Search for: centrifugation
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    Performance improvement of mixed-flow centrifugal pumps with new impeller shrouds: Numerical and experimental investigations

    , Article Renewable Energy ; Volume 163 , 2021 , Pages 635-648 ; 09601481 (ISSN) Bozorgasareh, H ; Khalesi, J ; Jafari, M ; Gazori, H. O ; Sharif University of Technology
    Elsevier Ltd  2021
    A new impeller configuration with innovatively-designed shrouds is introduced, and its impact on the pressure head and efficiency of the semi-open centrifugal pump is explored using experimental and numerical approaches. The proposed design includes attaching specific plates called bladelets to a semi-open impeller to limit the secondary flows over the blades resulting in an increase in the pump head and efficiency. Hydraulic performance of a centrifugal pump with three different bladelets at angles of 30°, 60°, and 90° is investigated experimentally, and the results are compared to semi-open and closed impellers. The values of pressure head and efficiency of the proposed centrifugal pump... 

    A new detection chamber design on centrifugal microfluidic platform to measure hemoglobin of whole blood

    , Article SLAS Technology ; Volume 26, Issue 4 , 2021 , Pages 392-398 ; 24726303 (ISSN) Mahmodi Arjmand, E ; Saadatmand, M ; Eghbal, M ; Bakhtiari, M. R ; Mehraji, S ; Sharif University of Technology
    SAGE Publications Inc  2021
    Undoubtedly, microfluidics has been a focal point of interdisciplinary science during the last two decades, resulting in many developments in this area. Centrifugal microfluidic platforms have good potential for use in point-of-care devices because they take advantage of some intrinsic forces, most notably centrifugal force, which obviates the need to any external driving forces. Herein, we introduce a newly designed detection chamber for use on microfluidic discs that can be employed as an absorbance readout step in cases where the final solution has a very low viscosity and surface tension. In such situations, our chamber easily eliminates the air bubbles from the final solution without... 

    High-throughput, label-free isolation of white blood cells from whole blood using parallel spiral microchannels with u-shaped cross-section

    , Article Biosensors ; Volume 11, Issue 11 , 2021 ; 20796374 (ISSN) Mehran, A ; Rostami, P ; Saidi, M. S ; Firoozabadi, B ; Kashaninejad, N ; Sharif University of Technology
    MDPI  2021
    Rapid isolation of white blood cells (WBCs) from whole blood is an essential part of any WBC examination platform. However, most conventional cell separation techniques are labor-intensive and low throughput, require large volumes of samples, need extensive cell manipulation, and have low purity. To address these challenges, we report the design and fabrication of a passive, label-free microfluidic device with a unique U-shaped cross-section to separate WBCs from whole blood using hydrodynamic forces that exist in a microchannel with curvilinear geometry. It is shown that the spiral microchannel with a U-shaped cross-section concentrates larger blood cells (e.g., WBCs) in the inner... 

    Performance of elevated energy pile groups with different pile spacing in clay subjected to cyclic non-symmetrical thermal loading

    , Article Renewable Energy ; Volume 172 , 2021 , Pages 998-1012 ; 09601481 (ISSN) Ng, C. W. W ; Farivar, A ; Gomaa, S. M. M. H ; Shakeel, M ; Jafarzadeh, F ; Sharif University of Technology
    Elsevier Ltd  2021
    There is an increasing interest and use of energy foundation worldwide. Full-scale tests, physical model tests at one Earth's gravity and at elevated gravity in a geotechnical centrifuge and numerical simulations have been widely reported in the literature. Almost all studies have focused on single energy piles (EPs) and pile groups subjected to symmetrical thermal loads, although it is not unusual to have energy pile groups stressed by non-symmetrical thermal loads. In this study, a series of non-symmetrical thermal loading centrifuge model tests were conducted in saturated soft clay (OCR = 1.7), which is much vulnerable to temperature changes. The tests aim to investigate the effects of... 

    Theoretical and experimental investigation of design parameter effects on the slip phenomenon and performance of a centrifugal compressor

    , Article Scientia Iranica ; Volume 28, Issue 1 , 2021 , Pages 291-304 ; 10263098 (ISSN) Rajabpour, S ; Hajilouy Benisi, A ; Manzari, M. T ; Sharif University of Technology
    Sharif University of Technology  2021
    Numerous studies have investigated driving equations used to predict the slip factor in centrifugal compressors so far. Inevitably, through these studies, the ow field characteristics have been simplified and the effects of the related parameters have been neglected. The present study, experimentally and numerically, investigates the slip phenomenon in a specific centrifugal compressor with complex blade curves and splitter blades, considering the main effective parameters such as the number of blades, exit angle, etc. To this end, a three-dimensional simulation of the viscous flow field of the compressor via an appropriate turbulence method was performed. In addition, an experimental study... 

