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Records of bridge fire incidents illustrate that bridge fires can have catastrophic consequences. The severity of these fires can be influenced by various factors such as bridge type, vehicle size, and wind. Contrary to building fires that have been extensively studied, scant attention has been paid to bridge fires and more specifically fire exposure to the suspension bridges. In addition, existing bridge fire literature is mostly concentrated on fire exposure to girders or cables of suspension bridges. Therefore, this study focused on the post-fire condition of a fire-exposed suspension bridge tower using computational fluid dynamics (CFD) modeling techniques and finite element analysis (FEA). The impacts of the main bridge fire parameters including vehicle size, exposure duration, distance between the fire source and tower, and wind effects were also evaluated. Initially, fire dynamic simulator (FDS) was used to simulate 12 different fire scenarios. The time–temperature histories obtained from each scenario were transferred to the ABAQUS finite element (FE) software to conduct transient thermal analysis and obtain the temperature development within the steel tower of the bridge. The post-fire evaluation was performed with respect to the temperature-induced reduction in the yield strength of steel. The results show that fire exposure from a fuel truck in the proximity of a steel tower could significantly reduce the strength of the tower and lead to severe damage. Early control of the fuel truck fire is crucial in reducing the severity of the damage and preventing temperature development in higher areas of the tower. Although a wind toward the tower can significantly increase the fire-induced damage to the bottom parts of the tower, it considerably reduces the temperature exposure to the higher parts of the tower. Fire exposure from a normal vehicle does not put the tower at risk of failure, and an unprotected steel tower can withstand it. However, a bus fire may lead to minor damage. The thermal strengthening of the first 20 m of the tower can help in preventing the potential fire damage. [ABSTRACT FROM AUTHOR]

The structural performance of a Tensile Membrane Surface (TMS) as a lightweight structure is significantly influenced by environmental factors such as wind load. Only a few studies have been conducted to elucidate the effect of wind load on the internal forces, deformation, and stresses on a TMS, whereas the majority of contributions have concentrated on form-finding analyses and the structural performance of TMS structures. The most difficult part in the structural design of a TMS is the realistic estimation of wind load. In the current study, we performed fluid–structure interaction (FSI) analysis for an umbrella TMS considering practical uncertainties such as wind directions and flow effect for a group of structures. The lack of comprehensive standard codes is a great motivation for assessing the performance of TMSs under wind load. The Computational Fluid Dynamics (CFD) technique is widely employed to simulate the effects of airflow around buildings and special structures. The validation example was performed in an experimental test to verify the CFD simulation results by using both steady-state and transient wind simulations. The results of the aerodynamic simulation and FSI analysis include the wind pressure value, deformation, stress, and strain. This experiment was carried out on a single TMS with regard to various wind directions and a group of TMS umbrellas. The reduction value, especially for the uplift drag force component (Fz) of structural responses, was obtained for the group of structures. Furthermore, the impact of large deformation on the wind pressure coefficient was investigated, showing critical changes compared to the rigid approach, especially in suction zones. The results of the current CFD simulation were compared with the experimental test and show good agreement in terms of predicting the effect of air flow on TMS. [ABSTRACT FROM AUTHOR]

This study uses the finite element technique to analyse a multi-dimensional model for a polyelectrolyte membrane fuel cell at high working temperature. A computational fluid dynamics (CFD) technique implements and solves this model. In addition, the membrane's thickness, and catalyst layer's thickness parameters have been studied. Membrane thickness is varied from to and the length of the fuel cell from to. The performance of the fuel cell was studied, analysed, and discussed for each case using the polarization curves and output power. The results indicate that the performance of fuel cells is enhanced by a thinner membrane than a thicker one with an increase in loading. The performance is approximated at light loads. Furthermore, the concentration of water at the cathode side of the fuel cell is highly affected by the change in fuel cell length more than the thickness of the membrane. Comparative analysis with prior research demonstrates strong agreement with our consequences. [ABSTRACT FROM AUTHOR]

Carotid atherosclerosis is a leading cause of ischemic stroke. As a result of atherosclerotic plaque formation, the carotid artery lumen narrows, leading to significant hemodynamic alterations. These changes can further contribute to the development of subsequent lesions. In this study, we built 54 idealized carotid artery stenosis (CAS) models by using a single healthy carotid artery to simulate six different degrees of stenosis at nine various locations. Computational fluid dynamics (CFD) was applied to analyze blood flow changes, focusing on three key hemodynamic indicators: wall shear stress (WSS), oscillatory shear index (OSI), and relative residence time (RRT). Numerical simulations and model validations were conducted to ensure the correctness and validity of the results. The results show that increasing stenosis severity leads to higher WSS values at the site of stenosis, which may facilitate plaque rupture, while OSI and RRT decrease at the stenosis site. In the external carotid artery (ECA) and internal carotid artery (ICA), increasing stenosis severity results in a reduction in WSS at bifurcation sites, promoting plaque formation. These findings offer new insights into the hemodynamic changes associated with carotid artery stenosis and provide a solid foundation for future research and clinical applications. [ABSTRACT FROM AUTHOR]

This article explores the crucial function that Shell and Tube Heat Exchangers (STHE) play in a variety of industrial applications. This research uses a three-dimensional computational fluid dynamics (CFD) simulation to model turbulent fluid flow and evaluate the performance of different baffle angle configurations. The study evaluates performance indicators such as overall heat transfer coefficient (OHT), shell side heat transfer coefficient (HTC), pressure drop (PD), and PEC (Performance Evaluation Criteria), this study evaluates their effect on Segmental STHE performance. The findings indicate that the PD in the shell section rises by a range of 56.8–60.9% for baffles inclined 0° to 30°. Additionally, compared to the 0° inclined baffles, the 30° inclined baffles exhibit a greater OHT of 4.5–6%. The PEC values that are determined for each type of baffle are the most crucial aspect to take into account while selecting the optimal STHE. The 25° inclined baffles have been selected as the most advantageous baffles due to their improved performance, as seen by their different PEC values. In the subsequent stage of the study, researchers investigated how changing the quantity of superior baffles (inclined) affects the STHE's efficiency. As the number of baffles was increased from 4 to 10, the OHT rose by 14.5–17% and the PD increased by 138.63–141.7%. This thorough simulation revealed that the STHE with the 8 inclined baffles had the highest PEC value and was therefore the most appropriate STHE. [ABSTRACT FROM AUTHOR]

The manufacturing of allogeneic cell therapeutics based on human-induced pluripotent stem cells (hiPSCs) holds considerable potential to revolutionize the accessibility and affordability of modern healthcare. However, achieving the cell yields necessary to ensure robust production hinges on identifying suitable and scalable single-use (SU) bioreactor systems. While specific stirred SU bioreactor types have demonstrated proficiency in supporting hiPSC expansion at L-scale, others, notably instrumented SU multiplate and fixed-bed bioreactors, remain relatively unexplored. By characterizing these bioreactors using both computational fluid dynamics and experimental bioengineering methods, operating ranges were identified for the Xpansion® 10 and Ascent™ 1 m2 bioreactors in which satisfactory hiPSC expansion under serum-free conditions was achieved. These operating ranges were shown not only to effectively limit cell exposure to wall shear stress but also facilitated sufficient oxygen transfer and mixing. Through their application, almost 5 × 109 viable cells could be produced within 5 days, achieving expansion factors of up to 35 without discernable impact on cell viability, identity, or differentiation potential. Key Points •Bioengineering characterizations allowed the identification of operating ranges that supported satisfactory hiPSC expansion •Both the Xpansion®10 multiplate and Ascent™ 1 m2fixed-bed reactor accommodated the production of almost 5 × 109viable cells within 5 days •Exposing the hiPSCs to a median wall shear stress of up to 8.2 × 10−5N cm−2 did not impair quality [ABSTRACT FROM AUTHOR]

