Realistic 3-D models of the human nasal passages were developed pre and post virtual uncinectomy ... more Realistic 3-D models of the human nasal passages were developed pre and post virtual uncinectomy and Middle Meatal Antrostomy. A 3-D computational domain was constructed by a series of coronal CT scan images from a healthy subject. Then a virtual uncinectomy intervention and maxillary antrostomy were performed on the left nasal passage by removing the uncinate process and exposing the maxillary sinus antrum. For several breathing rates corresponding to low or moderate activities, the airflows in the nasal passages were simulated numerically pre and post virtual routine maxillary sinus endoscopic surgery. The airflow distribution in the nasal airway, maxillary and frontal sinuses were analyzed and compared between pre and post surgery cases. A Lagrangian trajectory analysis approach was used for evaluating the path and deposition of microparticles in the nasal passages and maxillary sinuses. A diffusion model was used for nanoparticle transport and deposition analysis. The deposition rate of the inhaled micro and nanoparticles in the sinuses were evaluated and compared for pre and post operation conditions. The results showed that after maxillary sinus endoscopic surgery, the inhaled nano and microparticles can easily enter this sinus due to penetration of the airflow into the sinus cavity. This was in contrast to the preoperative condition in which almost no particles entered the sinuses. These results could be of importance for a better understanding of the effect of sinus endoscopic surgery on patient exposure to particulate pollution and inhalation drug delivery. The significantly higher airflow rate and particle deposition in the sinus could be a reason for the discomfort reported by some patient after maxillary sinus endoscopic surgery.
Computer Methods in Biomechanics and Biomedical Engineering, 2014
In this study, a numerical investigation is performed to evaluate the effects of high-pressure si... more In this study, a numerical investigation is performed to evaluate the effects of high-pressure sinusoidal and blast wave's propagation around and inside of a human external ear. A series of computed tomography images are used to reconstruct a realistic three-dimensional (3D) model of a human ear canal and the auricle. The airflow field is then computed by solving the governing differential equations in the time domain using a computational fluid dynamics software. An unsteady algorithm is used to obtain the high-pressure wave propagation throughout the ear canal which is validated against the available analytical and numerical data in literature. The effects of frequency, wave shape, and the auricle on pressure distribution are then evaluated and discussed. The results clearly indicate that the frequency plays a key role on pressure distribution within the ear canal. At 4 kHz frequency, the pressure magnitude is much more amplified within the ear canal than the frequencies of 2 and 6 kHz, for the incident wave angle of 90° investigated in this study, attributable to the '4-kHz notch' in patients with noise-induced hearing loss. According to the results, the pressure distribution patterns at the ear canal are very similar for both sinusoidal pressure waveform with the frequency of 2 kHz and blast wave. The ratio of the peak pressure value at the eardrum to that at the canal entrance increases from about 8% to 30% as the peak pressure value of the blast wave increases from 5 to 100 kPa for the incident wave angle of 90° investigated in this study. Furthermore, incorporation of the auricle to the ear canal model is associated with centerline pressure magnitudes of about 50% and 7% more than those of the ear canal model without the auricle throughout the ear canal for sinusoidal and blast waves, respectively, without any significant effect on pressure distribution pattern along the ear canal for the incident wave angle of 90° investigated in this study.
The nature of aqueous humor (AH) mixing in the anterior chamber (AC) of the human eye due to rapi... more The nature of aqueous humor (AH) mixing in the anterior chamber (AC) of the human eye due to rapid eye movement (REM) has not been fully understood and has been somewhat a controversial issue. This study uses a computational modeling approach to shed light on this issue. For this purpose a numerical method was developed and used to solve the mathematical equations governing the flow and mixing of aqueous humor motion in the eye subjected to such movements. Based on the experimental measurements available in the literature for the average and maximum amplitudes of the eye movements, a harmonic model for the REM was developed. The corresponding instantaneous and time-averaged velocity fields were evaluated. The simulation results showed that, contrary to earlier reports, the REM led to complex flow structures and a 3-D mixing of AH in the anterior chamber. In addition, the mixing velocity increased in direct proportion to the REM amplitudes. Thus, the AC flow generated by REM could carry nutrients to the posterior surface of the cornea during the sleep. Furthermore, the shear stress acting on the corneal endothelial cells due to REM was computed and compared with that of buoyancy driven flow in the AC due to temperature gradient. It was found that the shear stress generated by REM is much higher than that introduced by the natural convection. A video file for providing a better understanding of the AH mixing process in the AC was also prepared. This video is available on the web.
