In the present work, the shock train structure in a convergent-divergent nozzle investigated usin... more In the present work, the shock train structure in a convergent-divergent nozzle investigated using large eddy simulation (LES) methodology based on different subgrid models, including Smagorinsky-Lilly (SL), Wall-Adapting Local Eddy-Viscosity (WALE) and Algebraic Wall-Modeled LES (WMLES) as well as various analytical equations. For gaining a distinct illustration of shock-wave structures, shadowgraph contours are applied to analyze structures of fine flow. The simulated results are obtained at the same geometrical and boundary conditions used in the available experimental data to provide a rational validation. The results of different subgrid models are shown that the WMLES produces more accurate results than SL and WALE models. Thereupon, an investigation of the influence of convergency length and discontinuity of nozzle wall temperature on physics of flow for controlling the shock behavior is carried out. The results show that the minimum wall pressure as well as the maximum flow Mach number increase as the convergency length rises. In addition, by growth in discontinuous wall temperature, the minimum wall pressure and the maximum flow Mach number reduce.
Encapsulation of solid particles and liquid agents in a liquid shell is of exceptional interest i... more Encapsulation of solid particles and liquid agents in a liquid shell is of exceptional interest in biotechnological, chemical and pharmaceutical fields such as personalized medicine, fluidized catalytic cracking, wire fabrication, catalytic reactions. Looking at the interaction between liquid drop and solid particles, we can study the special, ideal case of spherical drops impacting solid spheres, in order to understand the basic phenomena and the effect of the physical variables on the spreading behavior. Considering the importance of dynamics of drop-particle collision, which directly affects the quality of film deposition during encapsulation, various aspects of drop impact on dry solid spherical surfaces are still lacking in the existing literature. The cases are studied with a 3D level-set method implemented in a standard finite-element-based solver platform. The impact Weber number, the size ratio (ratio of spherical particle diameter to droplet diameter), and the surface cont...
Objective(s): One applications of nanotechnology is in the area of medicine which is called nanom... more Objective(s): One applications of nanotechnology is in the area of medicine which is called nanomedicine. Primary instruments in nanomedicine can help us to detect diseases and used for drug delivery to inaccessible areas of human tissues. An important issue in simulating the motion of nanoparticles is modeling blood flow as a Newtonian or non-Newtonian fluid. Sometimes blood flow is simulated as a Newtonian fluid but actually blood has nature of non-Newtonian fluid. Simulation of targeted drug delivery and motion of nanoparticles in the blood flow as Newtonian and non-Newtonian fluid flow is investigated in this paperMaterials and Methods: In this paper, the blood flow is modeled as both Newtonian and non-Newtonian fluid and the effects of each case on the motion of nanoparticles in blood flow and targeted drug delivery is investigated. The flow is modeled with finite volume method. The particle modeled with discrete phase model.Results: Cross, Herschel-Bulkley and Power-law model...
The effects of plasma injection upon MILD combustion of a mixture of methane and hydrogen are inv... more The effects of plasma injection upon MILD combustion of a mixture of methane and hydrogen are investigated numerically. The injected plasma includes the flow of a highly air-diluted methane including C2H2, C2H4, C2H6, CH, CH2, CH3, CO, and CO2. The results show that among all the constitutes of plasma, CH3 is the most effective in improving the characteristics of MILD combustion. Injection of this radical leads to the occurrence of reactions at a closer distance to the burner inlet and thus provides longer time for completion of combustion. Further, mass fractions of OH, CH2O, and HCO are considerably affected by the injections of CH3, indicating structural modifications of the reacting flow. Importantly, as Reynolds number of the plasma flow increases, the volume and width of the flame decrease, while the formations of prompt and thermal NOx are intensified. However, injection of CH3, as plasma, reduces the emission of thermal NOx.
This paper examines the effects of swirl hot co-flow on the combustion behavior of a moderate or ... more This paper examines the effects of swirl hot co-flow on the combustion behavior of a moderate or intense low oxygen dilution (MILD) burner fueled by a mixture of methane and hydrogen. Toward this goal, the realizable k-ɛ turbulence model, GRI. 2.11 reaction mechanism, and the discrete ordinates radiation model are incorporated into a computational modeling of the reactive flow. The numerical results are, first, favorably compared against the existing experimental data. Subsequently, a number of swirl co-flows are implemented, and structures of the resultant reactive flows are investigated systematically. The outcomes indicate that increasing the swirl velocity leads to the reduction of ignition delay and significantly enhances the reaction completion. The analysis of the spatial distribution of hydroxyl and formyl (OH and HCO) radicals reveals that swirling MILD combustion radially extends the reaction zone in comparison with the conventional MILD combustion. Yet, it reduces the len...