To fully utilize the potential of human induced pluripotent stem cells (hiPSCs) for allogeneic stem cell–based therapies, efficient and scalable expansion procedures must be developed. For other adherent human cell types, the combination of microcarriers (MCs) and stirred tank bioreactors has been shown to meet these demands. In this study, a hiPSC quasi-perfusion expansion procedure based on MCs was developed at 100-mL scale in spinner flasks. Process development began by assessing various medium exchange strategies and MC coatings, indicating that the hiPSCs tolerated the gradual exchange of medium well when cultivated on Synthemax II–coated MCs. This procedure was therefore scaled-up to the 1.3-L Eppendorf BioBLU 1c stirred tank bioreactor by applying the lower limit of Zwietering's suspension criterion ( N s 1 u ), thereby demonstrating proof-of-concept when used in combination with hiPSCs for the first time. To better understand the bioreactor and its bioengineering characteristics, computational fluid dynamics and bioengineering investigations were performed prior to hiPSC cultivation. In this manner, improved process understanding allowed an expansion factor of ≈ 26 to be achieved, yielding more than 3 × 109 cells within 5 days. Further quality analyses confirmed that the hiPSCs maintained their viability, identity, and differentiation potential throughout cultivation. Key points: • N s 1 u can be used as a scale-up criterion for hiPSC cultivations in MC-operated stirred bioreactors • Uniform distribution and attachment of cells to the MCs are crucial for efficient expansion • Perfusion is advantageous and supports the cultivation of hiPSCs [ABSTRACT FROM AUTHOR]

The control efficacy of deep reinforcement learning (DRL) compared with classical periodic forcing is numerically assessed for a turbulent separation bubble (TSB). We show that a control strategy learned on a coarse grid works on a fine grid as long as the coarse grid captures main flow features. This allows to significantly reduce the computational cost of DRL training in a turbulent-flow environment. On the fine grid, the periodic control is able to reduce the TSB area by 6.8%, while the DRL-based control achieves 9.0% reduction. Furthermore, the DRL agent provides a smoother control strategy while conserving momentum instantaneously. The physical analysis of the DRL control strategy reveals the production of large-scale counter-rotating vortices by adjacent actuator pairs. It is shown that the DRL agent acts on a wide range of frequencies to sustain these vortices in time. Last, we also introduce our computational fluid dynamics and DRL open-source framework suited for the next generation of exascale computing machines. The control of turbulent flows is crucial for improving efficiency in engineering systems. Here, authors show in a numerical simulation that using deep reinforcement learning to control surface actuators can successfully mitigate turbulent flow separation, paving the way for new advancements in turbulence control. [ABSTRACT FROM AUTHOR]

For congenital heart disease patients, multiple imaging modalities are needed to discern anatomy and functional information such as differential blood flow. During cardiac catheterization, 3D rotational angiography (3DRA) can provide CTA-like images, enabling anatomical information and intraprocedural guidance. We seek to establish whether unique aspects of this technique can also generate quantitative functional blood flow information. We propose that systematic integration of 3DRA imaging, catheter hemodynamic information, and computational fluid dynamics (CFD), can provide quantitative information regarding blood flow dynamics and energetics, without additional imaging or procedures. We report a single center retrospective feasibility study comprising four patients with 3DRA imaging and a complete set of hemodynamic data. 3DRA was processed and segmented to reconstruct vascular regions of interest (ROI), and a computational grid for CFD modeling of blood flow through the ROI was generated. Blood flow was simulated by integrating catheter hemodynamic data to devise boundary conditions at vascular ROI inlets and outlets. The 3DRA-based workflow successfully generated key computational outputs commonly used for cardiovascular applications, including flow patterns, distribution fractions, wall shear stress. Computational outputs obtained were as detailed and resolved as those obtained from more commonly used CT or MR angiography. Accuracy was confirmed by comparing computed flow distributions with measurements for 2 cases, showing less than 2.0% error from the measured data. Systematic integration of catheter hemodynamic information, 3DRA imaging, and CFD modeling, provides an effective and feasible alternative to obtain important quantitative blood flow information and visualization, without additional imaging. [ABSTRACT FROM AUTHOR]

This paper describes a numerical study on micro-droplet generation in a microfluidic double T-junction device under the effects of channel depth using the Volume-Of-Fluid method. The effects of various parameters such as capillary number (Ca), water fraction (wf), viscosity ratio (β) , and particularly the channel depth ratio (ε) were examined. Consequently, the numerical results match well with the experimental data obtained in the literature. Additionally, the micro-droplet size increases with increasing the channel depth ratio. A phase diagram with four main micro-droplet generation regimes is provided. Particularly, the alternating mode is narrowed in both Ca and wf ranges when increasing ε . Moreover, four regimes of micro-droplet generation with the presence of channel depth were first discovered in the present study, and the stable micro-droplet generation regime can be gained within an effective range of both ε and β . These results are very useful and valuable for many applications in emulsion production, hydrogel particle generation, and drug delivery synthesis in biomedical treatment. [ABSTRACT FROM AUTHOR]

In this study, the effect of injection strategy on the mixture formation and combustion in a hydrogen direct injection engine using CFD analysis was investigated. Four Start of Injection timings and three types of injection rate were used to understand how the fuel and air mixing process and fuel distribution at the spark timing affect the start of combustion and flame propagation. The results shows that injection timing and rate shape significantly influence the formation of the fuel–air mixture and the subsequent combustion process. Uneven mixture formations from direct injection necessitate careful consideration of local equivalence ratios around the spark plug to ensure efficient combustion initiation and flame propagation. [ABSTRACT FROM AUTHOR]

Oxygen blast furnace is an important transformation method for the low-carbon and green development of traditional blast furnaces. This paper establishes a multi-zone mass and heat balance model and computational fluid dynamics model to study the influence of different hydrogen-rich gas composition on the smelting parameters, raceway state and combustion behavior of oxygen blast furnaces. The results show that the higher gas injection temperature can increase its physical heat, thereby reducing the coke ratio and improving the gas utilization rate. Furthermore, the injection amount of CH4 and H2 increases, resulting in lower raceway temperature and the direct reduction degree in the furnace, which can still meet the smelting requirements at lower raceway temperatures in actual production. Meanwhile, due to the oxygen competition relationship between coal and hydrogen-rich gas, as the proportion of CH4 and H2 injection increases, the coal burnout rate decreases. This research provides a theoretical basis for the regulation of low-carbon and high-efficiency oxygen blast furnace gas injection components. [ABSTRACT FROM AUTHOR]

