Effect of flow rate ratio and positioning on a lighthouse tip ECMO return cannula

Extracorporeal membrane oxygenation is a life-saving support therapy in the case of cardiopulmonary refractory failure. Its use is associated to complications due to the presence of artificial surfaces and supraphysiological stress conditions. Thus, knowledge of the fluid structures associated to each component can give insight into sources of blood damage. In this study, an experimentally validated numerical study of a conventional lighthouse tip cannula in return configuration was carried out to characterize the flow structures using water or a Newtonian blood analog with different flow rate ratios and cannula positioning and their influence on hemolysis. The results showed that strong shear layers developed where the jets from the side holes met the co-flow. Stationary backflow regions at the vessel wall were also present downstream of the cannula. In the tilted case, the recirculation was much more pronounced on the wide side and almost absent on the narrow side. Small vortical backflow structures developed at the side holes which behaved like obstacles to the co-flow, creating pairs of counter-rotating vortices, which induced locally higher risk of hemolysis. However, global hemolysis index did not show significant deviations. Across the examined flow rate ratios, the holes on the narrow side consistently reinfused a larger fraction of fluid. A radial force developed in the tilted case in a direction so as to recenter the cannula in the vessel.

Design of vortex-based cavitation devices/reactors: Influence of aspect ratio, number of inlets and shape

Vortex-based hydrodynamic cavitation devices are being used in a wide range of applications. However, adequate information on the design of such devices is not available. In this work, we have computationally investigated the influence of key design parameters such as the aspect ratio of the vortex chamber, the number of tangential inlets and the shape of the device on resulting flow characteristics and cavitation. Experiments were carried out to validate key findings from the computational studies. These investigations revealed that the aspect ratio of the vortex chamber as six may be considered as optimum. The performance of single and multiple inlet devices was found to be comparable at the same pressure drop (that is at same energy consumption per m3). Scale-up with a geometric similarity led to a reduction in the extent of cavitation for same energy consumption per m3. For facilitating scale-out option, an attempt was made to simplify the configuration of the vortex-based cavitation device. Computational results indicated that the cavitation performance of simplified configuration was not significantly inferior. A case of the formation of liquid-liquid emulsion was taken as a test case for evaluation of a modified cavitation device based on the present investigations. The droplet size distributions of emulsions generated by both the devices indicate that the proposed simplified configuration, which may facilitate fabrication and offer integrated scale-out options, performs almost at par with a complex configuration. The presented results will be useful for optimising designs of vortex-based hydrodynamic cavitation devices/ reactors.

Transarterial radioembolization: a systematic review on gaining control over the parameters that influence microsphere distribution

[Purpose] Transarterial radioembolization (TARE) is an established treatment modality for patients with unresectable liver cancer. However, a better understanding of treatment parameters that influence microsphere distribution could further improve the therapy. This systematic review examines and summarizes the available evidence on intraprocedural parameters that influence the microsphere distribution during TARE as investigated by in vivo, ex vivo, in vitro and in silico studies. [Methods] A standardized search was performed in Medline, Embase and Web of Science to identify all published articles investigating microsphere distribution or dynamics during TARE. Studies presenting original research on parameters influencing the microsphere distribution during TARE were included. [Results] A total of 42 studies reporting a total of 11 different parameters were included for narrative analysis. The investigated studies suggest that flow distribution is not a perfect predictor of microsphere distribution. Increasing the injection velocity may help increase the similarity between flow and microsphere distributions. Furthermore, the microsphere distributions are very sensitive to the radial and axial catheter position. [Conclusion] The most promising parameters for future research which can be controlled in the clinic appear to be microsphere injection velocity as well as the axial catheter position. Up to now, many of the included studies do not take clinical feasibility into account, limiting the translation of results to clinical settings. Future research should therefore focus on the applicability of in vivo, in vitro, or in silico research to patient specific scenarios to improve the efficacy of radioembolization as treatment for liver cancer.