2007 2nd IEEE International Conference on Nano/Micro Engineered and Molecular Systems, 2007
... An Axisymmetric Model for Diffusion of Nano-Particles Omid Aboualil* and Goodarz Ahmadi2 &... more ... An Axisymmetric Model for Diffusion of Nano-Particles Omid Aboualil* and Goodarz Ahmadi2 'MechanicalEngineering Department, Shiraz University, Iran ... This is done using the following transformations: GI = v/-2n21nU1 cos(2ffU2), (23) G2= - 2 In U1 sin(2iLU2T). (24) ...
ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels, 2012
ABSTRACT In the present work, the performance of pin-finned microchannels as the micromixers is i... more ABSTRACT In the present work, the performance of pin-finned microchannels as the micromixers is investigated. Different patterns for distribution of pin-fins were examined (staggered and oblique distribution of fins). A 3-D computational model was developed and the Navier-Stokes equations were solved and the corresponding flow fields were evaluated. The mass transport differential equation was also solved and the concentration of liquids in the mixture was evaluated. The results for the mixing efficiency were compared between the simple and pin-finned microchannels. The results suggest that the finned microchannels with staggered distribution of pins perform very well in mixing of liquids. The mixing efficiency reaches to 100 percent for the Reynolds numbers in which the mixing efficiency is less than 10 percent for the simple microchannels.
A 3-D realistic computational model of the airway system integrated into a standing male mannequi... more A 3-D realistic computational model of the airway system integrated into a standing male mannequin was developed. The computational domain includes the regions around the mannequin and the inside of the airway passages. The simulation was performed for low activity breathing rates with calm air around the mannequin. The flowfield of the inhaled air was first obtained from solving the Navier-Stokes and continuity equations. Then the particles were released in the domain around the mannequin and their trajectories were evaluated by using the Lagrangian approach for solving the particle equation of motion. The regional aerosols deposition was evaluated for different parts of the human airway system and the results were compared with those obtained from the separate modeling of the airway system without the interaction of the airflow with the mannequin external face. The results showed when the upper airway is integrated into the mannequin, the regional deposition of inhaled particles mainly changes in the airway system.
ABSTRACT In this paper, the motion and deposition of micro fibers in different regions of a reali... more ABSTRACT In this paper, the motion and deposition of micro fibers in different regions of a realistic human nasal airway were studied using a computational modeling approach. The airflow field in the nasal cavity was simulated by solving the Navier-Stokes and continuity equations. The coupled translational and rotation motion of the fibers were analyzed by a Lagrangian approach assuming one-way coupling. The fibers were assumed to be ellipsoids and a computer code was developed for solving the coupled translational and rotational equations of motion of the ellipsoidal fiber. A large number of fibers were injected at the nostril and the deposition pattern and deposition fraction (DF) of the fibers in different regions of the nasal cavity were evaluated for different breathing rates, various fiber diameters and different fiber aspect ratios. The simulation results for ellipsoidal fibers obtained by solving the coupled translational and rotational equations were compared with those obtained by solving only the translational equations of equivalent spherical particles with a shape factor, which were used in some earlier works.