Hollow fiber membrane contactors (HFMCs) for degasification offer several advantages, including compact design, reduced power consumption, and higher mass transfer rate compared to conventional technologies. These characteristics make HFMCs an ideal choice for applications such as ultrapure water production and wastewater treatment, where the removal of even trace amounts of dissolved gases is critical. In this study, we conducted 3D computational fluid dynamics (CFD) simulations to explore the impact of geometric features on HFMC hydrodynamic performance. A scaled-down version of a commercial module (3 M-Liqui-Cel™) was used, preserving the actual dimensions and spacing of the hollow fiber membranes. Four different configurations were considered in the simulations based on the presence of a baffle and variations in the size and arrangement of liquid distributors. Analyses of fluid motion and pressure drop indicated that designs with larger distributors and internal baffles may reduce stagnation zones and promote more uniform flow distribution. At higher velocities, multiple recirculation areas were observed within the domain, with the size and volume of these zones varying across the different designs. These enhancements, driven by velocity fluctuations, vortex formation, and eddies, could potentially lead to higher mass transfer rates, especially at elevated flow rates. Additionally, the swirling arrangement of distributor holes in varied sizes yielded the lowest pressure drop for all flow rates studied, offering benefits in reduced energy consumption and increased operational efficiency. Our simulation results highlight the potential of optimized distributor hole sizes and patterns to enhance flow mixing and minimize pressure drop. [ABSTRACT FROM AUTHOR]

When a ship moves in an oblique flow, its hydrodynamic loads and wake characteristics vary substantially from those in straight-ahead motion. This dissimilarity can be even more complex when the ship operates in a seaway of shallow water. In this paper, a numerical analysis of the shallow-water effect on the hydrodynamic forces and wake characteristics of an international ship model, KVLCC2, in oblique flows is conducted. Numerical simulations are performed based on the Reynolds Averaged Navier-Stokes equation in conjunction with the shear stress transport (SST) k-ω turbulence model. Four relative water depths (h = 1.2T, 1.5T, 3.0T, and 24T; T is the ship draft) and five different drift angles (β = 0°, 5°, 10°, 15°, and 20°) are considered. Results reveal the following: i) The shallow-water effect is strong and leads to nonlinear increases in the longitudinal force regardless of drift angles and on the transverse force and yaw moment whenever the drift angle increases. ii) In shallow water, the mean wake fraction is sensitive to the drift angle, and the strength of the aft-body vortex on the leeward side increases. [ABSTRACT FROM AUTHOR]

It is a common occurrence in the fracture processes of deep carbonate reservoirs that the fracturing construction pressure during hydraulic fracturing operation exceeds 80 MPa. The maximum pumping pressure is determined by the rated pressure of the pumping pipe equipment and the reservoir characteristics, which confine the fracture to the target area. When the pump pressure exceeds the safety limit, hydraulic fracturing has to reduce the construction displacement to prevent potential accidents caused by overpressure. Therefore, real-time prediction of the fracturing construction pressure and diagnosis of abnormal fluctuations during hydraulic fracturing of highly deviated wells are indispensable. Based on the well trajectory, pumping process, and string structure of highly deviated wells, a movement interface model for the fracturing fluid at different stages within the wellbore has been established, using the method of computational fluid dynamics. This model analyzes the fluid movement behavior with diverse properties at various fracturing times and determines the relationship between the pressure changes at the leading and trailing edges of fluid movement in each section of the wellbore over time by combining different string structures and preset pumping procedures. The frictional pressure within the wellbore fluid, the hydrostatic fluid pressure, and the near-well friction drags have been calculated and predicted. A real-time prediction model for diagnosing pumping fracturing has been constructed to further comprehend "abnormal" fracturing construction pressures in highly deviated wells. This offers a theoretical foundation for the correct diagnosis and decision-making regarding hydraulic fracturing in highly deviated wells while guiding its smooth implementation in real time. [ABSTRACT FROM AUTHOR]

This study employed large eddy simulation (LES) with the wall-adapting local eddy-viscosity (WALE) model to investigate transitional flow characteristics in an idealized model of a healthy thoracic aorta. The OpenFOAM solver pimpleFoam was used to simulate blood flow as an incompressible Newtonian fluid, with the aortic walls treated as rigid boundaries. Simulations were conducted for 30 cardiac cycles and ensemble averaging was employed to ensure statistically reliable results. Main hemodynamic parameters, such as velocity fields, turbulence intensity turbulent kinetic energy (TKE), oscillatory shear index (OSI) and wall shear stress (WSS), were analyzed throughout the circulatory system. Through 3D computational fluid dynamics (CFD) visualization, we explained the transition from laminar to turbulent flow and its development throughout the cardiac cycle. The results demonstrated that turbulence originates in the aortic arch following the peak systole phase and further develops in the aortic arch and descending aorta during the mid-deceleration and end-systole phases, with the maximum turbulence intensity exceeding 25%. WSS reached up to 30 Pa during the peak systole, with an average WSS of 6.5 Pa across the cardiac cycle. Low and oscillatory WSS were observed during diastole which can potentially contribute to the development of vascular diseases including, aortic dissection and atherosclerosis. [ABSTRACT FROM AUTHOR]

This study examines how heart rate (HR) affects hemodynamics in a South African infant with Coarctation of the Aorta. Computed tomography angiography segments aortic coarctation anatomy; Doppler echocardiography derives inlet flow waveforms. Simulations occur at 100, 120, and 160 beats per minute, representing reduced, resting, and elevated HR levels. Turbulence was analyzed over time and space using turbulence-resolving and pulsatile large-eddy simulations. Specifically, a 60% reduction in HR led to a reduction in maximum velocity by 45%, and a 57% decrease in pressure drop. The reduction in turbulence-related metrics was less significant. The ratio of turbulent kinetic energy to total kinetic energy decreased by 2%, while turbulent wall shear stress decreased by 3%. These results demonstrate that HR significantly affects velocity and pressure drop, while turbulence arising from the coarctation region is relatively unaffected. The balance between turbulent kinetic energy and total kinetic energy shows minimal enhancement due to the complex interplay among HR, turbulence, and geometry. This complexity prompts discussion on how HR-slowing medications, such as beta-blockers or ivabradine, could positively influence hemodynamic stresses. In particular, the results indicate that while HR modulation can influence flow dynamics, it may not significantly reduce turbulence-induced shear stresses within the coarctation zone. Therefore, further investigation is necessary to understand the potential impact of HR modulation in the management of CoA, and whether interventions targeting the anatomical correction of the coarctation may be more effective in improving hemodynamic outcomes. [ABSTRACT FROM AUTHOR]

The presented work is a study on additively manufactured electronics, specifically focusing on optimizing inkjet printing strategies for low-impedance electrically conductive structures in insulating housings, which has the ability to change the way electronics look like. It integrates computational fluid dynamics to simulate the printing process and machine learning algorithms to analyze the high-dimensional parameter space of the simulation results. The study investigates the influence of various material properties and manufacturing parameters on a new, multi-layer-based printing approach, named droplet stacking, which can be beneficial to smoothen the outline of electrically conductive structures. The results indicate a potential for significantly steeper droplet stacking angles, increasing from 63 to 85°, and identify contact angle, droplet velocity, and viscosity as the most important parameters influencing the droplet stacking capabilities. Optimizing these parameters can smooth the conductor's outline to improve its high-frequency properties. [ABSTRACT FROM AUTHOR]

In the manufacturing industries, noise is one of the most common health hazards at workplaces. In wood machining, for instance, circular sawing processes in particular produce high noise emissions that often exceed the permitted limits. The main source of noise is the rotating circular saw blade, whose aeroacoustic behavior is influenced by air turbulence on the tool contour. So far, no numerical approach to study and optimize the aeroacoustic noise emissions from circular saw blades has been investigated. This paper addresses this deficit and presents a methodology for modeling the flow-induced sound generation on rotating circular saw blades based on computational fluid dynamics (CFD) simulations. With the implementation of the acoustic analogy according to Ffowcs-Williams/Hawkings, the sound pressure levels could be calculated with sufficient accuracy. With deviations between 7 and 10%, the influence of the rotational speeds could be plausibly modeled. Based on the validated numerical model, geometry variants with various modifications were investigated regarding their potential for reducing sound pressure levels. Based on a conventional reference geometry, different chip space volumes and various modifications to the tooth rim and tooth shape were investigated and evaluated as part of simulative parameter studies. Sound pressure level reductions in the range of 2.2–10.8 dB were achieved. The results obtained and the systematic approach investigated provide a suitable set of instruments for industrial practice. Digital prototypes can be designed at an early stage in the product development phase of circular saw blades regarding their aeroacoustic properties. [ABSTRACT FROM AUTHOR]

