Computational Flow Model Research Articles

Computational modelling of radiative Maxwell fluid flow over a stretching sheet containing nanoparticles with chemical reaction

In the presence of thermal radiation, heat generation/absorption, and chemical reaction, the heat and mass transmission characteristics of a 2-D electrically conducting incompressible Maxwell fluid past a stretched sheet have been examined. There are various real-world applications for this issue, notably the extrusion of polymers and metal thinning. The transport equations take into account Brownian motion as well as thermophoresis when there is a chemical reaction involved. By making use of the relevant similarity variables, the PDEs that govern the stream and the boundary conditions that go along with them may be non-dimensionalized. The ensuing transformed ODEs are solved using the fourth- and fifth-order Runge-Kutta-Fehlberg scheme. It has been determined and quantitatively examined how the different embedded thermo-physical factors influence the velocity, temperature, and concentration. A case study comparison between our findings and those published in the literature reveals a high degree of agreement. Raising the value of the chemical reaction parameter causes a narrowing of the concentration distribution while increasing the temperature causes thermal radiation to have a greater impact. As the quantity of Nt increases, the thickness of the boundary layer grows, causing the surface temperature to increase, ensuing in a temperature increase.

Computational Multiphase Flow Modelling of Oil Spill Through a Hydrophobic Mesh

The current technologies for handling oil spill clean-up vary in expense and effectiveness and are largely ineffective. Oil spills occur due to accidents from well-heads and damaged facilities in the creeks of the Nigerian Delta and along the coastline of waters where hydrocarbons are prospected all over the world. They are unexpected and known to cause irreparable damage to aquatic environments and marine life. The development of a hydrophobic mesh is proposed to prevent oil from spreading into larger areas and from reaching sensitive coastlines. This will help engineers and clean-up crews in their quest to find an appropriate response to a given oil spill scenario as they race against the clock to prevent further damage and improve the oil recovery process. The overall goal of this project is to create a Numerical Simulation of meshes that repel water and attract oil using ANSYS, a Finite Element Analysis software. The mesh was modelled as a porous medium that acts like a filter that retains water on one side while allowing the passage of oil through it. In the course of this work, appropriate materials selection in fluid flow analysis was carried out. Also, the flow domain geometry was developed in such a way as to simulate a system containing an oil-water interface. Next, domain discretization (meshing) was carried out appropriately. After which appropriate boundary conditions and operating conditions were implanted in the model. Fluent was then set to initialize and run calculations. After calculations were run, results were gotten. These results were then interpreted pictorially. It was seen that the velocity streamlines for the oil phase passed through the hydrophobic mesh, while the velocity streamlines for the water phase were repelled from the hydrophobic mesh wall.

Augmenting cognitive training in older adults with transcranial direct current stimulation: Initial results from the Phase III ACT trial and new directions

AbstractBackgroundEffective non‐pharmacological interventions to remediate age‐related cognitive decline and alter trajectories toward dementia are limited. The Augmenting Cognitive Training in Older Adults trial (ACT) was the first phase III randomized clinical trial initiated for transcranial direct current stimulation.MethodThis NIA funded trial sought to evaluate whether 3 months of cognitive training paired with bilateral 2mA tDCS to the frontal lobes could produce clinically meaningful improvement in a composite measure of cognitive function in healthy older adults: the NIH Toolbox Fluid Cognition Composite score. The ACT trial will be unblinded April 30, 2022. Further still, over the past 5 years, it has become increasingly evident that fixed dosing approaches to tDCS, like those used in the ACT and every other trial to date, are insufficient for addressing individual differences and maximizing clinical outcomes.ResultsWe will present, for the first time, the primary outcome results from the ACT trial. In addition, we will present initial findings from related secondary neuroimaging and cognitive indices. In this talk, we will also present preliminary findings from our ongoing work to refine dosing technology for tDCS in older adults using computational modeling, artificial intelligence and multimodal imaging, paired with tDCS outcomes from the ACT trial.ConclusionWe will present new analyses, available only upon unblinding of ACT. These data use person‐specific computational models of tDCS current flow paired with machine learning and clinical outcomes to identify critical characteristics of tDCS current in the brain (e.g., intensity, direction of current flow) most strongly associated with response vs. non‐response. These data will provide initial insight into which regions of the brain and what characteristics of current were strongly associated with treatment response in the ACT trial. In addition, these data also provide critical insight into how stimulation dosing (electrode positioning, stimulation intensity) can be modified at a person‐specific level to potentially enhance clinical outcomes. Thus, the proposed talk will provide state of the art trial findings from the first completed tDCS Phase III clinical trial paired with next generation approaches to remediated age‐related cognitive decline using tDCS technology.

