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The present review focuses on the recent studies carried out in passive micromixers for understanding the hydrodynamics and transport phenomena of miscible liquid–liquid (LL) systems in terms of pressure drop and mixing indices. First, the passive micromixers have been categorized based on the type of complexity in shape, size, and configuration. It is observed that the use of different aspect ratios of the microchannel width, presence of obstructions, flow and operating conditions, and fluid properties majorly affect the mixing characteristics and pressure drop in passive micromixers. A regime map for the micromixer selection based on optimization of mixing index (MI) and pressure drop has been identified based on the literature data for the Reynolds number (Re) range (1 ≤ Re ≤ 100). The map comprehensively summarizes the favorable, moderately favorable, or non-operable regimes of a micromixer. Further, regions for special applications of complex micromixer shapes and micromixers operating at low Re have been identified. Similarly, the operable limits for a micromixer based on pressure drop for Re range 0.1 < Re < 100,000 have been identified. A comparison of measured pressure drop with fundamentally derived analytical expressions show that Category 3 and 4 micromixers mostly have higher pressure drops, except for a few efficient ones. An MI regime map comprising diffusion, chaotic advection, and mixed advection-dominated zones has also been devised. An empirical correlation for pressure drop as a function of Reynolds number has been developed and a corresponding friction factor has been obtained. Predictions on heat and mass transfer based on analogies in micromixers have also been proposed. [ABSTRACT FROM AUTHOR]

To achieve hydrodynamic design excellence in Autonomous Underwater Vehicles (AUVs) largely depends on the accurate prediction of lift and drag forces. The study presents Computational Fluid Dynamics (CFD)-based lift and drag estimations of a novel torpedo-shaped flight-style AUV with bow-wings. The horizontal bow-wings are provided to accommodate the electromagnetic arrays used to perform the cable detection and tracking operations near the seabed. The hydrodynamic performance of the AUV due to addition of these horizontal bow-wings is required to be investigated, particularly at the initial design stage. Hence, CFD techniques are employed to compute the lift and drag forces observed by the flight-style AUV, maneuvering underwater at different angles of attack and varying speeds. The Reynolds-Averaged Navier-Stokes Equations (RANSE) closure is achieved by employing the modified k − ϵ model and Two-Scale Wall Function (2-SWF) approach is used for boundary layer treatment. Further, the study also highlights the unique mesh refinement and solution-adaptive meshing techniques to perform the CFD simulations in Solidworks Flow Simulation (SWFS) environment. The drag polar curve for flight-style AUV with and without bow-wings is generated using the computed lift and drag coefficients. The curve provided essential insights for achieving hydrodynamically efficient and optimized AUV design. From the drag polar curve, it is revealed that due to horizontal bow-wings, the flight-style AUV is capable to generate higher lift with less drag and thus, it gives better lift-to-drag ratio compared to the AUV without bow-wings. Moreover, simulated results of axial drag observed by the AUV have also been compared with free-running experimental results and are found in good agreement. [ABSTRACT FROM AUTHOR]

This study addressed the challenge of forecasting the critical Angle of Attack (AOA) for tall buildings, which can significantly affect wind forces. Extensive assessments are needed to optimise the wind force on a tall building, either by wind tunnel testing or computational fluid dynamics (CFD), using various combinations of AOA and corner cut (CC). This process is time-consuming and complex. This study aims to develop an Adaptive Neuro-Fuzzy Interface System (ANFIS) approach for rapidly and effectively obtaining aerodynamic coefficients. Hence, two symmetrical C-shaped tall buildings, subjected to AOAs ranging from 0° to 90° and different CC modifications, are numerically simulated using CFD, and the outcomes (force coefficient (CF) and moment coefficient (CM)) are used to train and test ANFIS model. The validation showed that the maximum error is less than 4%, indicating its excellent predictability. Furthermore, it is observed that for models A1 (CF = 0.66 and CM = 0.76) and A2 (CF = 0.68 and CM = 0.75), the minimum CF and CM at 90° AOA with a 30% CC are much lower, i.e., 45.4% and 38.7%, 43.3% and 41.4%, respectively than the maximum values at 0° AOA with 0% CC. This ANFIS model can predict aerodynamic coefficients for various combinations of CC and AOAs. [ABSTRACT FROM AUTHOR]

The artificially submerged cavitation water jet is effectively utilized by ejecting a high-pressure water stream into a low-pressure water stream through concentric nozzles and utilizing the cavitation phenomenon generated by the shear layer formed between the two streams. In this study, we investigated the cavitation characteristics of artificially submerged cavitation water jets by combining numerical simulations and erosion experiments. The results indicate that an appropriate standoff distance can generate more cavitation clouds on the workpiece surface, and the erosion characteristics of the artificially submerged cavitation water jet are most pronounced at a dimensionless standoff distance of SD = 30. The shear effect formed between the two jets plays a crucial role in generating initial cavitation bubbles within the flow field of the artificially submerged cavitation water jet. Moreover, increasing the convergent angle between the two jets can significantly enhance the cavitation effect between them and lead to a more substantial cavitation effect. Simultaneously, increasing the pressure of the high-pressure inner nozzle also contributes to enhancing the cavitation effect of the artificially submerged cavitation water jet. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cooling processes are responsible for a significant portion (20%) of global energy consumption and raise environmental concerns such as ozone depletion, the greenhouse effect, and high energy use. This study investigates the potential of R152a, a refrigerant with low global warming potential (GWP), as a more sustainable alternative. The performance, safety, and operational efficiency of R152a were evaluated under various conditions. Although R152a offers high performance and low GWP, its flammability necessitates caution, especially in certain mixtures. A 12-pass tube-type heat exchanger model was simulated using computational fluid dynamics (CFD) to analyze the fluid behavior within the exchanger. The pressure, density, dynamic pressure, Prandtl number, total pressure, and temperature distributions for both R152a and H2O (water) were visualized using contour plots. The simulations comprehensively examined the fluid behavior inside and outside the heat exchanger. The results revealed the influence of the temperature on the internal dynamic pressure and density of R152a. Compared with R134a, R152a demonstrated superior performance but a lower coefficient of performance (COP) than R32. Studies also suggest that R152a exhibits lower irreversibility in Organic Rankine Cycle (ORC) systems than R245fa. These findings suggest that R152a holds promise for future refrigeration systems, as supported by existing research on its performance and compatibility. One study focused on optimizing the heat exchanger performance by maximizing the heat capacity and minimizing the pressure drop. This study employed a parallel-flow heat exchanger with R152a as the coolant for the hot process water. The temperature changes, pressure drops, and resulting energy efficiency and thermal performance of both fluids were analyzed. The results highlight the distinct energy efficiencies and thermal performance of the employed fluids. [ABSTRACT FROM AUTHOR]