Background: Wall shear stress (WSS) plays a crucial role in the natural history of intracranial aneurysms (IA). However, spatial variations among WSS have rarely been utilized to correlate with IAs' natural history. This study aims to establish the feasibility of using spatial patterns of WSS data to predict IAs' rupture status (i.e., ruptured versus unruptured). Methods: "Patient-specific" computational fluid dynamics (CFD) simulations were performed for 112 IAs; each IA's rupture status was known from medical records. Recall that CFD-simulated hemodynamics data (wall shear stress and its derivatives) are located on unstructured meshes. Hence, we mapped WSS data from an unstructured grid onto a unit disk (i.e., a uniformly sampled polar coordinate system); data in a uniformly sampled polar system is equivalent to image data. Mapped WSS data (onto the unit disk) were readily available for Radiomics analysis to extract spatial patterns of WSS data. We named this innovative technology "WSS-informatics" (i.e., using informatics techniques to analyze WSS data); the usefulness of WSS-informatics was demonstrated during the predictive modeling of IAs' rupture status. Results: None of the conventional WSS parameters correlated to IAs' rupture status. However, WSS-informatics metrics were discriminative (p-value < 0.05) to IAs' rupture status. Furthermore, predictive models with WSS-informatics features could significantly improve the prediction performance (area under the receiver operating characteristic curve [AUROC]: 0.78 vs. 0.85; p-value < 0.01). Conclusion: The proposed innovations enabled the first study to use spatial patterns of WSS data to improve the predictive modeling of IAs' rupture status. [ABSTRACT FROM AUTHOR]

Accurate rupture risk assessment is essential for optimizing treatment decisions in patients with cerebral aneurysms. While computational fluid dynamics (CFD) has provided critical insights into aneurysmal hemodynamics, most analyses focus on blood flow patterns, neglecting the biomechanical properties of the aneurysm wall. To address this limitation, we applied Fluid-Structure Interaction (FSI) analysis, an integrative approach that simulates the dynamic interplay between hemodynamics and wall mechanics, offering a more comprehensive risk assessment. In this study, we used advanced FSI techniques to investigate the rupture risk of middle cerebral artery bifurcation (MCA) aneurysms, analyzing a cohort of 125 patients treated for a MCA aneurysm at Kepler University Hospital, Linz, Austria. Multivariate analysis identified two significant rupture predictors: High Equivalent Stress Area (HESA; p = 0.049), which quantifies stress distribution relative to the aneurysm surface, and Gaussian curvature (GLN; p = 0.031), which captures geometric complexity. We also introduce the HGD index, a novel composite metric combining HESA, GLN, and Maximum Wall Displacement, designed to enhance predictive accuracy. With a threshold of 0.075, the HGD index exhibited excellent diagnostic performance; in internal validation, 24 of 25 ruptured aneurysms surpassed this threshold, yielding a sensitivity of 0.96. In a 5-fold cross validation the reliability of results was confirmed. Our findings demonstrate that the HGD index provides superior rupture risk stratification compared to conventional single-parameter models, offering a more robust tool for the assessment of complex aneurysmal structures. Further multicenter studies are warranted to refine and validate the HGD index, advancing its potential for clinical application and improving patient outcomes. [ABSTRACT FROM AUTHOR]

The laser-assisted wire-directed energy deposition (DED) process has distinct advantages over the laser-assisted powder DED process. The material usage efficiency of wire-DED is predominantly higher than the powder-DED process. As versatile as the DED process can be, its multiphysics in situ integrated with the process parameters is key to achieving a qualitative layer deposition. This research demonstrates a computational fluid dynamics (CFD) modeling of the coaxial multiple laser-assisted single wire-DED process in conjunction with the already published experimental coaxial laser-assisted single wire-DED process. This wire-DED process involves four lasers coaxially aligned with its central axis for a single wire feed. The CFD model helps predict the wire melting, mass transfer, and melt pool dynamics that are otherwise difficult to understand using the experiments. The geometric dimensions of the simulated thin wall and the experimental thin wall match greatly throughout the length of the deposition. This experimental validation further allows one to study the effect of multiple laser incident angles on the single wire, wire-multiple laser interactions, and its cumulative impact on the deposition. [ABSTRACT FROM AUTHOR]

This study investigates the application of various neural network-based models for predicting temperature distribution in freeze drying process of biopharmaceuticals. For heat-sensitive biopharmaceutical products, freeze drying is preferred to prevent degradation of pharmaceutical compounds. The modeling framework is based on CFD (Computational Fluid Dynamics) and machine learning (ML). The ML models explored include the Single-Layer Perceptron (SLP), Multi-Layer Perceptron (MLP), Fully Connected Neural Network (FCNN), and Deep Neural Network (DNN). Model optimization is achieved through the Fireworks Algorithm (FWA). Results reveal promising performance across all models, with the MLP demonstrating the highest accuracy on both test and training datasets, achieving an R2 score of 0.99713 and 0.99717 respectively. The SLP also exhibits strong performance, with an R2 of 0.88903 on the test dataset. The FCNN and DNN models also perform admirably, achieving R2 scores of 0.99158 and 0.99639 on the test dataset respectively. These results highlight the efficiency of neural network-driven models, specifically the MLP, in precisely forecasting temperature values based on spatial coordinates. Additionally, the integration of the Fireworks Algorithm for model refinement yields advantages in improving the predictive performance of these models. [ABSTRACT FROM AUTHOR]

Uneven of filling aggregate gradation may cause transportation problems such as pipe blockage due to segregation and stratification of filling slurry. To study the influence of aggregate gradation on the conveying performance of filler slurry, aggregate gradation experiments were carried out, rheological tests on slurries with coal gangue/aeolian sand ratios (6:4, 5:5 and 4:6) showed that appropriately increasing the proportion of aeolian sand can improve particle gradation. Computational fluid dynamics (CFD) scheme was used to simulate the pipeline transportation characteristics of the slurry under the conditions of three sets each of coal gangue/aeolian sand ratios, slurry concentrations (72%,74% and 76%), and inlet velocities (1.15,1.24 and 1.33 m/s). The results show that the pipeline resistance loss is directly proportional to the slurry concentration and inlet velocity, and inversely proportional to the coal gangue/aeolian sand, which indicates that the proportion of aeolian sand should be reduced in filling project to reduce the pipeline transportation resistance. [ABSTRACT FROM AUTHOR]