Nanobody-functionalized conduit with built-in static mixer for specific elimination of cytokines in hemoperfusion

Removing excessively produced cytokines is of paramount significance in blood purification therapy for hypercytokinemia-associated diseases. In this study, we devised a conduit that is modified with nanobodies (Nb) and incorporates static mixers (Nb-SMC) to eliminate surplus cytokines from the bloodstream. The low-pressure-drop (LPD) static mixer, with each unit featuring two 90°-crossed blades, was strategically arranged in a tessellated pattern on the inner wall of the conduit to induce turbulent mixing effects during the flow of blood. This arrangement enhances mass transfer and molecular diffusion, thereby assisting in the identification and elimination of cytokines. By utilizing computational fluid dynamics (CFD) studies, the Nb-SMC was rationally designed and prepared, ensuring an optimal interval between two mixer units (H/G = 2.5). The resulting Nb-SMC exhibited a remarkable selective clearance of IL-17A, reaching up to 85 %. Additionally, the process of Nb immobilization could be adjusted to achieve the simultaneous removal of multiple cytokines from the bloodstream. Notably, our Nb-SMC displayed good blood compatibility without potential adverse effects on the composition of human blood. As the sole documented static mixer-integrated conduit capable of selectively eliminating cytokines at their physiological concentrations, it holds promise in the clinical potential for hypercytokinemia in high-risk patients. STATEMENT OF SIGNIFICANCE: High-efficient cytokines removal in critical care still remains a challenge. The conduit technique we proposed here is a brand-new strategy for cytokines removal in blood purification therapy. On the one hand, nanobody endows the conduit with specific recognition of cytokine, on the other hand, the build-in static mixer enhances the diffusion of antigenic cytokine to the ligand. The combination of these two has jointly achieved the efficient and specific removal of cytokine. This innovative material is the only reported artificial biomaterial capable of selectively eliminating multiple cytokines under conditions close to clinical practice. It has the potential to improve outcomes for patients with hypercytokinemia and reduce the risk of adverse events associated with current treatment modalities.

Coupling synthetic and real-world data for a deep learning-based segmentation process of 4D flow MRI

BACKGROUND AND OBJECTIVE

Phase contrast magnetic resonance imaging (4D flow MRI) is an imaging technique able to provide blood velocity in vivo and morphological information. This capability has been used to study mainly the hemodynamics of large vessels, such as the thoracic aorta. However, the segmentation of 4D flow MRI data is a complex and time-consuming task. In recent years, neural networks have shown great accuracy in segmentation tasks if large datasets are provided. Unfortunately, in the context of 4D flow MRI, the availability of these data is limited due to its recent adoption in clinical settings. In this study, we propose a pipeline for generating synthetic thoracic aorta phase contrast magnetic resonance angiography (PCMRA) to expand the limited dataset of patient-specific PCMRA images, ultimately improving the accuracy of the neural network segmentation even with a small real dataset.

METHODS

The pipeline involves several steps. First, a statistical shape model is used to synthesize new artificial geometries to improve data numerosity and variability. Secondly, computational fluid dynamics simulations are employed to simulate the velocity fields and, finally, after a downsampling and a signal-to-noise and velocity limit adjustment in both frequency and spatial domains, volumes are obtained using the PCMRA formula. These synthesized volumes are used in combination with real-world data to train a 3D U-Net neural network. Different settings of real and synthetic data are tested.

RESULTS

Incorporating synthetic data into the training set significantly improved the segmentation performance compared to using only real data. The experiments with synthetic data achieved a DICE score (DS) value of 0.83 and a better target reconstruction with respect to the case with only real data (DS = 0.65).

CONCLUSION

The proposed pipeline demonstrated the ability to increase the dataset in terms of numerosity and variability and to improve the segmentation accuracy for the thoracic aorta using PCMRA.

