Research Paper
Computational Fluid Dynamics (CFD)
Seyed Masoud Vahedi; Mohammad Sadegh Valipour; Filippo de Monte
Abstract
Arterial drug concentration distribution determines local toxicity. The safety issues dealt with Drug-Eluting Stents (DESs) reveal the needs for investigation about the effective factors contributing to fluctuations in arterial drug uptake. The current study focused on the importance of hypertension ...
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Arterial drug concentration distribution determines local toxicity. The safety issues dealt with Drug-Eluting Stents (DESs) reveal the needs for investigation about the effective factors contributing to fluctuations in arterial drug uptake. The current study focused on the importance of hypertension as an important and controversial risk factor among researchers on the efficacy of Heparin-Eluting Stents (HES). For this purpose, the effect of blood pressure is systematically investigated in certain cardiac cycle modes. A comprehensive study is conducted on two classes, pulsatile (time-dependent), to have a more realistic simulation, and non-pulsatile (time-independent) blood flow, each one in four modes. The governing equations applied to drug release dynamics are obtained based on porous media theory. The equations are solved numerically using Finite Volume Method (FVM). Results reveal that there is a significant difference when the plasma flow considered and when it is neglected (regardless of time dependency). Moreover, the concentration level is more decreased in pulsatile blood flow rather than the non-pulsatile blood flow, although the penetration depth for pressure and concentration are nearly 20% and 5% of the wall thickness, respectively. In other words, the mass experienced by the arterial wall is lower in pulsatile blood flow in comparison to non-pulsatile blood flow. As a consequence, the risk of toxicity is declined as the blood pressure increases. Also, it can be seen that the polymer is diffusion-dominated so that no significant changes in the release characteristics are observed in the presence of the plasma filtration.
Research Paper
Manufacturing Processes
Ebrahim Haghani; Ahmad Gheysarian; Mohammad Honarpisheh
Abstract
One of the methods for making prototypes is incremental forming process. In this method, the forming tool, performs a pre-programmed movement by the CNC machine and runs the desired path. This modernization process is used in the automotive, aerospace, military, medical and other industries. One of the ...
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One of the methods for making prototypes is incremental forming process. In this method, the forming tool, performs a pre-programmed movement by the CNC machine and runs the desired path. This modernization process is used in the automotive, aerospace, military, medical and other industries. One of the most influential parameters in this process is forming tool. This parameter is effective in forming forces, surface roughness, sheet formability and thickness distribution. In this study, the forming tool was investigated and rotating geometry tool was compared with a rigid tool. Also, the effects of step down, feed rate and spindle speed were investigated on the forming force, surface roughness and thickness distribution by comparing mentioned forming tools. The results indicate that the forming forces, sheet surface quality and thickness changes increase with increasing step down and feed rate. Using the rotary tools improves the forming forces, surface roughness and thickness distribution rather than the non-rotating tool.
Research Paper
Computational Fluid Dynamics (CFD)
S. Harimi; Azam Marjani
Abstract
The present work deals with heat transfer characteristics as well as fluid flow patterns in laminar flow regime for a circular cylinder with six control rods arranged in equilateral triangular geometries. The computations have been carried out by a finite volume approach using the overset grid method. ...
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The present work deals with heat transfer characteristics as well as fluid flow patterns in laminar flow regime for a circular cylinder with six control rods arranged in equilateral triangular geometries. The computations have been carried out by a finite volume approach using the overset grid method. The unsteady flow at Re= 200 and Pr= 0.7 and 7.0 was examined. The effect of the control rods on suppression of the fluid forces applied on a main cylinder has been investigated by numerical solution of the Navier-Stokes equations. Based on the results obtained, the arrangement employed in this study indicated the significant performance in reducing the oscillatory force coefficients of the primary cylinder. Except for some gap ratios, it is indicated that both drag and lift coefficients are much lower than that for a single cylinder. Moreover, forced convection heat transfer was calculated using local and mean Nusselt numbers at the surface of the cylinders. The instantaneous streamlines, the vortices and isothermal contours were presented in order to analyze the temperature field and flow field around the cylinders.