This paper investigated the influence of various twisted angles of fin inserts integrated on the inner heated pipe wall of a double-pipe heat exchanger by analysing the thermal–hydraulic performance through numerical simulations. Results showed twisted angle fin (TAF) induced turbulent fluid flow phenomena, generating transverse and longitudinal vortices, along with swirling flow. This collaboration between the vortices and swirling flow effectively prevents heat trapping and enhances heat transfer from the inner pipe wall through the intensive fluid mixing. Despite longitudinal swirling vortices and turbulence significantly enhance local and global heat transfer performance, they led to increased pressure drop. However, TAF twisting reduces pressure drop by streamlining flow. The performance evaluation criterion (PEC) value is a dimensionless quantity that facilitates the comprehensive evaluation of optimal configurations by comparing the increment in Nusselt number and the increment in friction factor. PEC values greater than 1 indicate that the increase in Nusselt number exceeded the increase in friction factor. Among tested configurations, the twisted fin angles of 60° (TAF60) exhibited the highest improvement in Nusselt number and friction factor, also achieving the highest PEC of 1.59712 at Reynolds number of 1194.71. TAF40 and TAF50 were identified as optimal configurations for enhancing the thermal–hydraulic efficiency, with average PEC values of 1.26893 and 1.27030, respectively. Overall, the study indicated a consistent enhancement trend with increasing twisted angles and emphasizes the significant thermal performance improvement of TAF configurations compared to the smooth conduit. Furthermore, the results showed a converging tendency across all TAF configurations in the percentage improvement in Nusselt number and friction factor, as well as PEC compared to the baseline No fin configuration with increasing Reynolds number, suggesting that future improvements in thermal–hydraulic performance are more dependent on geometric angles than fluid flow velocity. [ABSTRACT FROM AUTHOR]

The constant evolution of computer-aided engineering techniques continues to enhance our understanding of the liquid metal cooling process. Conventional methodologies often rely on fixed heat exchange coefficients for computing the thermal interaction between casting modules and the liquid coolant. This paper introduces a novel coupled numerical scheme integrating computational fluid dynamics (CFD) and solidification analysis. Within this framework, the commercial software ANSYS Fluent® addresses the CFD aspect of the coolant, while the ProCAST® handles the solidification simulation. The solidification process is simulated through solving heat conduction equation in which the heat flux boundary condition on the external surface of the cast module is determined according to the convective coolant flow. The CFD simulation based on the Navier–Stokes equations furnishes the heat flux at the module-coolant interface, taking the temperature field of the cast module as input. The coupled method is validated first with a test case in which a module is immersed inside coolant, followed by a multiphase flow simulation, wherein a casting module is pulled into the liquid tin bath from a gas-phase position. Both simulations reveal temperature variations in the coolant. Comparison with conventional heat exchange coefficient approaches confirms the influence of these variations on cooling curves. The coupled model is further used to investigate the effect of withdrawal rates on the solidification process, exhibiting qualitative agreement with experiments. [ABSTRACT FROM AUTHOR]

Suffusion is a critical issue in geotechnical engineering. Despite extensive studies, the effect of soil specimen dimensions on suffusion remains unclear. In this paper, a coupled computational fluid dynamics and discrete element method (CFD-DEM) approach is employed to study the suffusion of gap-graded soils with varying aspect ratios, and the underlying physical mechanisms are discussed. The results indicate that as the aspect ratio increases, erosion degree, mechanical coordination numbers, and unevenness in the fines distribution decrease, while the likelihood of fine particles integrating into the soil skeleton rises. Before suffusion, specimens with lower aspect ratios show higher peak strengths. After suffusion, peak strength decreases with erosion degree. However, all specimens exhibit comparable residual strengths. The mechanism behind different suffusion behaviors in specimens with varying aspect ratios is primarily governed by their unique suffusion boundary conditions. Accounting for suffusion boundaries significantly modify erosion laws and eroded soil mechanics behaviors. A standardized specimen size is proposed to account for suffusion boundary effects, thereby minimizing errors attributed to variations in outlet sieve aperture sizes and inconsistencies in specimen dimensions. The results obtained highlight the influence of specimen size on suffusion, advancing our precise understanding of eroded soil behavior. [ABSTRACT FROM AUTHOR]

Surface roughness plays a critical role in ultrashort pulse laser ablation, particularly for industrial applications using burst mode operations, multi-pulse laser processing, and the generation of laser-induced periodic surface structures. Hence, we address the impact of surface roughness on the resulting laser ablation topography, comparing predictions from a simulation model to experimental results. We present a comprehensive multi-scale simulation framework that first employs finite-difference-time-domain simulations for calculating the surface fluence distribution on a rough surface measured by atomic-force-microscopy followed by the two-temperature model coupled with hydrodynamic/solid mechanics simulation for the initial material heating. Lastly, a computational fluid dynamics model for material relaxation and fluid flow is developed and employed. Final state results of aluminum and AISI 304 stainless steel simulations demonstrated alignment with established ablation models and crater dimension prediction. Notably, Al exhibited significant optical scattering effects due to initial surface roughness of 15 nm—being 70 times below the laser wavelength -leading to localized, selective ablation processes and substantially altered crater topography compared to idealized conditions. Contrary, AISI 304 with R q surface roughness of 2 nm showed no difference. Hence, we highlight the necessity of incorporating realistic, material-specific surface roughness values into large-scale ablation simulations. Furthermore, the induced local fluence variations demonstrated the inadequacy of neglecting lateral heat transport effects in this context. [ABSTRACT FROM AUTHOR]

The water consumption rate and the scarcity of water sources leads to the importance of proper water management, especially in the industrial context. Some of the many approaches that could be taken to help conserve industrial water resources include condensing part of the steam emitted in cooling towers, using finned tube heat exchangers, such as those with thermosyphons. This work aims to evaluate the performance of condensation of humid air in two different geometries, typical of these heat exchangers: fin-and-tube and parallel flat plates, using numerical simulations under steady-state conditions. To accomplish this goal, three evaluation methods were used. First, simulations were conducted using ANSYS CFX software on a section of the heat exchanger core. Then, also using CFX simulation, the condensation between parallel flat plates, which mimic tube fins, was performed. Finally, a semi-theoretical model available in the literature was employed. The findings indicate that, for a temperature difference between the heated wall and the humid air of 14.5 K, the heat exchanger could successfully recover up to 24% of steam. The results are far less favorable, when the temperature difference is only 4.5 K, with the effectiveness of the recovery of only about 2 percent. However, more water could be recovered, if the wall to humid air temperature difference was higher. More importantly, the semi-theoretical model shows that, by using a rectangular channel made up of parallel flat plates, it is possible to model the complex geometry of a finned tube heat exchanger, with results within 2% of the benchmark. The outputs obtained from the semi-theoretical model are also conservative, showing to be a good designing tool. [ABSTRACT FROM AUTHOR]

This study addresses the challenge of achieving uniform airflow distribution and minimizing pressure drop in fin-tube heat exchangers, where uneven flow can significantly influence heat transfer efficiency and overall system performance. To optimize header designs, computational fluid dynamics (CFD) simulations were conducted, evaluating models with varying port diameters, corner angles, and the inclusion of 2-stage perforated plates with and without reflectors. Increasing the corner angle of the header slightly improves the inflow velocity direction, however issues with longitudinal distribution persist. The 2-stage perforated plates effectively smooth out the airflow, resulting in more even distribution and enhanced overall efficiency. Additionally, the inclusion of reflectors helps distribute velocity more evenly, minimizing fluctuations. On the other hand, a smaller port diameter can lead to higher velocities and uneven distribution, increasing turbulence and recirculation, which reduces the consistency of airflow across the tubes. This study reveals that incorporating 2-stage perforated plates with reflectors significantly improves flow uniformity which achieved the lowest standard deviation of velocity profiles. [ABSTRACT FROM AUTHOR]

