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Achieving high fluidization quality and bed stability is a paramount challenge in pulsed fluidized beds. 2D hydrodynamics models were studied using the Eulerian-Eulerian method with KTGF. This study investigates the impact of rectangular pulsation superimposed on steady airflow, while maintaining a constant temporal average gas velocity, on fluidization quality. Numerical results indicated that superimposing pulsations on steady airflow and increasing the steady airflow velocity to three times the minimum fluidization velocity resulted in a decrease in the bed expansion ratio. This decrease was most notable particularly at a pulsation frequency of 0.05Hz, with a reducing of approximately by about 21%. By decreasing the velocity ratio from 9.52 to 6.52, the pressure drop increased by 27% and 4.5% at 0.05 Hz and 10 Hz, respectively. Additionally, the fluidization index increased by 32% and 2% under these conditions. The optimal range of pulsed airflow velocity fell between 2.76 and 1.17 times the steady airflow velocity and was most effective at 0.05 – 0.1 Hz. [ABSTRACT FROM AUTHOR]

To accurately predict the film thickness distribution during dynamic spraying performed with air guns and support accordingly the development of intelligent spray painting, the spray problem was analyzed numerically. In particular, the Eulerian-Eulerian approach was employed to calculate the paint atomization and film deposition process. Different spray heights, spray angles, spray gun movement speeds, spray trajectory curvature radii, and air pressure values were considered. Numerical simulation results indicate that the angle of spray painting significantly affects the velocity of droplets near the spray surface. With an increase in the spraying angle, spraying height and spray gun movement speed, the maximum film thickness decreases to varying degrees, and the uniformity of the film thickness also continuously worsens. When the spray gun moves along an arc trajectory, at smaller arc radii, the film thickness on the inside of the arc is slightly greater than that on the outside, but the impact on the maximum film thickness is minimal. Increasing air pressure expands the coating coverage area, results in finer atomization of paint droplets, and leads to a thinner and a more uniform paint film. However, if the pressure is too high, it can cause paint splattering. Using the orthogonal experimental method, multiple sets of simulation calculations were conducted, and the combined effects of spraying height, spray angle, and spray gun movement speed on the film thickness distribution were comprehensively analyzed to determine optimal configurations. Finally, the reliability of the numerical simulations was validated through dynamic spray painting experiments. [ABSTRACT FROM AUTHOR]

Improving the overall energy efficiency of thermodynamic cycles relies heavily on the replacement of traditional pure fluids with zeotropic mixtures. The selection of the optimal components within the zeotropic mixture depends on the specific operating conditions of the thermodynamic cycle. Therefore, significant enhancements in performance can be achieved across varying operating conditions by effectively controlling the composition of zeotropic mixtures in the cycle. According to the gas-liquid equilibrium characteristics of the zeotropic mixtures, the adjustment of the medium components and the boundary conditions can be realized if the components can be adjusted through the gas-liquid separation. In this study, a novel device is proposed for automatically regulating the speed of gas-liquid separation in order to separate the components of the zeotropic mixtures. The CFD simulation was utilized to analyze the structural parameters and boundary conditions that impact the efficiency of gas-liquid separation. The results indicate that the adjustable mass flow range of the optimal structure is broadened by 5.5 times compared to conventional gas-liquid separation devices, ranging from 0 kg/s to 0.15 kg/s. Additionally, within this range, the gas-liquid separation efficiency exceeds 95%, representing a 10% improvement over traditional phase separators. [ABSTRACT FROM AUTHOR]

The two‐fluid model–kinetic theory of granular flow (TFM–KTGF) model and the sub‐grid‐scale (SGS) model are used to conduct a three‐dimensional numerical simulation study on the hydrodynamic characteristics of a two‐stage fluidized bed with an integrated overflow pipe. Using various drag models, the gas–solid flows, bed expansions, pressure drop distributions, and equilibrium conditions in the two‐stage bed are compared, and the conditions for the formation of a stable overflow in the two‐stage bed are thoroughly investigated. In addition, during the simulation of the secondary distribution in the bed, the porous media model simulates the momentum loss caused by the redistribution plate to avoid the direct simulation of the redistribution plate, which requires extensive grid division work and calculation costs. This work can provide technical direction for the industrialization of one‐step coal to multistage fluidized bed natural gas technology. [ABSTRACT FROM AUTHOR]

A detailed computational investigation was conducted to explore the dynamics of high-speed free slurry jets, with a focus on how variations in abrasive size and concentration affect their behavior. The study yielded several significant observations: Firstly, it was observed that slurry jets containing larger particles exhibited notably higher average velocities, attributed to their inherent self-similar characteristics. Specifically, at the far field of the jet, slurry jets with larger particle sizes demonstrated a 15% increase in velocity compared to those with smaller particles. Additionally, an analysis of turbulent intensity revealed that beyond a certain axial distance (x/D = 10), turbulence levels progressively increased. However, intriguingly, for slurry jets with a high concentration (Co = 15%), there was a notable decrease (28%) in turbulent intensity compared to water jets, indicating a complex interplay between particle size and concentration. Secondly, the study found that as the concentration of particles in the slurry jet increased, there was a corresponding rise in the bulk temperature of the jet. This phenomenon was primarily attributed to the heightened thermal conductivity resulting from the increased density of particles in the water. Furthermore, an examination of the Nusselt number revealed interesting trends. While the Nusselt number exhibited a peak near the nozzle exit, indicative of enhanced heat transfer in this region, it showed a decremental trend along the axial direction of the jet, attributable to jet divergence. In summary, the computational analysis provided valuable insights into the behavior of high-speed slurry jets, highlighting the intricate relationships between abrasive size, concentration, velocity distribution, and thermal characteristics. These findings contribute to a deeper understanding of slurry jet dynamics and have significant implications for various industrial applications. [ABSTRACT FROM AUTHOR]

Severely cold weather reduces the willingness of residents to open windows while cooking. This results in an insufficient replenishment of makeup air and a reduction in the range hood discharge capacity. For an effective trade-off between indoor air temperature maintenance and air quality aggravation in winter, a new makeup air supply method (ceiling makeup air) was proposed and established both experimentally and numerically. The improvements in the kitchen air environment during cooking were studied through experimental tests and CFD simulations, considering different makeup air arrangements. The results reveal that the ceiling makeup air scheme can significantly reduce the concentration of PM2.5 compared with the cracks makeup air scheme (wherein the kitchen window and door are closed). Moreover, it increased the indoor temperature by over 11.9 °C compared with the open window makeup air scheme. The average relative error between the experimental and simulated data was within 6.1%. Among the considered factors, the size of the air inlet had the largest impact. This was followed by the layout, size, and shape of the ceiling inlets. The ceiling makeup air scheme demonstrated the potential for improving residential kitchen air environments in severely cold regions. [ABSTRACT FROM AUTHOR]