In the present study, the numerical analysis of blade tip geometry effect on the performance of a... more In the present study, the numerical analysis of blade tip geometry effect on the performance of a single-stage axial compressor has been the focus of attention. The studied geometries included a rotor with variable tip clearance. For the first model, the tip clearance increases as it moves toward the blade trailing edge. The tip clearance of the second model reduces as it approaches the trailing edge, whereas in the third model, the tip clearance remains constant. The results indicated that the tip clearance of the first sample, as the worst tip clearance case, creates a 10% reduction in the stall margin with respect to the third standard model, and the second sample tip clearance brings about a stall margin reduction of 4% efficiency with respect to the third standard model. Then, the effect of blade tip clearance geometry on outlet flow angle of the rotor was inspected. The results showed that in the first model, the outlet flow angle has the largest deviation than the third standard model and the second model performance places somewhere between the two other tip clearance geometries. Also evident from the result is that taking advantage of the variable blade tip clearance is not an appropriate method for improving compressor performance.
In the current study, the influence of blade tip clearance in different stages of a three-stage c... more In the current study, the influence of blade tip clearance in different stages of a three-stage compressor is investigated. Performance diagrams of compressor were verified against experiment when there is no change in the tip clearance, after which the effect of tip clearance for the cases, 1, 1.5 and 2 mm, in the first, second and third stages of rotor was studied. The results indicated that the impact of tip clearance increase did not have any effect on choked flow rate value in the first and second stages, and only the change in the third stage tip clearance reduced the choked flow rate. For the same tip clearance value, the highest compressor performance loss occurs in the case of applying the tip clearance in the third stage, which is also the final stage and is highly sensitive to tip clearance changes. Moreover, modifying the tip clearance is effective on the flow angle in the trailing edge and as the tip clearance increases, the same thing happens about the flow angle. The maximum value of flow angle changes by modifying the tip clearance belongs to the third stage of the compressor.
A comprehensive investigation of acoustic power level in a moderate or intense low oxygen dilutio... more A comprehensive investigation of acoustic power level in a moderate or intense low oxygen dilution in a jet-in-hot-coflow under various working conditions.
In the present paper, the performance of INVELOX wind turbine (IWT) in Sistan plain, as a low win... more In the present paper, the performance of INVELOX wind turbine (IWT) in Sistan plain, as a low wind speed region, is investigated by a finite volume code and field tests. At first, the numerical results are compared with available experimental data and it is found that the numerical method is consistent with experimental data. Afterward, the performance of various working conditions of IWT (such as assemble height) at Zabol plain, Iran, is investigated. It was revealed that by increasing the assemble height from 10 to 40 m, the output power rises by 87.5%, while the power acoustic level increases by 39.3%. Moreover, the feasibility of using the IWT in a day is examined based on wind day speed obtained by a statistical study in Sistan plain from 1997-2012. Furthermore, in order to increase the efficiency of IWT, a new structure is suggested. The results indicated that by using a two-storey INVELOX turbine, the output power increases up to 44% which indicates that adding a storey to the device is effective to reach a higher performance while the maintenance cost is not different from common INVELOX Turbine system.
Magnetic drug targeting (MDT) and magnetic-based drug/cargo delivery are emerging treatment metho... more Magnetic drug targeting (MDT) and magnetic-based drug/cargo delivery are emerging treatment methods which attracting the attention of many researchers for curing different cancers and artery diseases such as atherosclerosis. Herein, computational studies are accomplished by utilizing magnetic approaches for cancer and artery atherosclerosis drug delivery, including nanomagnetic drug delivery and magnetic-based drug/cargo delivery. For the first time, the four-layer structural model of the artery tissue and its porosity parameters are modeled in this study which enables the interaction of particles with the tissue walls in blood flow. The effects of parameters, including magnetic field strength (MFS), magnet size, particle size, the initial position of particles, and the relative magnetic permeability of particles, on the efficacy of MDT through the artery walls are characterized. The magnetic particle penetration into artery layers and fibrous cap (the covering layer over the inflamed part of the artery) is further simulated. The MDT in healthy and diseased arteries demonstrates that some of the particles stuck in these tissues due to the collision of particles or blood flow deviation in the vicinity of the inflamed part of the artery. Therefore the geometry of artery and porosity of its layers should be considered to show the real interaction of particles with the artery walls. Also, the results show that increasing the particles/drug/cargo size and MFS leads to more particles/drug/cargo retention within the tissue. The present work provides insights into the decisive factors in arterial MDT with an obvious impact on locoregional cancer treatment, tissue engineering, and regenerative medicine.