Anti-vortex device for stabilization of measuring parameters in apparatus for biofuel production

The article deals with the problem of metrological support of innovative technologies, in particular, related to the production of promising renewable energy sources such as biofuels. In the process of biofuel separation, it is very important to monitor various technological parameters: pressure, flow, liquid level, temperature, etc. For this purpose, measuring devices are used as part of the automation of technological processes. At the same time, flow turbulence can have a significant impact on the accuracy of the readings of these devices. Often, the transition from laminar to turbulent flow is associated with the formation of a vortex when overcoming the flow of various constrictions at the outlet of the installations. The paper considers a method for preventing the formation of vortices through the use of a anti-vortex device (AVD). Computer modeling of the fluid flow in the SolidWorks software package was carried out in order to determine the optimal geometric characteristics of the AVD. In particular, the influence of the gap in the AVD and its plate diameter was studied.

The Role of Immersion for Improving Extended Reality Analysis of Personalized Flow Simulations.

Computational models of flow in patient-derived arterial geometries have become a key paradigm of biomedical research. These fluid models are often challenging to visualize due to high spatial heterogeneity and visual complexity. Virtual immersive environments can offer advantageous visualization of spatially heterogeneous and complex systems. However, as different VR devices offer varying levels of immersion, there remains a crucial lack of understanding regarding what level of immersion is best suited for interactions with patient-specific flow models. We conducted a quantitative user evaluation with multiple VR devices testing an important use of hemodynamic simulations-analysis of surface parameters within complex patient-specific geometries. This task was compared for the semi-immersive zSpace 3D monitor and the fully immersive HTC Vive system. The semi-immersive device was more accurate than the fully immersive device. The two devices showed similar results for task duration and performance (accuracy/duration). The accuracy of the semi-immersive device was also higher for arterial geometries of greater complexity and branching. This assessment demonstrates that the level of immersion plays a significant role in the accuracy of assessing arterial flow models. We found that the semi-immersive VR device was a generally optimal choice for arterial visualization.

Biaxial mechanical properties of the bronchial tree: Characterization of elasticity, extensibility, and energetics, including the effect of strain rate and preconditioning

Distal airways commonly obstruct in lung disease and despite their importance, their mechanical properties are vastly underexplored. The lack of bronchial experiments restricts current airway models to either assume rigid structures, or extrapolate the material properties of the trachea to represent the small airways. Furthermore, past works are exclusively limited to uniaxial testing; investigating the multidirectional tensile loads of both the proximal and distal pulmonary airways is long overdue. Here we present comprehensive mechanical and viscoelastic properties of the porcine airway tree, including the trachea, trachealis muscle, large bronchi, and small bronchi, via measures of elasticity, extensibility, and energetics to explore regional and directional dependencies, cross-examining strain rate and preconditioning effects using planar equibiaxial tensile tests for the first time. We find bronchial regions are notably heterogeneous, where the trachea exhibits greater stiffness, energy loss, and preconditioning sensitivity than the smaller airways. Interestingly, the trachealis muscle is similar to the distal bronchi, despite being anatomically located adjacent to the proximal ring. Tissues are anisotropic and axially stiffer under initial loading, losing more energy with greater stress relaxation circumferentially. Strain rate dependency is also noted, where tissues are more energetically efficient at the faster strain rate, likely attributable to the microstructure. Findings highlight assumptions of homogeneity and isotropy are inadequate, and enable the improvement of aerosol flow and dynamic airway deformation computational predictive models. These results provide much needed fundamental material properties for future explorations contrasting healthy versus diseased pulmonary airway mechanics to better understand the relationship between structure and lung function. Statement of significanceWe present comprehensive multiaxial mechanical tensile experiments of the proximal and distal airways via measures of maximum stress, initial and ultimate moduli, strain and stress transitions, hysteresis, energy loss, and stress relaxation, and further assess preconditioning and strain rate dependencies to examine the relationship between lung function and structure. The mechanical response of the bronchial tree demonstrates significant anisotropy and heterogeneity, even within the tracheal ring, and emphasizes that contrary to past studies, the behavior of the proximal airways cannot be extended to distal bronchial tree analyses. Establishing these material properties is critical to advancing our understanding of airway function and in developing accurate computational simulations to help diagnose and monitor pulmonary diseases.

