In this study, a parallel computing technology is applied on the simulation of a wind turbine flo... more In this study, a parallel computing technology is applied on the simulation of a wind turbine flow problem. A third-order Roe type flux limited splitting based on a pre-conditioning matrix with an explicit time marching method is used to solve the Navier-Stokes equations. The original FORTRAN code was parallelized with Message Passing Interface (MPI) language and tested on a 64-CPU IBM SP2 parallel computer. The test results show that a significant reduction of computing time in running the model and a superlinear speed up rate is achieved up to 32 CPUs at IBM SP2 processors. The speed up rate is as high as 49 for using IBM SP2 64 processors. The test shows very promising potential of parallel processing to provide prompt simulation of the current wind turbine problems.
Maxillomandibular advancement is one of the treatments available for obstructive sleep apnea. The... more Maxillomandibular advancement is one of the treatments available for obstructive sleep apnea. The influence of this surgery on the upper airway and its mechanism are not fully understood. The present research simulates the flow fields of narrowed upper airways of 2 patients with obstructive sleep apnea treated with maxillomandibular advancement. The geometry of the upper airway was reconstructed from computed tomographic images taken before and after surgery. The consequent three-dimensional surface model was rendered for measurement and computational fluid dynamics simulation. Patients showed clinical improvement 6 months after surgery. The cross-sectional area of the narrowest part of the upper airway was increased in all dimensions. The simulated results showed a less constricted upper airway, with less velocity change and a decreased pressure gradient across the whole conduit during passage of air. Less breathing effort is therefore expected to achieve equivalent ventilation with the postoperative airway. This study demonstrates the possibility of computational fluid dynamics in providing information for understanding the pathogenesis of OSA and the effects of its treatment.
The three-dimensional multi-stage turbomachinery flow simulation is calculated on the PC cluster ... more The three-dimensional multi-stage turbomachinery flow simulation is calculated on the PC cluster environment in NCHC. The UTRC large-scale turbine is employed here as the baseline configuration. A compressible viscous finite volunie algorithm solving Reynolds averaged Navier-Stokes equations with artificial dissipation terms similar to Jameson's method is adopted. Circumferential average is pe@ormed between the interface of rotor and stator. The tnaster/slave algorithm is eniployed f o r the parallel iniplementation, and a processor calculates a blade row. Three, five, seven and nine blade rows are used to demonstrate the petjiorniance of parallel computation on the PC cluster. Those results are shown that the pe@ormance is very well, especially for more blade rows, i.e., nine blade rows, have the super speedup eflciency.
During the past years, some fundamental difficulties in the diagnosis and treatment of vascular d... more During the past years, some fundamental difficulties in the diagnosis and treatment of vascular disorders such that the re-stenosis and no-reflow phenomena of arteries after balloon angioplasty are still the unsolved problems and required in a further study. It is well known that blood flow characteristics in arteries are altered significantly by arterial disease, such as stenosis and aneurysm. In general, the prestenotic flow is usually laminar, flow in the post-stenotic region could become highly disordered or even turbulent depending upon the flow conditions and severity of the stenosis. The post-stenotic flow became unstable during this vortex generation phase of the cycle, resulting in intense fluctuations in the formation of wall shear stresses [1]. The study of physiologically realistic pulsatile flow through stenosis could have profound implications for the above-mentioned post-stenotic flow phenomena. In the current study, a dual-time stepping method based on a three-order upwind type approximated Riemann solvers [2,3] is used to solve the stationary and transient Navier- Stokes equations for analysis of separated blood flows in artery. A four-stage Runge-Kutta scheme is used in the pseudo-time iteration, also combining with MPI parallelized tool. The test results also display very promising potential of parallel processing. Newtonian flows through one curved stenosis model, one health aorta model and one aortic dissection model are performed to predict the wall stress distributions. The curved stenosis model with Reynolds numbers of 100, 200, 400, and 600 are constructed.
