Flow Stagnation Research Articles

Numerical Simulation of the Flow in a Sensor for Measuring the Flow Stagnation Temperature in Pulsed Aerodynamic Installations

Numerical Simulation of the Flow in a Sensor for Measuring the Flow Stagnation Temperature in Pulsed Aerodynamic Installations

Analysis of the Effect of Bend Angle Outlet Main Steam Line on the Steam Flow Characteristic

Pressure drop is one of the problems that can occur due to bend components in the piping system. To minimize the pressure drop, modification of the bend pipe component was made at the bend outlet of the main steam line. In this study, an analysis of the effect of the bend angle on the pressure drop was carried out on the pressure and velocity steam distribution. The angle variations used are 30°, 45°, and 60° with the Computational Fluid Dynamics (CFD) method simulated by CFD software. The simulation results show that the lower the angle of curvature of the pipe, the lower the pressure drop and the lowest pressure drop is obtained in the 30° bend domain of 26.2 kPa. The pressure distribution pattern shows that the pressure value will increase from the inner wall to the outer wall. The greater the bend pipe angle, the greater the possibility of flow separation and pressure drop value. The velocity distribution pattern shows that the flow velocity becomes non-uniform after passing through the bend pipe. The greater the bend angle, the sharper the flow direction so that the time taken is longer. In addition, the greater the bend pipe angle, the greater the flow stagnation.

CFD Study of Flow Characteristics and Pressure Distribution on Re-Entrant Wing Faces of L-Shape Buildings

The purpose of this research is to investigate the wind flow pattern and pressure distributions on the re-entrant wing facades of an irregular L-cross sectional shape model over the range of wind incidence angles. Computational simulation with ANSYS (CFX) solver has been used for the study on model of the building of cross-sectional area 300m² and height 50m at a length scale of 1:100. ANSYS (CFX) is a finite element modelling CFD program of pressure-based solver technology suitable for low Mach No. (Ma) fluid flow. Homogeneous flow of steady wind with gustiness of 5% turbulence in boundary layer of atmosphere is taken for the study. Investigation has been conducted for a range of wind angle of attack from 0° to 180° @ 15° interval. The findings were confirmed by examining similar wind flow on a rectangular model of same cross-sectional area and height under same boundary conditions as applied to L shape model. The results were compared with the values given in various international wind design codes/standards. For a better understanding of the flow characteristics around the L shape model in terms of flow stagnation, flow separation, creation of wakes & vortices and reattachment of flow; illustrations of flow patterns around the model for certain specific wind incidence angles are presented. On the basis of study of surface pressure generated on the model envelope, coefficient of pressure on the re-entrant corner faces has been discussed. The pressure on these wing faces has been found critical between 75° & 180° wind incident angles.

Motion analysis and modulation of steel particle swarm in high-pressure tank for particle impact drilling

Particle Impact Drilling (PID) is a new technology to effectively improve the rate of penetration (ROP) for oil and gas drilling in hard and strongly abrasive formations. In this paper, numerical simulation method is used to analyse the motion characteristics and the modulation method of particle swarm in high-pressure tank for the particle injection system based on differential pressure ejection in PID. The numerical simulation results show that: when there is no modulation elements, the motion of particle swarm in the high-pressure tank follows an asymmetric funnel flow with pulsating state, which could be divided into vertical flow domain, fast flow domain, slow flow domain and stagnation domain. The unstable dynamic arching effect of the funnel flow, the viscous effect of the liquid bridge force and the collapsing effect of the particle swarm could probably lead to the blockage of the discharge port of the high-pressure tank. When the semiapex angles of the high-pressure tank decreases, the volume flow rate of particles increases and the stagnation domain becomes smaller, but it becomes easier to form arching and blockage. The modelling results indicate that the pulsation of the funnel flow is minimum when the semiapex angle is 45° without the mutilation element, which means the funnel flow of the particle swarm is relatively stable. By introducing a conical modulating element above the discharge port, the unstable funnel flow of the particle swarm could be transformed to an overall uniform flow. The modelling results indicate that the installation height of the modulation element has the greatest influence on the pulsation degree. The optimized parameters for the conical modulation element based on numerical modelling tests are 70° for the vertex angle, 35 mm for the length of the flank and 70 mm for the installation heigh.