Computational Fluid Flow Model for the Development of an Arterial Bypass Graft

Intimal hyperplasia, an aberrant proliferation of smooth muscle cells that causes stenosis and graft occlusion, is the primary cause of the failure of grafts after a few years. In this way, and using the constructal design method, this study looks at how the stenosis degree, junction angle, and diameter ratio affect the flow through a bypass graft that goes around an idealised coronary artery partially blocked. The results show that the flow effect by several factors: Stenosis ratio (S), Bypass Attachment Point (L2), Bypass Angle (α), and Bypass Diameter (D1). The results indicate that the pressure drop is reduced when S is low, the optimal attachment point L2 = 4 Artery diameter (D), the optimal angle α = 30°, and the optimal D1 = 1.25D.

Arnold Verruijt (1940-2022).

Arnold Verruijt (1940-2022).

Comprehensive Computational Model for Coupled Fluid Flow, Mass Transfer, and Light Supply in Tubular Photobioreactors Equipped with Glass Sponges

The design and optimization of photobioreactor(s) (PBR) benefit from the development of robust and quantitatively accurate computational fluid dynamics (CFD) models, which incorporate the complex interplay of fundamental phenomena. In the present work, we propose a comprehensive computational model for tubular photobioreactors equipped with glass sponges. The simulation model requires a minimum of at least three submodels for hydrodynamics, light supply, and biomass kinetics, respectively. First, by modeling the hydrodynamics, the light–dark cycles can be detected and the mixing characteristics of the flow (besides the mass transport) can be analyzed. Second, the radiative transport model is deployed to predict the local light intensities according to the wavelength of the light and scattering characteristics of the culture. The third submodel implements the biomass growth kinetic by coupling the local light intensities to hydrodynamic information of the CO2 concentration, which allows to predict the algal growth. In combination, the novel mesoscopic simulation model is applied to a tubular PBR with transparent walls and an internal sponge structure. We showcase the coupled simulation results and validate specific submodel outcomes by comparing the experiments. The overall flow velocity, light distribution, and light intensities for individual algae trajectories are extracted and discussed. Conclusively, such insights into complex hydrodynamics and homogeneous illumination are very promising for CFD-based optimization of PBR.

In silico modeling for the hepatic circulation and transport: From the liver organ to lobules.

The function of the liver depends critically on its blood supply. Numerous in silico models have been developed to study various aspects of the hepatic circulation, including not only the macro-hemodynamics at the organ level, but also the microcirculation at the lobular level. In addition, computational models of blood flow and bile flow have been used to study the transport, metabolism, and clearance of drugs in pharmacokinetic studies. These in silico models aim to provide insights into the liver organ function under both healthy and diseased states, and to assist quantitative analysis for surgical planning and postsurgery treatment. The purpose of this review is to provide an update on state-of-the-art in silico models of the hepatic circulation and transport processes. We introduce the numerical methods and the physiological background of these models. We also discuss multiscale frameworks that have been proposed for the liver, and their linkage with the large context of systems biology, systems pharmacology, and the Physiome project. This article is categorized under: Metabolic Diseases > Computational Models Metabolic Diseases > Biomedical Engineering Cardiovascular Diseases > Computational Models.

Investigation of the effects of pipe diameter of internal multiphase flow on pipe elbow vibration and resonance

Computational fluid dynamics modelling of internal two-phase flow induced transient forces at 90° elbows have been carried out to evaluate the effect of pipe diameter on the characteristics of multiphase flow induced vibration. Simulations of two-phase flows of slug, cap bubbly and churn induced vibration at a pipe elbow were carried out using the volume of fluid model for the two-phase flows and the k – ε model for turbulence. Modal analysis has been carried out to evaluate the risk of resonance. Results were compared across three geometrically similar pipes of different diameters. Simulation results showed that the behaviours of the flow induced forces at the pipe elbow as a function of gas velocity for internal diameters of 0.0525 and 0.2032 m are similar. However, the multiphase flow induced force characteristics are different in the 0.1016 m diameter (intermediate) pipe. It can be attributed to the transition behaviour of gas–liquid two-phase flows caused by Taylor instability in an intermediate sized pipe. The predicted root-mean-square flow induced forces as a function of Weber number were correlated with an existing empirical correlation for a wider range of pipe sizes and gas volume fractions between 40% and 80%. Furthermore, the pipe natural frequencies increase with the increase of gas volume fraction in smaller pipes and the resonance risk increases with the increase of pipe diameter.