IEEE Transactions on Biomedical Engineering, Sep 1, 2013
We developed a novel aerosol-mediated drug delivery system for inner ear therapy by using a silic... more We developed a novel aerosol-mediated drug delivery system for inner ear therapy by using a silicon-based multiple-Fourier horn nozzle. Intratympanic aerosol (ITA) methylprednisolone (MP) delivery can protect hearing after acoustic trauma. The highest concentration of MP (38.9 ± 5.47 ppm) appeared at 2 h and declined rapidly within 10 h. The concentrations of MP remained at a relatively low level for more than 10 h. Compared to the baseline, the auditory brainstem response (ABR) thresholds shifted markedly at 1 h after noise exposure in all groups (p < 0.05). From the cochleograms, it can be noted that the main lesions encompassed the 2-20 kHz frequency range. Significant differences ( ) were observed for the range between 5 and 8 kHz in the cell loss of outer hair cells (OHCs). The losses for IHCs were lower than for OHCs. The MP movement in the middle ear was simulated by a convection diffusion equation with a relaxation time. The relaxation time was 0.5 h, and the concentration threshold of MP on the round window membrane (RWM) in the middle ear (C T) was 8900 ppm. Using the unit hydrograph (UH) method, we obtained a proper boundary concentration on the RWM at the cochlea, which resulted in a well-fit concentration. Finally, a linking mechanism between the middle ear and the cochlea was established by the RWM. The adjustable permeability and concentration threshold provide the flexibility to match the peak times and peak values of the concentration on the RWM in the middle ear and the cochlea.
We developed a novel aerosol-mediated drug delivery system for inner ear therapy by using a silic... more We developed a novel aerosol-mediated drug delivery system for inner ear therapy by using a silicon-based multiple-Fourier horn nozzle. Intratympanic aerosol (ITA) methylprednisolone (MP) delivery can protect hearing after acoustic trauma. The highest concentration of MP (38.9 ± 5.47 ppm) appeared at 2 h and declined rapidly within 10 h. The concentrations of MP remained at a relatively low level for more than 10 h. Compared to the baseline, the auditory brainstem response (ABR) thresholds shifted markedly at 1 h after noise exposure in all groups (p < 0.05). From the cochleograms, it can be noted that the main lesions encompassed the 2-20 kHz frequency range. Significant differences ( ) were observed for the range between 5 and 8 kHz in the cell loss of outer hair cells (OHCs). The losses for IHCs were lower than for OHCs. The MP movement in the middle ear was simulated by a convection diffusion equation with a relaxation time. The relaxation time was 0.5 h, and the concentration threshold of MP on the round window membrane (RWM) in the middle ear (C T) was 8900 ppm. Using the unit hydrograph (UH) method, we obtained a proper boundary concentration on the RWM at the cochlea, which resulted in a well-fit concentration. Finally, a linking mechanism between the middle ear and the cochlea was established by the RWM. The adjustable permeability and concentration threshold provide the flexibility to match the peak times and peak values of the concentration on the RWM in the middle ear and the cochlea.
The research proposed an inverse numerical simulation method to recognize the mechanisms of the d... more The research proposed an inverse numerical simulation method to recognize the mechanisms of the drug movement from the middle ear to the cochlea and calibrate the associated parameters. A real 3D model was obtained from the CT image and the relative geometry and mesh were built by ICEM-CFD. The simulation was processes by ANSYSCFX. A set of drug concentration measurement in the cochlea was used in calibrating the parameters. Two new mechanisms: a relaxation time of the absorption via the wall of the middle ear and a concentration threshold to start the permeation from the middle ear to the cochlea were also proposed in this research to complete the phenomena of drug movement. The results indicate a reasonable mechanism to expound the process of drug movement.
Percutaneous Transluminal Angioplasty (PTA) with stent is employed to treat the cardiovascular di... more Percutaneous Transluminal Angioplasty (PTA) with stent is employed to treat the cardiovascular diseases in clinical to dilate stenotic arteries. There have been two types of stents (helical coil shape and traditional mesh shape) wildly used in angioplasty in the past few years. This research studied the biomechanical effects on the expansion behavior of these two different stents with balloon in the artery vessel. The commercial three-dimensional finite element method (FEM) based software was employed to perform all the computations in this study. Simulation results reveal that the pressure is delivered uniformly by the balloon, which leads the stenosed vessel to dilate. The dog bone effect is more obvious in the helical coil stent than the traditional mesh stent. The regions close to both ends of the stent exhibit large deformation and high shear stress values for both stent types. In the clinical practices, large deformation may cause stress concentration which leads to the damage of the vessel.
Proceedings. Seventh International Conference on High Performance Computing and Grid in Asia Pacific Region, 2004.
ABSTRACT In the present study, a vertical, two-dimensional, two-phase flow model is developed, wh... more ABSTRACT In the present study, a vertical, two-dimensional, two-phase flow model is developed, which is capable of simulating the fluid and air flow fields simultaneously to capture the positions of the free surface. To deal with the discontinuity properties in density field near the free surface, the TVD-MUSCL scheme is employed to overcome the numerical oscillation problem. The numerical algorithm is developed using a conservative, explicit, finite volume discretization of the motion equation. The dam-breaking problem is employed to validate the proposed model. The good agreements between the computed and measured results demonstrate the applicability of the model.
