Loading...
Search for:
shear-stress
0.011 seconds
Total 207 records
Continuum Modeling of Biological Growth of Atheroma in Coronary
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor)
Abstract
Atherosclerosis is a vascular disorder caused by inflammation of the arterial wall. This inflammation leads to the accumulations of low-density lipoprotein (LDL) cholesterol, monocytes, macrophages and fat-laden foam cells at the site of inflammation, often referred to as plaque formation. This work uses a mathematical model for simulating the deposition of atheroma plaque in coronary arteries. In this study, the effect of time average wall shear stress (TAWSS), oscillatory shear index (OSI), non-Newtonian characteristics of blood and variable hematocrit values on the occurrence of atherosclerosis in a three-dimensional coronary artery was numerically investigated. Simulations was conducted...
Experimental and numerical investigations of radial flow compressor component losses
, Article Journal of Mechanical Science and Technology ; Vol. 28, issue. 6 , 2014 , p. 2189-2196 ; Hajilouy-Benisi, A ; Abolfazl Moussavi-Torshizi, S ; Movahhedy, M.R ; Durali, M ; Sharif University of Technology
Abstract
This research numerically and experimentally investigates a small turbocharger radial flow compressor with a vane-less diffuser and volute. The geometry of the compressor is obtained via component scanning, through which a 3D model is prepared. The flow inside this model is numerically analyzed by using a Navier-Stokes solver with a shear-stress transport turbulence model. The characteristic curves of the compressor and the contributions of its components to total pressure drop are acquired by measuring the static and total pressures at different cross sections of the compressor. Numerical results are verified with the experimental test results. The model results exhibit good agreement with...
Herschel-Bulkley rheological parameters of lightweight colloidal gas aphron (CGA) based fluids
, Article Chemical Engineering Research and Design ; Volume 93 , 2015 , Pages 21-29 ; 02638762 (ISSN) ; Arabloo, M ; Ghazanfari, M. H ; Rashtchian, D ; Sharif University of Technology
Institution of Chemical Engineers
2015
Abstract
The proper understanding of rheological characteristics of CGA based fluids is of crucial importance in determining the performance of the fluid, in order to maintain the most effective fluid properties for safe, efficient, and economical drilling operation. This paper presents a concise investigation on the effect of concentration of the three main components of a novel environmentally friendly lightweight CGA based drilling fluid, i.e., xanthan gum biopolymer, starch, and biosurfactant, to the Herschel-Bulkley rheological model parameters. The three parameters of Herschel-Bulkley model, i.e., yield stress, fluid consistency, and fluid flow index were calculated by fitting the experimental...
The measurement of suction stress characteristic curve for a highly collapsible loessial soil
, Article Geotechnical Special Publication, 17 March 2015 through 21 March 2015 ; Volume GSP 256 , 2015 , Pages 2482-2491 ; 08950563 (ISSN) ; 9780784479087 (ISBN) ; Khosravi, A ; Ghazizadeh, S ; Anderson, J. B ; Iskander, M ; Suleiman, M. T ; Laefer, D. F ; Sharif University of Technology
American Society of Civil Engineers (ASCE)
2015
Abstract
This paper describes results of an advanced suction controlled triaxial test device on a loessial soil in an attempt to define the constitutive relationship between suction stress and matric suction (suction stress characteristic curve) for highly collapsible soils. Due to the presence of void spaces with different degrees of collapse potential within the soil matrix, the collapse phenomenon in loess is believed to be a continuous-stepwise reduction in volume rather than a sudden drop during wetting. Due to this unique volume change behavior, the definition of the suction stress characteristic curve for loess may require a soil-specific experimental testing approach capable of making precise...
Selection and simulation of a proper microfluidic for hepatocyte culture
, Article 2015 22nd Iranian Conference on Biomedical Engineering, ICBME 2015, 25 November 2015 through 28 November 2015 ; 2015 , Pages 65-69 ; 9781467393515 (ISBN) ; Firoozabadi, B ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
The advent of microfluidics as suitable environments for culturing cells is associated with some challenges as shear stresses applied on the cells. Moreover, among all factors needed for cell viability, feeding hepatocytes with adequate oxygen is of great importance due to their high demand for oxygen compared the other cell types. In this paper three kinds of geometries has been studied in order that shear stresses would be in allowed range and provision of hepatocytes with sufficient oxygen concentrations has been ensured as well. In addition to supplying hepatocytes with oxygen, the range of its concentration has been adjusted in physiologic value so that it would be practical for further...