When loading liquefied natural gas (LNG) onto a dual-fuel LNG container ship fuelled by LNG, there is a considerable temperature difference between LNG and the fuel tank at room temperature. The current solution is to pre-cool the tank with LNG through a spray line but the cooling process, if not correctly handled, can result in excessive cooling rates and Boil-Off Gas (BOG), which can expose the tank to increased temperature stress and gas pressure. Therefore, this paper takes the Mark III fuel tank of a specific type of LNG container ship as the object and realises a real-time predictive control system by writing a UDF (User Defined Function) to simulate and analyse the influence of LNG spray rate on the change of cooling effect, cooling time and cooling cost under the unidirectional LNG spray cooling mode. Compared with the results of the fuel tank gas experiment, the deviation of numerical model simulation results is less than 5%. Under the same cooling rate, the real-time control scheme can achieve a more uniform cooling rate and reduce the total LNG consumption by 25%. With the increase in LNG cooling rate, the cooling time, LNG usage, and the total BOG exhaust volume all decrease; however, the decreased range gradually decreases as well. The results of this paper provide parameters and suggestions for optimising and improving the LNG fuel tank cooling monitoring and control system. [ABSTRACT FROM AUTHOR]

With the ability to manufacture complex functional structures, Additive Manufacturing (AM) enables new advanced applications which could not be realized before. An example of such structures is open porous structures. In the presented approach, the open porous structures are a result of the selected manufacturing parameters, instead of being defined in CAD models. Thereby, various porosities can be achieved flexibly without design adjustments. However, to comprehensively understand the correlation of manufacturing parameters and different properties, various tests are required. As an alternative, properties can be determined by means of simulation. This study presents 3D reconstructions of complex open porous structures, which are based on μ-CT imaging. The influence of the downsampling during voxelization on the 3D reconstructed geometry is studied. Further, different polyhedral mesh settings have been tested in order to find a mesh that minimizes the deviation between the CFD simulation results and the laboratory test results for flow resistance. A guideline for the creation of a calibrated CFD model based on μ-CT imaging is proposed. As it is acknowledged by the authors that the data availability to reconstruct shown cases is crucial, data for a reference case have been made freely available online. [ABSTRACT FROM AUTHOR]

Refractory materials are used worldwide in process equipment. However, gaseous and liquid process products penetrate the surface layer and deep into the volume of refractories, destroying rather expensive constructions that are complicated to repair. To address this challenge, there is a need to develop protective coatings for refractory materials that can limit the penetration of working media and extend their operational lifespan. In this work, the application of gas-dynamic cold spraying (CGDS) to produce a coating on the refractory materials using fine titanium dioxide (TiO2) particles is explored. These particles are accelerated within a nitrogen flow, passing through a Laval nozzle, and then sprayed onto a fireclay surface. The mechanisms of particle deposition and layer formation on porous surfaces through experiments and numerical simulations were investigated. The geometry of a typical refractory pore was determined, which was then incorporated into computational fluid dynamics (CFD) simulations to model the cold spraying process of porous substrates. As a result, the influence of the particle size on its velocity and angle of penetration into pores was established. Experimental findings demonstrate the effective closure of pores and the formation of a particle layer on the refractory surface. Furthermore, the nanoindentation tests for the refractory samples showcase capabilities for checking coating thickness for porous materials. [ABSTRACT FROM AUTHOR]

In the context of increasing global energy shortages and climate change, the human living environment, as a crucial component of residents' daily lives, has garnered growing attention from the academic community. Research on residential environments is vital for promoting the sustainable development of urban construction and constitutes an important aspect of sustainable development studies. This study focuses on the optimization strategy for the outdoor activity space wind environment in the Xihuayuan residential area in Lanzhou city, utilizing spatial syntax analysis and Computational Fluid Dynamics (CFD) simulation technology. Firstly, the outdoor activity space is analyzed for visibility and spatial accessibility using DepthmapX0.6 software. Then, the outdoor wind environment in the residential area is simulated using PHOENICS 2018 software, and the analysis is conducted on outdoor spaces with a poor wind environment in terms of high accessibility. The results indicate that residents' outdoor comfort in these spaces is poor, highlighting the urgent need for improvement in the wind environment. This research attempts to optimize the wind environment in high-accessibility spaces within the residential area by improving building layout, orientation, and height. The simulation results after optimization demonstrate an increase in the overall average wind speed to 1.44 m/s, with the proportion of spaces with a good wind environment in high-accessibility areas during summer rising from 33.4% to 59.2%. The optimization strategy effectively improves the wind environment in high-accessibility areas of the residential area. [ABSTRACT FROM AUTHOR]

The performance of continuous feeding fluidized bed reactors is significantly influenced by their design. These reactors can effectively operate with a wide range of biomass mixtures. Therefore, it is imperative to carefully design the gas distributor plate and solid tube inlet to ensure stable fluidization and uniform distribution of fluidizing gas and solid particles within the reactor. This study investigated the impact of gas–solid feeder design in bubbling fluidized bed gasifier for biomass mixtures on system hydrodynamics, employing a computational fluid dynamics–artificial neural network (CFD‐ANN) coupling model to achieve more realistic simulations. A 2k factorial experimental design was adopted to inquire the impact of gas and solid feeding systems. The responses under investigation included the gas–solid mixing index and the solid residence time, both of which hold pivotal roles in specific chemical processes related to biomass utilization in fluidized bed technology. All cases were successfully simulated, and the results uncovered that the position and length of the solid inlet tube wielded a significant influence on reactor performance, particularly concerning solid residence time. Furthermore, the designs of the gas distributor were identified as critical factors capable of enhancing system turbulence and mixing. In summary, the results showed the potential for enhancing reactor performance through the optimization of gas–solid feeding systems and underscored the efficacy of the ANN drag model in simulating continuous biomass gasification systems. [ABSTRACT FROM AUTHOR]

Summary: As one of major construction facilities, the safety concern about elevator outer‐attached to slender high‐rise buildings during construction needs to be seriously addressed. To specifically identify the risk of such slender building–elevator systems in extreme tornado wind field, a safety assessment strategy using the critical velocity envelope is systematically developed. To overcome the difficulties in modeling such building–elevator system, a modified generalized flexural‐shear model developed previously was employed to reach an efficient estimate on the response of a case high‐rise building under simulated tornado wind excitations. To account for the effect of the flexibility of high‐rise building on the response of its attached construction elevator, the response of the elevator was obtained by finite element analysis with applied wind forces, as well as the displacement excitations at its supports with the building. To simulate the typical failure modes of elevator in all states, some critical reference velocity‐based envelopes were generated for the safety assessment where the factors of wind velocity, wind direction, and cage level are systematically addressed. The safety envelopes of the building–elevator system were proved to be instinctively efficient for the assessment of its wind resistance under various scenarios. [ABSTRACT FROM AUTHOR]