The axial piston pump can switch the high and low pressure circulation through the valve plate in the working process, and the flow area of the valve plate is an important parameter affecting the smooth transition of internal pressure of the axial piston pump. In order to complete the flow area of the distribution structure, a method of flow area calculation based on multi-dimensional flow field point cloud was proposed. Firstly, the point cloud process of the valve plate flow field was analyzed theoretically, and the implementation method of point cloud processing was obtained. Then, a series of modifications were made to the three-dimensional basin model of the valve plate, and a method was proposed to modify the connecting stage model of the buffer groove, which improved the accuracy of the calculation of the flow area. Finally, the flow area of different distribution stages was calculated and compared with the results obtained by theoretical measurement and numerical simulation of computational fluid dynamics (CFD). The calculation results show that the peak value of the flow area obtained by the identification algorithm based on multi-dimensional flow field point cloud is 174. 5 mm², while the theoretical measurement value is 177. 5 mm², and the relative error rate of the two is about 1. 7% . The overall relative error rate of the results based on the CFD method is less than 5% . The results show that the method can solve and calculate the flow area of the valve plate directly and accurately, and effectively simplify the process of solving the flow area transformation trend. [ABSTRACT FROM AUTHOR]

Determination of the geometrical parameters of the heat exchanger has important effects on the thermohydraulic performance of the heat exchanger. In this study, the effects of geometric parameters of a plate heat exchanger on thermohydraulic performance have been extensively investigated using computational fluid dynamics (CFD). Parametric studies were performed on 8 different corrugated channel geometries with various chevron angles (β) and aspect ratios (2b/λ) for Reynolds numbers ranging from 500 to 3000. An entire fluid channel was numerically studied using the same mass flow rate and the Reynolds number. As results of the study, temperature distribution, pressure gradient, velocity, turbulent kinetic energy distribution, Nusselt number, friction factor, and flow properties were evaluated comparatively for each case. It was determined that the sinusoidal corrugations promote the turbulence intensity and the swirling flow which leads to thermal boundary layer mitigation and enhanced convection heat transfer in response to the increasing of aspect ratio. The results of the study show that the (CFD) model is a reasonable and effective technique for displaying 3D contour plots, streamlines, and determining performance parameters. [ABSTRACT FROM AUTHOR]

Performance improvement of heat exchangers is important since their size and manufacturing cost can be decreased. This study aims to evaluate two techniques, namely use of nanofluid and employment of vortex generator (VG) applicable in performance improvement of a fin–plate heat exchanger. In the present article, a numerical investigation is carried out on a fin–plate heat exchanger by considering effects of employment of hybrid nanofluid, MWCNT-Fe3O4/water with 0.3% concentration, and winglet VG with different angles. In this regard, computational fluid dynamics is applied by using SST turbulence models. Results of the simulation reveal that employment of the nanofluid and VG induces enhancement in the heat transfer. Heat transfer improvement by use of VG is mainly due to the boundary layer reduction and intensification of turbulent flow and nanofluids enhance thermal performance owing to the increase of the fluid thermal conductivity. The augmentation in the heat transfer in case of using VG was dependent on its configuration. Moreover, simultaneous usage of both of them would further augment the heat transfer. The maximum heat transfer rate improvement in case of using the nanofluid without VG, with vortex generator and without the nanofluid and with the nanofluid and vortex generator is around 5.2, 69.2 and 74.6%, respectively. [ABSTRACT FROM AUTHOR]

Objective: To explore the effects of Draf1–3 on frontal sinus airflow and frontal sinus irrigation in people with different frontal sinus development Methods: The development of the frontal sinus and the distribution of the frontal recess cells were evaluated by CT scan in 150 adults (300 sides). The airflow changes into the frontal sinus and frontal recess after Draf were analyzed by Fluent software under a steady state and quiet inspiratory state. Nasal irrigation after Draf in adults with well-developed frontal sinus was simulated using 120 mL saline at a rate of 12 mL/s in a position at 45° to observe the changes in transient flow distribution. Results: The moderately developed type of the frontal sinus was the most common. The airflow patterns in the frontal sinus and frontal recess in the moderate development group were laminar, while several large vortexes were formed between the frontal sinus and frontal recess in the well-development group. The Draf exerted more significant effects on the patterns, pressure, and velocity of the airflow in the frontal sinus and frontal recess in the well development group than in the moderate development group. The volume fraction of saline in the frontal sinus increased significantly from Draf1 to Draf3, and the time required for a complete infiltration of saline in the frontal sinus mucosa was significantly reduced. Conclusions: Draf1–3 has different effects on the airflow field of the frontal sinus with different developmental types; and Draf1–3 can significantly improve the postoperative flushing of the frontal sinus. [ABSTRACT FROM AUTHOR]

The studies on vascular flows have increased in the last decade. In this work; we have focused on the effects of flow model and blood rheology on hemodynamics for a real-subject scan using Computed Tomography Angiography (CTA) during numerical solutions. Various vascular flow studies using Newtonian or non-Newtonian blood models were presented in the literature with laminar or turbulent flow assumptions. In this study; six different turbulent models (Realizable k- ε , Standard k- ε , SST k- ω , Standard k- ω , Transition k-kl- ω , Transition SST) were compared to laminar flow to show whether turbulent flow solution is necessary. Blood rheology was investigated by using five different non-Newtonian models (Carreau, Herschel–Bulkley, Carreau–Yasuda, Casson, Power-Law) in addition to Newtonian model to indicate whether non-Newtonian blood assumptions is necessary. The In vivo boundary conditions were utilized by the UDF code which defines the real-patient cardiac cycle obtained by Echocardiography (ECHO) to present hemodynamics in the study. The results show that laminar flow well matched with the four turbulent models and two models shows by 4.8% and 19.5% differences in Wall Shear Stress (WSS) according to laminar flow. When the blood rheology was investigated, results revealed significant differences in WSS by 25.7%, 8.7%, 22.4%, 12.3%, and 32.5% for the non-Newtonian models in the given order, respectively, compared to Newtonian assumption. It concluded that laminar flow solution could be effective instead of solving turbulent flows in terms of computational cost, however, non-Newtonian blood effects could be considered to determine critical hemodynamics levels in a normal aortic arc. [ABSTRACT FROM AUTHOR]