Mechanical properties of graphene oxide: A molecular dynamics study
, Article Fullerenes Nanotubes and Carbon Nanostructures ; Volume 24, Issue 9 , 2016 , Pages 594-603 ; 1536383X (ISSN) ; Sarkari Khorrami, M ; Sharif University of Technology
Taylor and Francis Inc
Abstract
In this paper, the mechanical properties of graphene oxide are obtained using the molecular dynamics analysis, including the ultimate stress, Young modulus, shear modulus and elastic constants, and the results are compared with those of pristine graphene. It is observed that the increase of oxide agents (–O) and (–OH) leads to the increase of C–C bond length at each hexagonal lattice and as a result, alter the mechanical properties of the graphene sheet. It is shown that the elasticity modulus and ultimate tensile strength of graphene oxides (–O) and (–OH) decrease significantly causing the failure behavior of graphene sheet changes from the brittle to ductile. The results of shear loading...
Numerical simulation of the behavior of toroidal and spheroidal multicellular aggregates in microfluidic devices with microwell and U-shaped barrier
, Article Micromachines ; Volume 8, Issue 12 , 2017 ; 2072666X (ISSN) ; Saidi, M. S ; Kashaninejad, N ; Vadivelu, R ; Nguyen, N. T ; Sharif University of Technology
Abstract
A microfluidic system provides an excellent platform for cellular studies. Most importantly, a three-dimensional (3D) cell culture model reconstructs more accurately the in vivo microenvironment of tissue. Accordingly, microfluidic 3D cell culture devices could be ideal candidates for in vitro cell culture platforms. In this paper, two types of 3D cellular aggregates, i.e., toroid and spheroid, are numerically studied. The studies are carried out for microfluidic systems containing U-shaped barrier as well as microwell structure. For the first time, we obtain oxygen and glucose concentration distributions inside a toroid aggregate as well as the shear stress on its surface and compare its...
Graphene oxide in generation of nanobubbles using controllable microvortices of jet flows
, Article Carbon ; Volume 138 , 2018 , Pages 8-17 ; 00086223 (ISSN) ; Akhavan, O ; Madaah Hosseini, H. R ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Spontaneous generation of nanobubbles (NBs) was developed by using a controllable platform of superfast microvortices, based on turbulent jet flows in the presence of graphene oxide (GO) sheets. Very high energy dissipation rates through discharging warm water into cold N2 aqueous solutions resulted in creation of micro/submicro-vortices. Shear stresses in these domains generated gas local supersaturations, leading to the formation of high concentration (∼109 mL−1) of stable NBs. Introducing GO sheets into the microvortex system resulted in effective manipulation of NBs by providing energetically favorable sites for prompt heterogeneous nucleation as well as stronger shear rate fluctuations....
Spheroids-on-a-chip: recent advances and design considerations in microfluidic platforms for spheroid formation and culture
, Article Sensors and Actuators, B: Chemical ; Volume 263 , 15 June , 2018 , Pages 151-176 ; 09254005 (ISSN) ; Kashaninejad, N ; Ebrahimi Warkiani, M ; Lock, J. G ; Moghadas, H ; Firoozabadi, B ; Saidi, M. S ; Nguyen, N. T ; Sharif University of Technology
Elsevier B.V
2018
Abstract
A cell spheroid is a three-dimensional (3D) aggregation of cells. Synthetic, in-vitro spheroids provide similar metabolism, proliferation, and species concentration gradients to those found in-vivo. For instance, cancer cell spheroids have been demonstrated to mimic in-vivo tumor microenvironments, and are thus suitable for in-vitro drug screening. The first part of this paper discusses the latest microfluidic designs for spheroid formation and culture, comparing their strategies and efficacy. The most recent microfluidic techniques for spheroid formation utilize emulsion, microwells, U-shaped microstructures, or digital microfluidics. The engineering aspects underpinning spheroid formation...
A study on the mobility of [formula presented] edge dislocation in low-carbon α-Fe and its interactions with damage cascade: on picosecond time scale using molecular dynamics simulations
, Article Journal of Nuclear Materials ; Volume 527 , 2019 ; 00223115 (ISSN) ; Feghhi, A. H ; Samadfam, M ; Sharif University of Technology
Elsevier B.V
2019
Abstract
Molecular dynamics simulations were used to propose a closed-form expression for the mobility of the [Formula presented] edge dislocation in low-carbon α-Fe (up to 0.1 at.% C) at temperatures of 300, 400 and 500 K and applied shear stresses of 10–100 MPa. Considering this parameter helps us to understand the effect of damage cascade on the dislocation mobility. The results confirmed that the point defect clusters at the thermal spike stage of the cascade (that they can be considered as an unstable precipitation-like phase), the distance of damage cascade relative to the center of the dislocation core and forming carbon-vacancy (C–V) complexes are some rather stronger obstacles for movement...