Three dimensional computational models of both sides of human nasal passages were developed to in... more Three dimensional computational models of both sides of human nasal passages were developed to investigate the effect of septal deviation on the flow patterns and deposition of micro/nano-particles in the realistic human nasal airways before and after septoplasty. A series of coronal CT scan images from a live 25-year old nonsmoking male with septal deviation in his right nasal passage was used to construct the model. For low to moderate activities, the steady airflows through the nasal passages were simulated. Eulerian and Lagrangian approaches were used, respectively, for nano- and micro-particles. The results show that the flow field and particle deposition strongly depend on the passage geometry especially for micro particles. In particular, the deposition rate in the passage with septal deviation was much higher compared with those in the normal (left) passage and the postoperative passage. Despite the similarity of total micro-particle deposition in the postoperative and the normal cavities, the regional deposition patterns were quite different in these passages. The deposition of nano-particles, however, showed similar trends in the postoperative right nasal passage and the normal left passage. The simulation results showed that in addition to the major alteration of the airflow pattern after the septoplasty operation, there are significant changes in the deposition pattern of nano- and micro-particles. Despite the anatomical differences between the available experimental configuration and the present computer model, the simulation results for the deposition efficiency of particles of different sizes are in qualitative agreement with the available data.
Omid Abouali, Mohammad M Alishahi, Homayoon Emad, Goodarz Ahmadi Journal of Spacecraft and Rocket... more Omid Abouali, Mohammad M Alishahi, Homayoon Emad, Goodarz Ahmadi Journal of Spacecraft and Rockets 40:66, 893-897, 11/2003. ... a supersonic combined computer code to be used on microcomputers as an aerodynamic design tool in preliminary and mid-design stages. ...
In this study the performance of supersonic and hypersonic impactors for collection efficiency of... more In this study the performance of supersonic and hypersonic impactors for collection efficiency of nanoparticles (in the size range of 2–100 nm) under various operating conditions is analyzed. Axisymmetric forms of the compressible Navier–Stokes and energy equations are solved and the airflow and thermal condition in the impactor are evaluated. A Lagrangian particle trajectory analysis procedure is used and the deposition
To provide the details of the flow field in the anterior chamber during irrigation/aspiration (I/... more To provide the details of the flow field in the anterior chamber during irrigation/aspiration (I/A) in phacoemulsification using computational fluid-dynamics methods. School of Mechanical Engineering, Shiraz University, Dr. Khodadoust Eye Hospital, Shiraz, Iran, and Clarkson University, Potsdam, New York, USA. Theoretical study. A 3-dimensional model for the irrigating cannula, anterior chamber, capsular bag, and aspiration cannula was developed. The corresponding mathematic equations were solved numerically, and the details of the flow field were evaluated. The simulation was performed for coaxial and bimanual I/A systems with various flow rates. The pressure flow rate curve was evaluated, and the possibility of an unstable anterior chamber in different cases was assessed. The effects of flow turbulence on the corneal endothelium were lower for the coaxial handpiece. That is, inner placement of irrigation cannula tip lowered the effect of turbulence on the cornea. Assessment of the fluid dynamics of I/A using computational fluid dynamics provided details that cannot be obtained with the available experimental and analytic methods.
ABSTRACT In this study, CFD simulations of fibrous particle deposition in different realistic hum... more ABSTRACT In this study, CFD simulations of fibrous particle deposition in different realistic human nasal cavities were performed. The airflow field in the cavity was evaluated by solving the Navier-Stokes and continuity equations using commercial software, while a Lagrangian trajectory analysis approach for solving the coupled translational and rotational equations of motion of ellipsoids was developed and used to investigate fiber transport and deposition in the nasal passages. Different breathing rates in the laminar flow regime in the nose and a range of fiber lengths and diameters were used in these simulations. It was shown that the aerodynamic diameter based on the Stokes equivalent diameter is an appropriate parameter for correlating the fiber deposition rate. Presenting the deposition fraction results versus the Stokes-based and pressure-based impaction parameters collapsed the results of different cases for various nose models roughly to a single curve. The simulated regional fiber deposition results were also presented for different nasal cavities. A simple approach developed earlier for modeling non-spherical particles using the shape factor in the drag force was also studied, and the resulting deposition fraction was compared with the present coupled translational-rotational trajectory analysis approach.
There are some analytical methods which are still being used as the standard references to valida... more There are some analytical methods which are still being used as the standard references to validate numerical mod-els for continuous casting.13) For example Meng et al.2) and Park et al.3) presented an numerical approach and compared their results for the solidified shell thickness of slab ...