People in elevators are at risk of respiratory infection because the elevator cabin is crowded and has poor ventilation. The exhaled particles may be inhaled by the susceptible person, deposited on the surface and suspended in the elevator, which can result in direct and indirect transmission. However, whether the air vent designs adopted in the elevator can effectively reduce the transmission risk of respiratory particles remains unknown. In this study, the dispersion of particles under four common ventilation strategies used in the commercial elevator was investigated by proven computational fluid dynamics (CFD) simulations. The flow field was simulated with the RNG k-ξ turbulence model and the Lagrangian method was adopted to track particle trajectories. The effects of air vent layout and airflow rate on particle transmission were analyzed. We found that more than 50% of exhaled particles (average value) were suspended in the cabin and difficult to discharge under the investigated ventilation strategies. The deposited fraction of particles on the susceptible person reached up to 39.14% for infiltration ventilation, which led to a high risk of contact infection. Increasing the ventilation rate could not significantly reduce the inhalation proportion of particles due to the poor airflow distribution inside the elevator. A more proper ventilation strategy should be explored for the elevator to control transmission risk. [ABSTRACT FROM AUTHOR]

This study investigates the impact of small water bodies on outdoor temperatures in their vicinity, using a campus located in the subtropical region of Taichung City, Taiwan, as the research subject. By employing on-site measurements and Computational Fluid Dynamics (CFD) simulations, we examined their temporal and spatial influence, as well as comparisons between actual measurements and software predictions. Key findings include the following: (1) Small water bodies exhibit discernible temperature-regulating effects on their surrounding areas. While the influence diminishes with distance, this attenuation is not stark, and is potentially constrained by the water body's patch size. (2) Regulatory effects vary between day and night. In summer, temperature reductions of up to 3.5 °C (simulated) and 3.2 °C (measured) were observed. Conversely, in winter, daytime temperatures around water bodies may rise by up to 3.9 °C. (3) Discrepancies between CFD simulations and actual measurements, influenced by fluctuations in Global Horizontal Irradiation (GHI), range from +2.5 °C to −1.8 °C. During high GHI periods, measured values surpass simulations, whereas during low or zero GHI conditions, simulations exceed measurements. Moreover, high regression analysis R2 values validate the feasibility of CFD simulations for predicting water body-induced temperature changes. Insights from this study offer valuable guidance for urban planners and policymakers seeking sustainable urban climate management strategies. [ABSTRACT FROM AUTHOR]

The concentration of ammonia (NH3) and the temperature of the air surrounding the rabbit habitat in the farm condition basic health processes such as breathing and feeding. The indoor climate in a rabbit farm is largely conditioned by the ventilation system (air conditioning). The objective of this study was to build a numerical model based on computational fluid dynamics (CFD) in order to evaluate, by numerical simulations, the air dynamics of a rustic farm. After the validation of the computational model, the thermal gradient and ammonia concentration were analyzed under three wind incidence angles (0°, 45°, and 90° with respect to the horizontal Z axis of the facility). The results of the simulations showed that, in the area occupied by the rabbits (AOR), the concentration of ammonia with respect to the source was reduced by 37.3% in the most favorable case (wind direction at 45°), and 21.2% in the least favorable case (wind direction at 0°), and the indoor temperature presented a maximum difference of 2 °C with respect to the outside temperature. Climate control is a more expensive cost in rabbit farm exploitation; dynamics modulation can serve as an auxiliary tool for reducing health risks in rabbits. The use of models based on fluid dynamics allowed us to understand the efficiency of the ventilation system, which must be increased to reduce the found temperature gradient. Through numerical simulation it will be possible to find alternatives to increase the ventilation rate. [ABSTRACT FROM AUTHOR]

Even though inhalation dosimetry is determined by three factors (i.e., breathing, aerosols, and the respiratory tract), the first two categories have been more widely studied than the last. Both breathing and aerosols are quantitative variables that can be easily changed, while respiratory airway morphologies are difficult to reconstruct, modify, and quantify. Although several methods are available for model reconstruction and modification, developing an anatomically accurate airway model and morphing it to various physiological conditions remains labor-intensive and technically challenging. The objective of this study is to explore the feasibility of using an adjoint–CFD model to understand airway shape effects on vapor deposition and control vapor flux into the lung. A mouth–throat model was used, with the shape of the mouth and tongue being automatically varied via adjoint morphing and the vapor transport being simulated using ANSYS Fluent coupled with a wall absorption model. Two chemicals with varying adsorption rates, Acetaldehyde and Benzene, were considered, which exhibited large differences in dosimetry sensitivity to airway shapes. For both chemicals, the maximal possible morphing was first identified and then morphology parametric studies were conducted. Results show that changing the mouth–tongue shape can alter the oral filtration by 3.2% for Acetaldehyde and 0.27% for Benzene under a given inhalation condition. The front tongue exerts a significant impact on all cases considered, while the impact of other regions varies among cases. This study demonstrates that the hybrid adjoint–CFD approach can be a practical and efficient method to investigate morphology-associated variability in the dosimetry of vapors and nanomedicines under steady inhalation. [ABSTRACT FROM AUTHOR]

Computational Fluid Dynamics (CFD) simulations were utilized in this study to comprehensively explore the fluid dynamics within an accelerated toroidal vessel, specifically those central to Particle Imaging Velocimetry Gyroscope (PIVG) technology. To ensure the robustness of our simulations, we systematically conducted grid convergence studies and quantified uncertainties, affirming the stability, accuracy, and reliability of our computational grid and results. Comprehensive validation against experimental data further confirmed our simulations' fidelity, emphasizing the model's fidelity. As the PIVG is set up to address the primary flow through the toroidal pipe, we focused on the interaction between the primary and secondary flows to provide insights into the relevant dynamics of the fluid. In our investigation covering Dean numbers (De) from 10 to 70, we analyzed diverse aspects, including primary flow, secondary flow patterns, pressure distribution, and the interrelation between primary and secondary flows within toroidal structures, offering a comprehensive view across this range. Our research indicated stability and fully developed fluid dynamics within the toroidal pipe under accelerated angular velocity, particularly for low De. Furthermore, we identified an optimal Dean number of 11, which corresponded to ideal dimensions for the toroidal geometry with a curvature radius of 25 mm and a cross-sectional diameter of 5 mm. This study enhances our understanding of toroidal fluid dynamics and highlights the pivotal role of CFD in optimizing toroidal vessel design for advanced navigation technologies. [ABSTRACT FROM AUTHOR]

Electric desalination units in the crude oil refining process are becoming increasingly important with the growing trend towards heavy and poor crude oils. The oil–water mixing effect of the static mixer plays a crucial role in the electric desalination process. The present study investigated the effect of various variables, such as mixer type, number of mixing elements, washing water consumption, and oil viscosity and density on the oil–water mixing efficiency of a static mixer. In addition, this study also analyzed the effect of these variables on the salt washing process that occurs during mixing using a kinetic equation for the dissolution of inorganic salts. The results showed that the number of mixing elements was the most significant variable, followed by the amount of washing water injected. The density of the crude oil had a negligible effect. Based on these results, the use of four mixing elements in the SMX static mixer was recommended. The injection of washing water should be controlled at about 8%, while ensuring that the interfacial tension between oil and water remains below 0.01 N/m. Under these conditions, the salt washing efficiency reached 46.3%. This study provides a theoretical basis for designing static mixers and optimizing their operation in electric desalination processes. [ABSTRACT FROM AUTHOR]