A solid oxide fuel cell (SOFC) is a clean and very efficient electrochemical conversion device, which generates electricity directly from fuel electrochemical oxidation. In this paper, a three dimensional numerical model has been developed in order to analyse the role of some thermophysical and morphological parameters on the performance of the SOFC cell. In particular, we studied the effect of the variation of permeability of the electrodes: fuel distribution, ionic and electric current density, pressure and diffusion flux are analyzed and compared. The volume fraction of the ionic and electronic phase in the electrodes is studied using a parametric study. It was shown that the current density enhanced by decreasing the permeability, up to a defined value, and it diminished with very small permeability. A remarkable influence of pressure and diffusion of species on the performance of the cell, with the variation of permeability, has been recognized. Varying the permeability in the active layer of electrodes has a large impact on the current density, connected to the volume fraction of ionic phase. This study permits to comprehend the relationship between the performance and microstructure of SOFCs. Meanwhile, it furnishes theoretical guidance for an optimum design of the electrode permeability. • A three-dimensional model of a single SOFC is developed using CFD method. • Varying the permeability of electrode components affects the cell performance. • The impact of volume fractions for different permeabilities is studied. • It is concluded that there is an optimum design of the electrode permeability. [ABSTRACT FROM AUTHOR]

Water scarcity is a global challenge, underscoring the importance of efficient water resource management. Solar stills offer a cost-effective method to convert brackish water into potable water but face productivity limitations. This study aims to enhance solar still productivity through modifications using different fin materials and water depth. Computational Fluid Dynamics (CFD) simulations were employed to evaluate thermal performance across four scenarios: copper and aluminum fins at water depths of 20 mm and 40 mm. Key parameters including temperature distributions, friction volume, and fluid velocity were analyzed for each configuration (MSS-I to MSS-IV). Energy and exergy efficiencies were also assessed. MSS-III, utilizing copper fins at a 20 mm depth, demonstrated the highest daily productivity (8.33 liters) compared to MSS-IV (8.02 liters), MSS-I (7.81 liters), and MSS-II (6.71 liters). Energy efficiencies were highest for MSS-III (60.10%), followed by MSS-IV (57.41%), MSS-I (55.22%), and MSS-II (52.18%). MSS-III also exhibited the highest exergy efficiency (21.50%), with MSS-I (17.15%), MSS-IV (16.43%), and MSS-II (14.12%) following. The study underscores significant improvements in thermal and energy efficiency achieved through specific design modifications of solar stills. MSS-III's higher performance, attributed to the use of copper fins and optimized depth, highlights the critical role of material selection and structural design in enhancing solar still productivity. These findings have important implications for sustainable water resource management, emphasizing the potential of optimized solar still designs to address water scarcity challenges. [ABSTRACT FROM AUTHOR]

The probe chuck is an inspection device assessing the thermal durability of semiconductor wafers in various temperature environments before shipping. It is most important to ensure that the temperature of the chuck upper surface, on which the wafers are placed, is uniform. This study presents an axisymmetric chuck model to improve surface temperature uniformity in both radial and circumferential directions. The local distribution of the flow path height in the axisymmetric chuck was adjusted to make the chuck upper surface with a constant wall heat flux to simultaneously become as uniform temperature as possible. Three optimization algorithms, namely the genetic algorithm (GA), deep q-network (DQN), and actor-critic (AC) were applied. The optimized shape of the flow pathway, improved temperature uniformity, pressure drop, and local heat transfer coefficient profile by three different optimization algorithms are presented in detail. As a result, the surface temperature difference was significantly reduced from 7.137 K in the existing spiral model to 0.682 K. The optimal axisymmetric chuck could reduce surface temperature differences up to 90 % compared with the conventional spiral chuck. [ABSTRACT FROM AUTHOR]

The influence of the forced convection rate on the chemical structure of a polymethyl methacrylate (PMMA) flame in an oxidizer flow under microgravity conditions was studied using numerical modeling. Gas flow around a solid sphere was simulated using the full Navier–Stokes equations for a multicomponent mixture. A multistep chemical kinetic mechanism was considered in the gas phase. The heat transfer and radiation in both the condensed and gas phases were considered in the modeling. On the PMMA surface, the pyrolysis reaction leading to the transformation of fuel from the condensed phase to the gas phase is specified. The forced convection speed varied in the range from 3 to 20 cm/s. Analysis of CO2 concentration fields near the burning surface under microgravity conditions showed that the maximum CO2 concentration is observed in the downstream zone. The width of the flame zone and its chemical structure depend on the intensity of forced convection. The width of the flame against the flow decreases, and the maximum CO concentration increases as the forced convection rate increases. Analysis of the rates of fuel consumption reactions showed that at a low convection speed (vst=3 cm/s), the reaction with the H radical, which has the highest diffusion coefficient, plays a crucial role in MMA oxidation. [ABSTRACT FROM AUTHOR]

Accurate measurement of heterogeneous reaction kinetics in thermogravimetric analysis (TGA) requires accurate estimation of concentration and temperature in the sample. However, this information is difficult to estimate during the measurement, especially at high temperatures and pressures. Computational Fluid Dynamics (CFD) is used to perform a comprehensive analysis of the temperature and species distribution throughout a high‐temperature, high‐pressure test rig, including temperature and species transport within the probe sample. The temperature and gas concentration within the sample are accurately calculated by CFD, providing a much deeper insight into the local temperature and species distribution. The numerical results show a significant decrease in gas concentration and temperature in the core region of the packed bed, indicating that bed diffusion dominates the overall conversion for the char reaction studied in this article. The re‐evaluation based on the model considers the limitations of heat and mass transfer at each measurement point. This forms the basis for a novel, model‐driven approach that derives heterogeneous kinetics from TGA measurements with significantly improved accuracy and reliability. [ABSTRACT FROM AUTHOR]

Abstract A detailed computational investigation was conducted to explore the dynamics of high-speed free slurry jets, with a focus on how variations in abrasive size and concentration affect their behavior. The study yielded several significant observations: Firstly, it was observed that slurry jets containing larger particles exhibited notably higher average velocities, attributed to their inherent self-similar characteristics. Specifically, at the far field of the jet, slurry jets with larger particle sizes demonstrated a 15% increase in velocity compared to those with smaller particles. Additionally, an analysis of turbulent intensity revealed that beyond a certain axial distance (x/D = 10), turbulence levels progressively increased. However, intriguingly, for slurry jets with a high concentration (Co = 15%), there was a notable decrease (28%) in turbulent intensity compared to water jets, indicating a complex interplay between particle size and concentration. Secondly, the study found that as the concentration of particles in the slurry jet increased, there was a corresponding rise in the bulk temperature of the jet. This phenomenon was primarily attributed to the heightened thermal conductivity resulting from the increased density of particles in the water. Furthermore, an examination of the Nusselt number revealed interesting trends. While the Nusselt number exhibited a peak near the nozzle exit, indicative of enhanced heat transfer in this region, it showed a decremental trend along the axial direction of the jet, attributable to jet divergence. In summary, the computational analysis provided valuable insights into the behavior of high-speed slurry jets, highlighting the intricate relationships between abrasive size, concentration, velocity distribution, and thermal characteristics. These findings contribute to a deeper understanding of slurry jet dynamics and have significant implications for various industrial applications.

