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The research on the gas axial flow regulating valve is one of the key tasks for the localization of critical valves in natural gas pipelines. With the main purpose of improving the design of the sleeve of the gas axial flow regulating valve, numerical simulation calculations are conducted on the internal flow passage of the gas axial flow control valve by using fluid simulation software. According to the existing design of the valve sleeve, the design scheme of the valve sleeve is improved by changing the diameter of the throttle hole of the valve sleeve. After improving the valve sleeve, eight simulations have been performed at different openings to analyze the velocity field, pressure distribution, and variations in aerodynamic noise within the flow passage at two design schemes. A comparison is also made between two valves for their respective flow fields and noise characteristics which use two different sleeve designs. The simulation results indicate that appropriately increasing the throttle aperture can improve the flow performance of a gas axial flow regulating valve, reducing noise levels to below 100 dB at medium and small openings. [ABSTRACT FROM AUTHOR]

In this study, wind flow around a telecommunication tower (Milad Tower) model was numerically simulated. Several computational fluid dynamics (CFD) simulations were performed using the Reynolds Averaged Navier–Stokes (RANS) and the Delayed Detached Eddy Simulation (DDES) models. Two cases resembling the tower head with different inlet turbulence intensity profiles were considered, and computational results for wind flow and pressure distributions on various sections around the tower head and structure were presented and compared with the available wind tunnel data. Good agreement of the simulated pressure coefficient distributions around the head section in the windward and leeward sides of the tower with the wind tunnel data was observed. The regions with positive and negative pressures on the tower surface were identified based on the pressure coefficient distributions. In addition, the airflow characteristics around a model of the entire Milad Tower were studied. The simulation results for the airflow and the drag and lift coefficients acting on the tower for the high and low-intensity winds were evaluated and discussed. It was demonstrated that the DDES model was preferred for the simulation of mean pressure coefficients over the tower; however, the RNG k–ε model results, which were obtained at lower computational costs, were also satisfactory. In addition, the DDES showed better performance in simulating the maximum and minimum pressure coefficients on different tower levels and predicting the mean aerodynamics drag and lift coefficients. The results of the DDES model illustrated the higher power spectral density of velocity fluctuations on the leeward side of the tower compared with the windward side. [ABSTRACT FROM AUTHOR]

Numerical analysis of a U-type solid oxide fuel cell stack was performed using computational fluid dynamics to investigate the effects of stack capacities and fuel/air utilization rates on the internal flow uniformity. The results indicated that increasing the fuel/air utilization rate improved the gas flow uniformity within the stack for the same stack capacity. The uniformity in the anode fluid domain was better than that in the cathode fluid domain. Furthermore, the flow uniformity within the stack was associated with the percentage of pressure drop in the core region of the stack. The larger the percentage of pressure drop in the core region, the more uniform the flow inside the stack. Additionally, under a fuel utilization rate of 75%, the computational results exhibited excessively high fuel utilization rates in the top cell of a 3 kWe stack, indicating a potential risk of fuel depletion during actual stack operation. [ABSTRACT FROM AUTHOR]

In this paper, the friction properties of the port pair with non‐smooth surface in the pump were studied. The lubrication film was modelled and simulated to analyse dynamic pressure, velocity vector and friction coefficient. Tests were made for studying the effects of pit shape and revolution speed on friction properties of glass fibre epoxy resin (GFER) samples under seawater lubrication, with the wear of the surface and friction coefficient discussed. The results show that GFER is mainly manifested as adhesive and abrasive wear during the tests. The simulations and tests suggest that the hydrodynamic lubrication effect is improved by increasing revolution speed and using non‐smooth surfaces, with the friction coefficient being decreased. Moreover, a roughness test was conducted, and it was found that the Ra value of the 316L sample decreased, whereas the Ra value of the GFER sample increased. [ABSTRACT FROM AUTHOR]

Motivated by existing techniques for implementing roughness on cylinders to control flow disturbances, we performed delayed detached eddy simulations (DDES) at Re = 6 × 10 6 that generated unsteady turbulent flow around a rectangular cylinder with a controlled wrinkled surface and a 1:4 aspect ratio. A systematic study of the roughness effect was carried out by implementing different configurations of equally spaced grooves and bumps on the top-surface of the cylinder. Our results suggest that groove geometries reduce energy dissipation at higher rates than the smooth reference case, whereas bumped cylinders produce relative pressures characterized by a sawtooth pattern along the middle-upper part of the cylinder. Moreover, cylinders with triangular bumps increase mean drag and lift forces by up to 8% and 0.08 units, respectively, while circular bumps increase vorticity and pressure disturbances on the wrinkled surface. All of these effects impact energy dissipation, vorticity, pressure coefficients, and flow velocity along the wrinkled surface. Both the surface-manufactured cylinders and the proposed visualization techniques could be replicated in a variety of engineering developments involving flow characterization in the presence of roughness. [ABSTRACT FROM AUTHOR]