Optimizing indoor air quality: CFD simulation and novel air cleaning methods for effective aerosol particle inhibition in public spaces

In contemporary building ventilation, displacement and mixing ventilation demand high air volumes for rapid virus elimination, resulting in elevated energy consumption. To minimize the spread of viruses and decrease energy consumption for ventilation, this study employed CFD to explore the efficacy of a downward uniform flow field in impeding the transmission of aerosol particles in a high-traffic public facility, like a supermarket. The findings indicate that the downward uniform flow field proves insufficient when individuals remain static for extended periods. A wind speed of 0.1 m/s or higher becomes essential to overpower the stationary thermal plume, which disrupts this flow field. In areas with human presence, however, this technique is found to be particularly efficient since mobile heat sources do not generate a fixed thermal plume. A 0.05 m/s downward uniform flow field can settle 90% of particles within just 22 s. This flow pattern contributes to the swift settling of aerosol particles and effectively diminishes their dispersion. Employing this flow pattern in public places with increased foot traffic, like supermarkets, can lower the risk of contracting novel coronavirus without augmenting energy consumption. In order to implement the flow field in a part of the domain, a new air purification device is proposed in this study. The device combined with shelves can optimize the flow field uniformity through the MLA (PSO-SVR) algorithm and alteration of the air distribution structure. The uniformity of the final flow field increased to 0.925. The combination of data-driven MLA with CFD showed good performance in predicting the flow field uniformity. These findings offer valuable insights and practical applications for the prevention and control of respiratory diseases, particularly in post-epidemic scenarios.

Erosion-Corrosion Failure Analysis of a Mild Steel Nozzle Pipe in Water-Sand Flow

Several leaks appeared in a mild steel (MS) pipe jet nozzle installed in a direct impact test rig after a few months of operation in erosive flow at the Centre for Erosion-Corrosion Research. The locations of perforation leaks were primarily upstream, but severe wall thinning was also noticed adjacent to the exit section. In this paper, a failure analysis was carried out on the leaking of a pipe jet nozzle, and the results are discussed in detail. The investigation carried out includes visual observation, scanning electron microscopy, 3D scanning, energy-dispersive spectroscopy, and laser profilometry measurements. In addition, numerical simulations based on computational fluid dynamics (CFD) and the discrete phase model (DPM) were conducted to investigate the root cause of the failure of leaks in the pipe jet nozzle. Further CFD-DPM simulations were performed on three different pipe jet designs for liquid-solid flow conditions, and were compared to find an alternative design to prevent the failure of the pipe jet nozzles. It was found that the increase in turbulence along with multiple impacts of particles on the wall generate leaks and cracks in the pipe jet nozzle. Moreover, the CFD-DPM showed a five-fold reduction in the maximum erosion rate; this was observed in the replacement of failed pipes with the proposed alternative nozzle pipe design featuring a chamfer reducer section. The CFD-DPM analysis of all geometric configurations showed that alteration of reducer section design has the greatest impact on erosive wear mitigation.

Numerical investigation of the pharmacokinetics and pharmacodynamics of the chemotherapeutic drug in avascular and vascular stages of a brain tumor

One of the most commonly used approaches for treating solid tumors is the systemic delivery of chemotherapeutic drugs. However, our understanding of the factors influencing treatment efficacy through this method is still limited. This study presents a comprehensive and realistic mathematical model that incorporates the dynamics of tumor growth, capillary network extension, and drug delivery in a coupled and simultaneous manner. The model covers two stages of tumor growth: avascular and vascular. For tumor growth, a continuum model is employed using the phase field interface-capturing method. The neo-vascularization process is modeled using a hybrid discrete-continuum approach. Additionally, a multi-scale model is used to describe the pharmacokinetics of doxorubicin, considering various agents. The study investigates the effect of haptotaxis and reveals that a higher haptotaxis coefficient leads to faster tumor growth (up to 2.6 times) and a quicker progression to angiogenesis. The impact of tumor-related and drug-related parameters is also examined, including tumor size, tumor sensitivity to the drug, chemotherapy initialization, treatment cycle duration, drug affinity to cells, and drug dose. The findings indicate that chemotherapy is more effective during the angiogenesis stage when active loops have formed. Other clinical methods such as radiotherapy and surgery may be more appropriate during the avascular stage or the transition period between angiogenesis initialization and loop formation. The penetration depth of the drug decreases by approximately 50% with an increase in the drug binding rate to surface-cell receptors. As a result, high-associate-rate drugs are preferred for chemotherapy after active loops have formed, while low-associate-rate drugs are suitable for earlier stages.