Research Paper
Fluid Mechanics
Pedram Hanafizadeh; Amirmohammad Sattari; Seyed Erfan Hosseinidoost; Morteza Molaei; Mehdi Ashjaee
Abstract
Detecting bubble in two-phase flow has been a basic issue in two-phase flow systems. A new method for measuring the frequency of bubble formation is presented in this paper. For this purpose, an electronic device was designed and constructed which works based on a change in intensity of laser beam. For ...
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Detecting bubble in two-phase flow has been a basic issue in two-phase flow systems. A new method for measuring the frequency of bubble formation is presented in this paper. For this purpose, an electronic device was designed and constructed which works based on a change in intensity of laser beam. For this purpose, continues light beam is embedded just above the needle, which is received by a phototransistor. When bubbles go through this light beam, make a deviation on that and change the intensity of light. So, the electrical resistance between two bases of phototransistor changes and this variation sensed by an electronic board. According to the number of interruption and duration time, the frequency of bubble formation can be calculated. Liquid and gas phases of present work are water and air respectively. Tests are performed in constant liquid height (60 mm above the needle), constant needle diameter (1.6 mm), and gas flow rates between 50 to 1200 ml/hr. Also, three other methods utilized for measuring bubble frequency: image processing (IP), numerical modeling, and theoretical model. Results show that with increasing flow rate of the gas phase frequency of formation increases approximately in a linear manner. Validation of methods with IP method shows that the new device has very good accuracy for measuring bubble formation frequency. So because of the simplicity of using and low cost, it can be a superseded method of image processing.
Research Paper
Plasticity
Sadjad Pirmohammad; Sobhan Esmaeili-Marzdashti; Arameh Eyvazian
Abstract
In this article, crashworthiness performance and crushing behavior of tapered structures with four internal reinforcing plates under axial and oblique dynamic loadings have been investigated. These structures have a tapered form with five cross sections of square, hexagonal, octagonal, decagon and circular ...
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In this article, crashworthiness performance and crushing behavior of tapered structures with four internal reinforcing plates under axial and oblique dynamic loadings have been investigated. These structures have a tapered form with five cross sections of square, hexagonal, octagonal, decagon and circular shape. In the first step, finite element simulations performed in LS-DYNA were validated by comparing with experimental data. The code generated in LS-DYNA was then used to investigate energy absorption behavior of the tapered structures. Response surface methodology and historical data design technique were employed to optimize the cross section perimeter (tapered angle) of the tapered structures by considering two conflicting crashworthiness criteria including EA (energy absorption) and PCF (peak crushing force). The optimization results showed that the optimal tapered angle enhanced by increasing the number of cross section sides (or number of corners). Then, the optimized tapered structures with different cross-sections were compared with each other using a ranking method called TOPSIS to introduce the most efficient energy absorber. The decagonal structure was finally found to be the best energy absorber.
Research Paper
Computational Fluid Dynamics (CFD)
Brahim Rostane; Aliane Khaled; Said Abboudi
Abstract
The aim of our study is to analyze the impact of insertion holes in the middle of obstacles on the flow around a surface-mounted cube, In order to do this; we studied four configurations of obstacles in a channel with a Reynods number based on obstacle height ReH = 40000. The hexahedral structured meshes ...
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The aim of our study is to analyze the impact of insertion holes in the middle of obstacles on the flow around a surface-mounted cube, In order to do this; we studied four configurations of obstacles in a channel with a Reynods number based on obstacle height ReH = 40000. The hexahedral structured meshes were used to solve the fluid dynamics equations .The finite volume method are employed to solve the governing equations using the ANSYS CFX code and the turbulence model k-ω SST. The streamwise velocity profiles, the Time-averaged streamlines, the turbulence kinetic energy and the drag coefficient are presented. The results showed the appearance of a second vortex behind obstacles with hole from diameter D/H=0.2. The turbulence kinetic energy was greater on top of the obstacle, it was more intense for the obstacle without hole, this intensity decreased as the hole diameter increased. The drag coefficient was improved only for the case D/H=0.32
Research Paper
Fluid Mechanics
Kvenu Reddy; M. Gnaneswara Reddy
Abstract
In this paper, we analyze the thermal radiation and chemical reaction impacts on MHD peristaltic motion of the Eyring-Powell fluid through a porous medium in a channel with compliant walls under slip conditions for velocity, temperature, and concentration. Assumptions of a long wave length and low Reynolds ...