Numerical investigations of hepatic spheroids metabolic reactions in a perfusion bioreactor
, Article Frontiers in Bioengineering and Biotechnology ; Volume 7 , 2019 ; 22964185 (ISSN) ; Firoozabadi, B ; Firoozbakhsh, K ; Sharif University of Technology
Frontiers Media S.A
2019
Abstract
Miniaturized culture systems of hepatic cells are emerging as a strong tool facilitating studies related to liver diseases and drug discovery. However, the experimental optimization of various parameters involved in the operation of these systems is time-consuming and expensive. Hence, developing numerical tools predicting the function of such systems can significantly reduce the associated cost. In this paper, a perfusion-based three dimensional (3D) bioreactor comprising encapsulated human liver hepatocellular carcinoma (HepG2) spheroids are analyzed. The flow and mass transfer equations for oxygen as well as different metabolites such as albumin, glucose, glutamine, ammonia, and urea were...
A pressure-based algorithm for internal compressible turbulent flows through a geometrical singularity
, Article Numerical Heat Transfer, Part B: Fundamentals ; Volume 75, Issue 2 , 2019 , Pages 127-143 ; 10407790 (ISSN) ; Shafiei Ghazani, A ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
Compressible turbulent flow through the abrupt enlargement in pipes is studied numerically by means of Advection Upstream Splitting Method (AUSM+-up). In low Mach numbers, a pressure correction equation of elliptic type is derived. This equation is compatible with the nature of governing equations and retrieves hyperbolic characteristic at higher Mach numbers. It is shown that the proposed numerical algorithm is computationally more efficient than the preconditioned density-based methods. The flow parameters such as reattachment length, pressure loss coefficient and wall shear stress are predicted. It is found that the loss coefficient of the compressible flow rises drastically with...
High precision invasive FFR, low-cost invasive iFR, or non-invasive CFR?: optimum assessment of coronary artery stenosis based on the patient-specific computational models
, Article International Journal for Numerical Methods in Biomedical Engineering ; Volume 36, Issue 10 , 2020 ; Nikmaneshi, M. R ; Firoozabadi, B ; Pakravan, H. A ; Ahmadi Tafti, S. H ; Afshin, H ; Sharif University of Technology
Wiley-Blackwell
2020
Abstract
The objective of this paper is to apply computational fluid dynamic (CFD) as a complementary tool for clinical tests to not only predict the present and future status of left coronary artery stenosis but also to evaluate some clinical hypotheses. In order to assess the present status of the coronary artery stenosis severity, and thereby selecting the most appropriate type of treatment for each patient, fractional flow reserve (FFR), instantaneous wave free-ratio (iFR), and coronary flow reserve (CFR) are calculated. To examine FFR, iFR, and CFR results, the effect of geometric features of stenoses, including diameter reduction (%), lesion length (LL), and minimum lumen diameter (MLD), is...
Experimental study of stress anisotropy and noncoaxiality of dense sand subjected to monotonic and cyclic loading
, Article Transportation Geotechnics ; Volume 23 , 2020 ; Jafarzadeh, F ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The noncoaxiality of the principal stress direction and plastic principal strain increment has been broadly recognized as an influencing parameter for design of soil structures. Here we performed a series of systematic hollow cylinder experiments to study the effects of stress anisotropy on the noncoaxiality of dense Babolsar and Toyoura sands. A total of 25 undrained torsional shear tests were carried out under constant mean confining pressure, and fixed principal stress directions, α. We investigated the stress-strain behavior of dense sands for different α-directions, and cyclic stress ratio, CSR, under monotonic and cyclic loading conditions. The results show that the noncoaxiality value...
A fully explicit three-step SPH algorithm for simulation of non-Newtonian fluid flow
, Article International Journal of Numerical Methods for Heat and Fluid Flow ; Volume 17, Issue 7 , 2007 , Pages 715-735 ; 09615539 (ISSN) ; Taghizadeh Manzari, M ; Kazemzadeh Hannani, S ; Sharif University of Technology
2007
Abstract
Purpose - This paper sets out to present a fully explicit smoothed particle hydrodynamics (SPH) method to solve non-Newtonian fluid flow problems. Design/methodology/approach - The governing equations are momentum equations along with the continuity equation which are described in a Lagrangian framework. A new treatment similar to that used in Eulerian formulations is applied to viscous terms, which facilitates the implementation of various inelastic non-Newtonian models. This approach utilizes the exact forms of the shear strain rate tensor and its second principal invariant to calculate the shear stress tensor. Three constitutive laws including power-law, Bingham-plastic and...