Density currents are caused by the difference of potential energy among fluids of distinct densities. Turbidity currents correspond to a specific type of density current where there is a considerable concentration of suspended particles that are transported by the flow. This phenomenon is often seen as one of the main factors responsible for the generation of sedimentary deposits that form hydrocarbon reservoirs. Numerical modelling is one of the most used approaches to model this process, based on solving a set of partial differential equations employing numerical methods. This paper presents the main hydrodynamic and depositional characteristics of turbidity currents formed in an unbounded configuration. The SuLi code, used in the present work, solves the incompressible continuity and Navier-Stokes equations using the projection method and the Large Eddy Simulation methodology. A finite difference scheme was implemented in order to solve the linear advection-diffusion equation. The code verification was carried out based on results present in the literature, demonstrating that the implemented numerical schemes are adequate to satisfactorily reproduce the dynamics of turbidity currents. Significant results were obtained considering different particle sizes, allowing the development of a comprehensive methodology for estimating the run-out distance of the deposit and the sedimentation rate over time as a function of the characteristic diameter of the grain. [ABSTRACT FROM AUTHOR]

Purpose: Some children with sleep-disordered breathing (SDB) continue to experience symptoms after adenotonsillectomy. One possible cause is the excessive size of the torus tubarius. Methods: In this study, the relationship between torus tubarius size and surgical outcome in 24 children with SDB who underwent adenotonsillectomy was retrospectively analyzed based on cone beam computed tomography (CBCT) imaging measurements and medical records. A computational fluid dynamics (CFD) approach was used to quantitatively compare the effects of different torus tubarius sizes on upper airway (UA) aerodynamics in children. Results: The percentage of UA area occupied by the torus tubarius (TTA%) was significantly different between the excellent and poor groups (10.4 ± 3.58% vs. 17.71 ± 4.7%, p < 0.001). The results of CFD simulation showed that the mean airflow velocity, wall shear stress (WSS) and pressure drop (ΔP) in the nasopharynx significantly increased when the TTA% was > 15%. Conclusion: Our study confirmed the effect of round pillow size on the aerodynamics of the UA in children. When the TTA% exceeds 15%, it causes change in aerodynamics, which may affect the outcome of children with SDB. [ABSTRACT FROM AUTHOR]

On November 27, 2022, Mauna Loa (Hawai'i) erupted for the first time in ∼ 38 years, initially producing lava flows that covered the floor of its summit caldera, Moku'āweoweo. Over the first 12 h following the summit eruption, four main fissures opened on Mauna Loa's Northeast Rift Zone, with "fissure 3" quickly becoming the dominant source of lava flows. For the next 12 days, fissure 3 produced a 19-km-long lava flow to the north, crossing the Mauna Loa Weather Observatory access road and coming within 2.8 km of inundating the Daniel K. Inouye Highway (Saddle Road). Within 40 min of fissure 3 opening, inundation modeling efforts had begun. For the duration of the eruption, the computational fluid dynamics model Lava2d was run in real time, using flow front locations and other field observations to make sequential forecast improvements, eventually producing a set of models which accurately predicted the routing and arrival times of lava from fissure 3. These models were used to inform timing estimates of possible future inundation of the Saddle Road. As the eruption progressed, almost 4000 Lava2d models were made using high-performance computing resources, providing critical information on uncertainty in multi-week forecasts. To our knowledge, this was the first ever real-time physics-based ensemble lava flow modeling and forecasting effort. Here, we present a chronology of these real-time efforts, focusing on the successes and limitations of this approach. [ABSTRACT FROM AUTHOR]

A new approach using optimization techniques for controlling water flows is proposed in this work. The investigated problem is related to shallow water flows where a given time-evolution of outflow should be determined in order to control water elevation at some region. Typical applications are problems involving the control of movable barriers or water flowing through floodgates to prevent inundation. Usually, this type of problem is solved using gradient-based control techniques which can provide complex solutions that can be difficult to be implemented in practical situations. Here, the shape of the outflow discharge along time is predefined by a curve parametrization and used as design variable of an optimization problem. The shallow water equations are evaluated using the Finite Element Method (FEM). Numerical applications of water height control are presented and the different shapes of water outflow are investigated and discussed. As a result, the present framework can solve optimal flow control problems where an outflow discharge must satisfy a given type of variation along time. [ABSTRACT FROM AUTHOR]

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Purpose: The patchy anatomical distribution of atherosclerosis has been attributed to variation in haemodynamic wall shear stress (WSS). The consensus is that low WSS and a high Oscillatory Shear Index (OSI) trigger the disease. We found that atherosclerosis at aortic branch sites correlates threefold better with transverse WSS (transWSS), a metric which quantifies multidirectional near-wall flow. Coronary artery disease has greater clinical significance than aortic disease but computation of WSS metrics is complicated by the substantial vessel motion occurring during each cardiac cycle. Here we present the first comparison of the distribution of atherosclerosis with WSS metrics computed for moving coronary arteries. Methods: Maps of WSS metrics were computed using dynamic geometries reconstructed from angiograms of ten non-stenosed human right coronary arteries (RCAs). They were compared with maps of fatty streak prevalence derived from a previous study of 1852 RCAs. Results: Time average WSS (TAWSS), OSI, transWSS and the cross-flow index (CFI), a non-dimensional form of the transWSS, gave non-significant or significant but low spatial correlations with lesion prevalence. The highest correlation coefficient (0.71) was for the relative residence time (RRT), a metric that decreases with TAWSS and increases with OSI. The coefficient was not changed if RRT was calculated using CFI, which captures multidirectional WSS only, rather than OSI, which encompasses both multidirectional and oscillatory WSS. Conclusion: Contrary to our earlier findings in the aorta, low WSS in combination with highly multidirectional flow correlates best with lesion location in the RCA, explaining approximately half of its anatomical variation. [ABSTRACT FROM AUTHOR]

A sample return mission to deep space has been proposed. The orbital velocity of the deep space sample return capsule (DS-SRC) during atmospheric entry reaches 15 km/s, which results in extremely severe aerodynamic heating to the sample return capsule. We proposed a new concept of the DS-SRC with a lightweight and large-area aeroshell to reduce the severe heating environment at high altitudes through efficient aero-deceleration. The DS-SRC must be aerodynamically stable at all speeds because it is expected to be operated without a parachute at atmospheric entry. First, we showed the flight environment of the DS-SRC along the atmospheric entry trajectory obtained by trajectory analysis. Second, we investigated the aerodynamic characteristics and the static stability in the all-speed range using low-speed, transonic, and supersonic wind tunnels. Last, we used a computational science approach to conduct unsteady turbulent flow simulations to show its stability mechanism. The trajectory analysis indicated that the peak heat flux at the stagnation point of the capsule was kept approximately 10 MW/m2 when decelerating from high altitude because of its low ballistic coefficient. Based on the wind tunnel experimental results, we confirmed that this capsule is statically stable in attitude at all speeds. Furthermore, the computed results suggested that there is a difference in pressures at the windward and leeward sides of the front surface when the capsule is pitched up or down. This difference in pressure distribution acts as a static stability mechanism generating a moment in the direction that restores the pitching motion. [ABSTRACT FROM AUTHOR]