A proposed strategy for anticoagulation therapy in noncompaction cardiomyopathy.

Noncompaction cardiomyopathy (NCCM) is a rare condition characterized by prominent trabeculae, deep intertrabecular recesses, and a left ventricular myocardium with a two‐layered structure, characterized by a spongy endocardial layer and a thinner and compacted epicardial one. NCCM can be isolated or associated with other congenital heart diseases and complex syndromes involving neuromuscular disorders and facial dysmorphisms. To date, more than 40 genes coding for sarcomeric, cytoskeletal, ion channels, and desmosomal proteins have been identified. Clinical presentation is also highly variable, ranging from no symptoms to end‐stage heart failure (HF), lethal arrhythmias, sudden cardiac death, or thromboembolic events. In particular, the prevalence of thromboembolism in NCCM patients appears to be higher than that of a similar, age‐matched population without NCCM. Thromboembolism has a multifactorial aetiology, which is linked to genetic, as well as traditional cardiovascular risk factors. In previous studies, atrial fibrillation (AF) was observed in approximately 25–30% of adult NCCM patients and embolism had a cardiac source in ~63–69% of cases; therefore, AF represents a strong predictor of adverse events, especially if associated to HF and neuromuscular disorders. Left ventricular dysfunction is another risk factor for thromboembolism, as a result of blood stagnation and local myocardial injury. Moreover, it is not completely clarified if the presence of deep intertrabecular recesses causing stagnant blood flow can constitute per se a thrombogenic substrate even in absence of ventricular dysfunction. For the clinical management of NCCM patients, an appropriate stratification of the thromboembolic risk is of utmost importance for a timely initiation of anticoagulant therapy. The aim of the present study is to review the available literature on NCCM with particular attention on thromboembolic risk stratification and prevention and the current evidence for oral anticoagulation therapy. The use of direct oral anticoagulants vs. vitamin K antagonists is also discussed with important implications for patient treatment and prognosis.

Entropy generation and induced magnetic field in pseudoplastic nanofluid flow near a stagnant point

In this present article the entropy generation, induced magnetic field, and mixed convection stagnant point flow of pseudoplastic nano liquid over an elastic surface is investigated. The Buongiorno model is employed in modeling. Through the use of the boundary layer idea, flow equations are transformed from compact to component form. The system of equations is solved numerically. The Induced magnetic spectrum falls near the boundary and grows further away as the reciprocal of the magnetic Prandtl number improves. The fluctuation of induced magnetic rises while expanding the values of mixed convection, thermophoresis, and magnetic parameters, whereas it declines for increment in the Brownian and stretching parameters. The velocity amplitude ascends and temperature descends for the rise in magnetic parameter. The mass transfer patterns degrade for the higher amount of buoyancy ratio while it boosts by the magnification of mixed convection and stretching parameters. Streamlines behavior is also taken into account against the different amounts of mixed convection and magnetic parameters. The pseudoplastic nanofluids are applicable in all electronic devices for increasing the heating or cooling rate in them. Further, pseudoplastic nanofluids are also applicable in reducing skin friction coefficient.

Drag and wake structure of a quasi-dandelion pappus model at low and moderate Reynolds numbers: The effects of filament width

The aerodynamic performance and wake structure of dandelion seed pappus have been numerically studied based on a simplified quasi-dandelion pappus (QDP) model with its filaments represented by rectangular cylinders. The filament width is chosen as the major geometric parameter for investigation. A rigorous measuring strategy is developed for the identification of the recirculation region width in the wake of the QDP model. Three regimes are distinguished as the filament width increases, i.e., a dandelion-like regime, a transition regime, and a disk-like regime. In the dandelion-like regime, the recirculation region widths are relatively large and monotonously decrease with the increase in Reynolds number. In the transition regime, the recirculation region widths are moderate and first decrease sharply at low Reynolds number and subsequently maintain an approximately invariant value. In the disk-like regime, the recirculation region widths are relatively small. The Reynolds number based on the recirculation region width is defined, and its correlation to the drag coefficient in a different regime is also discussed. In addition, as the QDP model turns from the dandelion-like regime to the disk-like regime, the pressure distribution in the wake turns from the recirculation region type to the flow stagnation type. The current study may provide a reference for the design of more efficient dandelion-like aircraft.