The erosion-corrosion mechanism in rotary flowing seawater is hugely complicated due to the multiscale coupling processes of particle-surface impact, ion mass transfer, and interface electrochemistry. Therefore, developing erosion-corrosion resistant material and exploring the synergistic mechanism between sand erosion and electrochemical corrosion is vital. This study conducted the erosion-corrosion test on Ni2FeCrMo0.2 high-entropy alloy under the particle-seawater flow. Based on a coupled analysis of multi-component weight loss, electrochemical behavior, and microscopic damage morphology, the multiscale coupling processes of sand transportation, particle-surface impact, ion mass transfer, and interface electrochemistry were revealed. The present study found that with the increase of sand size, the energy carried by the particles promoted impact erosion. Additionally, particle movement enhanced ion mass transfer through turbulent effects, and the impact behavior disrupted the passivation film to promote electrochemical processes by reducing the thickness of the passivation film, leading to an increase in the erosion-corrosion rate. However, when the particle size continued to increase to a certain extent, the impact frequency decreased, reducing the erosion-corrosion rate. As the sand size grew, the dominant damage mechanism transitioned from pure corrosion (100 μm) to synergistic effects (200 μm, 400 μm) and then to pure erosion (800 μm). This study provides an in-depth understanding of the erosion-corrosion mechanism in seawater from the perspective of particle-ion-fluid-surface interaction by multi-element characterization.

Nowadays, there is an increasing demand for buildings that offer ideal ventilation and thermal conditions, particularly in hot-arid regions. Courtyards emerge as pivotal elements facilitating enhanced airflow and utilizing natural energy, resulting in reducing energy consumption in addition to controlling the pressure created by the wind. In response to the motivation of optimizing building performance in the face of harsh environmental challenges, our study aims to investigate how different courtyard orientations affect airflow patterns and ventilation performance in an educational building model located in Cairo and Delta region. The building, designed for the Pre-university education phase by the General Authority for Educational Buildings (GAEB), as a free-running building. Using a Computational Fluid Dynamics (CFD) simulations through ANSYS-Fluent software, we performed a parametric analysis testing four different orientations (0°, 15°, 30°, and 45°) in the northwest direction to identify the optimal orientation for enhancing ventilation performance. The results consistently indicated that the 0° scenario yielded the best results, followed notably by the 15° scenario which outperformed others by demonstrating superior airflow patterns and pressure differences conducive to enhanced ventilation rates. The 45° scenario was identified as the least favorable result among the four scenarios. These findings provide valuable methodological insights for architects and policymakers seeking to optimize natural ventilation strategies within Egypt's climates.

Abstract The implementation of the Gob-Side Entry Retaining Mining Mode with Roof Cutting and Pressure Relief (GERRCPR) results in the gob connecting to the retaining roadway, creating an open space that causes significant air leakage and increases the risk of spontaneous combustion. A study was conducted during the implementation of the GERRCPR in the Xiaonan Coal Mine N1-1502 working face to investigate spontaneous combustion characteristics, along with fire prevention and extinguishing measures. To analyze gob airflow, Computational Fluid Dynamics (CFD) was employed to collect data on airflow conditions, O2 concentration, and temperature. Based on this, this study focuses on exploring the effects of nitrogen injection treatment under various rates and positions to optimize parameters for buried pipe nitrogen injection. Results indicated that within the GERRCPR, air leakage in the gob increased, leading to an increase in O2 concentration, expansion of the oxidation zone, and an elevated risk of spontaneous combustion. Air leakage primarily occurred from the retaining roadway and the working face near the intake-air roadway, peaking at a retaining roadway length of 500 m, with a flow rate of 226 m3/min. Following nitrogen injection treatment, the oxidation zone was significantly reduced, with optimal treatment achieved at a nitrogen injection depth of 70 m and a rate of 600 m3/h. Field monitoring data showed that the inertization measure of using porous long pipes, a nitrogen injection spacing of 30 m, and a nitrogen injection rate of 600 m3/h significantly decreased the O2 concentration within the gob. This reduction meets safety production requirements and outperforms the effectiveness of traditional buried-pipe nitrogen injection methods, thereby validating the simulation accuracy. Understanding the laws governing spontaneous coal combustion in the GERRCPR and enacting preventive measures for nitrogen injection can improve safety standards in mining operations. This proactive approach can effectively prevent spontaneous coal combustion accidents, resulting in substantial social benefits.

Wind tunnel tests or computational fluid dynamics (CFD) simulations of the aeroelastic model of a bridge deck section are currently used to make sure that significant vortex-induced vibration (VIV) of a long-span bridge will not occur after the bridge is put into operation. However, significant VIV still occurred in several long-span bridges in operation, indicating that the currently used wind tunnel tests and CFD simulations have some drawbacks or uncertainties. This study aims at establishing a digital twin by interacting CFD simulation with wind tunnel test for accurately and efficiently predicting the VIV response of a bridge deck. The measurement information of VIV of the deck section is collected from the wind tunnel test and fused with the CFD simulation. The optimisation for reducing uncertainties existing in wind tunnel test and CFD simulation is then carried out to make the CFD simulation as a digital twin. The digital twin is finally used to investigate the blockage effect of wind tunnel test and give an accurate and efficient prediction of VIV of the bridge deck. The flat closed-box steel deck section used in the Xiangshan Harbor cable-stayed bridge is selected as a case study. The results from the case study show that the digital twin can be established and used for an accurate and efficient prediction of VIV of the bridge deck section. [ABSTRACT FROM AUTHOR]

Hydrodynamic separators are commonly used to control the total suspended solid concentration in stormwater before being discharged to natural water bodies. The separator studied in this paper, featuring a swirling flow generated by tangential inlet and outlet connections, was analyzed for its sediment removal efficiency in relation to sediment and flow rates. For the separator studied in this paper, the numerical model showed that the flow field was favorable for the sediments to gather at the center and settle. A higher flow rate or a smaller sediment diameter corresponded to a lower removal rate and vice versa. The dimension improvement for increasing the sediment removal rate was also studied. It was found that increasing the diameter of the separator showed a higher sediment removal rate compared with corresponding increase in the height of the separator. A dimensionless parameter J was proposed to assess the sediment removal rate of a separator, which may be used for designing and optimizing such a device. The removal rate is positively correlated with the J value. When the J value reaches 0.5 or above, the sediment removal rate exceeds 80%, which is a good initial target value for designing this type of separator. HIGHLIGHTS Provided an experimentally validated computational fluid dynamics model.; Changing the diameter has a greater impact on the removal rate of hydrodynamic separators than changing the height.; The J value can be used to evaluate the solids removal efficiency of a hydrodynamic separator.;

Achieving high fluidization quality and bed stability is a paramount challenge in pulsed fluidized beds. 2D hydrodynamics models were studied using the Eulerian-Eulerian method with KTGF. This study investigates the impact of rectangular pulsation superimposed on steady airflow, while maintaining a constant temporal average gas velocity, on fluidization quality. Numerical results indicated that superimposing pulsations on steady airflow and increasing the steady airflow velocity to three times the minimum fluidization velocity resulted in a decrease in the bed expansion ratio. This decrease was most notable particularly at a pulsation frequency of 0.05Hz, with a reducing of approximately by about 21%. By decreasing the velocity ratio from 9.52 to 6.52, the pressure drop increased by 27% and 4.5% at 0.05 Hz and 10 Hz, respectively. Additionally, the fluidization index increased by 32% and 2% under these conditions. The optimal range of pulsed airflow velocity fell between 2.76 and 1.17 times the steady airflow velocity and was most effective at 0.05 – 0.1 Hz.

