Showing 33 results for Newtonian
Volume 10, Issue 2 (7-2019)
Abstract
Aims: The study of the behavior of active suspended fluid introduced a new topic for a wide range of applications such as reactors, microfluidic pumps, cultivating surfaces and antibacterial surfaces. The motility of bacterial suspension has generated a shear force (Hydrodynamic interaction) across the cells, which has an effect on the fluid viscosity. In this study, shear rheometer was used to evaluate the viscosity behavior of Escherichia coli (E. coli) in a water/polymer environment as a function of bacteria concentration and shear rate.
Materials and Methods: In the experimental study, the activity of E. coli was evaluated by choosing the constant concentration (0.01g/ml) and molecular weight of polyvinylpyrrolidone (360KDa). Also, the surface tensions of E. coli, Acetobacter xylinum, and S. aureus solutions were calculated using Wilhelmy test.
Findings: Activity of E. coli suspension results the lower viscosity comparing with the bacteria-free solution. The relative viscosities of the solutions were analyzed in a wide range of shear rates and bacterial concentrations. At a low shear rate up to1S-1, the relative viscosity was found to be less than a unit value (Less than water). Also, due to the collective motility break up to smaller parts at high shear rates, the viscosity increased. The critical volume fraction was defined in determined bacterial concentration (0.8v/v) to analyze the collective movement of bacteria. The interfacial tension was reduced by bacteria presence of three different stain types that confirmed the effect of bacteria activity on the flow behavior.
Conclusion: The activity of E. coli bacteria makes it easy for fluid to flow at low shear rates. The viscosity reduction of active particle has a potential to demonstrate a variety of novel applications when a reduced energy level is needed.
Reza Rooki, Mahmood Norouzi, , ,
Volume 13, Issue 7 (10-2013)
Abstract
Accurate estimation of the pressure losses for non-Newtonian drilling fluids inside annulus is quite important to determine pump rates and select mud pump systems during wellbore drilling operation. The aim of this study is to simulate non-Newtonian (power law and Herschel-Bulkly) foam flow in underbalanced drilling condition through wellbore annulus using finite volume method. The effect of various operational parameters on pressure loss such as fluid rheology, foam fluid velocity, foam quality, drillpipe rotation and wellbore eccentricity, have been considered. Simulation results were compared with the previously published experimental data. The agreement was close with a relative error less than 5%. The results of numerical method are closer to experimental data for Herschel Bulkly model for foam fluid. Also, the results of numerical method, showed that pressure drop increases with increasing the foam fluid velocity and quality and it decreases with increasing eccentricity, but drillpipe rotation don’t have noticeable effect on pressure drop.
Mohammad Sefid, Ehsan Izadpanah,
Volume 13, Issue 14 (3-2014)
Abstract
The incompressible Newtonian and non-Newtonian fluid flow in a tube with disk insert is studied numerically using finite volume and boundary fitted coordinate method. The non-Newtonian fluid is time independent purely viscous that is simulated by the power law model. The effects of power law index, thickness, aspect ratio, Prandtl number and the distance between insert tubes on heat transfer, pressure drop and overall enhancement ratio (OER) are investigated for the Reynolds numbers 500, 1000 and 1500. The results show that the effect of power law index on pressure drop and overall enhancement ratio is more than the other parameters.
Mohammad Mohsen Shahmardan, Mahmood Norouzi, Amir Naqhikhani,
Volume 14, Issue 6 (9-2014)
Abstract
In this paper, numerical solution of non-Newtonian fluid flow through a channel with a cavity is studied. Carreau-Yasuda non-Newtonian model which represent dependence of stress on shear rate well is used and the effect of n index of model on attribute of flow is considered. Governing equations are discretized using finite difference method on staggered mesh and the form of allocating flow parameters on staggered mesh is based on marker and cell method. For dependence between continuity and momentum equations, artificial compressibility method is used. Numerical results express that with decrease of n index, the developing length is increased and the velocity in center of channel and pressure drop of flow are decreased.