Analytical and computer dynamic discrete simulation model of the mechanism for the formation of monetary amounts to be paid to the enterprise for the production of rocket and space equipment

The key point of flow process modeling is that it is based on the use of discrete models. In traditional approaches to modeling production processes, time is considered as a continuous quantity. Static models are far from reality, since any production has a cyclical nature, since any product is produced in a finite time. In the modern theory and practice of modeling, mathematical models of economic processes in which time changes discretely are of great importance. The work combines various aspects of management, found a common language and structure in describing various conditions in production, the supply of components, raw materials, materials, as well as research, based on investments in staff training and product quality. The key point of flow process modeling is that it is based on the use of discrete models. In traditional approaches to modeling production processes, time is considered as a continuous quantity. Static models are far from reality, since any production has a cyclical nature, since any product is produced in a finite time. In the modern theory and practice of modeling, mathematical models of economic processes in which time changes discretely are of great importance. The work combines various aspects of management, found a common language and structure in describing various conditions in production, the supply of components, raw materials, materials, as well as research, based on investments in staff training and product quality. This article discusses the actual problems of the formation of flows that characterize the financial results of the company's activities for the production of launch vehicles. It is shown that the main flow parameters characterizing the financial condition of the enterprise are the cash flow to be paid and the cash flow to receive incoming funds for the sale of rocket kits, each of these flows is represented by a discrete simulation equation, the solution of which is carried out using computer models. An equation has been formed to determine the cash flow for the payment of wages to the main production personnel at the enterprise. To assess the magnitude of the effect as the final result of the company's activities, an equation has been formed that allows determining the specific cost of the launch vehicle. At a known price and its unit cost, mathematical and computer models of the profit flow received by the enterprise are formed. The graphs of the trajectories of changes in the flow of profit and the expenditure on wages presented in the work allow us to determine the time of the transition process and its dynamic stability under imposed disturbances in the volume of the order from Roscosmos.

Measurement of low Reynolds number flow emanating from a Turing pattern microchannel array using a modified Bernoulli equation technique

An experimental investigation of the air flow emanating from a Turing pattern microchannel array into an open atmosphere at very low Reynolds (Re) numbers is presented. As designed, the microchannel structure has channel sizes ranging between 0.6 mm and 1.5 mm with a depth of 0.6 mm. The development of a modified Bernoulli equation analysis method to determine fluid flow speed is introduced. Specifically, a low cost, large (11.11 mm inner diameter) flexible tube probe was employed to measure the fluid total pressure field distribution at a fixed distance from the outlets of the microchannel array. Using subsequent numerical modeling of the outlet-to-tube fluid flow interactions, a flow speed dependent correction factor for the determined dynamic pressure field is proposed. The experimentally measured fluid flow distribution is consistent with the expected flow field pattern obtained by additional computational modeling of flow through and exiting the entire Turing pattern microchannel manifold structure. The pressure measurement and post-processing technique for determining flow velocity may be adapted to a wide range of low-speed (e.g., Re≤100) fluid flow measurement scenarios.

Environmental Effects on Viable Virus Transport and Resuspension in Ventilation Airflow.

To understand how SARS-CoV-2 spreads indoors, in this study bovine coronavirus was aerosolized as simulant into a plexiglass chamber with coupons of metal, wood and plastic surfaces. After aerosolization, chamber and coupon surfaces were swiped to quantify the virus concentrations using quantitative polymerase chain reaction (qPCR). Bio-layer interferometry showed stronger virus association on plastic and metal surfaces, however, higher dissociation from wood in 80% relative humidity. Virus aerosols were collected with the 100 L/min wetted wall cyclone and the 50 L/min MD8 air sampler and quantitated by qPCR. To monitor the effect of the ventilation on the virus movement, PRD1 bacteriophages as virus simulants were disseminated in a ¾ scale air-conditioned hospital test room with twelve PM2.5 samplers at 15 L/min. Higher virus concentrations were detected above the patient’s head and near the foot of the bed with the air inlet on the ceiling above, exhaust bottom left on the wall. Based on room layout, air measurements and bioaerosol collections computational flow models were created to visualize the movement of the virus in the room airflow. The addition of air curtain at the door minimized virus concentration while having the inlet and exhaust on the ceiling decreased overall aerosol concentration. Controlled laboratory experiments were conducted in a plexiglass chamber to gain more insight into the fundamental behavior of aerosolized SARS-CoV-2 and understand its fate and transport in the ambient environment of the hospital room.