Effect of stitter speed and aeration rate on the production of glucose oxidase by Aspergillus niger
, Article Journal of Biological Sciences ; Volume 7, Issue 2 , 2007 , Pages 270-275 ; 17273048 (ISSN) ; Sarrafzadeh, M. H ; Alemzadeh, I ; Vosoughi, M ; Sharif University of Technology
Asian Network for Scientific Information
2007
Abstract
Dissolved oxygen tension and shear stress as two very important factors in fungal fermentation were studied in the batch cultures of Aspergillus niger. The intention was to maximize the total activity of glucose oxidase produced in a 5-1 bench-top bioreactor. 300 rpm found to be optimum for enzyme production, however in higher mixing rates higher growth was achieved. The maximum activity of glucose oxidase was obtained in 1.5 vvm while the best aeration rate for growth was 2 vvm. Glucose oxidase with the activity of 548 U mL-1 was produced in 1.5 vvm and 300 rpm as the optimum conditions. © 2007 Asian Network for Scientific Information
Effect of unsteady friction models and friction-loss integration on transient pipe flow
, Article Scientia Iranica ; Volume 13, Issue 3 , 2006 , Pages 245-254 ; 10263098 (ISSN) ; Firoozabadi, B ; Sharif University of Technology
Sharif University of Technology
2006
Abstract
When velocities in the piping systems change rapidly, spectacular accidents occur, due to tranient-state pressures where the elastic properties of the pipe and liquid must be considered. This hydraulic transient is commonly known as water hammer. A conventional widely-used technique for analyzing this phenomenon is the Method Of Characteristic (MOC), in which, by introducing the characteristic lines, two ordinary differential equations, in lieu of the governing partial differential equations, are produced. In the undisturbed form of the equations, the energy dissipation is evaluated by the steady or quasi-steady approximation. But, there is experimental and theoretical evidence which shows...
The numerical investigation of the heat transport in the nanofluids under the impacts of magnetic field: applications in industrial zone
, Article Mathematical Problems in Engineering ; Volume 2021 , 2021 ; 1024123X (ISSN) ; Khan, U ; Ahmed, N ; Mohyud-Din, S. T ; Khan, I ; Fayz-Al-Asad, M ; Sharif University of Technology
Hindawi Limited
2021
Abstract
The dynamics of the nanofluid flow between two plates that are placed parallel to each other is of huge interest due to its numerous applications in different industries. Keeping in view the significance of such flow, investigation of the heat transfer in the Cu-H2O nanofluid is conducted between parallel rotating plates. For more significant results of the study, the squeezing effects are incorporated over the plates that are electrically conducting. The nondimensional flow model is then treated analytically (VPM), and the results are sketched against the preeminent flow parameters. The remarkable heat transfer in the nanofluid is noticed against the Eckert and Prandtl numbers, whereas the...
Simulation analysis of MHD hybrid Cu-Al2O3/H2O nanofluid flow with heat generation through a porous media
, Article International Journal of Energy Research ; Volume 45, Issue 13 , 2021 , Pages 19165-19179 ; 0363907X (ISSN) ; Ahmad, S ; Nisar, K. S ; Faridi, A. A ; Ashraf, M ; Sharif University of Technology
John Wiley and Sons Ltd
2021
Abstract
Hybrid nanoliquids comprise of better physical strength, mechanical resistance, thermal conductivity, and chemical stability as equated to individual nanoliquids. The present work investigates the MHD laminar flow, containing hybrid nanoparticles, with heat transfer phenomenon over a stretching sheet immersed in a porous medium. The effect of induced magnetic field has also been taken into account. The flow model PDEs are rehabilitated into ordinary ones using a persuasive tool of similarity variables. The analogous system of dimensionless equations alongside the boundary conditions is numerically treated with the Successive-Over-Relaxation (SOR) technique. Flow and heat transfer aspects of...
The numerical investigation of the heat transport in the nanofluids under the impacts of magnetic field: applications in industrial zone
, Article Mathematical Problems in Engineering ; Volume 2021 , 2021 ; 1024123X (ISSN) ; Khan, U ; Ahmed, N ; Mohyud Din, S. T ; Khan, I ; Fayz Al Asad, M ; Sharif University of Technology
Hindawi Limited
2021
Abstract
The dynamics of the nanofluid flow between two plates that are placed parallel to each other is of huge interest due to its numerous applications in different industries. Keeping in view the significance of such flow, investigation of the heat transfer in the Cu-H2O nanofluid is conducted between parallel rotating plates. For more significant results of the study, the squeezing effects are incorporated over the plates that are electrically conducting. The nondimensional flow model is then treated analytically (VPM), and the results are sketched against the preeminent flow parameters. The remarkable heat transfer in the nanofluid is noticed against the Eckert and Prandtl numbers, whereas the...