Hemolysis of red blood cells in blood vessels modeled via computational fluid dynamics

The research aims to verify the universal relationship between vessel shape and the risk of hemolysis using a rheological model of blood reflecting the physiological processes related to blood for any blood vessel. Blood is a multi-component fluid, the rheology of which depends on many factors, such as the concentration of red blood cells and local shear stress, which significantly affect the process of hemolysis. Blood rheology models used so far cannot be used for all flows and geometries. Therefore, a new rheology model has been introduced suitable for modeling hemolytic flows observed in arteries with atherosclerotic lesions in the in vivo environment. The previously presented model also has advantages in modeling local viscosity in stenosis. Geometries of the blood vessels from computed tomography scans and simplified models of the actual arteries observed during medical procedures were used in the calculations. Population Balance Based Rheology model predicts the concentration of single, deagglomerated red blood cells and the concentration and size of red blood cell agglomerates, which affect blood rheology and hemolysis. Based on the simulations carried out, a correlation was found between the shape of the vessel cavity and the risk of hemolysis. Presented results can be used in the future to create a correlation between the shape of the atherosclerotic lesions and the risk of hemolysis in the blood to make an initial risk assessment for a given patient.

Entrained-flow oxy-gasification of pulverized coal in CO2-H2O-O2 environment

Combustion or gasification of coal in nitrogen-free environment (CO2-H2O-O2) is a promising technology contributing to reduce the carbon footprint in the energy industry. Accordingly, this will make it quite easy to capture practically pure carbon dioxide for subsequent storage. The study presents numerical investigation of the entrained-flow oxy-gasification processes of pulverized coal in CO2-H2O-O2 environment. A numerical methodology for describing oxy-fuel gasification processes has been developed and tested. A study of the influence of the absorption of gas coefficient on the calculation results was carried out. Studies have been conducted on the effect of the excess oxygen ratio, the oxygen concentration in the blast, and the amount of moisture on the physicochemical processes and the composition of the syngas for the gasifier under consideration. It is shown that increasing the oxygen concentration in the blast allows stabilizing the ignition and combustion of pulverized coal at low excess oxygen ratio. The dependence of the chemical efficiency on the main regime parameters is determined. The results showed that a decrease in the excess oxygen ratio from 0.43 to 0.33 leads to an increase in combustible losses from 0.15 to 45% for this gasifier. In the mode with high fuel conversion in the gasifier, the produced syngas with a caloric value of 9.26 MJ/m3 comprised of CO, 40.3; H2, 32.4; and CO2, 25.5 (vol. % dry).

Comparative Study of Membrane Fouling with Aeration Shear Stress in Filtration of Different Substances

The formation process of membrane fouling is complex and diverse, which is an important problem that needs to be overcome in membrane applications. In this paper, three foulant systems consisting of humic acid, humic acid plus Ca2+ and humic acid plus Ca2+ plus yeast were selected to compare membrane fouling processes with different aeration intensities. The aim was to establish the quantitative relationship between membrane fouling rate and shear stress, respectively, in a large-scale flat sheet MBR (FSMBR). The shear stress values at different aeration intensities were obtained using computational fluid dynamics (CFD). The membrane fouling rate during the filtration of different substances was measured by performing experiments. The comparison results showed that the membrane fouling rate varied greatly during the filtration of different substances. With the help of particle size distribution, the effect of different shear forces on floc size was further explored. Using the dual control of fouling rate and floc size, the recommended aeration intensity was 6~8 L/(m2·min).

Computational fluid dynamics calculations in inferior turbinate surgery: a cohort study

PURPOSE

To investigate how the results of nasal computational fluid dynamics (CFD) simulations change due to inferior turbinate surgery and how the results correlate with patient specific subjective assessment and volumetric results in the nasal cavities.