Langmuir : the ACS journal of surfaces and colloids, Jan 17, 2018
The spreading and rebound patterns of low-viscous droplets upon impacting spherical solid surface... more The spreading and rebound patterns of low-viscous droplets upon impacting spherical solid surfaces are investigated numerically. The studied cases consider a droplet impinging onto hydrophobic and superhydrophobic surfaces with various parameters varied throughout the study, and their effects on the postimpingement behavior are discussed. These parameters include impact Weber number (through varying the surface tension and impingement velocity), the size ratio of the droplet to the solid surface, and the surface contact angle. According to the findings, the maximum spreading diameter increases with the impact velocity, with an increase of the sphere diameter, with a lower surface wettability, and with a lower surface tension. Typical outcomes of the impact include (1) complete rebound, (2) splash, and (3) a final deposition stage after a series of spreading and recoiling phases. Finally, a novel, practical model is proposed, which can reasonably predict the maximum deformation of lo...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2017
In the present study, characteristics of leaky dielectric droplets in electric fields are investi... more In the present study, characteristics of leaky dielectric droplets in electric fields are investigated numerically. In order to validate the numerical method, deformation of a leaky dielectric droplet in an electric field is studied and the numerical results are compared to Taylor theoretical model. After that, the effects of electrical parameters such as electric permittivity, conductivity, electric field strength, and physical parameters such as initial distance and size of droplets on the electrocoalescence are examined. Moreover, behaviors of non-Newtonian droplets in the electric field are surveyed to elucidate the underlying physics. According to the results, pseudoplastic droplets have more deformations in an electric field than Newtonian and dilatant ones, and they also have faster electrocoalescence.
In the present work, three-dimensional computational fluid dynamics analysis is employed to study... more In the present work, three-dimensional computational fluid dynamics analysis is employed to study the droplet dynamics of Newtonian and non-Newtonian droplets impinging on a hot surface under various impact conditions. The Navier–Stokes equations for unsteady, incompressible, and viscous fluid flow are solved using a control volume method. The volume-of-fluid (VOF) technique is also used to track the free-surface of the liquid. The effect of viscosity, density and surface tension on droplet dynamics is evaluated considering their dependence of temperature. The results indicate that the temperature dependence of the both Newtonian and non-Newtonian physicochemical liquid properties must be considered to obtain better agreement of the numerical results with experimental data. After ensuring the accuracy of the numerical methodology, the internal behavior of the droplets is examined, which is shown that the receding velocity of the non-Newtonian droplet is slower than the Newtonian one.
International Journal of Computational Fluid Dynamics, 2017
Curvature effect on droplet impacting onto hydrophobic and superhydrophobic spheres Droplet impac... more Curvature effect on droplet impacting onto hydrophobic and superhydrophobic spheres Droplet impact on hydrophobic and superhydrophobic solid surfaces finds numerous applications, while the wide range of the parameters affecting its outcome necessitate a thorough study to reveal the underlying physics. Specific applications are related to the drop impact upon curved surfaces, such as microencapsulation in fluidized beds. Three-dimensional numerical simulations by applying Level-Set Method have been performed to investigate the water droplet impact on curved and flat hydrophobic and superhydrophobic substrates. Parameters such as the impact Weber number, the surface curvature and the equilibrium contact angle have been varied in order to assess their effects on the dynamics of the impact process. After providing a strong validation, it is found that impact on spherical surfaces generally presents a higher area of liquid to be in contact with the substrate with respect to the case of flat surfaces, when all other impact conditions are the same.
