A microfluidic cell capture device was designed, fabricated, evaluated by numerical simulations and validated experimentally. The cell capture device was designed with a minimal footprint compartment comprising internal micropillars with the goal to obtain a compact, integrated bioanalytical system. The design of the device was accomplished by computational fluid dynamics (CFD) simulations. Various microdevice designs were rapidly prototyped in poly-dimethylsiloxane using conventional soft lithograpy technique applying micropatterned SU-8 epoxy based negative photoresist as moulding replica. The numerically modeled flow characteristics of the cell capture device were experimentally validated by tracing and microscopic recording the flow trajectories using yeast cells. Finally, we give some perspectives on how CFD modeling can be used in the early stage of microfluidics-based cell capture device development.
Due to the rise in awareness of global warming, many attempts to increase efficiency in the automotive industry are becoming prevalent. Design optimization can be used to increase the efficiency of electric vehicles by reducing aerodynamic drag and lift. The main focus of this paper is to analyse and optimise the aerodynamic characteristics of an electric vehicle to improve efficiency of using computational fluid dynamics modelling. Multiple part modifications were used to improve the drag and lift of the electric hatchback, testing various designs and dimensions. The numerical model of the study was validated using previous experimental results obtained from the literature. Simulation results are analysed in detail, including velocity magnitude, drag coefficient, drag force and lift coefficient. The modifications achieved in this research succeeded in reducing drag and were validated through some appropriate sources. The final model has been assembled with all modifications and is represented in this research. The results show that the base model attained an aerodynamic drag coefficient of 0.464, while the final design achieved a reasonably better overall performance by recording a 10% reduction in the drag coefficient. Moreover, within individual comparison with the final model, the second model with front spitter had an insignificant improvement, limited to 1.17%, compared with 11.18% when the rear diffuser was involved separately. In addition, the lift coefficient was significantly reduced to 73%, providing better stabilities and accounting for the safety measurements, especially at high velocity. The prediction of the airflow improvement was visualised, including the pathline contours consistent with the solutions. These research results provide a considerable transformation in the transportation field and help reduce fuel expenses and global emissions.
- Keywords
- aerodynamics, computational fluid dynamics, design, electric hatchback, electric vehicle, fuel efficiency, optimization,
- Publication type
- Journal Article MeSH
Passage of nasal airflow during breathing is crucial in achieving accurate diagnosis and optimal therapy for patients with nasal disorders. Computational fluid dynamics (CFD) is the dominant method for simulating and studying airflow. The present study aimed to create a CFD nasal airflow model to determine the major routes of airflow through the nasal cavity and thus help with individualization of surgical treatment of nasal disorders. The three-dimensional nasal cavity model was based on computed tomography scans of the nasal cavity of an adult patient without nasal breathing problems. The model showed the main routes of airflow in the inferior meatus and inferior part of the common meatus, but also surprisingly in the middle meatus and in the middle part of the common nasal meatus. It indicates that the lower meatus and the lower part of the common meatus should not be the only consideration in case of surgery for nasal obstruction in our patient. CFD surgical planning could enable individualized precise surgical treatment of nasal disorders. It could be beneficial mainly in challenging cases such as patients with persistent nasal obstruction after surgery, patients with empty nose syndrome, and patients with a significant discrepancy between the clinical findings and subjective complaints.
- Keywords
- 3D model, computational fluid dynamics, nasal airflow, nasal surgery, planning,
- Publication type
- Journal Article MeSH
This study investigates the influence of varying degrees of stenosis on blood flow within elliptic arteries, emphasizing the critical role of artery shape in clinical evaluations as opposed to the commonly studied circular arteries. Unlike prior work, this research offers a precise definition of stenosis by incorporating the measured length, height, and position of the narrowing. Employing the non-Newtonian Williamson fluid model, we conducted comprehensive numerical simulations to examine blood flow through four distinct stenosis formations. The novelty of this work lies in its accurate modeling of stenosis and use of advanced mesh generation, combined with commercial software and the finite volume method, to capture detailed hemodynamic behavior. Visualized results, including pressure profiles, velocity line graphs, and streamlines, further underscore the distinctive flow dynamics shaped by the elliptic geometry. Key findings of the obtained results reveal that blood velocity peaks near the stenosis and drops significantly post-stenosis, with notable variations in flow patterns, energy loss, and pressure distribution across different stenosis types. Further, higher velocity of blood flow is observed in elliptic arteries in comparison with circular ones. In the area of the high corners of stenotic segments, the pressure profile reaches high values. As a result of the narrowing of the arterial cross-section, the varied time shows that the post-stenotic segment of the artery has a higher pressure than the pre-stenotic section. The varied time suggests that an axially symmetric profile will eventually be the norm for the flow within the arterial portion. These insights have profound implications for improving clinical diagnosis and treatment strategies for conditions related to stenosed elliptic arteries.