METHODS

The steady inspiratory airflow of 25 patients was studied pre- and postoperatively with heat transfer from the mucous membrane by performing CFD calculations to patient-specific nasal cone beam computed tomography images. These results were then compared to the severity of the patients' nasal obstruction Visual Analogue Scale (VAS) and Glasgow Health Status Inventory assessments, and acoustic rhinometry measurements.

RESULTS

Total wall shear forces decreased statistically significantly (p < 0.01) in the operated parts of the inferior turbinates. Patients' subjective nasal obstruction VAS assessment changes between the pre- and postoperative conditions correlated statistically significantly (p = 0.04) with the wall shear force results.

CONCLUSION

Inferior turbinate surgery lead to decreased total wall shear force values postoperatively. Changes in subjective nasal obstruction VAS results against total wall shear force changes between the pre- and postoperative conditions were statistically significant. CFD data have a potential to be used for the evaluation of nasal airflow.

Physical and CFD model used in the analysis of particles dispersion

Air pollution, representing one of the major environmental crises affecting us all, is responsible for half a million deaths each year in Europe. This research shows a numerical model based on Computational Fluid Dynamics (CFD) and a methodology for its validation allowing to know the evolution of particles in open urban environments. In this case, the model represents an area of Gijón (Asturias), specifically chosen as it serves to highlight a location at which the daily limit values of PM10 set by the regulations are most frequently exceeded. A numerical model has been developed at a scale of 1:10,000 to simulate the dispersion of pollutants, including particulate emissions. A physical model at the same scale was built using 3D printing. This model was tested in a wind tunnel and analysed in the four main wind directions. To carry out the tests, a particle generation system was designed and manufactured, and the necessary infrastructure was built to take measurements using an optical particle meter. Results show that the numerical model meets the expected objectives and is capable of predicting the behaviour of particle dispersion in the air. The numerical model produces results in the same order of magnitude as the physical model, although there is a tendency to underestimate the maximum values with respect to the measured ones.

Numerical analysis of airflow and particle deposition in multi-fidelity designs of nasal replicas following nasal administration

BACKGROUND AND OBJECTIVE

An improved understanding of flow behaviour and particle deposition in the human nasal airway is useful for optimising drug delivery and assessing the implications of pollutants and toxin inhalation. The geometry of the human nasal cavity is inherently complex and presents challenges and manufacturing constraints in creating a geometrically realistic replica. Understanding how anatomical structures of the nasal airway affect flow will shed light on the mechanics underpinning flow regulation in the nasal pharynx and provide a means to interpret flow and particle deposition data conducted in a nasal replica or model that has reduced complexity in terms of their geometries. This study aims to elucidate the effects of sinus and reduced turbinate length on nasal flow and particle deposition efficiencies.

METHODS

A complete nasal airway with maxillary sinus was first reconstructed using magnetic resonance imaging (MRI) scans obtained from a healthy human volunteer. The basic model was then modified to produce a model without the sinus, and another with reduced turbinate length. Computational fluid dynamics (CFD) was used to simulate flow in the nasal cavity using transient flow profiles with peak flow rates of 15 L/min, 35 L/min and 55 L/min. Particle deposition was investigated using discrete phase modelling (DPM).

RESULTS

Results from this study show that simplifying the nasal cavity by removing the maxillary sinus and curved sections of the meatus only has a minor effect on airflow. By mapping the spatial distribution of monodisperse particles (10 μm) in the three models using a grid map that consists of 30 grids, this work highlights the specific nasal airway locations where deposition efficiencies are highest, as observed within a single grid. It also shows that lower peak flow rates result in higher deposition differences in terms of location and deposition quantity, among the models. The highest difference in particle deposition among the three nasal models is ∼10%, and this is observed at the beginning of the middle meatus and the end of the pharynx, but is only limited to the 15 L/min peak flow rate case. Further work demonstrating how the outcome may be affected by a wider range of particle sizes, less specific to the pharmaceutical industries, is warranted.

CONCLUSION

A physical replica manufactured without sections of the middle meatus could still be adequate in producing useful data on the deposition efficiencies associated with an intranasal drug formulation and its delivery device.