Realistic 3-D models of the human nasal passages were developed pre and post virtual uncinectomy ... more Realistic 3-D models of the human nasal passages were developed pre and post virtual uncinectomy and Middle Meatal Antrostomy. A 3-D computational domain was constructed by a series of coronal CT scan images from a healthy subject. Then a virtual uncinectomy intervention and maxillary antrostomy were performed on the left nasal passage by removing the uncinate process and exposing the maxillary sinus antrum. For several breathing rates corresponding to low or moderate activities, the airflows in the nasal passages were simulated numerically pre and post virtual routine maxillary sinus endoscopic surgery. The airflow distribution in the nasal airway, maxillary and frontal sinuses were analyzed and compared between pre and post surgery cases. A Lagrangian trajectory analysis approach was used for evaluating the path and deposition of microparticles in the nasal passages and maxillary sinuses. A diffusion model was used for nanoparticle transport and deposition analysis. The deposition rate of the inhaled micro and nanoparticles in the sinuses were evaluated and compared for pre and post operation conditions. The results showed that after maxillary sinus endoscopic surgery, the inhaled nano and microparticles can easily enter this sinus due to penetration of the airflow into the sinus cavity. This was in contrast to the preoperative condition in which almost no particles entered the sinuses. These results could be of importance for a better understanding of the effect of sinus endoscopic surgery on patient exposure to particulate pollution and inhalation drug delivery. The significantly higher airflow rate and particle deposition in the sinus could be a reason for the discomfort reported by some patient after maxillary sinus endoscopic surgery.
Computer Methods in Biomechanics and Biomedical Engineering, 2014
In this study, a numerical investigation is performed to evaluate the effects of high-pressure si... more In this study, a numerical investigation is performed to evaluate the effects of high-pressure sinusoidal and blast wave's propagation around and inside of a human external ear. A series of computed tomography images are used to reconstruct a realistic three-dimensional (3D) model of a human ear canal and the auricle. The airflow field is then computed by solving the governing differential equations in the time domain using a computational fluid dynamics software. An unsteady algorithm is used to obtain the high-pressure wave propagation throughout the ear canal which is validated against the available analytical and numerical data in literature. The effects of frequency, wave shape, and the auricle on pressure distribution are then evaluated and discussed. The results clearly indicate that the frequency plays a key role on pressure distribution within the ear canal. At 4 kHz frequency, the pressure magnitude is much more amplified within the ear canal than the frequencies of 2 and 6 kHz, for the incident wave angle of 90° investigated in this study, attributable to the '4-kHz notch' in patients with noise-induced hearing loss. According to the results, the pressure distribution patterns at the ear canal are very similar for both sinusoidal pressure waveform with the frequency of 2 kHz and blast wave. The ratio of the peak pressure value at the eardrum to that at the canal entrance increases from about 8% to 30% as the peak pressure value of the blast wave increases from 5 to 100 kPa for the incident wave angle of 90° investigated in this study. Furthermore, incorporation of the auricle to the ear canal model is associated with centerline pressure magnitudes of about 50% and 7% more than those of the ear canal model without the auricle throughout the ear canal for sinusoidal and blast waves, respectively, without any significant effect on pressure distribution pattern along the ear canal for the incident wave angle of 90° investigated in this study.
The nature of aqueous humor (AH) mixing in the anterior chamber (AC) of the human eye due to rapi... more The nature of aqueous humor (AH) mixing in the anterior chamber (AC) of the human eye due to rapid eye movement (REM) has not been fully understood and has been somewhat a controversial issue. This study uses a computational modeling approach to shed light on this issue. For this purpose a numerical method was developed and used to solve the mathematical equations governing the flow and mixing of aqueous humor motion in the eye subjected to such movements. Based on the experimental measurements available in the literature for the average and maximum amplitudes of the eye movements, a harmonic model for the REM was developed. The corresponding instantaneous and time-averaged velocity fields were evaluated. The simulation results showed that, contrary to earlier reports, the REM led to complex flow structures and a 3-D mixing of AH in the anterior chamber. In addition, the mixing velocity increased in direct proportion to the REM amplitudes. Thus, the AC flow generated by REM could carry nutrients to the posterior surface of the cornea during the sleep. Furthermore, the shear stress acting on the corneal endothelial cells due to REM was computed and compared with that of buoyancy driven flow in the AC due to temperature gradient. It was found that the shear stress generated by REM is much higher than that introduced by the natural convection. A video file for providing a better understanding of the AH mixing process in the AC was also prepared. This video is available on the web.
