Magnetic fluid hyperthermia (MFH) is a novel reliable technique with excellent potential for ther... more Magnetic fluid hyperthermia (MFH) is a novel reliable technique with excellent potential for thermal therapies and treating breast tumours. This method involves injecting a magnetic nanofluid into the tumour and applying an external AC magnetic field to induce heat in the magnetic nanoparticles (MNPs) and raise the tumour temperature to ablation temperature ranges. Because of the complexity of considering and coupling all different physics involves in this phenomenon and also due to the intricacy of a thorough FEM numerical study, few FEM-based studies address the entire MFH process as similar to reality as possible. The current study investigates a FEM-based three-dimensional numerical simulation of MFH of breast tumours as a multi-physics problem. An anatomically realistic breast phantom (ARBP) is considered, some magnetic nanofluid is injected inside the tumour, and the diffusion phenomenon is simulated. Then, the amount of heat generated in the MNP-saturated tumour area due to a...
We present direct numerical simulation data for turbulent duct flow of a finite-extensibility non... more We present direct numerical simulation data for turbulent duct flow of a finite-extensibility non-linear elastic dumbbell model with the Peterlin approximation (FENE-P) fluid in the high drag reduction regime. While the secondary flow pattern is qualitatively similar to that in a Newtonian fluid, its magnitude is significantly reduced, resulting in a less uniformly distributed velocity profile and hence smaller gradients at the wall. The Reynolds stress tensor in the polymer-laden flow was found to be increasingly anisotropic with most of the turbulent kinetic energy retained in the streamwise component, [Formula: see text]. We introduce a novel approach for investigating polymer stretching using the anisotropy invariant map of the polymer stress tensor and observe the persistence of both uniaxial and biaxial extension. Analysis of the transport equation for the mean kinetic energy indicates that polymer stretching and relaxation is a highly dissipative process; hence, the introduct...
Abstract. A three-dimensional two-phase lattice Boltzmann model is adopted to simulate bubble dyn... more Abstract. A three-dimensional two-phase lattice Boltzmann model is adopted to simulate bubble dynamics on multi-graphics processing unit (GPU) cluster. The spurious velocity caused by the force imbalance near the two-phase interface can be successfully suppressed by the adopted model. A single bubble rising in a rectangular domain is computed at different regimes of Bond number (Bo) and Morton number (Mo). The terminal Reynolds number (Re) and the deformed shape are consistent with both experimental results and benchmark solutions. Further, an efficient multi-GPU cluster implementation with two-dimensional decomposition is examined and the program maintains good scalability even in the case with high GPU number.
This paper studies the effects of compression, deformation, and the contact area in the membrane ... more This paper studies the effects of compression, deformation, and the contact area in the membrane electrode assembly (MEA). The electrical impedance of fuel cell stacks due to the assembly of the metallic bipolar plates is also considered. According to decades-long fuel cell (FC) assembly experience, an increase in compression force can result in adequate contact resistance, but excessive compression may cause extra contact resistance and damage to the MEA structure. The study suggests a design for improving the performance of the FC stack by proposing different fillet radii metallic bipolar plates. It is found that the appropriate fillet radius reduces contact resistance by 13% and avoids the accumulation of compression, thereby maintaining contact resistance at adequate levels. The current design proposes a simple and effective method to minimize the dimension tolerance of single fuel cell units and support sufficient compression.
Abstract A nonlinear multigrid solver for solutions of unsteady three-dimensional incompressible ... more Abstract A nonlinear multigrid solver for solutions of unsteady three-dimensional incompressible viscous flow working on multi-GPU cluster is developed. The solver consists of a full approximation scheme (FAS) V-cycle scheme to accelerate the computation, in which the artificial compressibility method based Navier-Stokes solver is used as a smoother. Multi-stream overlapping strategies are designed to assist multi-GPU computations. The numerical procedure is validated by computing 3D laminar and turbulent flows within a lid-driven cubic cavity. The predicted results compare favorably with previous benchmark solutions and measurements, both in mean and turbulent quantities. For the performance of the FAS V-cycle scheme, up to two orders of magnitude speedups are reported, and the relationship between work unit (WU) and total grid number N is O ( N 0.3 ) under the deepest FAS V-cycle. A detailed evaluation of the GPU implementation is carried out employing the Roofline model and the scalability analysis.