In the present study, the behaviors of Newtonian and shear-thinning non-Newtonian droplets imping... more In the present study, the behaviors of Newtonian and shear-thinning non-Newtonian droplets impinging on heated hydrophilic and hydrophobic surfaces have been investigated numerically using Ansys-Fluent. In this context, the volume-of-fluid technique is applied to track the free-surface of the liquid, and variable time-step is also utilized to control the Courant number. Furthermore, we have considered the dependence of viscosity, density and surface tension on temperature during the simulation. The results are compared to available experimental data at the same conditions, such as boundary conditions. The results demonstrate that there is a good agreement between the obtained results and the experimental trends, concerning normalized diameter profiles at various Weber numbers. Therefore, the focus of the present study is an assessment of the effects of variations in Weber number, contact angle and surface temperature for Newtonian and non-Newtonian liquids on dynamics behavior of droplet in collision with hydrophobic and hydrophilic surfaces. The results represent that the behaviors of Newtonian and non-Newtonian droplets are totally different, indicating the droplet sensitivity to the working parameters.
In the present work, the physics of a three-dimensional shock train in a convergent-divergent noz... more In the present work, the physics of a three-dimensional shock train in a convergent-divergent nozzle is numerically investigated. In this regards, the Ansys-Fluent Software with Algebraic Wall-Modeled Large-Eddy Simulation (WMLES) is used. To estimate precision and errors accumulation we used the Smirinov’s method; fine flow structures are obtained via Laplacian of density called shadowgraph and the shock parameter is defined as multiplication of flow Mach number by the normalized pressure gradient, in which shock wave structures are visible distinctly. The results are compared with the experimental data of Weiss et al. [Experiments in Fluids 49(2) (2010) 355–365], in the same conditions including geometry, boundary conditions, etc. The results show that there is good agreement with experimental trends concerning wall pressure and centerline Mach number profiles. Therefore, the focus of the present study is an assessment of various flow control methods to change the shock structures...
ASME 2009 7th International Conference on Nanochannels, Microchannels and Minichannels, 2009
The past decade has seen tremendous growth in areas of micro-and nano-fluidics, and MEMs flow con... more The past decade has seen tremendous growth in areas of micro-and nano-fluidics, and MEMs flow control. Nowadays, there is considerable interest in micro-and nano/technologies consisting of small structures in contact with liquid media. By increasing the motivations of using miniaturized devices such as MEMS and NEMS and inventing new methods of their manufacturing, the inspirations of their study and analysis have been increased more and more. One of the most important characteristics of these devices ...
ASME 2009 7th International Conference on Nanochannels, Microchannels and Minichannels, 2009
By entering technology to the area of micro and nano scales, the design and fabrication of miniat... more By entering technology to the area of micro and nano scales, the design and fabrication of miniaturized instruments such as microelectronic devices, MEMS, NEMS and..., become very desirable. Many of these devices deal with flow field in micro-and nano-channels. By decreasing the dimensions of channels, the influence of surface effects becomes prominent and cannot be ignored. One of the most charismatic categories of these phenomena is elecrokinetic effect which can result in electroosmotic flow field (EOF) that has many ...
Theoretical and Computational Fluid Dynamics, 2012
Operational state of many miniaturized devices deals with flow field in microchannels. Pressuredr... more Operational state of many miniaturized devices deals with flow field in microchannels. Pressuredriven flow (PDF) and electroosmotic flow (EOF) can be recognized as the two most important types of the flow field in such channels. EOF has many advantages in comparison with PDF, such as being vibration free and not requiring any external mechanical pumps or moving parts. However, the disadvantages of this type of flow such as Joule heating, electrophoresis demixing, and not being suitable for mobile devices must be taken into consideration carefully. By using mixed electroosmotic/pressure-driven flow, the role of EOF in producing desired velocity profile will be reduced. In this way, the advantages of EOF can be exploited, and its disadvantages can be prevented. Induced pressure gradient can be utilized in order to control the separation in the system. Furthermore, in many complicated geometries such as T-shape microchannels, turns may induce pressure gradient to the electroosmotic velocity. While analytical formulas are completely essential for analysis and control of any industrial and laboratory microdevices, lack of such formulas in the literature for solving Poisson-Boltzmann equation and predicting electroosmotic velocity field in rectangular domains is evident. In the present study, first a novel method is proposed to solve Poisson-Boltzmann equation (PBE). Subsequently, this solution is utilized to find the electroosmotic and the mixed electroosmotic/pressure-driven velocity profile in a rectangular domain of the microchannels. To demonstrate the accuracy of the presented analytical method in solving PBE and finding electroosmotic velocity, a general nondimensional example is analyzed, and the results are compared with the solution of boundary element method. Additionally, the effects of different nondimensional parameters and also aspect ratio of channels on the electroosmotic part of the flow field will be investigated.