Mohammad Hadi Sedaghat, Mohammad Mohsen Shahmardan, Mohsen Nazari, Mahmood Norouzi,
Volume 14, Issue 8 (11-2014)
Abstract
In this paper, the immersed boundary-lattice Boltzmann method has been employed to simulate non-Newtonian flow around curve boundaries. The pressure base lattice Boltzmann equations have been used to solve the Eulerian domain to estimate proper pressure gradient in the Poiseuille flow. In addition Immersed boundary method (IBM) utilizes a discrete set of force density is also used to represent the effect of boundary on flow domain. In addition to simulate the real physical dominate problem and study the right effects of non-Newtonian fluid properties, scaling parameters have been introduced to notice the relationship between physical and lattice variables. At First, the capability of present method is examined for simulating the power-law fluid flow around a confined circular cylinder and the results show good agreement with previous study. In the following, the power-law fluid flow around elliptical cylinder in a channel is investigated for three aspect ratios eta=1,1.5,2 and for 5
Ahmad Reza Haghighi, Mohammad Shahbazi Asl,
Volume 14, Issue 10 (1-2015)
Abstract
In the present study the problem of a two-layered model for an unsteady and pulsatile flow of blood through a stenosed artery is numerically simulated. The model consists of a core layer of suspension of erythrocytes and a peripheral plasma layer. The core is assumed to be represented using a micropolar fluid and the plasma layer using a Newtonian fluid. The artery is considered to be elastic and the geometry of the stenosis is taken as time-dependent, however a comparison has been made with the rigid ones. The shape of the stenosis in the arterial lumen is chosen to be axially non-symmetric but radially symmetric in order to improve resemblance to the in-vivo situations. By applying a suitable coordinate transformation, the stenosed artery turns into a rectangular and rigid artery. The Navier-Stokes equations of motion of the blood flow, subjected to a pulsatile pressure gradient are solved numerically using the finite difference scheme. Dynamical characteristics of the blood flow such as the velocity profile, the volumetric flow rate and the resistance to flow are obtained and the effects of the wall motion and the severity of the stenosis on these flow characteristics are discussed. The results are found to be in good agreement with the available analytical results.
Mahmood Norouzi, Behrooz Zare Vamerzani, Bahar Firoozabadi,
Volume 14, Issue 13 (3-2015)
Abstract
In this paper, steady creeping motion of non-Newtonian falling drop through a viscous fluid is investigated analytically. Here, the Upper Convected Maxwell model (UCM) is used for drop phase and Newtonian model is considered for external fluid. The perturbation technique is used to solve both exterior and interior flows and Deborah number that indicated the elastic effect is considered as the perturbation parameter. The present solution is derived up to second order of perturbation parameter so the present solution has a suitable accuracy for drops that made from dilute polymeric solutions. We found that the Newtonian drop has a spherical shape during the creeping motion but the non-Newtonian drop loses this shape and takes an oblate form. By increasing the elastic effect, a dimple at the rear end of the drop is created and developed. Here, it is shown that the present results have more agreement with experimental data than the previous analytical studies. The origin of drop deformation is also considered and it is proofed that the elastic property of drop phase creates a concentrated normal stress at the rear end of the drop that causes the dimple shape in this region.