Stabilizing viscous extensional flows using reinforcement learning.

The four-roll mill, wherein four identical cylinders undergo rotation of identical magnitude but alternate signs, was originally proposed by G. I. Taylor to create local extensional flows and study their ability to deform small liquid drops. Since an extensional flow has an unstable eigendirection, a drop located at the flow stagnation point will have a tendency to escape. This unstable dynamics can, however, be stabilized using, e.g., a modulation of the rotation rates of the cylinders. Here we use reinforcement learning, a branch of machine learning devoted to the optimal selection of actions based on cumulative rewards, in order to devise a stabilization algorithm for the four-roll mill flow. The flow is modelled as the linear superposition of four two-dimensional rotlets and the drop is treated as a rigid spherical particle smaller than all other length scales in the problem. Unlike previous attempts to devise control, we take a probabilistic approach whereby speed adjustments are drawn from a probability density function whose shape is improved over time via a form of gradient ascent know as actor-critic method. With enough training, our algorithm is able to precisely control the drop and keep it close to the stagnation point for as long as needed. We explore the impact of the physical and learning parameters on the effectiveness of the control and demonstrate the robustness of the algorithm against thermal noise. We finally show that reinforcement learning can provide a control algorithm effective for all initial positions and that can be adapted to limit the magnitude of the flow extension near the position of the drop.

Numerical analysis of shock wave train in single-expansion ramp nozzle under harmonic inlet and outlet conditions

The single-expansion ramp nozzle (SERN) is intensely over-expanded and leads to a large separation zone. The flow separation is the central phenomenon causing a reduction in thrust, and shock waves lead to a drop in the flow stagnation pressure and increase the energy loss. In this study, the unsteady compressible flow in a SERN was studied by employing the k-kl-ω transition turbulence model with high ability in separation flow prediction. In this regard, the finite volume code with the pressure-implicit with the splitting of operators algorithm and the adaptive mesh refinement technique were applied. Firstly, the results were compared with published data and it is revealed that the numerical methodology was capable of detecting the exact structure of lambda shock and wall pressure. Then, the influences of harmonic inlet and outlet conditions were evaluated on the flow behavior. The results showed that for harmonic inlet pressure conditions the value of friction coefficient in the case with wavelength of 0.3 is greater than the cases with the wavelength of 0.15 and 0.6. Also, it is found that the shock train did not form for the case with wavelength of 0.6. Furthermore, for the harmonic condition in outlet pressure, the minimum wall shear stress was obtained for the case with the wavelength of 015, and the shock strength, in this case, is more than the cases with wavelength of 0.6 and 0.3.

Numerical Analysis of the Influence of the Modification of the Ladle Shroud on Fluid Flow Behavior in a One-strand Tundish during Continuous Steel Casting

A tundish is a device from which liquid steel is pour into a mold. Therefore tundish hydrodynamic conditions have a significant impact on solidification during continuous steel casting (CSC) process. Modification of ladle shroud workspace, allows for the modification of liquid steel movement in the tundish. In the following work, numerical simulations were performed which allowed the impact of the modification of the ladle shroud workspace on the liquid steel flow structure in a one-strand tundish to be determined. In order to assess the impact of the modification of the ladle shroud on the behavior of the liquid steel in the tundish, simulations were performed, on the basis of which the percentage share of stagnant, ideal mixing and plug flow zones were determined. In addition, the mixing parameters were determined, allowing the estimation of casting duration during sequential casting. The flow fields of liquid steel for each modification of the ladle shroud were performed. The average velocity of liquid steel flowing through the tundish, the Reynolds number and turbulent intensity were also described. The obtained results showed, among others, that the application of three cylinders with a diameter of 0.041 m into the ladle shroud with a diameter of 0.11 m increases the share of active flow in the tundish in relation to the tundish with Conventional Ladle Shroud. At the same time, applying a ladle shroud with a diameter of 0.11 m during casting is the most favorable in relation to the hydrodynamics of the tundish.