Journal of Microelectronics and Electronic Packaging, 2004
The thermal characteristics of a flip-chip BGA package on board are numerically investigated unde... more The thermal characteristics of a flip-chip BGA package on board are numerically investigated under both natural and forced convection conditions. The possible heat transfer enhancement strategy using heat sink is also addressed. Heat generated at the junction could transfer in the upward and downward (through PCB) directions of the package, and then be dissipated to the ambient by both convection and radiation. For the cases without heat sink, the amount of the heat dissipated through the PCB comprises 90% and 75% of the power generated for the natural and forced convection regimes, respectively. With the proper heat sink attached the rate of the upward heat transfer increases and can reach 50% of the power dissipated under the forced convection condition. Detailed analysis is presented regarding the effects of the cross flow velocity, the number of fins and the height of the heat sink on the thermal resistance of the flip-chip BGA package.
In this paper, the lattice Boltzmann method is combined with the immersed boundary technique to s... more In this paper, the lattice Boltzmann method is combined with the immersed boundary technique to simulate complex geometry flows. The complex geometry is represented by Lagrangian markers and forces are exerted at the Lagrangian markers in order to satisfy the prescribed velocity of the boundary. This force at the Lagrangian markers is then distributed to the Eulerian grid by a well-chosen discretized delta function. With the known force field in the Eulerian grid to mimic the boundary, the lattice Boltzmann method is used to compute the flow field where the complex geometry is immersed inside the Cartesian computational domain. Numerical experiments show that the second-order accuracy of the adopted numerical scheme is degraded to 1.8 order. The proposed method is examined by computing decaying vortex, lid driven cavity flow and 2D and 3D flows over asymmetrically placed cylinder. All the numerical results are compatible with the benchmark solutions.
Lattice Boltzmann method (LBM) is adopted to compute two and three-dimensional lid driven cavity ... more Lattice Boltzmann method (LBM) is adopted to compute two and three-dimensional lid driven cavity flows to examine the influence of memory management on the computational performance using Graphics Processing Unit (GPU). Both single and multi-relaxation time LBM are adopted. The computations are conducted on nVIDIA GeForce Titan, Tesla C2050 and GeForce GTX 560Ti. The performance using global memory deteriorates greatly when multi relaxation time (MRT) LBM is used, which is due to the scheme requesting more information from the global memory than its single relaxation time (SRT) LBM counterpart. On the other hand, adopting on chip memory the difference using MRT and SRT is not significant. Also, performance of LBM streaming procedure using offset reading surpasses offset writing ranging from 50% to 100% and this applies to both SRT and MRT LBM. Finally, comparisons using different GPU platforms indicate that Titan as expected outperforms other devices, and attains 227 and 193 speedup...
Magnetic fluid hyperthermia (MFH) is a novel reliable technique with excellent potential for ther... more Magnetic fluid hyperthermia (MFH) is a novel reliable technique with excellent potential for thermal therapies and treating breast tumours. This method involves injecting a magnetic nanofluid into the tumour and applying an external AC magnetic field to induce heat in the magnetic nanoparticles (MNPs) and raise the tumour temperature to ablation temperature ranges. Because of the complexity of considering and coupling all different physics involves in this phenomenon and also due to the intricacy of a thorough FEM numerical study, few FEM-based studies address the entire MFH process as similar to reality as possible. The current study investigates a FEM-based three-dimensional numerical simulation of MFH of breast tumours as a multi-physics problem. An anatomically realistic breast phantom (ARBP) is considered, some magnetic nanofluid is injected inside the tumour, and the diffusion phenomenon is simulated. Then, the amount of heat generated in the MNP-saturated tumour area due to a...
We present direct numerical simulation data for turbulent duct flow of a finite-extensibility non... more We present direct numerical simulation data for turbulent duct flow of a finite-extensibility non-linear elastic dumbbell model with the Peterlin approximation (FENE-P) fluid in the high drag reduction regime. While the secondary flow pattern is qualitatively similar to that in a Newtonian fluid, its magnitude is significantly reduced, resulting in a less uniformly distributed velocity profile and hence smaller gradients at the wall. The Reynolds stress tensor in the polymer-laden flow was found to be increasingly anisotropic with most of the turbulent kinetic energy retained in the streamwise component, [Formula: see text]. We introduce a novel approach for investigating polymer stretching using the anisotropy invariant map of the polymer stress tensor and observe the persistence of both uniaxial and biaxial extension. Analysis of the transport equation for the mean kinetic energy indicates that polymer stretching and relaxation is a highly dissipative process; hence, the introduct...
Abstract. A three-dimensional two-phase lattice Boltzmann model is adopted to simulate bubble dyn... more Abstract. A three-dimensional two-phase lattice Boltzmann model is adopted to simulate bubble dynamics on multi-graphics processing unit (GPU) cluster. The spurious velocity caused by the force imbalance near the two-phase interface can be successfully suppressed by the adopted model. A single bubble rising in a rectangular domain is computed at different regimes of Bond number (Bo) and Morton number (Mo). The terminal Reynolds number (Re) and the deformed shape are consistent with both experimental results and benchmark solutions. Further, an efficient multi-GPU cluster implementation with two-dimensional decomposition is examined and the program maintains good scalability even in the case with high GPU number.