During the past years, some fundamental difficulties in the diagnosis and treatment of vascular d... more During the past years, some fundamental difficulties in the diagnosis and treatment of vascular disorders such that the re-stenosis and no-reflow phenomena of arteries after balloon angioplasty are still the unsolved problems and required in a further study. It is well known that blood flow characteristics in arteries are altered significantly by arterial disease, such as stenosis and aneurysm. In general, the prestenotic flow is usually laminar, flow in the post-stenotic region could become highly disordered or even turbulent depending upon the flow conditions and severity of the stenosis. The post-stenotic flow became unstable during this vortex generation phase of the cycle, resulting in intense fluctuations in the formation of wall shear stresses [1]. The study of physiologically realistic pulsatile flow through stenosis could have profound implications for the above-mentioned post-stenotic flow phenomena. In the current study, a dual-time stepping method based on a three-order upwind type approximated Riemann solvers [2,3] is used to solve the stationary and transient Navier- Stokes equations for analysis of separated blood flows in artery. A four-stage Runge-Kutta scheme is used in the pseudo-time iteration, also combining with MPI parallelized tool. The test results also display very promising potential of parallel processing. Newtonian flows through one curved stenosis model, one health aorta model and one aortic dissection model are performed to predict the wall stress distributions. The curved stenosis model with Reynolds numbers of 100, 200, 400, and 600 are constructed.
ABSTRACT A scour monitoring system with a micro camera tracking the bed-level images is proposed ... more ABSTRACT A scour monitoring system with a micro camera tracking the bed-level images is proposed in this study. Two image recognition algorithms have been developed to support the bed-level image tracking approach. Through the laboratory experiments of pier scour, this study demonstrates that the proposed system is able to accurately monitor the scour-depth evolution in real time. In addition, five commonly-used temporal scour models are employed to simulate scour-depth evolution and their results are compared with monitoring data. In general, the results indicate that the proposed scour monitoring system has the potential for further applications in the field.
2013 IEEE International Symposium on Multimedia, 2013
ABSTRACT In this paper, we present two types of the real-time water monitoring system using the i... more ABSTRACT In this paper, we present two types of the real-time water monitoring system using the image processing technology, the water level recognition and the surface velocity recognition. According to the bridge failure investigation, floods in the river often pose potential risk to bridges, and scouring could undermine the pier foundation and cause the structures to collapse. It is very important to develop monitoring techniques for bridge safety in the field. In this study, we installed two high-resolution cameras on the in-situ bridge site to get the real-time water level and surface velocity image. For the water level recognition, we use the image processing techniques of the image binarization, character recognition, and water line detection. For the surface velocity recognition, the proposed system apply the PIV(Particle Image Velocimetry, PIV) method to obtain the recognition of the water surface velocity by the cross correlation analysis. Finally, the proposed systems are used to record and measure the variations of the water level and surface velocity for a period of three days. The good results show that the proposed systems have potential to provide real-time information of water level and surface velocity during flood periods.
2012 IEEE Symposium on Robotics and Applications (ISRA), 2012
Neurosurgeons are required to perform craniotomies to remove brain tumors, hemangiomas, cerebral ... more Neurosurgeons are required to perform craniotomies to remove brain tumors, hemangiomas, cerebral aneurysms, blood clots in the brain, or relieve internal pressure in the brain. After a craniotomy, the cranial flaps removed from the skull must be set back and fixed appropriately. However, due to the different sizes and shapes of cranial flaps and the various fixation methods, in certain clinical cases, the fixed cranial flaps might be loosened or in dented condition after surgery. This study thus developed a cranioplasty surgical-planning platform to integrate medical imaging technology, computer-aided engineering, and a high-performance computing simulation and visualization. This platform provides an efficient approach to evaluate the structural strength of cranial flaps before an operation. Surgeons can execute preoperative biomechanical simulations of cranial flaps under different fixation methods to achieve optimal fixation planning.
Severe pier scour is usually the major cause of bridge failures. It is therefore crucial to devel... more Severe pier scour is usually the major cause of bridge failures. It is therefore crucial to develop various scour monitoring techniques and prediction models for real-time warning of bridge safety. In the present study, a multi-lens monitoring system for pier scour under laboratory conditions has been developed. By utilising a plurality of lenses, this system is capable of tracking scour images and obtaining real-time scour-depth variation through a series of image recognition processes. Laboratory experiments under unsteady flow conditions were carried out to validate the proposed monitoring method. Then, three time-dependent scour prediction models were employed for simulation and comparison with the measured data. In order to improve the scour prediction results, with the real-time scour monitoring data, a data assimilation scheme is proposed and applied to the scour model under clear-water scour conditions. The result shows that the accuracy of scour prediction for a lead time o...