In recent years, morphing wings have become not only a concept, but an aerodynamic solution for the aviation industry to take a step forward toward future technologies. However, continuously morphing airfoils became an interesting answer to provide green energy solutions. In this paper, the authors conducted experimental research on a continuously camber-morphing airfoil using the Particle Image Velocimetry (PIV) and Computational Fluid Dynamics (CFD) methods. The main objective of this work was to research a variety of morphing airfoils with different camber deflections. An average velocity distribution and turbulence distribution were compared and are discussed. The two-dimensional PIV results were compared to the CFD simulations to validate the numerical method's accuracy and obtain the aerodynamic coefficient's trends. A further comparison revealed that morphing airfoils have better aerodynamic performance than conventional airfoils for very low camber deflections and create substantial amounts of drag for significant camber deflections. [ABSTRACT FROM AUTHOR]

Three-dimensional microextrusion bioprinting technology uses pneumatics, pistons, or screws to transfer and extrude bioinks containing biomaterials and cells to print biological tissues and organs. Computational fluid dynamics (CFD) analysis can simulate the flow characteristics of bioinks in a control volume, and the effect on cell viability can be predicted by calculating the physical quantities. In this study, we developed an analysis system to predict the effect of a screw-based dispenser system (SDS) on cell viability in bioinks through rheological and CFD analyses. Furthermore, carboxymethylcellulose/alginate-based bioinks were used for the empirical evaluation of high-viscous bioinks. The viscosity of bioinks was determined by rheological measurement, and the viscosity coefficient for the CFD analysis was derived from a correlation equation by non-linear regression analysis. The mass flow rate derived from the analysis was successfully validated by comparison with that from the empirical evaluation. Finally, the cell viability was confirmed after bioprinting with bioinks containing C2C12 cells, suggesting that the developed SDS may be suitable for application in the field of bioengineering. Consequently, the developed bioink analysis system is applicable to a wide range of systems and materials, contributing to time and cost savings in the bioengineering industry. [ABSTRACT FROM AUTHOR]

Minimum quantity lubrication (MQL) has achieved excellent results in precision machining. The geometric parameters of the nozzle play a crucial role in determining the performance of MQL. In this study, the orthogonal experimental method was employed to improve and optimize the performance of MQL. Computational fluid dynamics (CFD) simulation using ANSYS Fluent software was conducted, and the simulation data were statistically analyzed. The effects of six influencing factors, namely, the width of the gas-phase narrow flow region, the taper, the output tube length, the length of the gas-phase narrow flow region, the output aperture, and the pressure, on the performance of MQL were investigated. The results revealed that the order of importance for the six influencing factors differed depending on the evaluation criteria used. The parameter that had the greatest impact on the composite index was the absolute gas velocity at a distance of 0.1 m from the outlet. The optimum combination of geometric parameters for the nozzle was an output aperture of 2 mm, a taper of 40°, a length of the gas-phase narrow flow region of 1.5 mm, a width of the gas-phase narrow flow region of 0.3 mm, an output tube length of 15.5 mm, and a pressure of 5 bar. [ABSTRACT FROM AUTHOR]

In order to meet the functional characteristics of the flying wall crawler, the structure of the flying wall crawler is such that the four rotors are not in the same plane but in a longitudinal arrangement when in flight. The CFD (computational fluid dynamics) simulation of the single-rotor flow field was carried out to verify its reliability. On the basis of these simulations, aerodynamic simulations were carried out for different horizontal spacing, different vertical spacing and different rotational speeds of the longitudinal double rotor. The results were then analysed to determine the effect of the horizontal and vertical spacing and the rotational speed on the aerodynamic characteristics of the front and rear rotor blades and the whole system. The simulation results show that the transverse pitch has a large aerodynamic interference between the longitudinal rotor blades, while the axial pitch is relatively small and the degree of interference is related to the rotational speed. It is clear that the conclusions can provide a basis for the rotor layout, rotational speed and feasibility of flying wall climbing robots. [ABSTRACT FROM AUTHOR]

This study investigates numerically the pressure behavior of hot gases and smoke in fires of large enclosures. It mainly covers the effectiveness of using natural and mechanical ventilation in changing the pressure behaviour of hot gases and smoke inside different structures. Fire Dynamics Simulator (FDS), provided by NIST, has been used to run the simulations for all proposed cases. For the assumed scenarios, the values of hot gas pressure and temperature are extracted at different points, especially in the hot layer close to the ceiling, for further analysis. The effect of changing the location of the fire source has been investigated, too. Final results show noticeable changes in the behavior of pressure, and temperature, in the presence of different ventilation systems, both natural and mechanical. Thus, appropriate ventilation systems can improve the pressure behaviour inside the place, which offers a better environment and higher safety level, in case of fire, in such large enclosures, open plan offices, T [ABSTRACT FROM AUTHOR]

The maintenance of body homeostasis relies heavily on physiological barriers. Dysfunction of these barriers can lead to various pathological processes, including increased exposure to toxic materials and microorganisms. Various methods exist to investigate barrier function in vivo and in vitro. To investigate barrier function in a highly reproducible manner, ethically, and high throughput, researchers have turned to non-animal techniques and micro-scale technologies. In this comprehensive review, the authors summarize the current applications of organ-on-a-chip microfluidic devices in the study of physiological barriers. The review covers the blood-brain barrier, ocular barriers, dermal barrier, respiratory barriers, intestinal, hepatobiliary, and renal/bladder barriers under both healthy and pathological conditions. The article then briefly presents placental/vaginal, and tumour/multi-organ barriers in organ-on-a-chip devices. Finally, the review discusses Computational Fluid Dynamics in microfluidic systems that integrate biological barriers. This article provides a concise yet informative overview of the current state-of-the-art in barrier studies using microfluidic devices. [ABSTRACT FROM AUTHOR]

The microclimate environment can be conveniently controlled with accuracy by plant incubators, in which the cuttings propagation method can efficiently enhance seedling production. To ensure air flow evenly throughout the incubator, the scientific design of the air inlet is crucial. This study utilized a computational fluid dynamics (CFD) model to simulate the airflow patterns in a culture layer under different air inlet conditions. Furthermore, the optimal design parameters were determined by way of response surface methodology (RSM) and the Non-dominated Sorting Genetic Algorithm-II (NSGA-II). Adopting the optimal parameters, a prototype was manufactured, and a cuttings experiment was carried out with apple cuttings in the incubator. The results showed that the optimal air inlet radius is 90 mm, the optimal air inlet height is 188 mm, and the optimal uniform flow plate hole diameter is 13 mm. Meanwhile, the apple cuttings were able to root. Therefore, this incubator with optimal parameters can be used for cuttings. The study provides a methodological and theoretical basis for the future optimizing of air inlet parameters and promoting cuttings rooting. [ABSTRACT FROM AUTHOR]