This paper studies the effects of compression, deformation, and the contact area in the membrane ... more This paper studies the effects of compression, deformation, and the contact area in the membrane electrode assembly (MEA). The electrical impedance of fuel cell stacks due to the assembly of the metallic bipolar plates is also considered. According to decades-long fuel cell (FC) assembly experience, an increase in compression force can result in adequate contact resistance, but excessive compression may cause extra contact resistance and damage to the MEA structure. The study suggests a design for improving the performance of the FC stack by proposing different fillet radii metallic bipolar plates. It is found that the appropriate fillet radius reduces contact resistance by 13% and avoids the accumulation of compression, thereby maintaining contact resistance at adequate levels. The current design proposes a simple and effective method to minimize the dimension tolerance of single fuel cell units and support sufficient compression.
Abstract A nonlinear multigrid solver for solutions of unsteady three-dimensional incompressible ... more Abstract A nonlinear multigrid solver for solutions of unsteady three-dimensional incompressible viscous flow working on multi-GPU cluster is developed. The solver consists of a full approximation scheme (FAS) V-cycle scheme to accelerate the computation, in which the artificial compressibility method based Navier-Stokes solver is used as a smoother. Multi-stream overlapping strategies are designed to assist multi-GPU computations. The numerical procedure is validated by computing 3D laminar and turbulent flows within a lid-driven cubic cavity. The predicted results compare favorably with previous benchmark solutions and measurements, both in mean and turbulent quantities. For the performance of the FAS V-cycle scheme, up to two orders of magnitude speedups are reported, and the relationship between work unit (WU) and total grid number N is O ( N 0.3 ) under the deepest FAS V-cycle. A detailed evaluation of the GPU implementation is carried out employing the Roofline model and the scalability analysis.
Journal of Microelectronics and Electronic Packaging, 2004
The thermal characteristics of a flip-chip BGA package on board are numerically investigated unde... more The thermal characteristics of a flip-chip BGA package on board are numerically investigated under both natural and forced convection conditions. The possible heat transfer enhancement strategy using heat sink is also addressed. Heat generated at the junction could transfer in the upward and downward (through PCB) directions of the package, and then be dissipated to the ambient by both convection and radiation. For the cases without heat sink, the amount of the heat dissipated through the PCB comprises 90% and 75% of the power generated for the natural and forced convection regimes, respectively. With the proper heat sink attached the rate of the upward heat transfer increases and can reach 50% of the power dissipated under the forced convection condition. Detailed analysis is presented regarding the effects of the cross flow velocity, the number of fins and the height of the heat sink on the thermal resistance of the flip-chip BGA package.
In this paper, the lattice Boltzmann method is combined with the immersed boundary technique to s... more In this paper, the lattice Boltzmann method is combined with the immersed boundary technique to simulate complex geometry flows. The complex geometry is represented by Lagrangian markers and forces are exerted at the Lagrangian markers in order to satisfy the prescribed velocity of the boundary. This force at the Lagrangian markers is then distributed to the Eulerian grid by a well-chosen discretized delta function. With the known force field in the Eulerian grid to mimic the boundary, the lattice Boltzmann method is used to compute the flow field where the complex geometry is immersed inside the Cartesian computational domain. Numerical experiments show that the second-order accuracy of the adopted numerical scheme is degraded to 1.8 order. The proposed method is examined by computing decaying vortex, lid driven cavity flow and 2D and 3D flows over asymmetrically placed cylinder. All the numerical results are compatible with the benchmark solutions.
Lattice Boltzmann method (LBM) is adopted to compute two and three-dimensional lid driven cavity ... more Lattice Boltzmann method (LBM) is adopted to compute two and three-dimensional lid driven cavity flows to examine the influence of memory management on the computational performance using Graphics Processing Unit (GPU). Both single and multi-relaxation time LBM are adopted. The computations are conducted on nVIDIA GeForce Titan, Tesla C2050 and GeForce GTX 560Ti. The performance using global memory deteriorates greatly when multi relaxation time (MRT) LBM is used, which is due to the scheme requesting more information from the global memory than its single relaxation time (SRT) LBM counterpart. On the other hand, adopting on chip memory the difference using MRT and SRT is not significant. Also, performance of LBM streaming procedure using offset reading surpasses offset writing ranging from 50% to 100% and this applies to both SRT and MRT LBM. Finally, comparisons using different GPU platforms indicate that Titan as expected outperforms other devices, and attains 227 and 193 speedup...
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Papers by Chao-An Lin