    Dna-Rna hybrid (R-loop): From a unified picture of the mammalian telomere to the genome-wide profile

    , Article Cells ; Volume 10, Issue 6 , 2021 ; 20734409 (ISSN) Rassoulzadegan, M ; Sharifi Zarchi, A ; Kianmehr, L ; Sharif University of Technology
    MDPI  2021
    Local three-stranded DNA/RNA hybrid regions of genomes (R-loops) have been detected either by binding of a monoclonal antibody (DRIP assay) or by enzymatic recognition by RNaseH. Such a structure has been postulated for mouse and human telomeres, clearly suggested by the identification of the complementary RNA Telomeric repeat-containing RNA “TERRA”. However, the tremendous disparity in the information obtained with antibody-based technology drove us to investigate a new strategy. Based on the observation that DNA/RNA hybrids in a triplex complex genome co-purify with the double-stranded chromosomal DNA fraction, we developed a direct preparative approach from total protein-free cellular... 

    Numerical study of stiff diaphragm walls used to improve the performance of rocking foundation systems

    , Article Journal of Earthquake Engineering ; Volume 25, Issue 13 , 2021 , Pages 2628-2650 ; 13632469 (ISSN) Sadjadi, M ; Fadaee, M ; Ghannad, M. A ; Jahankhah, H ; Sharif University of Technology
    Taylor and Francis Ltd  2021
    This research explores the effectiveness of the use of stiff diaphragm walls next to a rocking foundation through numerical simulation. This improvement technique is used as a means to increase in subsoil peripheral confinement and reduce rocking-induced settlement. The numerical model was verified by the centrifuge test of rocking shallow foundations on clay under cyclic loading. A parametric study was conducted to explore the effect of three stiff wall shapes on the performance of a rocking system. The general conclusion of the parametric investigation is that the use of stiff diaphragm walls reduced the sinking-dominated settlement response of the rocking system. © 2019 Taylor & Francis... 

    Evaluation of variable permeability model in simulation of seismic behavior of uniform level and gently sloping sand layers

    , Article Earth Sciences Research Journal ; Volume 24, Issue 3 , 2020 , Pages 328-336 Ghassemi, A ; Seyfi, S ; Shahir, H ; Sharif University of Technology
    Universidad Nacional de Colombia  2020
    In this study, a fully coupled dynamic finite element model was employed for numerical simulation of the response of level to gently sloping saturated sand layers subjected to cyclic loading. This model utilized a critical state two-surface-plasticity constitutive model to simulate the cyclic behavior of sandy soil. Moreover, a recently proposed variable permeability function was implemented in the numerical model to reflect the effects of soil permeability variations during the liquefaction phenomenon. The numerical model was validated by simulating a number of well-documented geotechnical centrifuge tests with different relative density of sand, base acceleration time history, and surface... 

    Modeling and simulation of flow and uranium isotopes separation in gas centrifuges using implicit coupled density-based solver in OpenFOAM

    , Article European Journal of Computational Mechanics ; Volume 29, Issue 1 , 2020 , Pages 1-26 Ghazanfari, V ; Salehi, A. A ; Keshtkar, A. R ; Shadman, M. M ; Askari, M. H ; Sharif University of Technology
    River Publishers  2020
    The performance of a gas centrifuge that is used for isotopes separation is dependent on the gas flow inside it. In this study, for modeling the UF6 gas flow, an Implicit Coupled Density-Based (ICDB) solver, was developed in OpenFOAM. To validate the ICDB solver, the gas flow within the rotor in total reflux state was compared with the analytical solution obtained by Onsager model and the numerical solution obtained by the Fluent software. The results showed that the ICDB solver had acceptable accuracy and validity. Also the computational efficiency of Roe, AUSM (Advection Upstream Splitting Method) and AUSM+ up schemes were compared. The results showed AUSM+ up scheme is efficient. Then,... 