Mojtaba Yazdani, Mehdi Tale Masouleh, Milad Hasanvand, Iman Yahyapour, Mahmoud Ghafouri Tabrizi,
Volume 14, Issue 13 (3-2015)
Abstract
This paper aims at obtaining the dynamic models of twoconstraint-over parallel mechanisms (PM) with 3-DOF (degree of freedom) and 4-DOF, the Tripteron and the Quadrupteron. The reasoning used in this paper is based on a judicious concept in detaching the whole mechanism into several subsystems and consecutive synergies between kinematic analysis, Lagrangian and Newtonian approaches. In this regard, the mechanisms are made equivalent to some subsystems and the equations of kinematic constraints are derived for all subsystems. Afterwards upon resorting to Lagrangian approach and blending it with the latter kinematic relations, the dynamic model of each leg in task space is obtained. The dynamic model of the end- effector is written in virtue of Newton-Euler’s approach where yields to three differential equations. Finally, the problem leads to a system of 12 equations for the Tripteron and 16 equations for the Quadrupteron, which do not need usaul simplifications in such problems. For the sake of comparison, the results are put into contrast by the one obtained with a dynamic analyzer software. The results obtained by both approaches are coherent which affirms the correctness of the proposed algorithm.
Mousa Mohammadpourfard,
Volume 15, Issue 1 (3-2015)
Abstract
This Study presents a numerical investigation of the hydro-thermal behavior of a Non-Newtonian ferrofluid (non-Newtonian base fluid and 4% Vol. Fe3O4) in a rectangular vertical duct in the presence of different magnetic fields, using two-phase mixture model, power-law model, and control volume technique. Considering the electrical conductivity of the base fluid, in addition to the ferrohydrodynamics principles, the magnetohydrodynamics principles have also been taken into account. To study the effects of non-Newtonian base fluid using power-law model, assuming the same flow consistency index with viscosity of Newtonian fluid, two different power law indexes (i.e., n=0.8 and 0.6), have been investigated and the results have been compared with that of Newtonian ones (i.e., n=1). Three cases for magnetic field have been considered to study mixed convection of the ferrofluid: non-uniform axial field, uniform transverse field and another case when both fields are applied simultaneously. The results indicate that the overall influence of magnetic fields on Nusselt number and friction factor is similar to the Newtonian case, although, by decreasing the power law index, the effect of axial field on velocity profile, Nusselt number and friction factor become more significant. Moreover, the results indicate that electrical conductivity has a significant effect on the behavior of ferrofluid and cannot be neglected and also negative gradient axial field and uniform transverse field act similarly and enhance both the Nusselt number and the friction factor, while positive gradient axial field decreases them.
Amir Torabi, Saleh Akbarzadeh, Mohammadreza Salimpour,
Volume 15, Issue 4 (6-2015)
Abstract
One of the challenging problems of tribology is cam and follower elastohydrodynamic lubrication due to the simultaneous effect of various lubrication mechanisms. These mechanisms are transient, squeeze film, elastic deformation of contacting surfaces and variation of lubricant properties with pressure. In this paper, besides studying the mentioned factors, the effect of using a non-Newtonian lubricant such as grease is numerically investigated. The lubrication governing equations and Oswald’s grease behavior equation have been discretized using finite difference technique. The system of equation has been solved via Multi-Grid method which is an advanced iterative method in solving system of partial differential equations. The results are showed for Newtonian oil comparing to grease for different cam rotational speed. Also different grease behaviors are investigated. The results are verified by a comparison to the results obtained using the famous Newton-Raphson method. Finding shows that the minimum lubricant thickness as well as the maximum pressures is lower when using grease compared to the case that a Newtonian lubricant is used. In the case of Newtonian lubricant, increasing the speed results in an increase in the lubricant film thickness but it is shown that the speed does not affect the lubricant thickness in the case of non-Newtonian lubricant.