Measurements of electron number density and temperature in a supersonic plasma jet by optical emission spectroscopy

The results of experimental studies of the shock-wave region of the supersonic plasma jet flow formed by a pulsed capillary discharge with a polymeric wall are presented. Using optical emission spectroscopy of high spatial resolution, a detailed picture of the evolution of the radial profiles of the electron number density and temperature along the initial section of an underexpanded plasma jet, starting from the capillary outlet and ending with the flow stagnation zone, has been obtained. It was found that the profiles of the electron number density and temperature reflect all the features of the shock-wave flow region, tracing the influence of intercepting, central and reflected shock waves.

Energy separation in a channel with permeable wall

The present paper is an experimental and numerical analysis of a new method of energy separation. By energy separation, we mean the spontaneous separation of the gas flow into two flows with stagnation temperatures above and below the initial (“hot” and “cold”). One of the most famous devices using the phenomenon of energy separation is the Rank-Hilsch vortex tube. The considered method is based on the well-known effect of the stagnation temperature profile curvature over the boundary layer thickness, which occurs when a high-speed gas flows around an adiabatic surface. It is known that the higher the flow velocity and the more the Prandtl number differs from unity, the higher the energy separation within the boundary layer. In a channel with a permeable wall, part of the high-speed flow can be sucked out through the wall due to the natural pressure drop. As a result, the flow's stagnation temperatures at the outlet of the channel and the flow sucked out through the wall are different: one is hotter, the other is colder compared to the initial stagnation temperature. Based on the obtained experimental data, validation of one- and two-dimensional mathematical models was carried out. The influences of the initial Mach number, the initial stagnation pressure, the relative channel length, and the Prandtl number on the energy separation were investigated. It was found that as the initial Mach number changes from Mis = 1 to Mis = 3, the air flow's cooling increases from −5 to −15 K. When the Prandtl number changes from Pr = 0.7 to Pr = 0.2, the flow's cooling is increased by factor of 2.25 from −20 to −45 K. It is shown that at a certain ratio of parameters, the heating and the cooling of flows pass through an extremum.The obtained temperature difference due to the suction of a part of the flow can find application in the analysis of flows with variable mass flow rates in power systems, such as heat pipes, boundary layer control devices, etc.

Comparison of Dural Venous Sinus Volumes Before and After Flight in Astronauts With and Without Spaceflight-Associated Neuro-Ocular Syndrome