In the present work, the shock train structure in a convergent-divergent nozzle investigated usin... more In the present work, the shock train structure in a convergent-divergent nozzle investigated using large eddy simulation (LES) methodology based on different subgrid models, including Smagorinsky-Lilly (SL), Wall-Adapting Local Eddy-Viscosity (WALE) and Algebraic Wall-Modeled LES (WMLES) as well as various analytical equations. For gaining a distinct illustration of shock-wave structures, shadowgraph contours are applied to analyze structures of fine flow. The simulated results are obtained at the same geometrical and boundary conditions used in the available experimental data to provide a rational validation. The results of different subgrid models are shown that the WMLES produces more accurate results than SL and WALE models. Thereupon, an investigation of the influence of convergency length and discontinuity of nozzle wall temperature on physics of flow for controlling the shock behavior is carried out. The results show that the minimum wall pressure as well as the maximum flow Mach number increase as the convergency length rises. In addition, by growth in discontinuous wall temperature, the minimum wall pressure and the maximum flow Mach number reduce.
Encapsulation of solid particles and liquid agents in a liquid shell is of exceptional interest i... more Encapsulation of solid particles and liquid agents in a liquid shell is of exceptional interest in biotechnological, chemical and pharmaceutical fields such as personalized medicine, fluidized catalytic cracking, wire fabrication, catalytic reactions. Looking at the interaction between liquid drop and solid particles, we can study the special, ideal case of spherical drops impacting solid spheres, in order to understand the basic phenomena and the effect of the physical variables on the spreading behavior. Considering the importance of dynamics of drop-particle collision, which directly affects the quality of film deposition during encapsulation, various aspects of drop impact on dry solid spherical surfaces are still lacking in the existing literature. The cases are studied with a 3D level-set method implemented in a standard finite-element-based solver platform. The impact Weber number, the size ratio (ratio of spherical particle diameter to droplet diameter), and the surface cont...
Objective(s): One applications of nanotechnology is in the area of medicine which is called nanom... more Objective(s): One applications of nanotechnology is in the area of medicine which is called nanomedicine. Primary instruments in nanomedicine can help us to detect diseases and used for drug delivery to inaccessible areas of human tissues. An important issue in simulating the motion of nanoparticles is modeling blood flow as a Newtonian or non-Newtonian fluid. Sometimes blood flow is simulated as a Newtonian fluid but actually blood has nature of non-Newtonian fluid. Simulation of targeted drug delivery and motion of nanoparticles in the blood flow as Newtonian and non-Newtonian fluid flow is investigated in this paperMaterials and Methods: In this paper, the blood flow is modeled as both Newtonian and non-Newtonian fluid and the effects of each case on the motion of nanoparticles in blood flow and targeted drug delivery is investigated. The flow is modeled with finite volume method. The particle modeled with discrete phase model.Results: Cross, Herschel-Bulkley and Power-law model...
The effects of plasma injection upon MILD combustion of a mixture of methane and hydrogen are inv... more The effects of plasma injection upon MILD combustion of a mixture of methane and hydrogen are investigated numerically. The injected plasma includes the flow of a highly air-diluted methane including C2H2, C2H4, C2H6, CH, CH2, CH3, CO, and CO2. The results show that among all the constitutes of plasma, CH3 is the most effective in improving the characteristics of MILD combustion. Injection of this radical leads to the occurrence of reactions at a closer distance to the burner inlet and thus provides longer time for completion of combustion. Further, mass fractions of OH, CH2O, and HCO are considerably affected by the injections of CH3, indicating structural modifications of the reacting flow. Importantly, as Reynolds number of the plasma flow increases, the volume and width of the flame decrease, while the formations of prompt and thermal NOx are intensified. However, injection of CH3, as plasma, reduces the emission of thermal NOx.
This paper examines the effects of swirl hot co-flow on the combustion behavior of a moderate or ... more This paper examines the effects of swirl hot co-flow on the combustion behavior of a moderate or intense low oxygen dilution (MILD) burner fueled by a mixture of methane and hydrogen. Toward this goal, the realizable k-ɛ turbulence model, GRI. 2.11 reaction mechanism, and the discrete ordinates radiation model are incorporated into a computational modeling of the reactive flow. The numerical results are, first, favorably compared against the existing experimental data. Subsequently, a number of swirl co-flows are implemented, and structures of the resultant reactive flows are investigated systematically. The outcomes indicate that increasing the swirl velocity leads to the reduction of ignition delay and significantly enhances the reaction completion. The analysis of the spatial distribution of hydroxyl and formyl (OH and HCO) radicals reveals that swirling MILD combustion radially extends the reaction zone in comparison with the conventional MILD combustion. Yet, it reduces the len...