Changing the metallic card clothing on a carding machine is costly when the spinning mills want to card different fibers from cotton to terylene or vice versa. This article proposes a newly developed cylinder card clothing compatible with cotton and terylene fibers by Nb alloying of AISI 1090 steel so that the spinning mills can change the type of fiber without changing the card clothing. Based on an idea developed from classical carding balance theory to study the adaptability of the cylinder card clothing for cotton and terylene fibers, the wall shear stress was used as the basis for compatibility analysis of carding behavior and bearing capacity with cotton and terylene fibers and as the focus of this study. Nb alloying of AISI 1090 steel showed good wear resistance in carding areas after heat treatment with high hardness above 840 Hv0.2 and extremely fine grain grade of 13.5 class, which increased about 25% compared to conventional 80 WV. The testing results in the spinning mills, including one cotton and two terylene fibers, showed good performance with this newly developed card clothing. In conclusion, the card clothing made of Nb alloying of AISI 1090 steel can handle different fibers with acceptable carding performance. [ABSTRACT FROM AUTHOR]

The effect of particle shape on the suffusion of gap-graded soils is an essential although poorly understood subject in geotechnical engineering that requires further investigation. This work presents a macroscale and microscale numerical investigation into the effect of particle shape on the suffusion of gap-graded granular materials. Rounded, elliptical, and convex particles with the same volume-equivalent diameter and varying shape coefficients were generated and used to produce samples. Next, a series of resolved coupled computational fluid dynamics (CFD) and discrete-element method (DEM) simulations were performed to provide evidence of the effect of particle shape on the suffusion susceptibility of gap-graded soils. The evolution of particle orientation, moment, and drag force coefficient were analyzed to determine the mechanisms by which particle shape exerts influence. The fine angular particles under seepage flow were found to adjust their orientation, reducing the projected area of the particle perpendicular to the fluid flow direction. Fine particles in high-flow-velocity regions had a smaller projected area and drag force coefficient. The continuous rotation of the irregularly shaped particles during suffusion implies that their migration should counteract the moments exerted by the surrounding particles. In the sample containing various irregularly shaped particles, the initial position of the most irregularly shaped particle was closer to the outlet, implying that irregularly shaped particles are less susceptible to suffusion. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical modelling approach to an investigation into the grinding temperature and the convective heat transfer coefficient of the grinding fluid using the computational fluid dynamics approach. The maximum grinding temperature varies from 325 K to 370 K as the grinding depth increases from 0.50 mm to 1.10 mm at 60 m/s wheel velocity for water as a grinding fluid and 419 K to 619 K for kerosene oil as a grinding fluid. The convective heat transfer coefficient depends on the density, specific heat, conductivity, and viscosity of the grinding fluid. It is observed that the value of the convective heat transfer coefficient increases with an increase in density, specific heat, and conductivity of the grinding fluid and decreases with an increase in viscosity of the grinding fluid. The convective heat transfer coefficient for water and kerosene oil is 137,730 W/m2-K and 23,512 W/m2-K, respectively, at a 76 m/s wheel velocity and 0.50 mm depth of cut. [ABSTRACT FROM AUTHOR]

It is well known that the type of drill pipe motion has an important effect on the cuttings transportation process and pressure loss gradient in the annular space, in particular for horizontal and deviated wells. For that, it is needed to understand more about the effect of planetary motion on the pressure loss gradient during circulation of the drilling mud in the bottom hole of explored wells. In the present paper, the influence of the drill pipe planetary motion on the pressure loss gradient of a mixture (Ostwald-de Waele fluid with solid particles) in a turbulent regime during its circulation through an annular space is evaluated for different drilling parameters including eccentricity, rate of penetration, and solid particles size. In addition, the effect of drill pipe planetary motion for various conditions of temperature and pressure is evaluated for two types of muds water-based and oil-based. The numerical analysis revealed that an angular speed of 120 rpm of planetary motion can be considered as an optimal value in terms of pressure loss gradient. In addition, it was observed that the effect of the planetary motion on the pressure loss gradient depends mainly on the fluid temperature for both types of mud. [ABSTRACT FROM AUTHOR]

Cyclodextrins (CDs), due to its unique 'outer hydrophilic and inner hydrophobic' structure, can be used as excellent carriers to protect active aroma compounds. The hydrodynamic conditions in the reactor substantially influence the characteristics of the cyclodextrin inclusions. Based on this, this study investigated the effects of the impeller type and the rotational speed on the characteristics of the inclusion complexes, meanwhile the corresponding scale-up process was also investigated. Results showed that the pitched blade turbine was the optimum impeller due to better axial flow performance. The average particle size, polydispersity index (PDI), loading capacity and the major aroma concentration of the inclusion complexes prepared at 5 and 120 L reactors did not have significant difference compared to the inclusion complexes prepared at 0.5 L reactor under conditions of geometry similarity and constant power per unit volume, which verified the feasibility of the scale-up rule of the encapsulation process. [ABSTRACT FROM AUTHOR]

Imitating Dolphin fish-like movement is productive method for enhancing their hydrodynamic capabilities. This work aims to analyze and understand the oscillations of tail fluke of Dolphin, which can be used as a propulsive mechanism for underwater fish robots and vehicles. The objective of the work is to achieve the desired oscillating amplitude by simulating the NACA 0012 profile using computational models and Set up the swimming movement of the dolphin, imitating a fish like model. Computational techniques were employed to examine the propulsive capabilities of the oscillating hydrofoil, inspired by the dolphin's biological propulsion. The evolutionary of fluid pattern in the field surrounding both Dolphin fish model and the NACA0012 hydrofoil, from initial motion to cruising, was established, and the hydrodynamic impact was subsequently studied. An user-defined function (UDF) was developed to create a dynamic mesh interface with CFD code ANSYS FLUENT for establishing the oscillations of Dolphin tail across the flow field. Influencing hydrodynamic coefficients such as lift and drag coefficients at different frequencies were also obtained. The findings shown that when the acceleration of the Dolphin fish model increases, the time averaged drag force coefficient drops because The wake field's vortex disperses to have some beneficial effects and pressure of water surrounding the fish head intensifies to produce a large resistance force. Simulation results show a 98% agreement at lower frequency and speed levels but a 5% deviation at higher frequency and speed due to turbulence effects in both models. It was established that the vortex superposition enhances the Dolphin fish like model rather than lowering its positive impacts. The Strouhal number, which is obtained by the fluid field's evolution rule, can be linked to the Kármán vortex street span with reverse. [ABSTRACT FROM AUTHOR]