    Investigation of the continuum-rarefied flow and isotope separation using a hybrid CFD-DSMC simulation for UF6 in a gas centrifuge

    , Article Annals of Nuclear Energy ; 2020 Ghazanfari, V ; Akbar Salehi, A ; Reza Keshtkar, A ; Mahdi Shadman, M ; Hossein Askari, M ; Sharif University of Technology
    Elsevier Ltd  2020
    UF6 gas flow in the total regions of a rotor with the radius of 0.1 m and the length of 1 m in axisymmetric and steady states was simulated using a new hybrid CFD-DSMC method in the OpenFOAM framework. Implicit coupled density-based scheme was performed for CFD method, and Variable Hard Sphere (VHS) and diffuse model were employed in DSMC method. Also, as an initial estimation, the local Knudsen number was applied to determine the interface location between the continuum-rarefied regions (r = 0.0855 m). Then it was modified (r = 0.084 m) to reduce the computational cost. The comparison results of pure CFD and CFD-DSMC methods illustrated that there were large differences between the flow... 

    Design and simulation of an integrated centrifugal microfluidic device for CTCs separation and cell lysis

    , Article Micromachines ; Volume 11, Issue 7 , July , 2020 Nasiri, R ; Shamloo, A ; Akbari, J ; Tebon, P ; Dokmeci, M. R ; Ahadian, S ; Sharif University of Technology
    MDPI AG  2020
    Separation of circulating tumor cells (CTCs) from blood samples and subsequent DNA extraction from these cells play a crucial role in cancer research and drug discovery. Microfluidics is a versatile technology that has been applied to create niche solutions to biomedical applications, such as cell separation and mixing, droplet generation, bioprinting, and organs on a chip. Centrifugal microfluidic biochips created on compact disks show great potential in processing biological samples for point of care diagnostics. This study investigates the design and numerical simulation of an integrated microfluidic device, including a cell separation unit for isolating CTCs from a blood sample and a... 

    Fluidic barriers in droplet-based centrifugal microfluidics: Generation of multiple emulsions and microspheres

    , Article Sensors and Actuators, B: Chemical ; Volume 311 , May , 2020 Madadelahi, M ; Madou, M. J ; Dorri Nokoorani, Y ; Shamloo, A ; Martinez Chapa, S. O ; Sharif University of Technology
    Elsevier B. V  2020
    Droplet generation is very important in biochemical processes such as cell encapsulation, digital PCR (Polymerase Chain Reaction), and drug delivery. In the present paper, a density-based method called “fluidic barrier” is introduced to produce multiple emulsions on a centrifugal microfluidic platform or Lab-on-a-CD (LOCD). We show that the density and the viscosity of the fluids involved are important parameters for predicting the characteristics of the droplets generated with this method. Moreover, we broadened this concept by using the fluidic barriers to separate reactive chemicals. As a proof of concept, alginate and CaCl2 solutions are separated by an oil barrier to control the... 

    Numerical simulation of mixing and heat transfer in an integrated centrifugal microfluidic system for nested-PCR amplification and gene detection

    , Article Sensors and Actuators, B: Chemical ; Volume 283 , 2019 , Pages 831-841 ; 09254005 (ISSN) Naghdloo, A ; Ghazimirsaeed, E ; Shamloo, A ; Sharif University of Technology
    Elsevier B.V  2019
    Nucleic acid amplification via polymerase chain reaction (PCR) is one of the essential and powerful methods used in a myriad of bio-assays in clinical laboratories. Application of microfluidic devices in biologically-related processes like PCR can result in the usage of less volume of reactant samples and reduce the processing time. By implementing PCR systems on centrifugal microfluidic platforms, automation and portability can be easily achieved. Although several methods have been developed, most of them are still dealing with challenges of the required high processing time. This study presents the numerical simulation of a fully automated PCR system with the goal of enhancing the mixing... 

    Prediction of erosive wear locations in centrifugal compressor using CFD simulation and comparison with experimental model

    , Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 41, Issue 2 , 2019 ; 16785878 (ISSN) Biglarian, M ; MomeniLarimi, M ; Ganji, B ; Ranjbar, A ; Sharif University of Technology
    Springer Verlag  2019
    Erosive wear is one of the efficiency reduction causes in centrifugal compressors. The presence of suspended solid particles in the fluid causes deformations in different parts of the compressor, especially blades of the impeller. Therefore, erosion not only decreases the part lifetime by destruction of blades form, but also increases energy losses. For this reason, specifying the erosion locations and choosing a suitable material have an important effect on optimum functionality of the machine. In this paper, erosion locations of a compressor impeller by using computational fluid dynamics (CFD) in high temperature and pressure are attained and compared with experimental model. The... 