Coupled multiphase flow and pore compression computational model for extraction of offshore gas hydrates

During gas hydrate extraction multiphase flow occurs with transitioning gas hydrate phase followed by pore compression. Effective theoretical and numerical models with the ability to account gas hydrate are key to evaluate the feasibility of gas hydrate extraction and understand the physical mechanisms behind it. In this manuscript, a coupled multiphase flow computational model is developed to simulate the gas hydrate extraction where phase transition and pore compression occurs. The compressibility of each phase is coupled with the variation of gas hydrate saturation and porosity. An efficient decoupled implicit iteration method is proposed to solve the highly non-linear equations. Differing from the known implicit iteration, an algorithm with dynamic time step was used to consider gas hydrate mass in each grid and to maintain the stability of simulation. The proposed model is validated using Masuda’s core sample experimental data. Then a conceptual offshore gas hydrate chimney is simulated, and the impacts of intrinsic permeability, lithology and gas hydrate saturation heterogeneity, and reservoir compression modulus on gas hydrate extraction efficiency are investigated using the model. The model shows the ability to predict the long-term gas hydrate production and correlated seabed stability problems.

Capillary module haemodynamics and mechanisms of blood flow regulation in skeletal muscle capillary networks: Experimental and computational analysis.

The capillary module (CM), consisting of parallel capillaries from terminal arteriole to post-capillary venule, is classically considered to be the building block of complex capillary networks. In skeletal muscle, CMs form interconnected columns spanning thousands of microns, which we recently described as the capillary fascicle. However, detailed evaluation of CM haemodynamics has not been described, and may provide insight into mechanisms of blood flow regulation in the microcirculation. We used intravital videomicroscopy from resting extensor digitorum longus muscle in rats (n=9 networks, 112 capillary modules), as well as dual-phase computational modelling of blood flow in simulated CM geometries. We found that the mean driving pressure across CMs was 3.236±1.833mmHg. Red blood cell (RBC) flow was independent of CM resistance, and the ratio of blood flow in adjacent modules was not correlated with their ratio of resistances. In simulated CM geometries, increases to driving pressure produced a direct linear increase to RBC and plasma flow, with no changes to RBC distribution; increases to arteriolar inflow haematocrit resulted in increased RBC flow, but with viscosity-dependent increases to CM resistance. CM RBC flow heterogeneity was higher than plasma flow heterogeneity in experimental data, in contrast to simulated geometries, suggesting that time-dependent flow variability may have important consequences for RBC distribution. In summary, these findings suggest that CMs are active participants in microvascular flow regulation, likely achieved through adjustments to CM driving pressure using pre- and post-capillary loci of flow control. Increases to CM viscosity may be important during the regulation of functional hyperaemia. KEY POINTS: The capillary module (CM), consisting of parallel capillaries from the arteriole to venule, is classically considered to be the building block of capillary networks in skeletal muscle. A detailed evaluation of module haemodynamics may provide insight into mechanisms of blood flow regulation in the microcirculation. Using experimental data from resting skeletal muscle in rats, as well as dual-phase computational models of blood flow, we analysed haemodynamic relationships and the impact of variations to boundary conditions on red blood cell and plasma distribution. We showed that driving pressure across CMs is low, and that simulated increases to inflow haematocrit have important viscosity-dependent effects on module resistance. We found that red blood cell flow was independent from module resistance, which strongly suggests the regulation of driving pressure at the level of the capillary module using pre- and post-capillary loci of flow control. These findings place CMs as central participants in microvascular flow regulation, with important consequences for disease and functional hyperaemia.

Numerical Simulation of Heat Transfer and Fluid Flow at Different Stacking Modes in a Refrigerated Room: Application of Pyramidal Stacking Modes

By means of the porous media theory, computational fluid dynamic models of heat transfer and fluid flow at different pack stacking modes in a refrigerated room are elaborated. A practical case is simulated, where brick-shaped packs with aquatic products, partially frozen to 261.15 K, are loaded in the room to complete the freezing process down to 255.15 K, followed by long-term frozen food storage at the latter standard temperature. The best freezing completion effect (defined as the maximum reduction of the highest product temperature during a certain residence time) is achieved by using the pyramidal stacking mode whose upper package is in the center of four lower packages (UPF-PSM) with two piles. The highest temperature of aquatic products at a two-pile-UPF-PSM can be reduced from 261.15 to 255.60 K for a residence time of 24 h. Within the same time, the product temperature becomes most uniform at a UPF-PSM. Simultaneously, the best uniformity of flow distribution and highest efficiency of air circulation in a refrigerated room are obtained by using the neat stacking mode (NSM) during the long-term frozen storage. Furthermore, a comprehensive stacking mode is proposed (using UPF-PSM for freezing completion and NSM for long-term frozen storage), which enhances both the freezing completion effect and the efficiency of air circulation in the studied refrigerated room.