In the present study, the numerical analysis of blade tip geometry effect on the performance of a... more In the present study, the numerical analysis of blade tip geometry effect on the performance of a single-stage axial compressor has been the focus of attention. The studied geometries included a rotor with variable tip clearance. For the first model, the tip clearance increases as it moves toward the blade trailing edge. The tip clearance of the second model reduces as it approaches the trailing edge, whereas in the third model, the tip clearance remains constant. The results indicated that the tip clearance of the first sample, as the worst tip clearance case, creates a 10% reduction in the stall margin with respect to the third standard model, and the second sample tip clearance brings about a stall margin reduction of 4% efficiency with respect to the third standard model. Then, the effect of blade tip clearance geometry on outlet flow angle of the rotor was inspected. The results showed that in the first model, the outlet flow angle has the largest deviation than the third standard model and the second model performance places somewhere between the two other tip clearance geometries. Also evident from the result is that taking advantage of the variable blade tip clearance is not an appropriate method for improving compressor performance.
In the current study, the influence of blade tip clearance in different stages of a three-stage c... more In the current study, the influence of blade tip clearance in different stages of a three-stage compressor is investigated. Performance diagrams of compressor were verified against experiment when there is no change in the tip clearance, after which the effect of tip clearance for the cases, 1, 1.5 and 2 mm, in the first, second and third stages of rotor was studied. The results indicated that the impact of tip clearance increase did not have any effect on choked flow rate value in the first and second stages, and only the change in the third stage tip clearance reduced the choked flow rate. For the same tip clearance value, the highest compressor performance loss occurs in the case of applying the tip clearance in the third stage, which is also the final stage and is highly sensitive to tip clearance changes. Moreover, modifying the tip clearance is effective on the flow angle in the trailing edge and as the tip clearance increases, the same thing happens about the flow angle. The maximum value of flow angle changes by modifying the tip clearance belongs to the third stage of the compressor.
A comprehensive investigation of acoustic power level in a moderate or intense low oxygen dilutio... more A comprehensive investigation of acoustic power level in a moderate or intense low oxygen dilution in a jet-in-hot-coflow under various working conditions.
In the present paper, the performance of INVELOX wind turbine (IWT) in Sistan plain, as a low win... more In the present paper, the performance of INVELOX wind turbine (IWT) in Sistan plain, as a low wind speed region, is investigated by a finite volume code and field tests. At first, the numerical results are compared with available experimental data and it is found that the numerical method is consistent with experimental data. Afterward, the performance of various working conditions of IWT (such as assemble height) at Zabol plain, Iran, is investigated. It was revealed that by increasing the assemble height from 10 to 40 m, the output power rises by 87.5%, while the power acoustic level increases by 39.3%. Moreover, the feasibility of using the IWT in a day is examined based on wind day speed obtained by a statistical study in Sistan plain from 1997-2012. Furthermore, in order to increase the efficiency of IWT, a new structure is suggested. The results indicated that by using a two-storey INVELOX turbine, the output power increases up to 44% which indicates that adding a storey to the device is effective to reach a higher performance while the maintenance cost is not different from common INVELOX Turbine system.
Magnetic drug targeting (MDT) and magnetic-based drug/cargo delivery are emerging treatment metho... more Magnetic drug targeting (MDT) and magnetic-based drug/cargo delivery are emerging treatment methods which attracting the attention of many researchers for curing different cancers and artery diseases such as atherosclerosis. Herein, computational studies are accomplished by utilizing magnetic approaches for cancer and artery atherosclerosis drug delivery, including nanomagnetic drug delivery and magnetic-based drug/cargo delivery. For the first time, the four-layer structural model of the artery tissue and its porosity parameters are modeled in this study which enables the interaction of particles with the tissue walls in blood flow. The effects of parameters, including magnetic field strength (MFS), magnet size, particle size, the initial position of particles, and the relative magnetic permeability of particles, on the efficacy of MDT through the artery walls are characterized. The magnetic particle penetration into artery layers and fibrous cap (the covering layer over the inflamed part of the artery) is further simulated. The MDT in healthy and diseased arteries demonstrates that some of the particles stuck in these tissues due to the collision of particles or blood flow deviation in the vicinity of the inflamed part of the artery. Therefore the geometry of artery and porosity of its layers should be considered to show the real interaction of particles with the artery walls. Also, the results show that increasing the particles/drug/cargo size and MFS leads to more particles/drug/cargo retention within the tissue. The present work provides insights into the decisive factors in arterial MDT with an obvious impact on locoregional cancer treatment, tissue engineering, and regenerative medicine.