    Design and fabrication of a centrifugal microfluidic disc including septum valve for measuring hemoglobin A1c in human whole blood using immunoturbidimetry method

    , Article Talanta ; Volume 190 , 2018 , Pages 134-139 ; 00399140 (ISSN) Mahmodi Arjmand, E ; Saadatmand, M ; Bakhtiari, M. R ; Eghbal, M ; Sharif University of Technology
    Elsevier B.V  2018
    Diabetes mellitus is a global endemic with a rapidly increasing prevalence in both developing and developed countries. Recently, hemoglobin A1c has been recommended by the American Diabetes Associations as a possible substitute for fasting blood glucose for the diagnosis of diabetes, because it is an indicator of long-term glycemic control. Also, centrifugal microfluidic systems have good potential for use in the point of care testing systems. In this study, a centrifugal microfluidic disc was designed and manufactured to measure hemoglobin A1c in whole blood using an immunoturbidimetry based method. Also, a new passive valve, named septum valve, was presented to precisely control the entry... 

    Newtonian and generalized Newtonian reacting flows in serpentine microchannels: pressure driven and centrifugal microfluidics

    , Article Journal of Non-Newtonian Fluid Mechanics ; Volume 251 , January , 2018 , Pages 88-96 ; 03770257 (ISSN) Madadelahi, M ; Shamloo, A ; Sharif University of Technology
    Elsevier B.V  2018
    This paper presents a comprehensive 3D numerical simulation of reacting flows in micro scale dimension through centrifugal, or Lab-On-a-CD (LOCD), and pressure-driven, or Lab-On-a-Chip (LOC) devices. Three different serpentine channel configurations (rectangular, triangular and sinusoidal) are investigated. In these configurations, two chemical species enter from two inlets and according to an irreversible chemical reaction, start yielding other species. Both Newtonian and generalized Newtonian fluids are considered in the simulations and the results are compared for both LOC and LOCD devices. Besides, the effects of different parameters such as the aspect ratio of channels’ cross section,... 

    Inertial particle focusing in serpentine channels on a centrifugal platform

    , Article Physics of Fluids ; Volume 30, Issue 1 , 2018 ; 10706631 (ISSN) Shamloo, A ; Mashhadian, A ; Sharif University of Technology
    American Institute of Physics Inc  2018
    Inertial particle focusing as a powerful passive method is widely used in diagnostic test devices. It is common to use a curved channel in this approach to achieve particle focusing through balancing of the secondary flow drag force and the inertial lift force. Here, we present a focusing device on a disk based on the interaction of secondary flow drag force, inertial lift force, and centrifugal forces to focus particles. By choosing a channel whose cross section has a low aspect ratio, the mixing effect of the secondary flow becomes negligible. To calculate inertial lift force, which is exerted on the particle from the fluid, the interaction between the fluid and particle is investigated... 

    Thermal performance of rotating closed-loop pulsating heat pipes: experimental investigation and semi-empirical correlation

    , Article International Journal of Thermal Sciences ; Volume 123 , 2018 , Pages 14-26 ; 12900729 (ISSN) Ebrahimi Dehshali, M ; Alhuyi Nazari, M ; Behshad Shafii, M ; Sharif University of Technology
    Elsevier Masson SAS  2018
    A rotating closed loop pulsating heat pipe (RCLPHP) was experimentally investigated as a passive heat sink for rotary equipment cooling. The effects of heat input, rotational speed, filling ratio, and working fluid on the thermal resistance of RCLPHP were studied. Pure water and ethanol were used as working fluids with filling ratios of 30%, 50%, and 70% by volume, and the RCLPHP was tested at four rotational speeds: 200, 400, 600, and 800 rpm. The results showed that the best filling ratio for both water and ethanol is 50% and proved that the RCLPHP is able to work efficiently in a wide range of rotational speed. Moreover, it was observed that at the optimum filling ratio for ethanol and... 

    Design and implementation of an online precise monitoring and performance analysis system for centrifugal pumps

    , Article IEEE Transactions on Industrial Electronics ; 2017 ; 02780046 (ISSN) Emami, S. A ; Emami, M. H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Development of design and production technology of centrifugal pumps for achieving better performance and less energy consumption in these devices has increasingly been taken into consideration. This is due to the fact that centrifugal pumps have an important contribution in industrial applications and energy consumption around the world. Accordingly, the international standards of centrifugal pumps, urge more precise analysis systems for obtaining the performance curves of these pumps. For this reason, a complete, precise and real-time monitoring and performance analysis system for centrifugal pumps is introduced in this paper. The pump characteristics are measured by precise measuring... 

    Analyzing mixing quality in a curved centrifugal micromixer through numerical simulation

    , Article Chemical Engineering and Processing: Process Intensification ; Volume 116 , 2017 , Pages 9-16 ; 02552701 (ISSN) Shamloo, A ; Vatankhah, P ; Akbari, A ; Sharif University of Technology
    Elsevier B.V  2017
    The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over...