2007 2nd IEEE International Conference on Nano/Micro Engineered and Molecular Systems, 2007
... An Axisymmetric Model for Diffusion of Nano-Particles Omid Aboualil* and Goodarz Ahmadi2 &... more ... An Axisymmetric Model for Diffusion of Nano-Particles Omid Aboualil* and Goodarz Ahmadi2 'MechanicalEngineering Department, Shiraz University, Iran ... This is done using the following transformations: GI = v/-2n21nU1 cos(2ffU2), (23) G2= - 2 In U1 sin(2iLU2T). (24) ...
ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels, 2012
ABSTRACT In the present work, the performance of pin-finned microchannels as the micromixers is i... more ABSTRACT In the present work, the performance of pin-finned microchannels as the micromixers is investigated. Different patterns for distribution of pin-fins were examined (staggered and oblique distribution of fins). A 3-D computational model was developed and the Navier-Stokes equations were solved and the corresponding flow fields were evaluated. The mass transport differential equation was also solved and the concentration of liquids in the mixture was evaluated. The results for the mixing efficiency were compared between the simple and pin-finned microchannels. The results suggest that the finned microchannels with staggered distribution of pins perform very well in mixing of liquids. The mixing efficiency reaches to 100 percent for the Reynolds numbers in which the mixing efficiency is less than 10 percent for the simple microchannels.
A 3-D realistic computational model of the airway system integrated into a standing male mannequi... more A 3-D realistic computational model of the airway system integrated into a standing male mannequin was developed. The computational domain includes the regions around the mannequin and the inside of the airway passages. The simulation was performed for low activity breathing rates with calm air around the mannequin. The flowfield of the inhaled air was first obtained from solving the Navier-Stokes and continuity equations. Then the particles were released in the domain around the mannequin and their trajectories were evaluated by using the Lagrangian approach for solving the particle equation of motion. The regional aerosols deposition was evaluated for different parts of the human airway system and the results were compared with those obtained from the separate modeling of the airway system without the interaction of the airflow with the mannequin external face. The results showed when the upper airway is integrated into the mannequin, the regional deposition of inhaled particles mainly changes in the airway system.
ABSTRACT In this paper, the motion and deposition of micro fibers in different regions of a reali... more ABSTRACT In this paper, the motion and deposition of micro fibers in different regions of a realistic human nasal airway were studied using a computational modeling approach. The airflow field in the nasal cavity was simulated by solving the Navier-Stokes and continuity equations. The coupled translational and rotation motion of the fibers were analyzed by a Lagrangian approach assuming one-way coupling. The fibers were assumed to be ellipsoids and a computer code was developed for solving the coupled translational and rotational equations of motion of the ellipsoidal fiber. A large number of fibers were injected at the nostril and the deposition pattern and deposition fraction (DF) of the fibers in different regions of the nasal cavity were evaluated for different breathing rates, various fiber diameters and different fiber aspect ratios. The simulation results for ellipsoidal fibers obtained by solving the coupled translational and rotational equations were compared with those obtained by solving only the translational equations of equivalent spherical particles with a shape factor, which were used in some earlier works.