Floods, which cause loss of life and property and destruction of the environment, have devastating effects on socio-economic welfare. Slit-check dams are essential structures for managing the transport of silt and woody debris, especially in events of significant floods. The current study presents the hydraulic characteristics of slit-check dams with different geometries for experimental and numerical tests. First, the Butterfly model was produced with a 3D printer and examined experimentally. Then, the Butterfly model was validated extensively using OpenFOAM (v7) software for the numerical analysis. Finally, the other models were examined numerically using the k-ε turbulence model. The changes in water surface profile, velocity profiles, energy dissipation rates, and streamlines were comprehensively examined and discussed. The results showed that slit-check dams caused hydraulic jumps and dissipated flow energy. The Arced and Rectangular models, in particular, demonstrated a significant performance for energy dissipation, which is essential for flood management. Water surface profiles are directly affected by discharge. Moreover, the cross-sectional length of the model in question significantly affects the water surface profile. Accordingly, an increase was observed in the velocity profiles along the slit-check dam. While the maximum velocity for all unit discharge was observed in the V-shaped model, the minimum velocities were observed for the Arced and Rectangular models. Thus, the energy absorption performance of Arced and Rectangular models is higher. [ABSTRACT FROM AUTHOR]

The steel-shell concrete immersed tube (SSIT) with the self-compacting concrete (SCC) has been applied in the Shenzhen–Zhongshan Link, and the SSIT is prone to the void defect during the concrete pouring process. This work aims to study the flow behavior of the SCC and investigate the generation and distribution of the void defect in the SSIT, and the computational fluid dynamics (CFD) models are adopted to solve the above problems. To verify the CFD models, the slump test, L-box test, and field test based on Ok. the impact image method are carried out. The effects of the connecting hole spacing, the exhaust hole number, the exhaust hole position and the pouring speed on the flow behavior and the void defects distribution are quantitatively compared. According to the comparison results, the standard compartment with 300 mm connecting hole spacing and 10 exhaust holes is the optimal compartment structure design, and the concrete pouring speed of 15 m3/h is the optimal construction method. This work demonstrates that the CFD model offers a useful way to evaluate the generation and distribution features of the void defects for the steel–concrete-steel structure. [ABSTRACT FROM AUTHOR]

Investigating the diffusion characteristics of leaked crude oil in heterogeneous porous media is crucial for accurately predicting the location of oil leaks from buried pipelines, emergency response, and reducing the hazards of pipeline leakage accidents. This study establishes a leakage model for buried pipelines using computational fluid dynamics methods to simulate multiphase flow in porous media, focusing on the effects of different backfill soil porosities and leakage velocity on oil diffusion and temperature field evolution. Results reveal that the diffusion process consists of acceleration, transition, and stabilization phases. At a leakage velocity of 1 m/s, the oil reaches the surface in 169 s, while velocities of 2 m/s and 3 m/s reduce this to 77 s and 48 s, respectively. Higher leakage velocities significantly increase diffusion speed, with the volume fraction of crude oil in backfill soil reaching 75.68%, 91.90%, and 95.99% at 1 m/s, 2 m/s, and 3 m/s, respectively, after 180 s. The temperature field of the soil porous media after leakage is not sensitive to changes in backfill soil porosity, and the leakage rate is one of the main factors driving changes in the temperature field. [ABSTRACT FROM AUTHOR]

This study investigates the use of multi-layered porous media (MLPM) to enhance thermal energy transfer within a counterflow double-pipe heat exchanger (DPHE). We conducted computational fluid dynamics (CFD) simulations on DPHEs featuring five distinct MLPM configurations, analyzed under both fully filled and partially filled conditions, alongside a conventional DPHE. The impact of various parameters such as porous layer arrangements, thickness, and flow Reynolds numbers on pressure drop, logarithmic mean temperature difference (LMTD), and performance evaluation criterion (PEC) was assessed. The results demonstrate that the PEC improves by approximately three times with the optimal MLPM configuration, where the porous layers decrease from the interfacial wall outward under fully filled conditions. To further optimize performance, we trained a neural network using 507 simulations to establish a continuous correlation between input variables and output results. A multi-objective optimization was then implemented using the non-dominated sorting genetic algorithm II (NSGA-II) to identify the optimal operating conditions. The Pareto front of the optimal points was established, allowing designers to select specific points based on their operational requirements. This research provides valuable insights into the potential of MLPM to significantly enhance the thermohydraulic performance of DPHEs and establishes a framework for future optimization studies. [ABSTRACT FROM AUTHOR]

Intraluminal prosthetic graft thrombus (IPT) has been described in case of endovascular aortic pathology repair. This study aimed to assess hemodynamic indicators associated with various anatomical morphologies following endovascular aortic repair (EVAR), aiming to offer further references for the choice of clinical therapy. Six model models (normal, iliac compression, aortic compression, aortoiliac compression, iliac distortion, and long-leg stent) were established based on common anatomical morphologies following EVAR. Hemodynamic indicators, such as flow velocity, time-average wall shear stress (TAWSS), oscillatory shear stress index (OSI), and relative residence time (RRT), were captured using computational fluid dynamics (CFD), and the differences between the six models were examined. The peak blood flow velocity at the compressed side iliac artery and the uncompressed side iliac artery corresponding to the aortoiliac artery compression model and the aortic compression model decreased by 30.63% to 48.62%, compared with that in the normal model. Compared with that in the normal model, the peak blood flow velocity at the aorta and the distorted side iliac artery in the iliac distortion model decreased by 7.89% and 41.13%, respectively. The length of the iliac artery stent has little effect on the blood flow velocity. The TAWSS at Iliac grafts showed varying degrees of decline in the other three compression models, particularly in the aortic compression model compared to the normal model. The TAWSS increases at the corner of the artery showing distortion but exhibited a significant decrease toward the distal end of the corner. The areas with higher OSI, and longer RRT were concentrated in the aortoiliac compression model and the iliac distortion model. We found that endograft compression and distortion may be risk factors for IPT. Moreover, the influence of longer stents on the hemodynamics inside stent-grafts is negligible. However, future real-world studies should be conducted to test and verify this speculation. [ABSTRACT FROM AUTHOR]

By employing the stabilizer in the supersonic gas nozzle to produce the plasma density profile with a sharp downramp, we have experimentally demonstrated highly stable electron beam acceleration based on the shock injection mechanism in laser wakefield acceleration with the use of a compact Ti:sapphire laser. A quasi-monoenergetic electron beam with a peak energy of 315 MeV ± 12.5 MeV per shot is generated. The electron pointing fluctuations are less than 1 mrad, which is a significant improvement over previous results. This is due to the precise control of the target density distribution and the relative distance between the shock and the laser focal position. The Particle-in-cell simulations demonstrate the sensitivity of electron acceleration to the target profile, while the computational fluid dynamics prove the stabilizer's effect on gas formation. Further developments of this scheme have the potential to deliver a high repetition rate gas target. The corresponding reproducibility of the accelerated electron beam paves the way for the realisation of compact laser plasma accelerators and the potential application of free electron lasers. [ABSTRACT FROM AUTHOR]