Underground coal gasification (UCG) as an alternative coal mining technology is attracting much attention. However, due to the high experimental cost of UCG, the evolution mechanism of coal seam should be deeply explored prior to the implement of experiments. By virtue of the great computational power of computers, the computational fluid dynamics (CFD) is able to simulate the production process of UCG at a relatively lower cost. The in-situ ignition and combustion of deep coal seam heated by 1 000 K flue gas is simulated and the changes of temperature, molar O2 fraction and porosity are analyzed by the CFD software, Fluent, developed by Ansys cor-poration. It is elucidated that pumping 1 000 K flue gas for 500 s is inadequate for coal seam ignition, while 1 000 s heating has been enough for coal seam ignition. On the internal surface of coal seam, the high temperature is accumulated in the 0−0.6 m coal seam near inlet. The maximum temperature before ignition is below inlet temperature of heating flue gas, 1 000 K, while the maximum temperature after ignition exceeds 1 000 K and reaches up to 1 250 K. Almost all O2 is consumed in the high-temperature zone, while less than 2% molar O2 fraction arrives at the internal surface of coal seam in other lower-temperature zones. The porosity rapidly increases in high-temperature zone and at 1000 s the porosity in the part of coal seam reaches up to 0.9. In the interior of coal seam, the thicker the coal seam is, the lower the temperature rises. The maximum temperature on 7 cm line is only 500 K at 1 000 s and 2 000 s, much lower than that on the internal surface of coal seam when it is heated for the same time. During 2 000 s ignition, little O2 penetrates 7 cm and 14 cm coal seam and the porosities of interior coal seam are all below 0.4. The low porosities are attributed to the low temperature and low molar O2 fraction. The simulation on temperature, molar O2 fraction and porosity may provide a reference for how to promote the reaction in the interior of coal seam.

Wire electrical discharge machining (WEDM) is a non-conventional machining process renowned for precision in machining complex profiles, especially in high-strength and hard materials. This process also found other functions in machining cylindrical workpieces, known as wire electrical discharge turning (WEDT). The material removal mechanism of this process is based on electrical discharges, and evaluating the productivity of the continuous process to a great extent depends on the material removal of individual single discharges. In order to study the influence of rotational speed in material removal of erosion in cylindrical workpieces, theoretical and experimental studies of each single spark are necessary. This comprehensive study delves into the influence of rotational speed in WEDM processes applied to cylindrical workpieces. The research includes a series of single discharge experiments, and introduces a computational fluid dynamics (CFD) thermal model. The developed thermal model demonstrates the capability to predict the material removal rate of a single discharge with an error of 8.6% relative to experimental data. Furthermore, the investigation extends to continuous erosion studies, analyzing the material removal rate under varying rotational speeds. The overall material removal rate decreases 13% due to the declining material removal rate of each single discharge. Additionally, a removal efficiency parameter of erosion of cylindrical workpieces is introduced to provide an evaluation of the process and the influence of crater overlaps. The removal efficiency for various rotational speeds ranges between 22 and 24%, influenced by the proportion of normal discharges and the efficiency of crater overlaps. [ABSTRACT FROM AUTHOR]

The field of nitric oxide (NOx) production combined with turbulent flow is a complex issue of combustion, especially for the different time scales of reactions and flow in numerical simulations. Around this, a series of approach methods, including the empirical formula approach, the computational fluid dynamics (CFD) approach coupling with an infinite rate chemical reaction, the chemical reaction networks (CRNs), and the CFD approach coupling with CRNs, were classified, and we discussed its advantages and applicability. The empirical-formula approach can provide an average range of NOx concentration, and this method can be involved only in special scenarios. However, its simplicity and feasibility still promote practical use, and it is still widely applied in engineering. Moreover, with the help of artificial intelligence, this method was improved in regard to its accuracy. The CFD approach could describe the flow field comprehensively. In compliance with considering NOx formation as finite-rate chemical reactions, the NOx concentration distribution via simulation cannot match well with experimental results due to the restriction caused by the simplification of the combustion reaction. Considering NOx formation as a finite-rate chemical reaction, the CRNs approach was involved in CFD simulation, and the CRNs approach could forecast the NOx concentration distribution in the flow field. This article mainly focuses on the simulation method of nitric oxide (NOx) production in different combustion conditions. This review could help readers understand the details of the NOx formation mechanism and NOx formation prediction approach. [ABSTRACT FROM AUTHOR]

As an essential part of hydrogen removal system in nuclear power plants, PARs could effectively eliminate released hydrogen and prevent potential hydrogen combustion during severe accidents. Serving as a basic composition in the catalytic section of PARs, catalytic element has a direct influence on the hydrogen removal capability of the PAR device. The CFD software STAR-CCM+ was utilized to develop models of catalytic channels containing three common catalytic elements (including catalytic plates, catalytic cylinders, and catalytic spheres). The elementary reaction mechanism was employed as the reaction kinetics model to define the chemical reaction process. This paper aims to evaluate the hydrogen removal capability of the catalytic elements in same operating conditions and analyze important factors for designing the structure of catalytic elements. All the catalytic surface area of catalytic elements was set to 0.045 m2 and inlet boundary conditions were settled identically. Our findings show that catalytic sphere exhibits the best hydrogen removal capability, which is attributed to the large lower half catalytic surface area of spheres. Catalytic plate with a lower height also demonstrates excellent hydrogen removal capability because of the presence of a larger catalytic area in the leading section. However, the hydrogen removal capability of catalytic cylinder is affected by the boundary layer separation vortex. A noticeable decrease in reaction rate occurs on the lower part of the sidewall surface, especially in the catalytic cylinder with a larger radius. In the structure design of catalytic elements, enlarging the catalytic surface area in the leading section and avoiding boundary layer separation on the catalytic surface are essential to further improve the hydrogen removal capability. • Investigation on hydrogen removal capability of common catalytic elements. • Catalytic sphere exhibits the best hydrogen removal capability. • Enlarging catalytic surface area in the leading section eliminate more hydrogen. • Boundary layer separation retards the hydrogen removal rate. [ABSTRACT FROM AUTHOR]