A model adopting the surface capturing method is developed for the simulation of dam-break flows ... more A model adopting the surface capturing method is developed for the simulation of dam-break flows by solving the Navier-Stokes equations of weakly compressible and variable density flows in open channels. Due to the characteristics of weakly compressible flow equations, a compressibility parameter describing the compressibility of fluid is determined to obtain the time-accurate flow fields in both liquid and gas regions simultaneously. Accordingly, the location of free surface can be captured as a discontinuity of the density field for dam-break flow simulations. The numerical algorithm in the proposed method is based on the framework of the finite volume method for discretization in space. To deal with the discontinuity property of fluid density near the free surface, the TVD-MUSCL scheme is adopted to overcome numerical oscillations and dissipation. For discretization in time, the explicit 4-stage Runge-Kutta scheme is employed in the model. Finally, several typical dam-break flow ...
Maxillomandibular advancement is one of the treatments available for obstructive sleep apnea. The... more Maxillomandibular advancement is one of the treatments available for obstructive sleep apnea. The influence of this surgery on the upper airway and its mechanism are not fully understood. The present research simulates the flow fields of narrowed upper airways of 2 patients with obstructive sleep apnea treated with maxillomandibular advancement. The geometry of the upper airway was reconstructed from computed tomographic images taken before and after surgery. The consequent three-dimensional surface model was rendered for measurement and computational fluid dynamics simulation. Patients showed clinical improvement 6 months after surgery. The cross-sectional area of the narrowest part of the upper airway was increased in all dimensions. The simulated results showed a less constricted upper airway, with less velocity change and a decreased pressure gradient across the whole conduit during passage of air. Less breathing effort is therefore expected to achieve equivalent ventilation with the postoperative airway. This study demonstrates the possibility of computational fluid dynamics in providing information for understanding the pathogenesis of OSA and the effects of its treatment.
The apnea-hypopnea index (AHI) is a widely accepted measure for the severity of obstructive sleep... more The apnea-hypopnea index (AHI) is a widely accepted measure for the severity of obstructive sleep apnea (OSA). Current methods to determine AHI fail to provide anatomic information for treatment decisions. In this report, we studied three-dimensional models of upper airways acquired by computed tomographic scanning with geometric measurements and computational fluid dynamics (CFD) analysis and evaluated the correlations with AHI. Participants had CT scans of their upper airways after standard polysomnography studies. Three-dimensional surface models of upper airways were generated for cross-sectional area measurements of the choanae (A CH) and the smallest cross-sectional area (A min). Computational fluid dynamic analysis was then performed by using this three-dimensional model. Pressure differences required to set tidal volume during inspiration ($P min-INSP) and expiration ($P max-EXP) and minimum negative pressure produced in the level of A CH (Pmin-INSP at A CH) and A min (P min-INSP at A min) were calculated. Correlations of these parameters and the body mass index with AHI were analyzed. Statistical differences between groups of different AHI ranges were also compared. The pressure distribution simulated by CFD demonstrated abrupt pressure drops in A min level, and this phenomenon was more significant in severe OSA. All parameters except A CH and P min-INSP at A min significantly correlated with the AHI, and there were significant statistical differences between the OSA groups and the normal group. The results indicate that, in our study group, the geometry of pharyngeal airway and its CFD simulation correlate well with AHI. This model may be further applied for clinical evaluation.
In this study, a parallel computing technology is applied on the simulation of a wind turbine flo... more In this study, a parallel computing technology is applied on the simulation of a wind turbine flow problem. A third-order Roe type flux limited splitting based on a pre-conditioning matrix with an explicit time marching method is used to solve the Navier-Stokes equations. The original FORTRAN code was parallelized with Message Passing Interface (MPI) language and tested on a 64-CPU IBM SP2 parallel computer. The test results show that a significant reduction of computing time in running the model and a superlinear speed up rate is achieved up to 32 CPUs at IBM SP2 processors. The speed up rate is as high as 49 for using IBM SP2 64 processors. The test shows very promising potential of parallel processing to provide prompt simulation of the current wind turbine problems.
Biomedical Engineering: Applications, Basis and Communications, 2002
In this study, Newtonian flows passing through three-dimensional curved and straight axissymmetri... more In this study, Newtonian flows passing through three-dimensional curved and straight axissymmetrical stenotic tubes are investigated. The geometry effects and Reynolds numbers of 100, 200, 400, and 600 on the formation of the shear rate over arterial walls are studied. It is noted that geometric effects on flow features such as velocity profiles, pressure and wall shear stress distributions in the post-stenotic region are significant. The location of maximum wall shear stress is found to relate to the geometric effect much than the Reynolds number effect.
