic devices for cancer cell separation, including a serpentine inertial device and an integrated inertial-magnetophoretic device. Firstly, numerical modeling was carried out to study the fluid flow, particles’ trajectories in the inertial device. Then the device was fabricated using soft photolithography and suspension of two types of microparticles with the size of 10 and 15 µm were injected into the microchannel separately to investigate the particles’ trajectories and focusing behavior at...