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In this paper, we analyze the thermal radiation and chemical reaction impacts on MHD peristaltic motion of the Eyring-Powell fluid through a porous medium in a channel with compliant walls under slip conditions for velocity, temperature, and concentration. Assumptions of a long wave length and low Reynolds number are considered. The modeled equations are computed by using the perturbation method. The resulting non-linear system is solved for the stream function, velocity, temperature, concentration, skin-friction coefficient, heat transfer coefficient and mass transfer coefficient. The flow quantities are examined for various parameters. Temperature depresses with an enhancee in the radiation parameter, while the opposite effect is observed for the concentration. The fluid concentration enhances and depresses with generative and destructive chemical reaction respectively. The trapped bolus whose size diminishes as the Powel-Eyring parameter increases while it enhances as another Powell fluid parameter increases. The trapped bolus whose size rises when Darcy number enhances.
Research Paper
Computational Fluid Dynamics (CFD)
Mohammad Saeed Sharifi; Miralam Mahdi; Karim Maghsoudi Mehraban
Abstract
The shape of the air flow in the interior is heavily influenced by the air distribution system and the way air enters and exits. By numerically simulating flow by computational fluid dynamics, one can determine the flow pattern and temperature distribution and, with the help of the results, provide an ...
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The shape of the air flow in the interior is heavily influenced by the air distribution system and the way air enters and exits. By numerically simulating flow by computational fluid dynamics, one can determine the flow pattern and temperature distribution and, with the help of the results, provide an optimal design of the air conditioning system. In this study, a chamber was first constructed and the temperature distribution inside it was measured. There was a fan installed at the back of the chamber for drainage. At the chamber entrance, three inlet for entering the flow were considered. The air from the middle inlet was heated by a heater. To prevent heat loss, the body of the enclosure was insulated. Several temperature sensors were installed at certain positions of the chamber for temperature measurement. Using Fluent software, the model of a full-sized chamber was created. Meshing is a hybrid and was used as a boundary layer Mesh. The inlet and outlet temperature of the chamber and the air output rates as boundary conditions were used in the simulation. Numerical analysis for K-ε and K-ω turbulence models was performed and different wall conditions were investigated. The numerical simulation results were in good agreement with the measurement results. Using the K-ε turbulence model with a scalable wall function had a better accuracy than other models. Changes in velocity and temperature were presented in graphs and contours at different positions of the compartment.
Research Paper
Fluid Mechanics
Neetu Kanaujia; Uday Singh Rajput
Abstract
Unsteady flow with magneto-hydrodynamics and heat generation through porous medium past an impulsively started vertical plate with constant wall temperature and mass diffusion is considered here. The effect studied is a combination of Hall current and chemical reaction. The motivation behind this study ...
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Unsteady flow with magneto-hydrodynamics and heat generation through porous medium past an impulsively started vertical plate with constant wall temperature and mass diffusion is considered here. The effect studied is a combination of Hall current and chemical reaction. The motivation behind this study is the applications of such kind of problems in industry. In many industrial applications electrically conducting fluid is subjected to magnetic field. The fluid is passed through porous medium. The flow may be on a plate. There may be substance on the plate which may cause chemical reaction. The solution of flow model studied here is obtained by using Laplace transform method. The respective profiles have been drawn for velocity. The numerical data have been obtained using latest software techniques available. The profiles have been analyzed and discussed. The values of Nusselt number, Sherwood number, and drag on plate have been tabulated for analysis. The findings have been summarized in conclusion section.