PURPOSE: Pituitary adenoma, a relatively common intracranial tumor, is often treated surgically through the nasal cavity, which alters its anatomy. This study aims to determine the severity of these changes in airflow and flow distribution within the nasal cavity, focusing on the anterior nasal region's role in airflow redistribution. Computational fluid dynamics (CFD) was employed to analyze these changes before and after surgery. METHODS: Data from four patients of the Department of Neurosurgery and Neuro-oncology of the Military University Hospital, Prague, were analyzed using CFD simulations in Ansys Fluent 2021 R1. Computed tomography (CT) scans were used to model the nasal cavities pre- and post-surgery, creating polyhedral meshes of 1.8 million cells before surgery and 2.2 million cells after surgery. The k-ε turbulent model was applied to compute flow fields, providing consistent results across patients. RESULTS: The surgery increased the nasal cavity volume, primarily due to the endonasal transsphenoidal approach. Cross-sectional areas, particularly in the middle nasal meatus, were enlarged, reducing airflow velocity without altering total volume flow. Most airflow was redistributed through the middle nasal meatus, while flow in peripheral regions decreased. The anterior part of the nasal cavity was identified as having the most significant influence on airflow redistribution. CONCLUSION: Surgery impacts nasal anatomy and airflow dynamics significantly, particularly in the anterior part of the nasal cavity. These findings emphasize the need for surgical precision to minimize unintended shifts in airflow patterns. Further studies are recommended to validate these observations.
- Keywords
- adenomas, computational fluid dynamics (cfd), computed tomography (ct), nasal cavity, pituitary tumour,
- Publication type
- Journal Article MeSH
The scale-up of bioprocesses remains one of the major obstacles in the biotechnology industry. Scale-down bioreactors have been identified as valuable tools to investigate the heterogeneities observed in large-scale tanks at the laboratory scale. Additionally, computational fluid dynamics (CFD) simulations can be used to gain information about fluid flow in tanks used for production. Here, we present the rational design and comprehensive characterization of a scale-down setup, in which a flexible and modular plug-flow reactor was connected to a stirred-tank bioreactor. With the help of CFD using the realizable k-ε model, the mixing time difference between a 20 and 4000 L bioreactor was evaluated and used as scale-down criterion. CFD simulations using a shear stress transport (SST) k-ω turbulence model were used to characterize the plug-flow reactor in more detail, and the model was verified using experiments. Additionally, the model was used to simulate conditions where experiments technically could not be performed due to sensor limitations. Nevertheless, verification is difficult in this case as well. This was the first time a scale-down setup was tested on high-cell-density Escherichia coli cultivations to produce industrially relevant antigen-binding fragments (Fab). Biomass yield was reduced by 11% and specific product yield was reduced by 20% during the scale-down cultivations. Additionally, the intracellular Fab fraction was increased by using the setup. The flexibility of the introduced scale-down setup in combination with CFD simulations makes it a valuable tool for investigating scale effects at the laboratory scale. More information about the large scale is still necessary to further refine the setup and to speed up bioprocess scale-up in the future.
- Keywords
- CFD, E. coli cultivation, fab, plug-flow reactor, scale-down,
- MeSH
- Biomass MeSH
- Bioreactors * MeSH
- Biotechnology MeSH
- Escherichia coli genetics MeSH
- Hydrodynamics * MeSH
- Computer Simulation MeSH
- Publication type
- Journal Article MeSH
CONTEXT: The increase in the detection of unruptured cerebral aneurysms has led to management dilemma. Prediction of risk based on the size of the aneurysm is not always accurate. There is no objective way of predicting rupture of aneurysm so far. Computational fluid dynamics (CFDs) was proposed as a tool to identify the rupture risk. AIMS: To know the correlation of CFD findings with intraoperative microscopic findings and to know the relevance of CFD in the prediction of rupture risk and in the management of unruptured intracranial aneurysms. SETTINGS AND DESIGN: A prospective study involving nine cases over a period of 6 months as an initial analysis. SUBJECTS AND METHODS: Both males and females were included in the study. Preoperative analysis was performed using computed tomography angiogram, magnetic resonance imaging in all cases and digital substraction angiogram in some cases. Intraoperatively microscopic examination of the aneurysm wall was carried out and images recorded. The correlation was done between microscopic and CFD images. RESULTS: Seven cases were found intraoperatively to have a higher risk of rupture based on the thinning of the wall. Two cases had an atherosclerotic wall. All cases had low wall shear stress (WSS).Only two cases with atherosclerotic wall had a correlation with low WSS. CONCLUSIONS: While the pressure measured with CFD technique is a good predictor of rupture risk, the WSS component is controversial. Multicentric trials involving a larger subset of population are needed before drawing any definite conclusions. On-going development in the CFD analysis may help to predict the rupture chances accurately in future.