Three dimensional computational models of both sides of human nasal passages were developed to in... more Three dimensional computational models of both sides of human nasal passages were developed to investigate the effect of septal deviation on the flow patterns and deposition of micro/nano-particles in the realistic human nasal airways before and after septoplasty. A series of coronal CT scan images from a live 25-year old nonsmoking male with septal deviation in his right nasal passage was used to construct the model. For low to moderate activities, the steady airflows through the nasal passages were simulated. Eulerian and Lagrangian approaches were used, respectively, for nano- and micro-particles. The results show that the flow field and particle deposition strongly depend on the passage geometry especially for micro particles. In particular, the deposition rate in the passage with septal deviation was much higher compared with those in the normal (left) passage and the postoperative passage. Despite the similarity of total micro-particle deposition in the postoperative and the normal cavities, the regional deposition patterns were quite different in these passages. The deposition of nano-particles, however, showed similar trends in the postoperative right nasal passage and the normal left passage. The simulation results showed that in addition to the major alteration of the airflow pattern after the septoplasty operation, there are significant changes in the deposition pattern of nano- and micro-particles. Despite the anatomical differences between the available experimental configuration and the present computer model, the simulation results for the deposition efficiency of particles of different sizes are in qualitative agreement with the available data.
Omid Abouali, Mohammad M Alishahi, Homayoon Emad, Goodarz Ahmadi Journal of Spacecraft and Rocket... more Omid Abouali, Mohammad M Alishahi, Homayoon Emad, Goodarz Ahmadi Journal of Spacecraft and Rockets 40:66, 893-897, 11/2003. ... a supersonic combined computer code to be used on microcomputers as an aerodynamic design tool in preliminary and mid-design stages. ...
In this study the performance of supersonic and hypersonic impactors for collection efficiency of... more In this study the performance of supersonic and hypersonic impactors for collection efficiency of nanoparticles (in the size range of 2–100 nm) under various operating conditions is analyzed. Axisymmetric forms of the compressible Navier–Stokes and energy equations are solved and the airflow and thermal condition in the impactor are evaluated. A Lagrangian particle trajectory analysis procedure is used and the deposition
To provide the details of the flow field in the anterior chamber during irrigation/aspiration (I/... more To provide the details of the flow field in the anterior chamber during irrigation/aspiration (I/A) in phacoemulsification using computational fluid-dynamics methods. School of Mechanical Engineering, Shiraz University, Dr. Khodadoust Eye Hospital, Shiraz, Iran, and Clarkson University, Potsdam, New York, USA. Theoretical study. A 3-dimensional model for the irrigating cannula, anterior chamber, capsular bag, and aspiration cannula was developed. The corresponding mathematic equations were solved numerically, and the details of the flow field were evaluated. The simulation was performed for coaxial and bimanual I/A systems with various flow rates. The pressure flow rate curve was evaluated, and the possibility of an unstable anterior chamber in different cases was assessed. The effects of flow turbulence on the corneal endothelium were lower for the coaxial handpiece. That is, inner placement of irrigation cannula tip lowered the effect of turbulence on the cornea. Assessment of the fluid dynamics of I/A using computational fluid dynamics provided details that cannot be obtained with the available experimental and analytic methods.
ABSTRACT In this study, CFD simulations of fibrous particle deposition in different realistic hum... more ABSTRACT In this study, CFD simulations of fibrous particle deposition in different realistic human nasal cavities were performed. The airflow field in the cavity was evaluated by solving the Navier-Stokes and continuity equations using commercial software, while a Lagrangian trajectory analysis approach for solving the coupled translational and rotational equations of motion of ellipsoids was developed and used to investigate fiber transport and deposition in the nasal passages. Different breathing rates in the laminar flow regime in the nose and a range of fiber lengths and diameters were used in these simulations. It was shown that the aerodynamic diameter based on the Stokes equivalent diameter is an appropriate parameter for correlating the fiber deposition rate. Presenting the deposition fraction results versus the Stokes-based and pressure-based impaction parameters collapsed the results of different cases for various nose models roughly to a single curve. The simulated regional fiber deposition results were also presented for different nasal cavities. A simple approach developed earlier for modeling non-spherical particles using the shape factor in the drag force was also studied, and the resulting deposition fraction was compared with the present coupled translational-rotational trajectory analysis approach.
There are some analytical methods which are still being used as the standard references to valida... more There are some analytical methods which are still being used as the standard references to validate numerical mod-els for continuous casting.13) For example Meng et al.2) and Park et al.3) presented an numerical approach and compared their results for the solidified shell thickness of slab ...
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