Preliminary assessment of the NACA0021 trailing edge wedge for wind turbine application

The airfoil blade is the primary component of a wind turbine, and its aerodynamic properties play a crucial role in determining the energy conversion efficiency of these blades. Many researchers have proposed different airfoil modifications intending to enhance the aerodynamic characteristics and limit the unsteady interaction with the atmospheric boundary layer. This study evaluates the benefits of mounting wedge tails (WTs) on the trailing edge of an airfoil. The aerodynamic characteristics of a 2-D, steady-state NACA 0021 airfoil featuring the wedge tails (WT) and fish wedge tails (FWT) were studied computationally by employing the shear stress transport (SST) k-ω turbulence model. Different WT and FWT configurations were studied at various wedge length (L) to wedge height (H) ratios, L/H, at the airfoil's trailing edge. The effects of different L/H ratios, including L/H > 1, L/H = 1, and L/H < 1, were considered in the present study to determine the optimal configuration to achieve the maximum glide ratio, CL/CD at the Reynolds number of 180,000. The findings indicate that the performance of the NACA 0021 airfoil was notably affected by the height of the tail; however, the length had only a minor impact when L/H was less than 1. The mounted FWT resulted in significant enhancements to both the lift and glide ratio of the airfoil. Specifically, the lift ratio experienced an increase of over 41 % compared to the clean airfoil, while the glide ratio increased by more than 31 %. These improvements were observed at an ideal height and length of 2.5 % and 1 % of the airfoil, respectively. Moreover, the mounted FWT performed better than the Gurney flap using the same configurations.

Troubleshooting dioxins stack emissions in an industrial waste gas incinerator

An important source of dioxins and furans at present is waste incineration, utmost formed during combustion processes and emitted to the environment without being fully captured by waste-gas treatment equipment. In this study, monitoring campaign of International Toxic Equivalents for dioxins and furans (I-TEQDF), was carried out at pharmaceutical industrial waste incinerator to find a correlation between combustion parameters and feed composition with potential emission. Principal Component Analysis (PCA) shows that high values of dioxin emission correlate with short residence time of the flue gas in the furnace as well as low oxygen concentration. These operating conditions were further investigated, using COMSOL Computational Fluid Dynamics (CFD) simulation to calculate the temperature profiles along the furnace. The results suggest that the flame temperature profile is anticipated to exhibit cold areas (cold spots), which may be used as a proxy for dioxin formation due to incomplete combustion. Additionally, the calculated congeners furan to dioxin concentration ratio, points to their formation via de novo mechanism. SEM-EDS analysis preformed on the bag filter upstream the feed following its filtration, have shown large amount of iron, which may have served as a metal catalytic source for dioxin formation. The iron origin is most likely from corrosion of the feeding pipe, drifted with the waste gas and trapped on the bag filter. The results of this study provide a better understanding of the parameters controlling dioxin formation and emission from the plant and may assist a planning of process optimization in such a plant.

Aneurysm Rupture Prediction Based on Strain Energy-CFD Modelling

This paper presents a Patient-Specific Aneurysm Model (PSAM) analyzed using Computational Fluid Dynamics (CFD). The PSAM combines the energy strain function and stress-strain relationship of the dilated vessel wall to predict the rupture of aneurysms. This predictive model is developed by analyzing ultrasound images acquired with a 6-9 MHz Doppler transducer, which provides real-time data on the arterial deformations. The patient-specific cyclic loading on the PSAM is extrapolated from the strain energy function developed using historical stress-strain relationships. Multivariant factors are proposed to locate points of arterial weakening that precede rupture. Biaxial tensile tests are used to calculate the material properties of the artery wall, enabling the observation of the time-dependent material response in wall rupture formation. In this way, correlations between the wall deformation and tissue failure mode can predict the aneurysm's propensity to rupture. This method can be embedded within the ultrasound measures used to diagnose potential AAA ruptures.