In this study, a parallel computing technology is applied on the simulation of a wind turbine flo... more In this study, a parallel computing technology is applied on the simulation of a wind turbine flow problem. A third-order Roe type flux limited splitting based on a pre-conditioning matrix with an explicit time marching method is used to solve the Navier-Stokes equations. The original FORTRAN code was parallelized with Message Passing Interface (MPI) language and tested on a 64-CPU IBM SP2 parallel computer. The test results show that a significant reduction of computing time in running the model and a superlinear speed up rate is achieved up to 32 CPUs at IBM SP2 processors. The speed up rate is as high as 49 for using IBM SP2 64 processors. The test shows very promising potential of parallel processing to provide prompt simulation of the current wind turbine problems.
Maxillomandibular advancement is one of the treatments available for obstructive sleep apnea. The... more Maxillomandibular advancement is one of the treatments available for obstructive sleep apnea. The influence of this surgery on the upper airway and its mechanism are not fully understood. The present research simulates the flow fields of narrowed upper airways of 2 patients with obstructive sleep apnea treated with maxillomandibular advancement. The geometry of the upper airway was reconstructed from computed tomographic images taken before and after surgery. The consequent three-dimensional surface model was rendered for measurement and computational fluid dynamics simulation. Patients showed clinical improvement 6 months after surgery. The cross-sectional area of the narrowest part of the upper airway was increased in all dimensions. The simulated results showed a less constricted upper airway, with less velocity change and a decreased pressure gradient across the whole conduit during passage of air. Less breathing effort is therefore expected to achieve equivalent ventilation with the postoperative airway. This study demonstrates the possibility of computational fluid dynamics in providing information for understanding the pathogenesis of OSA and the effects of its treatment.
The three-dimensional multi-stage turbomachinery flow simulation is calculated on the PC cluster ... more The three-dimensional multi-stage turbomachinery flow simulation is calculated on the PC cluster environment in NCHC. The UTRC large-scale turbine is employed here as the baseline configuration. A compressible viscous finite volunie algorithm solving Reynolds averaged Navier-Stokes equations with artificial dissipation terms similar to Jameson's method is adopted. Circumferential average is pe@ormed between the interface of rotor and stator. The tnaster/slave algorithm is eniployed f o r the parallel iniplementation, and a processor calculates a blade row. Three, five, seven and nine blade rows are used to demonstrate the petjiorniance of parallel computation on the PC cluster. Those results are shown that the pe@ormance is very well, especially for more blade rows, i.e., nine blade rows, have the super speedup eflciency.
During the past years, some fundamental difficulties in the diagnosis and treatment of vascular d... more During the past years, some fundamental difficulties in the diagnosis and treatment of vascular disorders such that the re-stenosis and no-reflow phenomena of arteries after balloon angioplasty are still the unsolved problems and required in a further study. It is well known that blood flow characteristics in arteries are altered significantly by arterial disease, such as stenosis and aneurysm. In general, the prestenotic flow is usually laminar, flow in the post-stenotic region could become highly disordered or even turbulent depending upon the flow conditions and severity of the stenosis. The post-stenotic flow became unstable during this vortex generation phase of the cycle, resulting in intense fluctuations in the formation of wall shear stresses [1]. The study of physiologically realistic pulsatile flow through stenosis could have profound implications for the above-mentioned post-stenotic flow phenomena. In the current study, a dual-time stepping method based on a three-order upwind type approximated Riemann solvers [2,3] is used to solve the stationary and transient Navier- Stokes equations for analysis of separated blood flows in artery. A four-stage Runge-Kutta scheme is used in the pseudo-time iteration, also combining with MPI parallelized tool. The test results also display very promising potential of parallel processing. Newtonian flows through one curved stenosis model, one health aorta model and one aortic dissection model are performed to predict the wall stress distributions. The curved stenosis model with Reynolds numbers of 100, 200, 400, and 600 are constructed.
IEEE Transactions on Biomedical Engineering, Sep 1, 2013
We developed a novel aerosol-mediated drug delivery system for inner ear therapy by using a silic... more We developed a novel aerosol-mediated drug delivery system for inner ear therapy by using a silicon-based multiple-Fourier horn nozzle. Intratympanic aerosol (ITA) methylprednisolone (MP) delivery can protect hearing after acoustic trauma. The highest concentration of MP (38.9 ± 5.47 ppm) appeared at 2 h and declined rapidly within 10 h. The concentrations of MP remained at a relatively low level for more than 10 h. Compared to the baseline, the auditory brainstem response (ABR) thresholds shifted markedly at 1 h after noise exposure in all groups (p < 0.05). From the cochleograms, it can be noted that the main lesions encompassed the 2-20 kHz frequency range. Significant differences ( ) were observed for the range between 5 and 8 kHz in the cell loss of outer hair cells (OHCs). The losses for IHCs were lower than for OHCs. The MP movement in the middle ear was simulated by a convection diffusion equation with a relaxation time. The relaxation time was 0.5 h, and the concentration threshold of MP on the round window membrane (RWM) in the middle ear (C T) was 8900 ppm. Using the unit hydrograph (UH) method, we obtained a proper boundary concentration on the RWM at the cochlea, which resulted in a well-fit concentration. Finally, a linking mechanism between the middle ear and the cochlea was established by the RWM. The adjustable permeability and concentration threshold provide the flexibility to match the peak times and peak values of the concentration on the RWM in the middle ear and the cochlea.