- Keywords
- Computational flow dynamics, intraoperative microscopic findings, unruptured intracranial aneurysms, wall changes,
- Publication type
- Journal Article MeSH
BACKGROUND: Photosynthetic microalgae have been in the spotlight of biotechnological production (biofuels, lipids, etc), however, current barriers in mass cultivation of microalgae are limiting its successful industrialization. Therefore, a mathematical model integrating both the biological and hydrodynamical parts of the cultivation process may improve our understanding of relevant phenomena, leading to further optimization of the microalgae cultivation. RESULTS: We introduce a unified multidisciplinary simulation tool for microalgae culture systems, particularly the photobioreactors. Our approach describes changes of cell growth determined by dynamics of heterogeneous environmental conditions such as irradiation and mixing of the culture. Presented framework consists of (i) a simplified model of microalgae growth in a culture system (the advection-diffusion-reaction system within a phenomenological model of photosynthesis and photoinhibition), (ii) the fluid dynamics (Navier-Stokes equations), and (iii) the irradiance field description (Beer-Lambert law). To validate the method, a simple case study leading to hydrodynamically induced fluctuating light conditions was chosen. The integration of computational fluid dynamics (ANSYS Fluent) revealed the inner property of the system, the flashing light enhancement phenomenon, known from experiments. CONCLUSION: Our physically accurate model of microalgae culture naturally exhibits features of real system, can be applied to any geometry of microalgae mass cultivation and thus is suitable for biotechnological applications.
- Keywords
- CFD, Flashing light enhancement, Mathematical modeling, Microalgae, Microalgae culture systems, Photosynthesis,
- MeSH
- Models, Biological MeSH
- Photosynthesis * MeSH
- Hydrodynamics * MeSH
- Culture Techniques * MeSH
- Microalgae growth & development physiology radiation effects MeSH
- Computer Simulation MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- MeSH
- Anterior Cerebral Artery diagnostic imaging physiopathology MeSH
- Brain Edema diagnostic imaging MeSH
- Fatal Outcome MeSH
- Glasgow Coma Scale MeSH
- Intracranial Aneurysm diagnostic imaging physiopathology MeSH
- Middle Aged MeSH
- Humans MeSH
- Cerebral Angiography MeSH
- Cerebrovascular Circulation MeSH
- Tomography, X-Ray Computed MeSH
- Computer Simulation MeSH
- Aneurysm, Ruptured diagnostic imaging physiopathology MeSH
- Subarachnoid Hemorrhage diagnostic imaging physiopathology surgery MeSH
- Check Tag
- Middle Aged MeSH
- Humans MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Case Reports MeSH
Needle-shaped crystals are a common occurrence in many pharmaceutical and fine chemicals processes. Even if the particle size distribution (PSD) obtained in a crystallization step can be controlled by the crystal growth kinetics and hydrodynamic conditions, further fluid-solid separation steps such as filtration, filter washing, drying, and subsequent solids handling can often lead to uncontrolled changes in the PSD due to breakage. In this contribution we present a combined computational and experimental methodology for determining the breakage kernel and the daughter distribution functions of needle-shaped crystals, and for population balance modeling of their breakage. A discrete element model (DEM) of needle-shaped particle breakage was first used in order to find out the appropriate types of the breakage kernel and the daughter distribution functions. A population balance model of breakage was then formulated and used in conjunction with experimental data in order to determine the material-specific parameters appearing in the breakage functions. Quantitative agreement between simulation and experiment has been obtained.
- MeSH
- Models, Chemical * MeSH
- Filtration MeSH
- Hydrodynamics MeSH
- Crystallization MeSH
- Pharmaceutical Preparations chemistry MeSH
- Computer Simulation * MeSH
- Particle Size MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- Pharmaceutical Preparations MeSH