Spaceflight-associated neuro-ocular syndrome (SANS) occurs in 40% to 60% of National Aeronautics and Space Administration (NASA) International Space Station (ISS) astronauts who present postflight with ophthalmological findings and elevated intracranial pressure. The etiology of SANS is unknown; it is hypothesized that venous outflow congestion from the head and neck occurs because of microgravity, which is supported by the finding of internal jugular vein stagnant flow and thrombosis in some astronauts, but the impact on intracranial dural venous sinus structures remains unknown. To clarify the potential risk of retrograde extension of clot intracranially among astronauts with internal jugular venous thrombosis by evaluating intracranial venous structures following spaceflight and to assess for any association between intracranial venous congestion and SANS. This retrospective cohort study of all NASA astronauts who had undergone magnetic resonance (MR) venography at the time of the study included quantitative and qualitative assessments of the intracranial venous system on preflight and postflight MR venograms. Data were collected a mean (SD) of 525.8 (187.5) days before spaceflight and 2.0 (1.5) days after return to Earth. A semiautomated segmentation of the venogram images was used, which was then compared with a neuroradiologist's assessment. A mean (SD) 184.3 (66.0) days of ISS spaceflight missions. Dural venous sinus volumes before and after spaceflight. A total of 12 astronauts (2 [16.67%] women; 10 [83.33%] men), with a mean (SD) age of 47.8 (5.8) years, were included. Overall, 4 astronauts (33.33%) met the diagnostic criteria for SANS. No dural venous sinus thrombosis was detected for any astronaut. Astronauts with SANS had significantly greater median (range) preflight to postflight increases in volume vs astronauts without SANS for all 3 venous sinus structures: superior sagittal sinus (13.40% [8.70% to 17.47%] vs -2.66% [-15.84% to 5.31%,]; P = .004), right transverse/sigmoid sinus (17.15% [7.63% to 30.08%] vs 0.77% [-14.98% to 15.12%]; P = .02), and left transverse/sigmoid sinus (9.40% [5.20% to 15.50%] vs -1.40% [-14.20% to 12.50%]; P = .03). There was a positive correlation between the neuroradiologist's evaluation and the semiautomated method for the superior sagittal sinus (rpb = 0.64; P = .02) and the right transverse/sigmoid sinus (rpb = 0.58; P = .050). These findings, in conjunction with the growing body of evidence of abnormal blood flow dynamics during spaceflight, suggest an association between intracranial venous congestion and SANS. Thus, there is an implication that individuals with increased venous sinus compliance may be at increased risk of developing SANS. These findings should be confirmed in a larger astronaut population and may contribute to understanding disorders of intracranial venous outflow on Earth.

Development of methods for assessing the safety of light hydrocarbon storage facilities in emergency situations

The risk of accidents involving light hydrocarbons is caused by the physicochemical properties of the components, primarily propane and butane. The most catastrophic accidents involving these substances were on November 19, 1984, in the city of San Juan Ixhuatepec (Mexico) and on June 4, 1989, on the Asha - Ulu-Telyak section (USSR), in each of which more than 500 people died. The novelty of the study is determined by the requirement to ensure industrial and fire safety of storage facilities for light hydrocarbons by predicting probable zones of air flow stagnation. The authors calculated the formation of probable air stagnation zones for various space-planning solutions by using a three-dimensional modelling system and the finite volume method. The paper developed a methodology for assessing the safety of storage facilities for light hydrocarbons in emergency situations, which is based on the analysis of probable air stagnation zones by using three-dimensional modelling systems. The practical significance of the study is determined by the additional development of a parameter for assessing the safety state of a storage facility for light hydrocarbons (Ks) and a resulting parameter (Kr) for calculating the optimal location of structures and their structural changes. Integration of stagnation zone sizes into a single formula with the results of other safety calculations is an urgent scientific and applied problem.

INDUSTRY CLUSTER ECONOMY (ON THE EXAMPLE OF TOURISM)

The purpose of study is to study cluster organization of management on example of tourism in context of problem of creating an economy of an industry cluster. The research method is a methodological analysis of problem of creating clusters in Kazakhstan tourism in context of problems of its organization and individualization. Modern tourism has become one of spheres of national economy and traditional business. Tourism has an impact on development of national economy, providing employment and additional jobs. In sectoral structure of national economy, tourism has a strong multiplier effect. Tourism influences development of transport, hospitality industry, public catering, and national crafts. Expanding scope of employment of population, tourism contributes to solving social problems of society, improving standard of living of people, quality of human potential. By developing tourism, country's economy can get not only these positive effects. But also effect of inflow of foreign currency and thus a positive impact on balance of payments and total exports of country. Kazakhstan has a diverse raw material base for development of tourism. The raw material base of tourism is represented by tourist and recreational resources. The development of tourism and contribution to GNP of Kazakhstan is characterized by a low level. Currently, an external factor–COVID-19-has a negative impact. The introduction of sanitary quarantine on a global scale, closure of national borders has led to stagnation of both external and internal tourist flows. As a result, tourism industry is in crisis. The creation of clusters contributes to competitiveness of Kazakhstan's tourism. The role of clusters is to develop partnerships between state and business. In Concept of development of tourism industry of Kazakhstan until 2023 it is expected to create six cultural tourism clusters:Astana - heart of Eurasia,Almaty – free cultural zone of Kazakhstan, Pearl of Altai, Revival of Great Silk Road, the Caspian gates,the Unity of nature and nomadic culture. Building a cluster is not simply a matter of adding up production and services. The tourism cluster creates its own Economy, which has an intersectoral nature of product design, preparation for production of new products.