We developed a novel aerosol-mediated drug delivery system for inner ear therapy by using a silic... more We developed a novel aerosol-mediated drug delivery system for inner ear therapy by using a silicon-based multiple-Fourier horn nozzle. Intratympanic aerosol (ITA) methylprednisolone (MP) delivery can protect hearing after acoustic trauma. The highest concentration of MP (38.9 ± 5.47 ppm) appeared at 2 h and declined rapidly within 10 h. The concentrations of MP remained at a relatively low level for more than 10 h. Compared to the baseline, the auditory brainstem response (ABR) thresholds shifted markedly at 1 h after noise exposure in all groups (p < 0.05). From the cochleograms, it can be noted that the main lesions encompassed the 2-20 kHz frequency range. Significant differences ( ) were observed for the range between 5 and 8 kHz in the cell loss of outer hair cells (OHCs). The losses for IHCs were lower than for OHCs. The MP movement in the middle ear was simulated by a convection diffusion equation with a relaxation time. The relaxation time was 0.5 h, and the concentration threshold of MP on the round window membrane (RWM) in the middle ear (C T) was 8900 ppm. Using the unit hydrograph (UH) method, we obtained a proper boundary concentration on the RWM at the cochlea, which resulted in a well-fit concentration. Finally, a linking mechanism between the middle ear and the cochlea was established by the RWM. The adjustable permeability and concentration threshold provide the flexibility to match the peak times and peak values of the concentration on the RWM in the middle ear and the cochlea.
The research proposed an inverse numerical simulation method to recognize the mechanisms of the d... more The research proposed an inverse numerical simulation method to recognize the mechanisms of the drug movement from the middle ear to the cochlea and calibrate the associated parameters. A real 3D model was obtained from the CT image and the relative geometry and mesh were built by ICEM-CFD. The simulation was processes by ANSYSCFX. A set of drug concentration measurement in the cochlea was used in calibrating the parameters. Two new mechanisms: a relaxation time of the absorption via the wall of the middle ear and a concentration threshold to start the permeation from the middle ear to the cochlea were also proposed in this research to complete the phenomena of drug movement. The results indicate a reasonable mechanism to expound the process of drug movement.
Percutaneous Transluminal Angioplasty (PTA) with stent is employed to treat the cardiovascular di... more Percutaneous Transluminal Angioplasty (PTA) with stent is employed to treat the cardiovascular diseases in clinical to dilate stenotic arteries. There have been two types of stents (helical coil shape and traditional mesh shape) wildly used in angioplasty in the past few years. This research studied the biomechanical effects on the expansion behavior of these two different stents with balloon in the artery vessel. The commercial three-dimensional finite element method (FEM) based software was employed to perform all the computations in this study. Simulation results reveal that the pressure is delivered uniformly by the balloon, which leads the stenosed vessel to dilate. The dog bone effect is more obvious in the helical coil stent than the traditional mesh stent. The regions close to both ends of the stent exhibit large deformation and high shear stress values for both stent types. In the clinical practices, large deformation may cause stress concentration which leads to the damage of the vessel.
Proceedings. Seventh International Conference on High Performance Computing and Grid in Asia Pacific Region, 2004.
ABSTRACT In the present study, a vertical, two-dimensional, two-phase flow model is developed, wh... more ABSTRACT In the present study, a vertical, two-dimensional, two-phase flow model is developed, which is capable of simulating the fluid and air flow fields simultaneously to capture the positions of the free surface. To deal with the discontinuity properties in density field near the free surface, the TVD-MUSCL scheme is employed to overcome the numerical oscillation problem. The numerical algorithm is developed using a conservative, explicit, finite volume discretization of the motion equation. The dam-breaking problem is employed to validate the proposed model. The good agreements between the computed and measured results demonstrate the applicability of the model.