The load rejection transient process of bulb turbine units is critical to safety of hydropower stations, and determining appropriate closing laws of guide vanes (GVs) and runner blades (RBs) for this process is of significance. In this study, we proposed a procedure to optimize the co-closing law of GVs and RBs by using computational fluid dynamics (CFD), combined with the design of experiment (DOE) method, approximation model, and genetic optimization algorithm. The sensitivity of closing law parameters on the histories of head, speed, and thrust was analyzed, and a two-stage GVs' closing law associating with a linear RBs' closing law was proposed. The results show that GVs dominate the transient characteristics by controlling the change of discharge. Speeding GVs' first-stage closing speed while shortening first-stage closing time can not only significantly reduce the maximum rotational speed but also suppress the water hammer pressure; slowing GVs' second-stage closing speed is conducive to controlling the maximum reverse axial force. RBs directly affect the runner force. Slowing RBs' closing speed can further reduce the rotational speed and the maximum reverse axial force. The safety margin of each control parameter, flow patterns, and pressure pulsations of a practical hydropower station were all improved after optimization, demonstrating the effectiveness of this method. [ABSTRACT FROM AUTHOR]

Accurate modeling for highly non-linear coupling of a damaged ship with liquid sloshing in waves is still of considerable interest within the computational fluid dynamics (CFD) and AI framework. This paper describes a data-driven Stacking algorithm for fast prediction of roll motion response amplitudes in beam waves by constructing a hydrodynamics model of a damaged ship based on the dynamic overlapping grid CFD technology. The general idea is to optimize various parameters varying with four types of classical base models like multi-layer perception, support vector regression, random forest, and hist gradient boosting regression. This offers several attractive properties in terms of accuracy and efficiency by choosing the standard DTMB 5415 model with double damaged compartments for validation. It is clearly demonstrated that the predicted response amplitude operator (RAO) in the regular beam waves agrees well with the experimental data available, which verifies the accuracy of the established damaged ship hydrodynamics model. Given high-quality CFD samples, therefore, implementation of the designed Stacking algorithm with its optimal combination can predict the damaged ship roll motion amplitudes effectively and accurately (e.g., the coefficient of determination 0.9926, the average absolute error 0.0955 and CPU 3s), by comparison of four types of typical base models and their various forms. Importantly, the established Stacking algorithm provides one potential that can break through problems involving the time-consuming and low efficiency for large-scale lengthy CFD simulations. [ABSTRACT FROM AUTHOR]

The authors of the discussed paper presented an interesting study in which a moat is introduced just downstream of an overflowing levee for reducing the energy of the overflowing water. The authors investigated the effect of the geometric parameter of the moat downstream of the overflowing levee on its hydraulic characteristics and energy reduction. The Reynolds-Averaged Navier-Stokes and Volume of Fluid methods were implemented to simulate and measure water depths and flow structures in order to optimize the geometric parameters of the moat, including dimensionless depths and lengths, and then to explore the effect of downstream slope, upstream slope, levee crest length, and levee height on energy reduction. Following the turbulence model validation and mesh convergence analysis were both satisfactory, an enormous amount of numerical simulations for overflowing levees with a moat under various hydraulic circumstances were conducted. The present discussion paper shows that when the dimensionless overflow depth is less than 0.81, the ideal dimensionless length of the moat is 1.50 and the optimal dimensionless depth is 0.35, which may fulfill energy dissipation requirements while saving construction costs. Moreover, when the dimensionless overflow depth is larger, it can be beneficial to reduce downstream energy by improving the overflow levee structure, which primarily involves steepening the upstream slope, reducing the downstream slope, increasing the levee crest length, and decreasing the levee height. However, when the dimensionless overflow depth decreases, the effect of these factors diminishes gradually. [ABSTRACT FROM AUTHOR]

Centrifugal pumps are used extensively in various everyday applications. The occurrence of corrosion phenomena during operation often leads to the failure of a pump's operating components, such as the impeller. The present research study examines the utilization of composite materials for fabricating centrifugal pump components using additive manufacturing as an effort to fabricate corrosion resistant parts. To achieve the latter two nanocomposite materials, carbon fiber reinforced polyamide and carbon fiber reinforced polyphenylene sulfide were compared with two metal alloys, cast iron and brass, which are currently used in pump impeller manufacturing. The mechanical properties of the materials are extracted by performing a series of experiments, such as uniaxial tensile tests, nanoindentation and scanning electron microscope (SEM) examination of the specimen's fracture area. Then, computational fluid dynamics (CFD) analysis is performed using various impeller designs to determine the fluid pressure exerted on the impeller's geometry during its operation. Finally, the maximum power rating of an impeller that can be made from such composites will be determined using a static finite element model (FEM). The FEM static model is developed by integrating the data collected from the experiments with the results obtained from the CFD analysis. The current research work shows that nanocomposites can potentially be used for developing impellers with rated power of up to 9.41 kW. [ABSTRACT FROM AUTHOR]

Compact spinning has emerged as a contemporary spinning technology that has garnered significant attention due to its capacity to produce yarns with excellent properties. The strategy is a variation of conventional ring spinning that seeks to get rid of the spinning triangle while improving the uniformity, strength, and hairiness of the yarn. In compact spinning, fiber condensation is achieved by negative pressure airflow, which compresses the fibers and reduces their thickness. This results in a higher packing density of the fibers, leading to stronger and more uniform yarns. In this article, we provide a comprehensive overview of compact spinning technology, covering its principle, fiber condensation method, and the types of machines used. The quality of the yarn is greatly influenced by various systems and parameters such as lattice apron, air suction slot geometry, airflow fields, and twist mechanism employed in compact spinning. We present a compendium of the various developments established in studies on compact spinning, which could serve as a platform for developing new techniques in compact spinning for the production of high-quality yarns with low economic burdens. This review discusses compact spinning, two main systems, machines, influential parameters/peripherals, disadvantages, and the future prospects of compact spinning. Additionally, we provide a summary of previous research on compact spinning, highlighting its benefits and advantages over traditional ring spinning. Furthermore, we discuss the impact of guiding devices and lattice apron type on yarn quality. We also explore the potential of three-dimensional (3D) printing technology in enhancing the performance and design of compact spinning machines. [ABSTRACT FROM AUTHOR]