Research Paper
Perturbation Technique
Abbas Kosarineia
Abstract
The entropy generation analysis of non-Newtonian fluid in rotational flow between two concentric cylinders is examined when the outer cylinder is fixed and the inner cylinder is revolved with a constant angular speed. The viscosity of non-Newtonian fluid is considered at the same time interdependent ...
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The entropy generation analysis of non-Newtonian fluid in rotational flow between two concentric cylinders is examined when the outer cylinder is fixed and the inner cylinder is revolved with a constant angular speed. The viscosity of non-Newtonian fluid is considered at the same time interdependent on temperature and shear rate. The Nahme law and Carreau equation are used to modeling dependence of viscosity on temperature and shear rate, respectively. The viscous dissipation term is adding elaboration to the formerly highly associate set of governing motion and energy equations. The perturbation method has been applied for the highly nonlinear governing equations of base flow and found an approximate solution for narrowed gap limit. The effect of characteristic parameter such as Brinkman number and Deborah number on the entropy generation analysis is investigated. The overall entropy generation number decays in the radial direction from rotating inner cylinder to stationary outer cylinder. The results show that overall rate of entropy generation enhances within flow domain as increasing in Brinkman number. It, however, declines with enhancing Deborah number. The reason for this is very clear, the pseudo plastic fluid between concentric cylinders is heated as Brinkman number increases due to frictional dissipation and it is cooled as Deborah number increases which is due to the elasticity behavior of the fluid. Therefore, to minimize entropy need to be controlled Brinkman number and Deborah number.
Research Paper
Vibration
RAJASEKHARA REDDY MUTRA; Srinivas J
Abstract
Turbochargers are most widely used in automotive, marine and locomotive applications with diesel engines. To increase the engine performance nowadays, in aerospace applications also turbochargers are used. Mostly the turbocharger rotors are commonly supported over the fluid film bearings. With the operation, ...
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Turbochargers are most widely used in automotive, marine and locomotive applications with diesel engines. To increase the engine performance nowadays, in aerospace applications also turbochargers are used. Mostly the turbocharger rotors are commonly supported over the fluid film bearings. With the operation, lubricant properties continuously alter leading to different load bearing capacities. This paper deals with the diagnostic approach for prediction of shaft unbalance and the bearing parameters using the measured frequency responses at the bearing locations. After validating the natural frequencies of the rotor finite element model with experimental analysis, the response histories of the rotor are recorded. The influence of the parameters such as bearing clearance, oil viscosity and casing stiffness on the unbalance response is studied. By considering three levels each for shaft unbalance and oil viscosity, the output data in terms of four statistical parameters of equivalent Hilbert envelopes in the frequency domain are measured. The data is inversely trained using Radial Basis Function (RBF) neural network model to predict the unbalance and oil viscosity indices from given output response characteristics. The outputs of the RBF model are validated thoroughly. This approach finds changes in the rotor bearing parameters from the measured responses in a dynamic manner. The results indicate that there is an appreciable effect of lubricant viscosity at two different temperatures compared to other parameters within the operating speed range. The identification methodology using the neural network is quite fast and reliable
Research Paper
Composite Materials
Erfan Mirshekari; Arash Reza
Abstract
In this work, transient dynamic stress concentration in a hybrid composite laminate subjected to a sudden internal crack is examined. It is assumed that all fibers lie in one direction and the applied load acts along direction of fibers. Two types arrangements are considered for the fiber; square and ...
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In this work, transient dynamic stress concentration in a hybrid composite laminate subjected to a sudden internal crack is examined. It is assumed that all fibers lie in one direction and the applied load acts along direction of fibers. Two types arrangements are considered for the fiber; square and hexagonal arrangement. Using shear lag model, equilibrium equations are deduced and upon proper application of initial and boundary conditions, the complete field equations are obtained using finite difference method. The results of dynamic effect of fiber breakage on stress concentration are well examined in presence of a second type fiber. These results are compared to those of their static values in both models. The effect of surface cracks on stress concentration, as a result of fiber breakage, is also examined. The values of dynamic stress concentrations is deduced and compared to those of a lamina. Also, the peak stress concentration during transition time for fibers to reach static equilibrium is calculated and compared with those of static values.