Langmuir : the ACS journal of surfaces and colloids, Jan 17, 2018
The spreading and rebound patterns of low-viscous droplets upon impacting spherical solid surface... more The spreading and rebound patterns of low-viscous droplets upon impacting spherical solid surfaces are investigated numerically. The studied cases consider a droplet impinging onto hydrophobic and superhydrophobic surfaces with various parameters varied throughout the study, and their effects on the postimpingement behavior are discussed. These parameters include impact Weber number (through varying the surface tension and impingement velocity), the size ratio of the droplet to the solid surface, and the surface contact angle. According to the findings, the maximum spreading diameter increases with the impact velocity, with an increase of the sphere diameter, with a lower surface wettability, and with a lower surface tension. Typical outcomes of the impact include (1) complete rebound, (2) splash, and (3) a final deposition stage after a series of spreading and recoiling phases. Finally, a novel, practical model is proposed, which can reasonably predict the maximum deformation of lo...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2017
In the present study, characteristics of leaky dielectric droplets in electric fields are investi... more In the present study, characteristics of leaky dielectric droplets in electric fields are investigated numerically. In order to validate the numerical method, deformation of a leaky dielectric droplet in an electric field is studied and the numerical results are compared to Taylor theoretical model. After that, the effects of electrical parameters such as electric permittivity, conductivity, electric field strength, and physical parameters such as initial distance and size of droplets on the electrocoalescence are examined. Moreover, behaviors of non-Newtonian droplets in the electric field are surveyed to elucidate the underlying physics. According to the results, pseudoplastic droplets have more deformations in an electric field than Newtonian and dilatant ones, and they also have faster electrocoalescence.
In the present work, three-dimensional computational fluid dynamics analysis is employed to study... more In the present work, three-dimensional computational fluid dynamics analysis is employed to study the droplet dynamics of Newtonian and non-Newtonian droplets impinging on a hot surface under various impact conditions. The Navier–Stokes equations for unsteady, incompressible, and viscous fluid flow are solved using a control volume method. The volume-of-fluid (VOF) technique is also used to track the free-surface of the liquid. The effect of viscosity, density and surface tension on droplet dynamics is evaluated considering their dependence of temperature. The results indicate that the temperature dependence of the both Newtonian and non-Newtonian physicochemical liquid properties must be considered to obtain better agreement of the numerical results with experimental data. After ensuring the accuracy of the numerical methodology, the internal behavior of the droplets is examined, which is shown that the receding velocity of the non-Newtonian droplet is slower than the Newtonian one.
International Journal of Computational Fluid Dynamics, 2017
Curvature effect on droplet impacting onto hydrophobic and superhydrophobic spheres Droplet impac... more Curvature effect on droplet impacting onto hydrophobic and superhydrophobic spheres Droplet impact on hydrophobic and superhydrophobic solid surfaces finds numerous applications, while the wide range of the parameters affecting its outcome necessitate a thorough study to reveal the underlying physics. Specific applications are related to the drop impact upon curved surfaces, such as microencapsulation in fluidized beds. Three-dimensional numerical simulations by applying Level-Set Method have been performed to investigate the water droplet impact on curved and flat hydrophobic and superhydrophobic substrates. Parameters such as the impact Weber number, the surface curvature and the equilibrium contact angle have been varied in order to assess their effects on the dynamics of the impact process. After providing a strong validation, it is found that impact on spherical surfaces generally presents a higher area of liquid to be in contact with the substrate with respect to the case of flat surfaces, when all other impact conditions are the same.