Dynamic stratified porosity computation from canopy interaction simulation between airflow and leaves

The main goal of wind-driven spraying is to use assisted airflow to disrupt the structure of branches and leaves and broaden the air delivery channel, so as to achieve uniform droplet deposition in the middle and lower parts of the canopy. Due to the complex branch and leaf structure inside the canopy, there is currently no effective method to express the dynamic changes of canopy porosity and the law of airflow attenuation under assisted airflow. In this study, based on the two-way fluid-structure interaction numerical simulation method, the relating between the assisted airflow and the structural parameters of the cotton canopy is analyzed, and a new method for predicting and simulating the dynamic porosity of the canopy is proposed. Firstly, a two-way fluid-structure interaction model based on Lattice Boltzmann (LB) solver and Finite Element (FE) solver is developed to simulate the deformation motion of cotton leaves and the spatial distribution of airflow field, and the correctness of the numerical simulation is verified based on indoor measurement data. Secondly, the post-processing method of Computational Fluid Dynamics (CFD) is used to obtain images of leaves at different canopy positions under assisted airflow, and the porosity changes are calculated and analyzed by image processing. The research results show that under different initial wind speeds (5 m·s-1, 10 m·s-1, 15 m·s-1), the maximum normalized mean absolute error (NMAE) between the simulated values and the measured values is 13.99%, 20.72% and 16.08%, respectively. The coefficient of determination (R2) for linear fitting between simulated values and measured values is 0.9221. These validation results indicate the effectiveness of the numerical simulation method. The validated CFD model is applied to predict leaf deformation and porosity changes within the canopy under various wind loads and times. The application results have well revealed the interaction between crop leaves and airflow, and will be beneficial to make a better understanding of the effect of assisted airflow on droplet deposition.

Semi-surrogate modelling of droplets evaporation process via XGBoost integrated CFD simulations

The applications of machine learning (ML) based approach are emerging as possible tools to accelerate CFD simulations. This study proposed a semi-surrogate model for CFD with integration of the cutting-edge ML algorithm, eXtreme Gradient Boosting (XGB), which enlightened a possible pathway to effectively and efficiently solve and predict those costly but highly repetitive fluid dynamics-related problems. Droplet evaporation, a complex but essential phenomenon in respiratory droplets transport, was studied as the practical case using the proposed model. Droplets evaporation and dynamic size distributions were firstly tracked under various combinations of indoor humidity and temperature using traditional Eulerian-Lagrangian CFD framework, followed by generating several datasets for XGB training. The trained XGB was then used to interpret the evaporated droplets size over time under new combinations of indoor conditions. Outcomes revealed that well-trained XGB-base semi-surrogate model was capable of interpreting complex non-linear relationships between droplets dynamic parameters (diameter and time) and indoor parameters (humidity and temperature). For each specific parameter, the predictive error of well-trained XGB could retain below 5 % and its prediction speed was found nearly 1 million times faster than that of new CFD simulations. Successful applications of XGB in conjunction with CFD demonstrated its great potential on providing rapid and more efficient predictions of complex, costly and repetitive fluid dynamics-related phenomenons (e.g. droplets evaporation). Also, the XGB predicted droplets evaporation data from this study could be further applied as initial conditions into new simulations via the User-defined function (UDF).

In Situ Observation of Bubbles and the Effect of Ultrasonic Vibration on Bubble Behavior in EDM

Accumulation and concentration of debris in deep hole electrical discharge machining (EDM) significantly hinder its machining efficiency and accuracy. It is believed that the movement of bubbles associated with the discharge gap flow field play a pivotal role in debris removal and influence the discharge conditions. Ultrasonic vibration (USV) of the electrode is thought to be an effective method for improving EDM-generated bubbles and debris exclusion. In this study, we first elucidated the behavior of bubbles during EDM of holes with varying aspect ratios. Subsequently, USV was introduced to EDM. The behavior of dielectric fluid flow under the influence of ultrasonic vibration was analyzed using computational fluid dynamics (CFD), which revealed time-varying changes in discharge gap flow pressure and velocity. The velocity of the dielectric flow field near the electrode's side face was found to reach a maximum of approximately 15.2 m/s, greatly facilitating debris removal. High-speed camera observations revealed that bubbles were dispersed within the side gap, with most of them adhering to the electrode's wall. Furthermore, the bubbles exhibited a tendency to continuously break up and coalesce near the hole's outlet before escaping in the USV-assisted EDM. These observed characteristics of bubble behavior under the influence of USV are expected to significantly enhance debris removal and promote efficient dielectric exchange.