Due to their thermal performance, domed roofs are one of the passive solutions that affect energy consumption in buildings. The thermal performance of domed roofs has been investigated in many naturally ventilated spaces. However, few studies have discussed their performance in conditioned spaces. Therefore, this study introduces a computational comparison between domed and flat roofs to investigate their impact on thermal comfort inside a conditioned mosque. At an earlier stage, field measurements were carried out inside a Bahraini mosque to acquire its indoor air conditions during the summer period of 2021, in addition to validating the computational model. The findings of this study confirm that, under mechanical cooling conditions, the flat roof offers a lower indoor temperature than the domed roof by 0.4 °C and 0.1 °C for open and closed doors, respectively. Similarly, the air velocity is lower by approximately 0.01 m/s for both door modes. The overall PMV values of the flat roof are also lower by 0.07 and 0.01, while the PPD values are lower by 0.20, and 0.34 for open and closed doors, respectively. Based on these small differences, it can be concluded that the thermal performance of both roofing systems behaves equally in conditioned spaces. However, the air patterns are substantially different, the overall thermal performance is similar. This similarity drives building designers to rethink the thermal performance of the domed roofs in air-conditioned spaces with such a hot climate, regardless of their aesthetic and acoustical behaviour. [ABSTRACT FROM AUTHOR]

The increase in water content during biodiesel storage poses a significant challenge that necessitates finding a solution. One proposed approach is the implementation of a thermal vacuum dewatering system for biodiesel, which effectively reduces the water content to meet the required specifications. In this study, the evaporator tank is the main component of the dewatering system. While the current water content reduction meets the standard, continuous optimization is essential to achieve a water content in biodiesel below 200 ppm. This research aims to optimize the turbulent flow within the evaporator tank by employing a pipe sparger with various hole configurations through computational fluid dynamics (CFD) simulations. Additionally, these simulations aim to enhance the understanding of biodiesel flow behavior as it passes through the orifice plate and pipe sparger, ultimately identifying the best operational conditions. The research encompasses CFD simulations of the evaporator tank using both orifice plate and pipe sparger setups. Four models were investigated: evaporator tank equipped with an orifice plate, pipe sparger A, pipe sparger B, and pipe sparger C. The simulation results indicate that the evaporator tank with pipe sparger C offers the most optimal turbulent flow, as evidenced by the velocity distribution observed at Re=5000, Re=10000, and Re=50000. Consequently, installing pipe sparger C in the evaporator tank holds promise for achieving higher water content reduction compared to the orifice plate, pipe sparger A, and pipe sparger B configurations. [ABSTRACT FROM AUTHOR]

This study aims to investigate the influence of wheel configurations on hydrodynamic resistance of an amphibious vessel through experiments and simulations. To evaluate the resistance performance associated with wheel attachments, three configurations were examined: vessel without attachments, with caterpillars, and with both caterpillars and shoe−paddles. A comprehensive series of computational fluid dynamics (CFD) simulations were conducted for these attachment types, complemented by experimental validations. The Volume-of-Fluid (VOF) model was employed in CFD simulations to capture the free surface movement, and the Dynamic Fluid–Body Interaction (DFBI) model was adopted to represent the two-degree-of-freedom motion of the vessel, specifically trim and sinkage. The total resistance derived from CFD simulations was calculated across a range of Froude numbers (Fns), including the design speed of the target vessel, and validated through model tests conducted in a wave basin equipped with a towing facility. The analysis indicated a general increase in resistance when attachments were added to the amphibious vessel. Remarkably, at the design speed (Fn = 0.27), the total resistance with both caterpillars and shoe−paddles exceeded that of the configuration without any attachments by more than 75.7%. These results provide crucial insights for the preliminary design stage of amphibious vessels, particularly those intended for marine debris collection in hard-to-reach areas. [ABSTRACT FROM AUTHOR]

When tidal turbines are deployed in water areas with significant waves, assessing the surface wave effects becomes imperative. Understanding the dynamic impact of wave–current conditions on the fluid dynamic performance of tidal turbines is crucial. This paper aims to establish a fundamental understanding of the influence of surface waves on tidal turbines. OpenFOAM, an open-source computational fluid dynamics (CFD) library platform, is utilized to predict the performance of current turbine under waves and currents. This research investigates the effects of two critical wave parameters, wave height and wavelength, on the fluid dynamics and wake structures of current turbine. Additionally, this study explores the influence of various submersion depths on turbine performance. The findings indicate that, under various wave conditions, the turbine's average power coefficient remains constant, but significant fluctuations are shown. Increasing submersion depth can mitigate the impact of waves. However, in regions characterized by longer wavelengths, altering the submersion depth has limited effects on turbine performance. [ABSTRACT FROM AUTHOR]

Understanding the erosion characteristics of different pipe materials is of paramount importance in the field of pipeline transportation due to its critical role in maintaining operational efficiency and safety. However, erosion caused by entrained particles during fluid flows poses a significant challenge to pipeline integrity. This study employs Computational Fluid Dynamics (CFD) to comprehensively analyze and compare the erosion behaviors of stainless steel XS80S and steel XS80 pipes with 90° elbows. The investigation focuses on turbulent oil and sand particle transportation conditions, enabling the prediction of erosion rate distribution and particle trajectories, particularly within the elbow region. The results highlight the superior erosion resistance of stainless steel XS80S over steel XS80 across various simulation models. The study underscores the significance of material selection in combating erosion and enhancing pipeline integrity. The XS80S pipes performed better than the XS80 Pipes. The maximum Dpm Erosion Rate Finnie model for the XS80S and XS80 pipes were 8.62 E-25 mm3 kg-1 and 9.17 E-25 mm3 kg-1, respectively; for the McLaury model they were 2.94E-24 mm3 kg-1 and 3.10E-24 mm3 kg-1, respectively; for the Oka model they were 5.68E-26 mm3 kg-1 and 6.75E-26 mm3 kg-1, respectively. The maximum Dpm Accretion Rate for the XS80S and XS80 pipes were 2.01E-17 mm3 kg-1 and 2.06E-17 mm3 kg-1, respectively. Furthermore, the investigation sheds light on the vulnerabilities of the elbow region within pipelines, providing insights into targeted design modifications and maintenance protocols. This research advances the understanding of erosion mechanisms, fluid dynamics, and material performance, offering actionable insights for pipeline industry stakeholders. The findings lay the groundwork for future research avenues and contribute to the evolution of corrosion management practices. [ABSTRACT FROM AUTHOR]

Fluid flows containing dispersed particles are abundant in both nature and industry. Simulating such flows, especially with high volumetric fractions of the dispersed solid phase, is challenging due to the complexity of solid–fluid and solid–solid interactions. In this paper, we introduce OpenHFDIB-DEM, an open-source software that couples computational fluid dynamics (CFD) with hybrid fictitious domain immersed boundary method (HFDIB) and discrete element method (DEM). The software is developed as an extension of the OpenFOAM library. The main contribution lies in a custom DEM implementation that is fully integrated in the OpenFOAM framework and allows for CFD-DEM simulations of various flows with arbitrarily shaped solids defined by triangulated surfaces in stereolithographic (STL) format.