Protective mechanisms of betablockers for coronary artery disease are by distal vasoconstriction and slower speed: a study by angiographic assessment and artificial intelligence program

Abstract Background Patients with coronary artery disease (CAD) were protected with betablockers (BB) for lower mortality and lower rate of new myocardial infarction. What are the protective mechanisms? In prior studies, our hypothesis was that damage to the intima of the coronary arteries was caused by cavitation or rupture of bubbles which was seen frequently in industrial pipes. The bubbles ruptured when they flew in areas of different pressures among the layers and segments of the coronary flows. How did BB change the dynamic of coronary flow? Methods After percutaneous coronary interventions (PCI) patients were started on BB. Later, when there was indication, the patient underwent another angiogram. The diameter of the distal LAD was measured and compared between the two angiograms. The distance reached the coronary flow after 0.6seconds was calculated in both angiograms and compared. In the reviewing protocol, the coronary angiograms were done with the contrast injected until the index coronary artery was completely opacified. As the injection of contrast stopped, the blood in white color moved in and displaced the contrast in black color. The morphologies, movements, directions, and interactions of the blood flow in white color above a black background were reviewed frame by frame by investigators analyzing flow dynamics. At the same time, the artificial intelligence (AI) program has 2 models (build on Python), The model 1 was built based on U-net and Densenet-121 for vessel segmentation. Model 2 was used for classification of stagnant flow or normal, the model 2 was trained based on the convolutional neural network with the dataset selected from model 1 results. Results In total, 50 patients were included with a total of 50 pairs of angiograms. In 80% patients, the diameter of the distal segment of the LAD was 20% smaller in BB compared with before BB (p≤0.05). In 75%, the speed of the coronary after BB was lower (p<0.05), A lower speed guaranteed laminar flow and less chance for cavitation. The above data was confirmed by the AI programs. Conclusion BB improved the coronary flow by decreasing the diameter of the arteries so decreased the turbulent flow and promoted laminar flow. BB also decreased the speed of the flow so decreased the chance for cavitation. Both decreased the possibility of ACS. Funding Acknowledgement Type of funding sources: None. Artery with centerlineMeasuring the diameter of the artery by

Transradial quadraxial system for coil embolization of distal anterior cerebral artery aneurysms: A radial-first center case series and literature review

PurposeEndovascular treatment is technically challenging as distal anterior cerebral artery (DACA) aneurysms have distal location, small-caliber parent artery, and small size/wide neck. This study evaluated the feasibility and safety of the transradial approach (TRA) with a radial-specific neurointerventional guiding sheath as the first-line technique for DACA aneurysms. MethodsWe retrospectively analyzed an institutional database of consecutive patients with DACA aneurysm who underwent coil embolization using TRA. Ten consecutive patients were included in this study. After the radial-specific 6F Simmons guiding sheath (0.088″ inner diameter) was completely engaged into the target common carotid artery, a quadraxial system (6F Simmons guiding sheath/6F intermediate catheter/3.2F intermediate catheter/single microcatheter) was used for embolization. Then, we assessed for procedural success, angiographic outcomes, and procedure-related or vascular access site complications. ResultsEmbolization procedures were conducted using simple coiling in eight and stent-assisted coiling with the trans-cell approach in two patients. The embolization procedure was successful in all patients (n = 10). Moreover, none presented with catheter kinking, parent artery flow stagnation, or system instability during the procedure. Immediate postprocedural angiography revealed complete obliteration in six and residual neck in four patients. Then, eight patients underwent follow-up angiography at a mean of 7.1 months, and none developed recanalization or required retreatment. The postprocedural course was uneventful, and there were no complications. ConclusionThe transradial quadraxial system had the ability to achieve sufficient stability and kink resistance in DACA aneurysm embolization. Thus, this method was feasible and safe and had a high success rate.

