1,721,250 research outputs found
Computational modeling of passive furrowed channel micromixers for lab-on-a-chip applications
Full text linkBackground: Effective micromixers represent essential components for micro total analysis systems or lab-on-a-chip. Indeed,
mixing is a key process for the success of all chemical or biochemical reactions. Most microfluidic systems operate in a laminar
flow regime dominated by molecular diffusion, which is not favorable to mixing. In the present work, numerical analyses
of mixing in 3-dimensional channels with obstacles on the walls were performed to investigate mixing behavior and flow
characteristics with geometric parameters as well as Reynolds number.
Methods: Several channel wall geometries were numerically modeled, and the influence of obstacle height, phase shift between
the walls, channel cross-section shape (aspect ratio) and Reynolds number on mixer performances was investigated.
Wall geometries were evaluated comparatively in terms of index of mixing and pressure drops caused.
Results: Results indicated that furrowed channels with proper triangle-shaped obstacles show good performances in terms
of achieving complete mixing in a very short length of channel, and at the same time offer low pressure losses. Convective
motions are the main influences responsible for successful mixing, and micromixers with triangle-shaped obstacles show an
improvement in the mixing performances for increasing Reynolds numbers. Moreover, short times are required for the mixing
process. Finally, depending on the Reynolds number that one works at, there is also some flexibility in the choice of the
channel geometry, as the occurrence of effective chaotic advection was obtained for several conformations of the channels
proposed in this study.
Conclusions: Mixing enhancement can be achieved by optimizing the shape of the furrowed channel
Performance of a thrombectomy device for aspiration of thrombus with various sizes based on a computational fluid dynamic modelling
Full text linkIt is important to thoroughly remove the thrombus within the course of aspiration thrombectomy; otherwise, it may lead to further embolization. The performance of the aspiration thrombectomy device with a generic geometry is studied through the computational approach. In order to model the thrombus aspiration, a real left coronary artery is chosen while thrombi with various sizes are located at the bifurcation area of the coronary artery and, depending on the size of the thrombus, it is stretched toward the side branches. The thrombus occupies the artery resembling the blood current obstruction in the coronary vessel similar to the situation that leads to heart attack. It is concluded that the aspiration ability of the thrombectomy device is not linked to the thrombus size; it is rather linked to the aspiration pressure and thrombus age (organized versus fresh thrombus). However, the aspiration time period correlates to the thrombus size. The minimum applicable aspiration pressure is also investigated in this study
Editorial: Verification and Validation of in silico Models for Biomedical Implantable Devices
Full text linkComputational Analysis of the Effects of Fiber Deformation on the Microstructure and Permeability of Blood Oxygenator Bundles
No full textMechanical loads on the polymeric fibers of oxygenating bundles are commonly present due to bundle press-fitting during device assembly and blood pressure load. However, computational fluid dynamics (CFD) simulations for fiber bundle optimization neglect possible changes in microstructure due to such deformations. The aim of this study is to investigate the impact of fiber deformability on bundle microstructure and fluid dynamics mainly in terms of permeability. Fibers from commercial mats typically used for blood oxygenators were mechanically tested and based on these experimental data, a material model was developed to simulate the structural deformations the fibers undergo under press-fitting and blood pressure loads. Then, CFD simulations were performed on deformed bundle repetitive units to investigate permeability under varying loading conditions. The effects of different bundle geometric parameters on the variation of bundle permeability due to press-fitting were evaluated. Bundle press-fitting results in significant changes in microstructure that are reflected in a bundle permeability more than halved for a 15% press-fitting. This impact on permeability is present in all the simulated fiber bundles and becomes more pronounced as the pitch between fibers and thus bundle porosity decreases. Instead, the analyses on pressurized bundle show only small deformations caused by pressure load, with permeability changes below 1%. While blood pressure effects could be neglected, bundle press-fitting turns out to have a significant impact on bundle microstructure and permeability. Neglecting such microstructure variations during CFD simulations could also lead to incorrect assessment of the local fluid dynamics within the bundle
A mathematical model of a two-dimensional end-to-side anastomosis: fluid dynamics and tissue overgrowth interaction
No full textScaling approach to study the changes through the gestation of human fetal cardiac and circulatory behaviors.
No full textMathematical modelling of the human foetal cardiovascular system based on Doppler ultrasound data.
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