One of the most expensive power system components is transformer. The correct use and health of the transformer increase the reliability of the power network.The transformer health is depend on careful planning for it. Therefore, hot spot temperature must be calculated for accurate transformer planning. Also, in order to increase the accuracy of transformer hot spot temperature estimation, the dynamic thermal model is used. On the other hand, the use of meta-heuristic algorithms has been less considered by researchers to calculate the transformer hot spot temperature. Thus, in this paper, the grey wolf, imperialist competitive and artificial bee colony algorithms are used to estimate the transformer hot spot temperature. Besides, electromagnetic analysis of the transformer is investigated using ANSYS-MAXWEL software. On the other hand, conjugate heat transfer modeling in the transformer is presented to compare the results with the grey wolf optimization algorithm. The results show that the grey wolf optimization algorithm can be a good alternative for transformer hot spot temperature estimation.

Indoor air quality (IAQ) in confined spaces like bank vaults and basements is influenced by complex factors such as building layout and HVAC systems. This study examines how mechanical ventilation impacts IAQ in a bank building's occupied basement vault, addressing significant challenges posed by pollutant exposure in these air-tight environments. This study advances safe IAQ in confined spaces, crucial for occupant health and safety, using CFD (ANSYS Fluent Workbench 16.0) and CONTAM 3.2 software for multi-zone ventilation and air quality analysis. It analysed three indoor pollutants: Radon (Rn), Carbon dioxide (CO2), and Particulate Matter (PM2.5), enhancing the reliability and applicability of the findings. The findings indicated that the simulated indoor pollutants concentrations did not exceed the indoor air quality guideline levels. The CFD simulations predicted average steady-state values of 27.2 Bq/m3 for Radon, 574.80 ppm for CO2, and 69.36 µg/m3 for PM2.5 in the basement. For different outdoor air floor rates, an optimal ventilation rate of 4.7 ACH and a cooling load of 17 kW were determined to maintain Radon concentrations below 15 Bq/m3. This provides a practical and actionable solution for maintaining safe IAQ in confined spaces, which is a significant step forward compared to similar studies. These results align with other experimental research, validating the use of numerical techniques in indoor air quality studies. By optimizing HVAC systems to maintain IAQ and minimize energy consumption, the study supports SDG 7 (Affordable and Clean Energy) by enhancing energy efficiency, SDG 3 (Good Health and Well-being) by reducing exposure to indoor pollutants, and SDG 11 (Sustainable Cities and Communities) by improving air quality management in confined spaces. The findings are particularly relevant for Africa, offering practical solutions, informing policy direction, and supporting the African Union's Agenda 2063 and SDGs 3, 7, and 11.

Boiling flow presents a significant concern, especially when a liquid surpasses its boiling point, potentially leading to catastrophic consequences. This research utilizes a two-phase code in the OpenFOAM software to investigate bubble formation during flow boiling. The well-established empirical models for calculating wall heat components were selected based on the operating conditions. The study incorporates experimental data from high-pressure boiling flow (10–30 bars) with variable properties of refrigerant R-12. The predictions reveal underpredictions in void fraction and liquid temperature compared to experimental observations. Significantly, the impact of the subcooling degree on void fraction behaviour is emphasized, and a potential underprediction of the evaporation portion is highlighted, particularly near the wall. Challenges in modelling bubble size distribution are evident through discrepancies in bubble diameter and velocity data, indicating the necessity for further advancements in the code. In summary, this numerical study provides valuable insights into the intricate dynamics of high-pressure subcooled boiling flow, especially when considering variable working fluid properties. Future efforts will focus on refining models for nucleation site density, bubble departure size, and lift-off frequency to enhance prediction accuracy.

Abstract Objective To review the existing literature on the application of computational fluid dynamics methods to study nasal particle deposition and to summarize and analyze the factors affecting nasal particle deposition in order to provide theoretical references for the development of future transnasal drug delivery devices and the prevention of respiratory‐related diseases. Data Source PubMed and CNKI databases. Methods A search of all current literature (up to and including February 2023) was conducted. Search terms related to the topic of factors influencing nasal particle deposition were identified, and queries were conducted to identify relevant articles. Results Both the properties of the particles themselves and the environmental conditions external to the particles can affect particle deposition in the nasal cavity, with particle deposition showing a positive correlation with particle size, particle density, and airflow velocity, with increasing subject age leading to a decrease in deposition, and with the relationship between airflow temperature and humidity still requiring more research to further explore. Conclusions With the popularity of computational fluid dynamics, more and more scholars have applied computational fluid dynamics technology to explore the influence of different parameters on particle deposition. By summarizing and analyzing the influence law of various factors on deposition, it can provide a theoretical basis for the future development and application of transnasal drug delivery devices and the prevention of respiratory‐related diseases, which makes a significant contribution to the optimization of clinical disease prevention and treatment. Level of Evidence NA.

ObjectiveTo characterize the gas production phenomenon in the animal model of left ventricular assist device (LVAD), and study its mechanism.MethodsAn in vitro bubble precipitation experiment was conducted, and the blood samples of Parma spp. animals were divided into ordinary group and oxygen-enriched group according to whether they were oxygenated or not at the time of blood collection, and a static control group was set up respectively. Blood gases were drawn and analyzed before and after the experiment. Activate the pump, and the number of air bubbles in the loop was measured by ultrasound at different rotational speeds; CFD was applied to simulate the flow field in the blood pump, and pressure, fluid velocity vector and shear force diagrams were plotted, and a thrombus model was constructed and the flow field was simulated and plotted as a cloud diagram.ResultsThere was a statistical difference in the number of bubbles in the inflow and outflow tubes of the blood pump (P values of 0.04 and 0.023, respectively), and the number of bubbles in the outflow tubes of both groups was significantly higher than the number of bubbles in the inflow tubes. The number of bubbles in the tubes of both the oxygen-enriched and normal groups was significantly higher than that in the inflow group. In both the normal and oxygen-enriched groups, more gas was produced at higher speeds than at lower speeds. Blood gas analysis showed that the reduced gas composition in the blood was mainly oxygen. Flow field simulation results: the high rotation speed group had lower central pressure and greater scalar shear. The thrombus simulation group was more prone to turbulence, sudden pressure changes, and greater shear than the normal group.ConclusionBlood gas production is associated with higher partial pressures of blood oxygen, higher rotation speed, and intrapump thrombosis, and the mechanism of pump gas production is degassing of dissolved gases rather than cavitation of water, and the gas released is most likely to have oxygen. The degassing phenomenon is an warning factor for pump thrombosis.