In hot and humid regions, many classrooms depend on air conditioning systems equipped with mixing ventilation to maintain acceptable indoor temperatures. However, this method often proves inadequate in delivering satisfactory thermal comfort due to elevated temperature and poor air distribution. This research explores the potential of zonal air supply strategies to enhance thermal comfort in a classroom situated in Jeddah, Saudi Arabia. During July 2024, field data—including measurements of airflow velocity, air temperature, relative humidity, and globe temperature—were collected to find key thermal comfort indices: Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD). In addition, a survey was administered to assess students' thermal perceptions. Computational Fluid Dynamics (CFD) simulations were utilized to predict air temperature, velocity, and humidity distribution, evaluating the impact of zonal air supply designs on thermal comfort within the classroom. Parametric analysis was used to identify the most effective zonal air supply configuration for reducing PMV and PPD values. The findings show that, under existing ventilation conditions, PMV and PPD indices at different heights exceed the recommended limits established by ASHRAE Standard-55, indicating thermal discomfort during peak temperature periods. Further investigation demonstrated that introducing a 4-zonal air supply system could reduce PMV by 16–32% and PPD by 32–36%, thereby significantly improving thermal comfort in the classroom. Article Highlights: Thermal indices and surveys showed that the existing ventilation failed to ensure classroom summer comfort. Field measurements and CFD simulations show strong agreement with ± 5% deviation. The four-zonal air supply system with mixing ventilation improved the thermal comfort inside the classroom. [ABSTRACT FROM AUTHOR]

In this study, a numerical investigation into the sustained aerodynamic performance of a morphing wing equipped with a flexible leading edge, employing a 2-dimensional NACA0012 airfoil configuration, is conducted. The compressible governing equations of the flow are employed, simulating 2 distinct states: the airfoil without motion and the airfoil featuring a flexible leading edge with a chord length of 0.856 m, assessing various angles of attack utilizing the k-ω SST turbulence approach within Fluent software. Dynamic mesh, facilitated by a user-defined function, is utilized in Fluent software to simulate the movement of the airfoil wall at the leading edge. The study thoroughly analyzes the flow behavior concerning diverse angles of attack and deviations, evaluating their impact on aerodynamic coefficients, velocity, and pressure fields under steady-state settings. Validation of the chosen numerical approach demonstrates close alignment of the front and back coefficients with experimental settings. Outcomes from the steady-state flow simulation of the morphing wing reveal that positive deflection angles correspond to increased lift coefficients and decreased drag coefficients, with lift coefficient increases of up to 15% and drag coefficient reductions of up to 10% at specific angles. Meanwhile, the negative deflection angles have shown a decline in lift coefficients, with the drag coefficients increasing with the decrease in deflection angle. All these observations show that at the flexible leading edge, there is a considerable improvement in aerodynamic efficiency. Hence, it should find more applications in different regimes of flight. [ABSTRACT FROM AUTHOR]

Sandstorms have destructive effects on railway infrastructures due to the movement and erosion of sand. One of the proposed solutions to reduce the impact of windblown sand on desert railways is the hump slab track superstructure. This system entails removing the ballast layer and elevating the rails using concrete foundations called humps, which create sand movement channels beneath the rails. The hump's geometry must not only meet optimal aerodynamic conditions but also ensure ample clearance for sand passage, maintaining structural stability and efficient railway performance. In this study, the aerodynamic evaluation of various hump geometry is examined considering the elliptical (EL) and semicircular-rectangular (CR) shapes. Simulations are carried out using 3D computational fluid dynamics in ANSYS Fluent software. A gas–solid two-phase model, comprising a distinct phase for sand particles and another for air, is developed to assess the sand movement capacity through the selected hump geometries. A wind tunnel experiment is then performed on a prototype of a hump slab track to validate the software model. The findings highlighted that the CR shape, with a height of 25 cm, resulted in the most favorable outputs. [ABSTRACT FROM AUTHOR]

The reduction of emissions from compression ignition (CI) engines is a major area of research in response to increasing environmental regulations and the need for cleaner energy solutions. This study presents a comprehensive computational fluid dynamics (CFD) study on a sector combustor of a CI engine, focusing on the effects of injection parameters and combustion chamber design on emissions. Four distinct combustion chamber designs—rectangular, shallow depth combustion chamber (SCC), hemispherical combustion chamber (HCC), and toroidal combustion chamber (TCC)—were analyzed. Key parameters such as tumble ratio, swirl ratio, cross-tumble ratio, soot formation, and NOx emissions were observed and compared. This study uniquely combines a comparative analysis of these combustion chamber designs with an advanced optimization of injection parameters using a Multi-Objective Genetic Algorithm (MOGA), an approach not widely explored in previous CI engine research. Additionally, response surface methodology (RSM) and design of experiments (DOE) were employed to gain further insights into the influence of individual variables, providing a thorough understanding of their impact on emissions and combustion performance. The results show that SCC chambers are most effective at reducing soot emissions, while TCC designs are better at lowering NOx emissions. Later injection timings showed a 450% decrease in soot rate compared to earlier timings, whereas NOx has significantly benefited from earlier injections, which presented about a 1600% difference in the NOx production when compared to late injections. These findings offer valuable contributions to the design of cleaner and more efficient CI engines, with the potential to significantly impact future engine development. [ABSTRACT FROM AUTHOR]

Brain-on-a-chip is an emerging field involving microfluidic devices capable of mimicking the structure and function of the human brain. Existing research often focuses on single barriers, such as the blood–brain barrier or blood–cerebrospinal fluid barrier (BCSFB). However, the brain has both barriers working together, and mimicking this dual system is crucial for better understanding of brain (patho)physiology. In this work, we present a four-channel microfluidic chip model that incorporates both the BBB and BCSFB, to reproduce physiologically correct architecture. Using computer simulations, we demonstrate that this model can mimic both healthy and diseased states by adjusting the shear stress experienced by the barriers, which is a key factor in their function. These findings offer valuable insights for designing future brain-on-a-chip devices with improved accuracy. This improved technology could contribute to wider advancements in tissue engineering and the study of brain function and diseases. [ABSTRACT FROM AUTHOR]

This study looks at the modeling and stability analysis of an existing elevated solar structure to allow solar energy production and agriculture on the same land (Agrivoltaics). The existing elevated structure accommodates 32 solar panels, each with a capacity of 345 W at a height of approximately 6 m at the center. The impact of the gaps in the 32-panel configuration at this height on the wind load in the elevated solar structure is determined.The study uses computational fluid dynamics (Solid Works Flow simulation) followed by the results used in the static study (Solid Works simulation) to assess the overall stress and strain resulting in the elevated structure. Distortion Energy theory is followed to compare the von Mises stress resulting from the simulation with the Yield strength of the material used to construct the elevated support structure. The findings demonstrate that solar panel spacing can be a key factor in lowering wind loads on the raised support structure. [ABSTRACT FROM AUTHOR]

Purpose: The investigation of fluid-borne noise in the balanced vane type hydraulic steering pump is focused in this study, which is the main source of noise in the hydraulic steering system of commercial vehicles. Turbulence development at the suction connection point to the bypass hole is the source of the noise. This creates a greater pressure ripple in the fluid flow, which leads to a low pressure zone at the Cartridge Inlet Region (CIR) within the pump housing. This creates a cavitation and results in fluid borne noise and further transmits as airborne noise. Methods: The different factors like pump operating speed, pressure, bypass geometry, suction passage volume and its geometry have been examined in this study using computational fluid dynamics (CFD). It is observed that the modified parameters such as suction passage geometry and its conduit capacity and the diameter and angle of the bypass hole are the features involved in decreasing the fluid borne noise generation. Results: The optimization is performed in pump housing suction passage geometry in the form of cylindrical shape and angular bypass hole with increased volume. The simulation results indicate that the pressure at CIR increases substantially above 90%, thus the cavitation effect is reduced and the expected level of reduction in airborne noise is about 15%. Conclusion: Finally, it is concluded that based on the CFD analysis with the improved configuration level of reduction in airborne noise is expected about 88 dBA at 2000 rpm and 50 bar static pressure, which is much below the customers threshold limits. [ABSTRACT FROM AUTHOR]