Atrial Fibrillation and Anterior Cerebral Artery Absence Reduce Cerebral Perfusion: A De Novo Hemodynamic Model

Background: Atrial fibrillation is a prevalent cardiac arrhythmia and may reduce cerebral blood perfusion augmenting the risk of dementia. We hypothesize that geometric variations in the cerebral arterial structure called the Circle of Willis (CoW) play an important role in influencing cerebral perfusion. The objective of this work was to develop a novel cardio-cerebral lumped parameter hemodynamic model to investigate the role of CoW variants on cerebral blood flow dynamics under atrial fibrillation conditions. Methods: A computational blood flow model was developed by coupling whole-body and detailed cerebral circulation descriptions, modified to represent six common variations of the CoW. Cerebral blood flow dynamics were simulated in common CoW variants, under control and imposed atrial fibrillation conditions. Risk was assessed based on the frequency of beat-wise hypoperfusion events, and sensitivity analysis was performed with respect to this model output. Results: It was found that the geometry of the CoW influenced the frequency of hypoperfusion events at different heart rates, with the variant missing a P1 segment having the highest risk. Sensitivity analysis revealed that intrinsic heart rate is most associated with the considered outcome. Conclusions: Our results suggest that CoW geometry plays an important role in influencing cerebral hemodynamics during atrial fibrillation. The presented study may assist in guiding our future clinical-imaging research.

Fully compressible multiphase model for computation of compressible fluid flows with large density ratio and the presence of shock waves

We propose a fully compressible multiphase model for simulating compressible interfacial flows. The mathematical model is formulated on the basis of the typical conservation laws for mixtures, including mass, momentum, and energy balance. The mass balance equation in each phase is considered to discretely conserve the mass of each phase; therefore, it is always mass conservative for each phase. The numerical solution procedure for this model is developed using a high-resolution shock-capturing finite-volume method based on the Harten–Lax–van Leer-contact (HLLC) Riemann solver and total variation diminishing (TVD) time-integration schemes for simulating unsteady multiphase flows and capturing strong shocks. The finite-volume Riemann solver is combined with a monotonic upstream-centered scheme for conservation laws (MUSCL) and compressive limiters to maintain a sharp interface. The numerical framework yields a conceptually simple but robust and versatile numerical procedure. Numerical results of benchmark Riemann problems demonstrate the ability of the proposed method to obtain sharp interfaces, free of spurious oscillations, high accuracy, conservation properties, and thermodynamic consistency over various Mach numbers.

Computational investigation of blood cell transport in retinal microaneurysms.

Microaneurysms (MAs) are one of the earliest clinically visible signs of diabetic retinopathy (DR). MA leakage or rupture may precipitate local pathology in the surrounding neural retina that impacts visual function. Thrombosis in MAs may affect their turnover time, an indicator associated with visual and anatomic outcomes in the diabetic eyes. In this work, we perform computational modeling of blood flow in microchannels containing various MAs to investigate the pathologies of MAs in DR. The particle-based model employed in this study can explicitly represent red blood cells (RBCs) and platelets as well as their interaction in the blood flow, a process that is very difficult to observe in vivo. Our simulations illustrate that while the main blood flow from the parent vessels can perfuse the entire lumen of MAs with small body-to-neck ratio (BNR), it can only perfuse part of the lumen in MAs with large BNR, particularly at a low hematocrit level, leading to possible hypoxic conditions inside MAs. We also quantify the impacts of the size of MAs, blood flow velocity, hematocrit and RBC stiffness and adhesion on the likelihood of platelets entering MAs as well as their residence time inside, two factors that are thought to be associated with thrombus formation in MAs. Our results show that enlarged MA size, increased blood velocity and hematocrit in the parent vessel of MAs as well as the RBC-RBC adhesion promote the migration of platelets into MAs and also prolong their residence time, thereby increasing the propensity of thrombosis within MAs. Overall, our work suggests that computational simulations using particle-based models can help to understand the microvascular pathology pertaining to MAs in DR and provide insights to stimulate and steer new experimental and computational studies in this area.