Mehdi Ramezanpour, Mehdi Maerefat, Manijhe Mokhtari-Dizaji,
Volume 15, Issue 5 (7-2015)
Abstract
Compliance mismatch is one of the reasons of the coronary artery bypass graft (CABG) failure. The purpose of this study is to investigate the effect of compliance mismatch on the End to Side bypass graft. In order to model non Newtonian behavior of the blood flow, the Carreau–Yasuda model was employed and the graft and artery wall was assumed to be isotropic and modeled as a linearly elastic. In this study also the effects of blood rheology and wall distensibility on the wall shear stress distribution and velocity profile were investigated. The results of the simulation show that the maximum deformation occurs in the critical position of graft-artery junction and compliance mismatch cause smaller wall deformation in comparison to the cases in which the materials of the graft and artery are the same which leads to a higher intramural shear stress in graft-artery junction. The anastomotic wall deforms in a way that always tends to separate the graft and artery. Wall shear stress distribution on the bed centerline and the toe of the bypass graft indicates that the differences between the homologous and non-homologous material case are visible only when the internal pressure is lower than the external one. In the distal location of the artery after the toe of the anastomotic, the values of wall shear stress in the homologous material case are lower than the non-homologous material one.
Vahid Esfahanian, Iman Rahbari, Mohammad Hossein Mortazavi,
Volume 15, Issue 5 (7-2015)
Abstract
Non-Newtonian fluid flows experience turbulent regime in some industrial applications. Several approaches have been proposed for numerical simulation of turbulent flows that each one has specific features. RANS turbulence models have reasonable computational costs, while include several sources of uncertainties affecting simulation results. In addition, developed RANS models for non-Newtonian fluids are modified versions of available models for Newtonian fluids, therefore, they cannot provide reliable estimation for viscoplastic stress term. On the contrary, DNS delivers accurate results but with high computational costs. Consequently, use of DNS data for estimation of uncertainty in RANS models can provide better decision making for engineers based on RANS results. In the present study, a turbulence model based on for power-law non-Newtonian fluid is developed and employed for simulation of flow in a pipe. Then, an efficient method is proposed for quantification of available model-form uncertainty. Moreover, it is assumed that uncertainties originating from various sources are combined together in calculation of Reynolds stress as well as viscoplastic stress. Deviation of the stresses, computed using RANS turbulence model, from DNS data are modeled through Gaussian Random Field. Thereafter, Karhunen-Loeve expansion is employed for uncertainty propagation in simulation process. Finally, the effects of these uncertainties on RANS results are shown in velocity field demonstrating the fact that the presented approach is accurate enough for statistical modeling of model-form uncertainty in RANS turbulence models.
Afrasiab Raisi,
Volume 15, Issue 11 (1-2016)
Abstract
In this study, the natural convection heat transfer is numerically examined in a square enclosure filled with a non-Newtonia power-law fluid. Two fixed temperature baffles are mounted on the left wall of the enclosure. The left wall of the enclosure and the baffles installed on it, are at a constant temperature of T_h and the right wall of the enclosure is at a constant temperature of T_c, while its horizontal walls are thermally insulated. The governing equations for the power-law fluid flow are solved with the numerical finite difference method based on the control volume formulation and SIMPLE algorithm. The study investigates the effects of relevant parameters such as the Rayleigh number (〖10〗^3≤Ra≤〖10〗^6), the power-law index (0.8≤n≤1.4), the baffles length (0≤B≤0.5) and the baffles distance from each other (0.1≤D≤0.8) on flow and temperature fields and the rate of heat transfer. The results show that an increase in Rayleigh number, particularly when n
Hamed Eshgarf, Masoud Afrand, Mohammad Hemmat Esfe,
Volume 16, Issue 3 (5-2016)
Abstract
In this paper, the effects of temperature and nanoparticles volume fraction on the viscosity of non-Newtonian hybrid nanofluid, containing water and ethylene glycol as a base fluid and multi-walled carbon nanotubes (MWCNTs) and silica (SiO2) as additives, have been investigated experimentally. The measurements have been carried out in temperatures range of 27.5°C - 50°C by using a Brookfield DV-I PRIME digital Viscometer for different shear rates. The stable and homogeneous samples, with the solid volume fractions of 0.0625%, 0.25%, 0.5%, 0.75%, 1%, 1.5% and 2%, were prepared by dispersing the equal volumes of dry MWCNTs and SiO2 nanoparticles in a specified amount of the binary mixture of water/EG (50:50 %vol.). The measurement results at different shear rates showed that the base fluid possessed Newtonian behavior, while all nanofluid samples exhibit a pseudoplastic rheological behavior with a power law index of less than unity (n<1). Moreover, the consistency index and power law index have been obtained by accurate curve-fitting for all nanofluid samples. The results also revealed that the apparent viscosity generally increases with an increase in the solid volume fraction and decreases with temperature rising.