Study of the heat flux fluctuations intensity during flow around a circular cylinder

An experimental study performed in an air channel using gradient heatmetry is presented, for a configuration of three heated circular cylinders with different distance between them. Cylinders were installed one by one. The main objective is to analyze the heat flux fluctuations, employing gradient heat flux sensor. The behavior of the flow in the wake behind the first cylinder under various regimes, for the specified configuration, changes the fluctuations level at the surface of the second and third cylinders. By visualizing the flow using PIV, it was possible to see areas of stagnation, separation points and other features of flow around the model. The results showed that the fluctuations level for the second cylinder is an order of magnitude lower than for the first. We can say that the first cylinder stabilizes the flow. However, at the third cylinder, this level is comparable and even higher than on the first. Use of gradient heatmetry thus made it possible for the first time to estimate the fluctuating nature of the flow and heat transfer around cylinders.

4D-исследование вихревых движений жидкостей внутри глаза

The eye is a complex system of boundaries and fluids with different viscosities within the boundaries. At present, there are no experimental possibilities to thoroughly observe the dynamic 4D processes after one or another method of eye treatment is applied. The complexity of cumulative, i.e., focusing, and dissipative, i.e., scattering, convective and diffusion 4D fluxes of fluids in the eye requires 4D analytical and numerical models of fluid transfer in the human eyeball to be developed. The purpose of the study was to develop and then verify a numerical model of 4D cumulative-dissipative processes of fluid transfer in the eyeball. The study was the first to numerically evaluate the values of the characteristic time of the drug substance in the vitreous cavity until it is completely washed out, depending on the injection site; to visualize the paths of the vortex motion of the drug in the vitreous cavity; to determine the main parameters of the 4D fluid flows of the medicinal substance in the vitreous cavity, depending on the presence or absence of vitreous detachment from the wall of the posterior chamber of the eye. The results obtained are verified by the experimental data available to doctors. In the eye, as a partially open cumulative-dissipative system, Euler regions with high rates of cumulative flows and regions with low speeds or stagnant Lagrange flow zones are defined

Contributions towards Data driven Deep Learning methods to predict Steady State Fluid Flow in mechanical Heart Valves

Abstract It is commonly accepted that hemodynamic situation is related with cardiovascular diseases as well as clinical post-procedural outcome. In particular, aortic valve stenosis and insufficiency are associated with high shear flow and increased pressure loss. Furthermore, regurgitation, high shear stress and regions of stagnant blood flow are presumed to have an impact on clinical result. Therefore, flow field assessment to characterize the hemodynamic situation is necessary for device evaluation and further design optimization. In-vitro as well as in-silico fluid mechanics methods can be used to investigate the flow through prostheses. In-silico solutions are based on mathematical equitation’s which need to be solved numerically (Computational Fluid Dynamics - CFD). Fundamentally, the flow is physically described by Navier-Stokes. CFD often requires high computational cost resulting in long computation time. Techniques based on deep-learning are under research to overcome this problem. In this study, we applied a deep-learning strategy to estimate fluid flows during peak systolic steady-state blood flows through mechanical aortic valves with varying opening angles in randomly generated aortic root geometries. We used a data driven approach by running 3,500 two dimensional simulations (CFD). The simulation data serves as training data in a supervised deep learning framework based on convolutional neural networks analogous to the U-net architecture. We were able to successfully train the neural network using the supervised data driven approach. The results showing that it is feasible to use a neural network to estimate physiological flow fields in the vicinity of prosthetic heart valves (Validation error below 0.06), by only giving geometry data (Image) into the Network. The neural network generates flow field prediction in real time, which is more than 2500 times faster compared to CFD simulation. Accordingly, there is tremendous potential in the use of AIbased approaches predicting blood flows through heart valves on the basis of geometry data, especially in applications where fast fluid mechanic predictions are desired.