Drying and sanitising equipment has been very common in industrial plants since the pandemic. These are devices that consume significant amounts of energy. The best solution is to use a drying chamber equipped with a heat pump, which allows partial recovery of the energy. In the design of the drying chamber, the drying time is important, which depends both on the parameters of the heat pump itself, and the geometry and airflow of the drying chamber. The geometry and airflow supply should be arranged to ensure a uniform distribution of velocity throughout the drying area. For this purpose, the use of CFD simulations has been proposed. A model was developed in ANSYS/FLUENT where all model parameters, including the optimal mesh density, turbulence models, etc., were determined. The model was verified on the experimental results of the basic design of the chamber. Then an innovative design was proposed that was modelled and optimised in terms of the distribution of the inlet's perforation. The final design was made, and, at the same time, the simulation's results were verified by measuring the velocity of airflow in the new design. Together with the optimisation of the heat pump, this made it possible to reduce the drying time by 50%, with a simultaneous reduction in the energy consumed. [ABSTRACT FROM AUTHOR]

Urbanization has caused increasingly severe heat island effect in cites, which also has worsened air quality in the urban areas due to a combination of factors. To reduce the impacts, several studies have proposed strategies based on different planning and design principles. Although some strategies were found to be useful for mitigating air pollution or urban heat island, the simultaneous effects were rarely discussed in the past studies. Therefore, this research tries to develop a framework that is able to evaluate the relative benefits of different mitigation methods on both urban heat island and air pollution, using a scenario-based computational fluid dynamics (CFD) modeling method. Six scenarios of different strategies were comprehensively evaluated and compared. It is found that pavement materials and rooftop greening showed more significant effects on reducing the heat island temperature and air pollutant concentration than that of changes in building volumes and water bodies in the study area. In addition, there are differences in mitigation effects on the two impacts, suggesting that careful comparative analysis should always be done before implementing the strategies. The proposed method could be very useful in the process of developing coping strategies for both heat island effect and air pollution in the urban areas. [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum Naturalium Universitatis Sunyatseni / Zhongshan Daxue Xuebao is the property of Sun-Yat-Sen University 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.)

Controlling the distribution of the abrasive grains on the surface of the grinding tools in an appropriate way is important for improving the quality of grinding processing and meeting the workpiece precision requirements. In the present study, a novel method for the orderly arrangement of abrasive particles is proposed by using the liquid film flow on the surface of the rotating disk as the driving and controlling means for the uniform dispersion and position arrangement of abrasive particles. Computational fluid dynamics (CFD) simulations have been performed to clearly illustrate the trajectories of abrasive particles under the strong influence of liquid film flow on the rotating disk and reveal the effects of fluid flow, disk rotational motion, and the mixture viscosity on the particle distribution. A new abrasive grain arrangement device is designed and fabricated using this novel method. The operating parameters such as liquid volume flow rate, disk rotational speed, and liquid viscosity are adjusted to control the placement of abrasive grains on the surface of the grinding tool. An image processing tool is used to examine and analyze the arrangement results. The experimental results indicated that the application of the liquid film flow on a rotating disk to the abrasive grain arrangement can improve the arrangement of abrasive grains and get rid of the dependence on the template. [ABSTRACT FROM AUTHOR]

To enhance air–fuel mixing and turbulence during combustion, spark ignition internal combustion engines commonly employ tumble vortices of the charge inside the cylinder. The intake phase primarily dictates the generated tumble, which is influenced by the design of the intake system. Utilizing steady-state flow rigs provides a practical method to assess an engine's cylinder head design's tumble-generating characteristics. This study aims to conduct computational fluid dynamics (CFD) numerical simulations on various configurations of steady-state flow rigs and compare the resulting tumble ratios. The simulations are conducted for different inlet valve lifts of a four-valve cylinder head with a shallow pent-roof. The findings highlight variations among these widely adopted configurations. [ABSTRACT FROM AUTHOR]

In this work, a desilting chamber of the Kholongchhu Hydroelectric Project, Bhutan, was used to test the settling efficiency using physical model and Flow-3D, a three-dimensional computational fluid dynamics (CFD) software. As sediment particles greater than a particular size can cause erosion and damage to underwater machinery, the estimation of settling efficiency is essential during the planning, designing and implementation phases of hydropower projects. These studies were carried out using 12 distinct particle sizes (0.25 mm, 0.24 mm, 0.23 mm, 0.22 mm, 0.21 mm, 0.2 mm, 0.19 mm, 0.18 mm, 0.17 mm, 0.16 mm, 0.15 mm and 0.1 mm). The settling efficiency for the particle size 0.2 mm obtained by physical model and CFD simulations were 92.2% and 93.6%, respectively. [ABSTRACT FROM AUTHOR]

The power battery is a key component of electric vehicles and its performance is greatly affected by temperature. Battery thermal management systems based on phase change materials can effectively control the battery temperature and at the same time have the advantages of simple structures, energy savings, and good temperature uniformity, and has broad development prospects. In this paper, expanded graphite–paraffin composite phase change materials were prepared, phase change material cooling experiments were carried out, and a phase change material cooling simulation model was also established using the Fluent software to study the influence of phase change material thermophysical parameters on thermal management performance. The results show that the phase change material thermal management method has excellent cooling performance. The best thermal management performance is achieved at the 3C discharge rate, with a phase change material filling thickness of 4 mm, a melting point of 40 °C above ambient temperature, and a thermal conductivity of 3 W/(m·K). When the phase change latent heat was increased from 150 J/g to 250 J/g, the liquid phase ratio decreased from 0.84 to 0.51, and the subsequent cooling performance was greatly improved, so the phase change latent heat should be increased as much as possible. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Geoscience is the property of Natural Gas Geoscience 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.)

To control the diffusion of high concentrations of coal dust during tunnel boring and minimize the threat to the life and health of coal miners, theoretical analysis, numerical simulations, and field measurements were combined in this study. First, computational fluid dynamic simulation software was used to simulate the generation of dust particles and their transport pattern in the tunnel. Subsequently, an innovative orthogonal test was performed to study the effect of four ventilation parameters [the pressure airflow rate (Q), distance between the air duct center and heading face (LA), distance between the air duct center and tunnel floor (LB), and distance between the air duct center and nearest coal wall (LC)] on dust diffusion. According to the orthogonal test results, the optimal ventilation parameters for effective dust control are as follows: Q = 1400 m3/min, LA = 7 m, LB = 2.8 m, and LC = 1 m. The optimized set of ventilation parameters was applied to the Wangpo 3206 working face. The results show that dust diffusion in the tunnel was effectively controlled and that the air quality was sufficiently improved. [ABSTRACT FROM AUTHOR]

Cementing technology is crucial to the development of oil and gas resources, and the quality of cement slurry required is an important factor affecting the cementing effect. Previous studies ignored mixing speed effect on cement slurry quality. CFD numerical model is established to simulate the flow filed of the agitated slurry tank under various operation and structural parameters. The multiphase flow model and the k-ε turbulence model are used to describe the turbulence characteristics in the agitated slurry tank. The multiple reference frame (MRF) model is used to realize the rotation of the area near the stirring blade. The results indicate that the density of the cement slurry in the agitated slurry tank can finally reach a stable state, and the concentration distribution is uniform. Increasing the rotational speed, the stirring time needed to achieve stability becomes shorter, and the uniformity of the cement slurry will also be improved. Reducing the distance between the impeller and the bottom of the agitated slurry tank, the mixing effect can be improved. It provides certain theoretical guidance for the practical application of this agitated slurry tank and has certain reference significance for research on improving the quality of cement slurry required for cementing. [ABSTRACT FROM AUTHOR]