Sima Baheri Islami, Marzieh Khezerloo, Reza Gharraei,
Volume 16, Issue 5 (7-2016)
Abstract
Since the majority of fluids in engineering and biologic applications are non-Newtonian, the study on mixing of non-Newtonian fluids is very important. Secondary flows are used in curved micromixers to improve the mixing of fluids. In this study, a numerical study was performed on the mixing of non-Newtonian fluids in curved micromixers using Open source CFD code of OpenFOAM. The flow was assumed three-dimensional, steady and incompressible and Reynolds numbers were between 0.1-300. Also, water and CMC solution were used for simulation of Newtonian and non-Newtonian fluid flows, respectively. The effect of Reynolds number, power-law viscosity parameters and micromixer geometry on mixing index and non-dimensional pressure drop was studied and results were compared with those of the straight channel micromixer. The results showed that the mixing index decreased by decreasing the power law index. The mixing index was high for shear thinning flows in micromixers with sharp turns. Also, by increasing the Reynolds number, and therefore velocity, centrifugal force effects increased and mixing improved. Simultaneous investigation of mixing index and pressure drop showed that for low Reynolds numbers and small power law indexes micromixer-b had better performance.
Majid Siavashi, Behrooz Zare Vamerzani,
Volume 16, Issue 7 (9-2016)
Abstract
In this paper, the non-Newtonian immiscible two-phase polymer flow in a petroleum reservoir has been investigated numerically. The fluid flow in a porous medium is simulated as a compressible flow. The Carreau-Yasuda constitutive equation is employed as the model of non-Newtonian fluid. The IMPES method is used for numerical simulation, in which the pressure equation is discretized and solved by an implicit approach and the saturation equation is solved by an explicit method. Results reveal that zero-shear rate viscosity has a high impact on the sweep efficiency of the reservoir and also controls the channeling and viscous fingering effects. In addition increasing the viscosity of non-Newtonian fluid improves cumulative oil production and diminishes the viscous fingering phenomenon caused by injected fluid. The relaxation time of Carreau-Yasuda fluid, which is the elastic characteristic of the non-Newtonian fluid, for low permeability values cannot influence flow characteristics inside the reservoir, however for higher permeability values its effect becomes more sensible. Increasing the injection rates leads to the increase of fluid production, while the injection rate has an optimum range to reach the optimum oil production. In addition, the effect of variation of the injected fluid properties on the polymer breakthrough time has been investigated and results presented.
Roozbeh Aayani, Azadeh Shahidian, Majid Ghassemi,
Volume 16, Issue 7 (9-2016)
Abstract
Ultrasonic waves have variety of applications in bio field. The most important applications are diagnosis and treatment of diseases, drug delivery, cell separation and cell study. Passing ultrasonic waves through tissues and organs, which creates heat, bubble, stress and vibration, can result in chemical reactions, physical and biological changes. What exacerbated the researchers' scientific activities in this area is reducing the harmful effects and increasing the usefulness of this beneficial tool. In current research, the interaction of two nonlinear phenomena, acoustic streaming due to passing ultrasonic waves through bio-fluid and non-Newtonian viscosity is studied numerically. Taking into account nonlinear effects of ultrasonic field, continuity, momentum and state equations are used. In this paper, parametric effects of wall impedance, inlet flow velocity and non-Newtonian viscosity models on acoustic streaming are investigated. Results indicate influence of inlet speed on acoustic streaming velocity magnitude and its ineffectiveness on acoustic streaming profile. By increasing wall impedance, acoustic streaming magnitude decreases. This reduction is more intensive for non-Newtonian fluid. Considering non-Newtonian viscosity model for bio-fluid leads to velocity changes near boundaries, while it has less influence at domain middle.