During the past years, some fundamental difficulties in the diagnosis and treatment of vascular d... more During the past years, some fundamental difficulties in the diagnosis and treatment of vascular disorders such that the re-stenosis and no-reflow phenomena of arteries after balloon angioplasty are still the unsolved problems and required in a further study. It is well known that blood flow characteristics in arteries are altered significantly by arterial disease, such as stenosis and aneurysm. In general, the prestenotic flow is usually laminar, flow in the post-stenotic region could become highly disordered or even turbulent depending upon the flow conditions and severity of the stenosis. The post-stenotic flow became unstable during this vortex generation phase of the cycle, resulting in intense fluctuations in the formation of wall shear stresses [1]. The study of physiologically realistic pulsatile flow through stenosis could have profound implications for the above-mentioned post-stenotic flow phenomena. In the current study, a dual-time stepping method based on a three-order upwind type approximated Riemann solvers [2,3] is used to solve the stationary and transient Navier- Stokes equations for analysis of separated blood flows in artery. A four-stage Runge-Kutta scheme is used in the pseudo-time iteration, also combining with MPI parallelized tool. The test results also display very promising potential of parallel processing. Newtonian flows through one curved stenosis model, one health aorta model and one aortic dissection model are performed to predict the wall stress distributions. The curved stenosis model with Reynolds numbers of 100, 200, 400, and 600 are constructed.
ABSTRACT A scour monitoring system with a micro camera tracking the bed-level images is proposed ... more ABSTRACT A scour monitoring system with a micro camera tracking the bed-level images is proposed in this study. Two image recognition algorithms have been developed to support the bed-level image tracking approach. Through the laboratory experiments of pier scour, this study demonstrates that the proposed system is able to accurately monitor the scour-depth evolution in real time. In addition, five commonly-used temporal scour models are employed to simulate scour-depth evolution and their results are compared with monitoring data. In general, the results indicate that the proposed scour monitoring system has the potential for further applications in the field.
2013 IEEE International Symposium on Multimedia, 2013
ABSTRACT In this paper, we present two types of the real-time water monitoring system using the i... more ABSTRACT In this paper, we present two types of the real-time water monitoring system using the image processing technology, the water level recognition and the surface velocity recognition. According to the bridge failure investigation, floods in the river often pose potential risk to bridges, and scouring could undermine the pier foundation and cause the structures to collapse. It is very important to develop monitoring techniques for bridge safety in the field. In this study, we installed two high-resolution cameras on the in-situ bridge site to get the real-time water level and surface velocity image. For the water level recognition, we use the image processing techniques of the image binarization, character recognition, and water line detection. For the surface velocity recognition, the proposed system apply the PIV(Particle Image Velocimetry, PIV) method to obtain the recognition of the water surface velocity by the cross correlation analysis. Finally, the proposed systems are used to record and measure the variations of the water level and surface velocity for a period of three days. The good results show that the proposed systems have potential to provide real-time information of water level and surface velocity during flood periods.
2012 IEEE Symposium on Robotics and Applications (ISRA), 2012
Neurosurgeons are required to perform craniotomies to remove brain tumors, hemangiomas, cerebral ... more Neurosurgeons are required to perform craniotomies to remove brain tumors, hemangiomas, cerebral aneurysms, blood clots in the brain, or relieve internal pressure in the brain. After a craniotomy, the cranial flaps removed from the skull must be set back and fixed appropriately. However, due to the different sizes and shapes of cranial flaps and the various fixation methods, in certain clinical cases, the fixed cranial flaps might be loosened or in dented condition after surgery. This study thus developed a cranioplasty surgical-planning platform to integrate medical imaging technology, computer-aided engineering, and a high-performance computing simulation and visualization. This platform provides an efficient approach to evaluate the structural strength of cranial flaps before an operation. Surgeons can execute preoperative biomechanical simulations of cranial flaps under different fixation methods to achieve optimal fixation planning.
Severe pier scour is usually the major cause of bridge failures. It is therefore crucial to devel... more Severe pier scour is usually the major cause of bridge failures. It is therefore crucial to develop various scour monitoring techniques and prediction models for real-time warning of bridge safety. In the present study, a multi-lens monitoring system for pier scour under laboratory conditions has been developed. By utilising a plurality of lenses, this system is capable of tracking scour images and obtaining real-time scour-depth variation through a series of image recognition processes. Laboratory experiments under unsteady flow conditions were carried out to validate the proposed monitoring method. Then, three time-dependent scour prediction models were employed for simulation and comparison with the measured data. In order to improve the scour prediction results, with the real-time scour monitoring data, a data assimilation scheme is proposed and applied to the scour model under clear-water scour conditions. The result shows that the accuracy of scour prediction for a lead time o...