In the present study, the behaviors of Newtonian and shear-thinning non-Newtonian droplets imping... more In the present study, the behaviors of Newtonian and shear-thinning non-Newtonian droplets impinging on heated hydrophilic and hydrophobic surfaces have been investigated numerically using Ansys-Fluent. In this context, the volume-of-fluid technique is applied to track the free-surface of the liquid, and variable time-step is also utilized to control the Courant number. Furthermore, we have considered the dependence of viscosity, density and surface tension on temperature during the simulation. The results are compared to available experimental data at the same conditions, such as boundary conditions. The results demonstrate that there is a good agreement between the obtained results and the experimental trends, concerning normalized diameter profiles at various Weber numbers. Therefore, the focus of the present study is an assessment of the effects of variations in Weber number, contact angle and surface temperature for Newtonian and non-Newtonian liquids on dynamics behavior of droplet in collision with hydrophobic and hydrophilic surfaces. The results represent that the behaviors of Newtonian and non-Newtonian droplets are totally different, indicating the droplet sensitivity to the working parameters.
In the present work, the physics of a three-dimensional shock train in a convergent-divergent noz... more In the present work, the physics of a three-dimensional shock train in a convergent-divergent nozzle is numerically investigated. In this regards, the Ansys-Fluent Software with Algebraic Wall-Modeled Large-Eddy Simulation (WMLES) is used. To estimate precision and errors accumulation we used the Smirinov’s method; fine flow structures are obtained via Laplacian of density called shadowgraph and the shock parameter is defined as multiplication of flow Mach number by the normalized pressure gradient, in which shock wave structures are visible distinctly. The results are compared with the experimental data of Weiss et al. [Experiments in Fluids 49(2) (2010) 355–365], in the same conditions including geometry, boundary conditions, etc. The results show that there is good agreement with experimental trends concerning wall pressure and centerline Mach number profiles. Therefore, the focus of the present study is an assessment of various flow control methods to change the shock structures...
ASME 2009 7th International Conference on Nanochannels, Microchannels and Minichannels, 2009
The past decade has seen tremendous growth in areas of micro-and nano-fluidics, and MEMs flow con... more The past decade has seen tremendous growth in areas of micro-and nano-fluidics, and MEMs flow control. Nowadays, there is considerable interest in micro-and nano/technologies consisting of small structures in contact with liquid media. By increasing the motivations of using miniaturized devices such as MEMS and NEMS and inventing new methods of their manufacturing, the inspirations of their study and analysis have been increased more and more. One of the most important characteristics of these devices ...
ASME 2009 7th International Conference on Nanochannels, Microchannels and Minichannels, 2009
By entering technology to the area of micro and nano scales, the design and fabrication of miniat... more By entering technology to the area of micro and nano scales, the design and fabrication of miniaturized instruments such as microelectronic devices, MEMS, NEMS and..., become very desirable. Many of these devices deal with flow field in micro-and nano-channels. By decreasing the dimensions of channels, the influence of surface effects becomes prominent and cannot be ignored. One of the most charismatic categories of these phenomena is elecrokinetic effect which can result in electroosmotic flow field (EOF) that has many ...
Theoretical and Computational Fluid Dynamics, 2012
Operational state of many miniaturized devices deals with flow field in microchannels. Pressuredr... more Operational state of many miniaturized devices deals with flow field in microchannels. Pressuredriven flow (PDF) and electroosmotic flow (EOF) can be recognized as the two most important types of the flow field in such channels. EOF has many advantages in comparison with PDF, such as being vibration free and not requiring any external mechanical pumps or moving parts. However, the disadvantages of this type of flow such as Joule heating, electrophoresis demixing, and not being suitable for mobile devices must be taken into consideration carefully. By using mixed electroosmotic/pressure-driven flow, the role of EOF in producing desired velocity profile will be reduced. In this way, the advantages of EOF can be exploited, and its disadvantages can be prevented. Induced pressure gradient can be utilized in order to control the separation in the system. Furthermore, in many complicated geometries such as T-shape microchannels, turns may induce pressure gradient to the electroosmotic velocity. While analytical formulas are completely essential for analysis and control of any industrial and laboratory microdevices, lack of such formulas in the literature for solving Poisson-Boltzmann equation and predicting electroosmotic velocity field in rectangular domains is evident. In the present study, first a novel method is proposed to solve Poisson-Boltzmann equation (PBE). Subsequently, this solution is utilized to find the electroosmotic and the mixed electroosmotic/pressure-driven velocity profile in a rectangular domain of the microchannels. To demonstrate the accuracy of the presented analytical method in solving PBE and finding electroosmotic velocity, a general nondimensional example is analyzed, and the results are compared with the solution of boundary element method. Additionally, the effects of different nondimensional parameters and also aspect ratio of channels on the electroosmotic part of the flow field will be investigated.
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