Hosein Sadeghi, Ali Akbar Dehghan, Mohammad Sefid,
Volume 16, Issue 12 (2-2017)
Abstract
The cavity problem always has been considered as a classic and fundamental problem. Specific materials like Bingham viscoplastic which is sort of Non-newtonian fluids shows resistance in a certain range of stress, calling yield stress, and almost acts like rigid body in this limited area. In case of increase applied stress, flows like fluid. Considering heat transfer in this type of material and investigate it, yield stress and viscosity variations with temperature as in practice we face will not be far-fetched. In the present work the numerical solution of the problem of Bingham material inside lid-driven cavity, investigating fluid flow and heat transfer in view of the changes in material properties has been done and results have shown with change in dimensionless numbers and parameters of Re=10-1000, Bn=1-2000, Pr=0.01-100 and E=5000-50000. In this study, using the finite volume method to discretize governing equations and the use of collocated grid, effect of viscosity and yield stress dependence to temperature compared with independence mode and then distribution of horizontal and vertical components of velocity, yield areas and flow inside cavity, center of vortex and then heat transfer due to the stream lines next to side walls, have been analyzed.
Ghassem Heidarinejad, Hamidreza Babakhani, Alireza Rostami,
Volume 16, Issue 12 (2-2017)
Abstract
Stenosis in coronary artery and the other cardiac diseases such as Atherosclerosis is major cause of death in the world. Numerical simulation of blood flow can help medical evaluation to curve arteries have been stenosis. The purpose of this paper is to find the effect of arteries stenosis on the hemodynamic parameters by simulation of blood flow in LAD branch of coronary artery. The computational domain has been determined from CT images of human heart. In this study, blood is assumed to be homogeneous, Newtonian and the blood flow assumed to be pulsatile. In order to more realistic modeling of flow and pressure, Seven–element lumped model has been used in coronary artery outlet, in order words the 0D and 3D models are coupled together. The results indicate that the calculated flow wave is the minimum in systolic phase and maximum in diastolic phase in coronary artery, in contrast with Aorta. On the other hand, by increasing the stenosis percent from 30 to 60 percent, no significant drop of flow has been observed in the state of rest, and it has been validated with experimental results. The results indicate that with increasing stenosis, time average wall shear stress in the stenosis region increases, while it decreases before and after the stenosis, also the investigation of oscillating shear index indicates that in the state of 60% of stenosis and in the main downstream branch, it has the maximum value, that is indicative of the presence of turbulent flow in this region.
Alireza Aghaei, Hossein Khorasanizadeh, Ghanbar Ali Sheikhzadeh,
Volume 16, Issue 12 (2-2017)
Abstract
In this experimental study dynamic viscosity of hybrid engine oil (5w-50)-Cuo-MWCNT nanofluid for volume fractions of 0.05, 0.1, 0.25, 0.5, 0.75 and 1 percent of nanoparticles for temperatures of 5, 15, 25, 35, 45, 55 °C has been measured. This hybrid nanofluid has been prepared utilizing the two steps method. For viscosity measurement, the Brookfield viscometer has been used. The experimental measurments indicate that by increasing volume fraction of nanoparticles the viscosity increases; also by increasing the temperature the viscosity decreases. Based on the experimental results the maximum and minimum viscosity increases with volume fraction increase from 0.05 to 1 at a constant tempearture are 35.52 and 12.92 percent, respectively, relating to 55 and 15 °C. Measurement of the nanofluid viscosity with different volume fractions, shear rates and tempeartures indicate its Newtonian behavior. A new temperature and volume fraction dependent viscosity correlation, developed in this study to be used in numerical simulations, shows very good agreement with experimental results.