In this study, the SUBOFF UUV is numerically modelled in order to investigate the hydrodynamic features and effects of submerged navigation near the free surface. At various speeds and depths below the surface, the hydrodynamic behaviors of the SUBOFF UUV are examined. From the CFD results, we can deduce that submergence depth significantly affects total resistance of SUBOFF navigation nearby free surface. Because the Kelvin wake of SUBOFF creates wave-making resistance when approaching the open surface head-on, the fraction of pressure difference resistance becomes dramatically with an increase in Fr. The principle of superposition of the divergent wave system and the transverse wave system gradually reveals the divergent wave system as Fr grows larger. The wave making energy is greater, and the UUV needs more power to overcome the wave making resistance. [ABSTRACT FROM AUTHOR]

The use of existing natural gas pipelines for the transport of hydrogen/natural gas mixtures can achieve large-scale, long-distance and low-cost hydrogen transportation. A jet fire induced by the leakage of high-pressure pure hydrogen and hydrogen-blended natural gas pipelines may pose a severe threat to life and property. Based on the Abel–Nobel equation of state and a notional nozzle model, an equivalent pipe leakage model is established to simulate high-pressure pipeline gas leakage jet fire accidents. Large-scale high-pressure hydrogen and natural gas/hydrogen mixture jet fires are simulated, showing the jet impingement process and obtaining an accurate and effective simulation framework. This framework is validated by comparing the simulated and experimental measured results of flame height, flame appearance and thermal radiation. Several combustion models are compared, and the simulated data show that the non-premixed chemical equilibrium combustion model is superior to other combustion models. The influence of the pipe pressure and the hydrogen blending ratio on the consequences of natural gas/hydrogen mixture pipeline leakage jet fire accidents is explored. It is found that when the hydrogen blending ratio is lower than 22%, the increase in the hydrogen blending ratio has little effect on the decrease in the thermal radiation hazard distance. [ABSTRACT FROM AUTHOR]

Measuring nasal obstruction should be mandatory before every nasal surgery to determine the necessary surgical steps and to separate mucosal congestion from skeletal deformity. Rhinomanometry is considered the "golden standard" for measuring nasal airway resistance. An extension of the diagnostic power was achieved by the introduction of the four-phase rhinomanometry (4PR), which provides additional information about the influence of the elasticity of the nasal wall. Also, a high correlation to the subjective sensing of obstruction could be achieved by the introduction of logarithmic parameters. The parameters of 4PR could be classified by evaluating 36,500 measurements. The International Standardization Committee on the Objective Assessment of the Upper Airway (ISCOANA) determined it as the new standard. Adding a visual analog scale (VAS) to every measurement is a documentation of the feeling of obstruction at the moment of measurement. Practical hints for 4PR are given. The determination of obstruction for both nasal sides or the calculation of the total nasal resistance should be followed by a second analysis of the detailed obstruction anatomy. In the future, pressure losses or temperature gradients can be determined by computational fluid dynamics (CFD). A reliable way to simulate the success of single surgical steps with a high didactical meaning is the three-dimensional (3D) print of sliced nose models and to measure the effect of stepwise mechanical corrections. [ABSTRACT FROM AUTHOR]

To achieve Germany's 2045 goal of climate‐neutral building stock, the integration of renewable energies in retrofitting is necessary. The project 'CO2‐neutrales Welterbe Speicherstadt Hamburg' situated in the historic warehouse district, focuses on the sustainable heat supply in listed buildings. The project consists of two main approaches: a practical approach combining historically sensitive components for heat supply to create a comprehensive energy retrofitting concept with renewable energies in the listed area, and a methodological approach using Building Information Management (BIM) to integrate various simulation models and centralize outcomes efficiently. This enables a holistic and energy‐efficient retrofit, addressing flow‐specific, thermal, and ecological aspects, thereby marking a significant step toward achieving a CO2 neutral listed building stock. [ABSTRACT FROM AUTHOR]

The study described here analyzed natural ventilation techniques, operated in a real building in the United Arab Emirates (UAE), to assist passive cooling. The assessment has been conducted by comparing digital simulation results and field measurements. Computational fluid dynamics (CFD) was used to retrospectively understand and quantify the monitored contribution of natural ventilation toward cooling the building. After calibrating the model with the field monitored data, the CFD simulations showed that the predicted ventilation strategies (buoyancy and stack effect to remove indoor heat; "wind catcher" effect to provide indoor passive cooling) contribute to lower the indoor temperature by an average of 0.7°C throughout the day. The outcomes of the study contributes to assist early stage design, with special regard to passive cooling via natural ventilation, to achieve more sustainable buildings. Nevertheless, while it is quite reliable to plan for main air flow and direction, in a real building alternative behavior might occur that is difficult to control and might affect the ventilation purpose and efficiency. [ABSTRACT FROM AUTHOR]

CFD‐based compartment (CPT) models offer a promising modeling method and trade‐off between computational effort and required accuracy. The models combine the relevant fluid dynamics from the computational expensive CFD and the incorporation of complex reaction mechanisms usually used in basic reactor models. However, one criticism is their reliance on specific operating points, rendering them invalid when boundary conditions change. This study explores using a CFD‐based CPT model for static mixing elements across multiple operating points by making use of the creeping flow. The mean age theory facilitates a comprehensive comparison between CFD and CPT models. Results indicate that within this flow region, the CPT model can be extrapolated to other operating points via linear scaling. [ABSTRACT FROM AUTHOR]

The air infiltration rate of buildings strongly influences indoor environment and energy consumption. In this study, several traditional methods for determining the air infiltration rate were compared, and their accuracy in different scenarios was examined. Additionally, a method combining computational flow dynamics (CFD) with the Swami and Chandra (S-C) model was developed to predict the influence of the surrounding environment on the air infiltration rate. Two buildings in Dalian, China, were selected: one with a simple surrounding environment and the other with a complex surrounding environment; their air infiltration rates were measured. The test results were used to validate the accuracy of the air infiltration rate solution models in different urban environments. For the building with a simple environment, the difference between the simulation and experimental results was 0.86%–22.52%. For the building with a complex environment, this difference ranged from 17.42% to 159.28%. We found that most traditional models provide accurate results for buildings with simple surrounding and that the simulation results widely vary for buildings with complex surrounding. The results of the method of combining CFD with the S-C model were more accurate, and the relative error between the simulation and test results was 10.61%. The results indicate that the environment around the building should be fully considered when calculating the air infiltration rate. The results of this study can guide the application of methods of determining air infiltration rate. [ABSTRACT FROM AUTHOR]