A model adopting the surface capturing method is developed for the simulation of dam-break flows ... more A model adopting the surface capturing method is developed for the simulation of dam-break flows by solving the Navier-Stokes equations of weakly compressible and variable density flows in open channels. Due to the characteristics of weakly compressible flow equations, a compressibility parameter describing the compressibility of fluid is determined to obtain the time-accurate flow fields in both liquid and gas regions simultaneously. Accordingly, the location of free surface can be captured as a discontinuity of the density field for dam-break flow simulations. The numerical algorithm in the proposed method is based on the framework of the finite volume method for discretization in space. To deal with the discontinuity property of fluid density near the free surface, the TVD-MUSCL scheme is adopted to overcome numerical oscillations and dissipation. For discretization in time, the explicit 4-stage Runge-Kutta scheme is employed in the model. Finally, several typical dam-break flow ...
Maxillomandibular advancement is one of the treatments available for obstructive sleep apnea. The... more Maxillomandibular advancement is one of the treatments available for obstructive sleep apnea. The influence of this surgery on the upper airway and its mechanism are not fully understood. The present research simulates the flow fields of narrowed upper airways of 2 patients with obstructive sleep apnea treated with maxillomandibular advancement. The geometry of the upper airway was reconstructed from computed tomographic images taken before and after surgery. The consequent three-dimensional surface model was rendered for measurement and computational fluid dynamics simulation. Patients showed clinical improvement 6 months after surgery. The cross-sectional area of the narrowest part of the upper airway was increased in all dimensions. The simulated results showed a less constricted upper airway, with less velocity change and a decreased pressure gradient across the whole conduit during passage of air. Less breathing effort is therefore expected to achieve equivalent ventilation with the postoperative airway. This study demonstrates the possibility of computational fluid dynamics in providing information for understanding the pathogenesis of OSA and the effects of its treatment.
The apnea-hypopnea index (AHI) is a widely accepted measure for the severity of obstructive sleep... more The apnea-hypopnea index (AHI) is a widely accepted measure for the severity of obstructive sleep apnea (OSA). Current methods to determine AHI fail to provide anatomic information for treatment decisions. In this report, we studied three-dimensional models of upper airways acquired by computed tomographic scanning with geometric measurements and computational fluid dynamics (CFD) analysis and evaluated the correlations with AHI. Participants had CT scans of their upper airways after standard polysomnography studies. Three-dimensional surface models of upper airways were generated for cross-sectional area measurements of the choanae (A CH) and the smallest cross-sectional area (A min). Computational fluid dynamic analysis was then performed by using this three-dimensional model. Pressure differences required to set tidal volume during inspiration ($P min-INSP) and expiration ($P max-EXP) and minimum negative pressure produced in the level of A CH (Pmin-INSP at A CH) and A min (P min-INSP at A min) were calculated. Correlations of these parameters and the body mass index with AHI were analyzed. Statistical differences between groups of different AHI ranges were also compared. The pressure distribution simulated by CFD demonstrated abrupt pressure drops in A min level, and this phenomenon was more significant in severe OSA. All parameters except A CH and P min-INSP at A min significantly correlated with the AHI, and there were significant statistical differences between the OSA groups and the normal group. The results indicate that, in our study group, the geometry of pharyngeal airway and its CFD simulation correlate well with AHI. This model may be further applied for clinical evaluation.
In this study, a parallel computing technology is applied on the simulation of a wind turbine flo... more In this study, a parallel computing technology is applied on the simulation of a wind turbine flow problem. A third-order Roe type flux limited splitting based on a pre-conditioning matrix with an explicit time marching method is used to solve the Navier-Stokes equations. The original FORTRAN code was parallelized with Message Passing Interface (MPI) language and tested on a 64-CPU IBM SP2 parallel computer. The test results show that a significant reduction of computing time in running the model and a superlinear speed up rate is achieved up to 32 CPUs at IBM SP2 processors. The speed up rate is as high as 49 for using IBM SP2 64 processors. The test shows very promising potential of parallel processing to provide prompt simulation of the current wind turbine problems.
Biomedical Engineering: Applications, Basis and Communications, 2002
In this study, Newtonian flows passing through three-dimensional curved and straight axissymmetri... more In this study, Newtonian flows passing through three-dimensional curved and straight axissymmetrical stenotic tubes are investigated. The geometry effects and Reynolds numbers of 100, 200, 400, and 600 on the formation of the shear rate over arterial walls are studied. It is noted that geometric effects on flow features such as velocity profiles, pressure and wall shear stress distributions in the post-stenotic region are significant. The location of maximum wall shear stress is found to relate to the geometric effect much than the Reynolds number effect.
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Papers by Lung-Cheng Lee