Influence of Blood Rheology and Turbulence Models in the Numerical Simulation of Aneurysms

An aneurysm is a vascular malformation that can be classified according to its location (cerebral, aortic) or shape (saccular, fusiform, and mycotic). Recently, the study of blood flow interaction with aneurysms has gained attention from physicians and engineers. Shear stresses, oscillatory shear index (OSI), gradient oscillatory number (GON), and residence time have been used as variables to describe the hemodynamics as well as the origin and evolution of aneurysms. However, the causes and hemodynamic conditions that promote their growth are still under debate. The present work presents numerical simulations of three types of aneurysms: two aortic and one cerebral. Simulation results showed that the blood rheology is not relevant for aortic aneurysms. However, for the cerebral aneurysm case, blood rheology could play a relevant role in the hemodynamics. The evaluated turbulence models showed equivalent results in both cases. Lastly, a simulation considering the fluid-structure interaction (FSI) showed that this phenomenon is the dominant factor for aneurysm simulation.

Complement factor D targeting protects endotheliopathy in organoid and monkey models of COVID-19

COVID-19 is linked to endotheliopathy and coagulopathy, which can result in multi-organ failure. The mechanisms causing endothelial damage due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remain elusive. Here, we developed an infection-competent human vascular organoid from pluripotent stem cells for modeling endotheliopathy. Longitudinal serum proteome analysis identified aberrant complement signature in critically ill patients driven by the amplification cycle regulated by complement factor B and D (CFD). This deviant complement pattern initiates endothelial damage, neutrophil activation, and thrombosis specific to organoid-derived human blood vessels, as verified through intravital imaging. We examined a new long-acting, pH-sensitive (acid-switched) antibody targeting CFD. In both human and macaque COVID-19 models, this long-acting anti-CFD monoclonal antibody mitigated abnormal complement activation, protected endothelial cells, and curtailed the innate immune response post-viral exposure. Collectively, our findings suggest that the complement alternative pathway exacerbates endothelial injury and inflammation. This underscores the potential of CFD-targeted therapeutics against severe viral-induced inflammathrombotic outcomes.

Conceptual Design and Numerical Validation of a Carbon-Based Ink Injector

This paper shows the design of an injector, using carbon nanotubes as inkjet material, implemented in a 3D printer. According to the available literature, few injectors are capable of depositing material. Due to the lack of information, the central part of this research is to develop a suitable device for ink injection that is capable of applying the Fused Deposition Modeling (FDM) method to print nanomaterial ink. The injector was designed using a CAD program based on an open-source desktop 3D printer, which allows it to be modified according to the needs of the injector. This prototype was manufactured in aluminum alloy 7075T6. Computational fluid dynamics (CFD) were carried out to analyze the behavior of the fluid when it passes through the injector, obtaining parameters such as pressure, velocity, and vorticity. An experimental matrix of the injector operation was carried out to achieve an adequate printing speed. The results show that the optimum speed was 250 ms, considering that a temperature of 100 °C is needed in the heated bed to dry the ink so that it does not undergo expansion.

Effect of laryngeal jet on dry powder inhaler aerosol deposition: a numerical simulation

Although pulmonary drug delivery has been deeply investigated, the effect of the laryngeal jet on particle deposition during drug delivery with dry powder inhalers (DPI) has not been evaluated profoundly. In this study, the flow structure and particle deposition pattern of a DPI in two airway models, one with mouth-throat region including the larynx and the other one without it, are numerically investigated. The results revealed that the laryngeal jet has a considerable effect on particle deposition. The presence of laryngeal jet leads to 4-fold and 2-fold higher deposition efficiencies for inlet flow rates of 30 and 90 L/min, respectively.