Introduction: Compliance mismatch between the aortic wall and Dacron Grafts is a clinical problem concerning aortic haemodynamics and morphological degeneration. The aortic stiffness introduced by grafts can lead to an increased left ventricular (LV) afterload. This study quantifies the impact of compliance mismatch by virtually testing different Type-B aortic dissection (TBAD) surgical grafting strategies in patient-specific, compliant computational fluid dynamics (CFD) simulations. Materials and Methods: A post-operative case of TBAD was segmented from computed tomography angiography data. Three virtual surgeries were generated using different grafts; two additional cases with compliant grafts were assessed. Compliant CFD simulations were performed using a patient-specific inlet flow rate and three-element Windkessel outlet boundary conditions informed by 2D-Flow MRI data. The wall compliance was calibrated using Cine-MRI images. Pressure, wall shear stress (WSS) indices and energy loss (EL) were computed. Results: Increased aortic stiffness and longer grafts increased aortic pressure and EL. Implementing a compliant graft matching the aortic compliance of the patient reduced the pulse pressure by 11% and EL by 4%. The endothelial cell activation potential (ECAP) differed the most within the aneurysm, where the maximum percentage difference between the reference case and the mid (MDA) and complete (CDA) descending aorta replacements increased by 16% and 20%, respectively. Conclusion: This study suggests that by minimising graft length and matching its compliance to the native aorta whilst aligning with surgical requirements, the risk of LV hypertrophy may be reduced. This provides evidence that compliance-matching grafts may enhance patient outcomes. [ABSTRACT FROM AUTHOR]

Investigations into the aerodynamic properties of vertical sound barriers exposed to high-speed operations employ computational fluid dynamics. The primary focus of this research is to evaluate the influence of train speed and the distance (D) from the track centerline under various operating conditions. The findings elucidate a marked elevation in the aerodynamic effect amplitude on sound barriers as train speeds increase. In single-train passages, the aerodynamic effect amplitude manifests a direct relationship with the square of the train speed. When two trains pass each other, the aerodynamic amplitude intensifies due to an additional aerodynamic increment on the sound barrier. This increment exhibits an approximate quadratic correlation with the retrograde train speed. Notably, the impact of high-speed trains on sound barrier aerodynamics surpasses that of low-speed trains, and this discrepancy amplifies with larger speed differentials between trains. Moreover, the train-induced aerodynamic effect diminishes significantly with greater distance (D), with occurrences of pressure coefficient (CP) exceeding the standard thresholds during dual-train passages. This study culminates in the formulation of universal equations for quantifying the influence of train speed and distance (D) on sound barrier aerodynamic characteristics across various operational scenarios. [ABSTRACT FROM AUTHOR]

Solid–liquid separation plays a decisive role in various industrial applications particularly in the treatment and purification of suspensions. Solid bowl centrifuges, such as the decanter centrifuge, are commonly employed in these processes as they operate continuously and enable high throughputs with short processing times. However, predicting the separation performance of solid bowl centrifuges proves to be challenging due to dynamic phenomena within the apparatus, such as particle settling, sediment build-up, consolidation and sediment transport. In practice, design considerations and the dimensioning of the apparatus rely on analytical models and the manufacturer's expertise. Computational Fluid Dynamics (CFD) offers a way to deepen our understanding of these devices by allowing detailed examination of flow phenomena and their influence on the separation processes. This study utilizes the open-source software OpenFOAM to simulate multiphase flow in a laboratory-scale decanter centrifuge, solving individual transport equations for each particle size class. The basis is the characterization of the material through targeted laboratory experiments to derive material functions that describe the hindered settling and the sediment consolidation. Furthermore, experiments on a laboratory decanter served as validation. The results demonstrate the solver's capability to replicate clarification and classification within the apparatus. Furthermore, the solver supports the definition of geometries tailored to specific separation tasks. This research demonstrates the potential of CFD for a better understanding of complex centrifuge processes and for optimizing their design to improve performance. [ABSTRACT FROM AUTHOR]

Agricultural unmanned aerial vehicles (UAVs), increasingly integral to crop protection through spraying operations, are significantly influenced by their downwash fields, which in turn affect the distribution of spray droplets. The key parameters impacting spray deposition patterns are the velocity of the downwash airflow and its spatial extent. Understanding the interplay of these parameters can enhance the efficacy of UAV applications in agriculture. Previous research has predominantly focused on downwash airflow velocity, often neglecting the spatial scope of the downwash. This paper presents an applied foundational study grounded in the compressible Reynolds-averaged Navier–Stokes (RANS) equations. Leveraging a dependable k - ε turbulence model and dynamic mesh technology, it develops an effective three-dimensional computational fluid dynamics (CFD) approach to analyze the downwash field's distribution characteristics during UAV hover. To validate the CFD method, a visualization test was conducted using EPS (expanded polystyrene foam) balls dispersed in the airspace beneath the UAV, illustrating the airflow's spatial distribution. Additionally, a parameter η was introduced to quantify changes in the wind field's range, enabling the mapping of the cross-sectional area of the downwash airflow at various velocities within the UAV's airspace. The study reveals that the downwash field's overall shape evolves from a "four-point type" to a "square-like" and then to an "ellipse-like" configuration. Lower downwash airflow velocities exhibit a more rapid expansion of the wind field area. High-velocity downwash areas are concentrated beneath each rotor, while lower-velocity zones coalesce under each rotor and extend downward, forming a continuous expanse. Within the UAV's downwash area, the deposition of droplets is more pronounced. At a given nozzle position, an increase in downwash airflow velocity correlates with greater droplet deposition within the downwash field. This research bridges a gap in downwash field studies, offering a solid theoretical foundation for the development of future UAV downwash field models. [ABSTRACT FROM AUTHOR]

This paper takes an old office building in Hefei as the research object to explore the influence of the thermal buffering performance of the case building buffer space on the air speed and thermal environment of the office space based on the field measurement and simulation. As the thermal buffer layer of the main space, the buffer space is the layout mode that follows the thermal transfer law. Building buffer space variables were evaluated and compared by orthogonal tests to determine the better combination of buffer space sizes. The results show that when the air speed is taken as the evaluation index, the influence of each buffer space on the indoor environment is ordered: courtyard > corridor > foyer; when the temperature is taken as the evaluation index, the influence of each buffer space on the indoor environment is ordered: courtyard > foyer > corridor. From the perspective of green transformation, this paper selects two better schemes. Through comparison, it is found that when the buffer space size is: corridor (16 m × 2 m × 3.3 m), courtyard (16 m × 12 m) and foyer (7.2 m × 6 m × 3.3 m) is the optimal scheme, the indoor air speed is increased by 0.1 m/s, and the temperature is reduced to 27.0 °C, which is within the thermal comfort range of the human body. It is found that optimizing the buffer space size of the case building can effectively improve its indoor air speed and thermal environment, and provide theoretical basis and reference for the green transformation of existing buildings of the same type in this area. [ABSTRACT FROM AUTHOR]