The flow characteristics of homogeneous gases in complex systems are an important issue in many areas, including underground mines. The flow in mine excavations and ventilation systems is described by known mathematical relationships that could be applied to various cases. In this paper, a flow in a duct with a local sink of mass and momentum for multiple variants of cooperation of a mechanical fan was analyzed. The relationships for the total and static pressure of air in the duct were derived. In the next stage, a calculation example of how the mass flow rate of air, and the total and static pressure of the flowing air will change in the tested sections for the duct with and without a sink, is presented. The derived formulas and calculated values for the considered calculation case allow the verification of the obtained relationships at the measurement station. Analyzing the results of the examples presented in the article, it can be concluded that the total and static pressure at the sink point differ depending on the equation of motion used. In the case of the classic equation, the value of total pressure is lower than the value calculated from the new equation of motion, and the difference between them is about 20 Pa. In the case of static pressure, this difference is about 46 Pa. Qualitative differences in the static pressure distribution at the release location were also demonstrated. Depending on the applied approach, positive or negative changes in the static pressure are noticed. The presented form of the equation of motion made it possible to determine the flow characteristics in the duct with a point mass and momentum sink in the case of the operation with and without a fan. [ABSTRACT FROM AUTHOR]

Forward-swept wings were researched and introduced to improve maneuverability, control, and fuel efficiency while reducing drag and they are often used alongside canards, to further enhance their characteristics. In this research, the effects of canard dihedral angles on the wing loading of a forward-swept wing in transonic flow conditions were studied, as the wing loading provides a measure of wing's efficiency (lift/drag). A generic aircraft model from literatures was selected, simulated, and compared to, using CFD software ANSYS/Fluent where the flow equations were solved to calculate the aerodynamic characteristics. The research was carried at two different Mach numbers, 0.6 and 0.9, for five different canard dihedral angles which traverses from below the wing plane to above it, at various flow angles of attack. It was concluded that as the dihedral angle increased, lift increases for the same angle of attack for Mach 0.6 and 0.9 which increases the efficiency of the wing. The wing span loading occur at 10° dihedral angle for both Mach speeds, while, at 10° anhedral, the lift was minimal due to leading-edge flow separation on the FSW's lower surface. Thus, it is concluded that the canard at positive dihedral angles ensures increased wing span loading efficiency. [ABSTRACT FROM AUTHOR]

The direct extraction of clear water from a sandy river is a difficult task and can only be achieved through specific engineering measures. This paper proposes an artificial percolation riverbed structure for extracting clean water from sandy rivers, using a numerical simulation to study the flow field distribution characteristics of the structure under clean water conditions. The main conclusions are as follows: When the percolation vortex tube opening rate is 1.4%, the vortex tube with or without opening the percolation hole has little influence on the distribution characteristics of the flow field in the artificial riverbed, and the purpose of water extraction can be achieved while constructing a helical flow field. The axial flow velocity and circumferential flow velocity of the vortex tube cross-section under different Reynolds numbers show the distribution of a low-flow velocity close to the center of the vortex tube, and a high-flow velocity close to the vortex tube side-wall area. The average axial flow velocity and average circumferential flow velocity of the vortex tube show a trend of increasing and then decreasing distribution along the axial axis of the vortex tube in the direction of the sediment transport flume. The mean axial flow velocity of the vortex tube along the axis of the vortex tube toward the sediment transport flume and the mean circumferential flow velocity both show a distribution trend of increasing and then decreasing. At the junction of the vortex tube and the sediment transport flume, there are obvious pressure changes, and the pressure changes drastically under the same horizontal line. Along the direction of the bottom line of the vortex tube, the pressure at the vortex tube is obviously greater than that at the sediment transport flume. The vortex of the artificial percolation riverbed is mainly concentrated in the vicinity of the vortex tube, and the maximum value of the vortex intensity generally occurs at the junction of the vortex tube and the sediment transport flume. With the increase in the Reynolds number, the vortex intensity has an overall increasing trend, and the distribution of the vortex is more complex. This study helps to elucidate the distribution characteristics of the flow field in the artificial percolation riverbed, and it provides a reference basis for the future study of the flow field of artificial percolation riverbeds of sandy rivers. [ABSTRACT FROM AUTHOR]

This research analyses the flow patterns in an Oscillatory Central Baffled Reactor (OCBR) using Computational Fluid Dynamics (CFD) simulations under various oscillation conditions. Frequency (f and amplitude (x0) are examined as critical parameters for enhancing fluid mixing and energy efficiency in high viscosity fluids, such as biofuels. The findings highlight the significant impact of the Strouhal number (St) on the flow behavior, showing improved fluid mixing with an increase in the oscillatory Reynolds number (Re0) from 125.6 f = 2 Hz, x0 = 2 mm) to 392.7 f = 2.5 Hz, x0 = 5 mm), corresponding to a decrease in the St from 0.2 to 0.08. The simulations indicated the appearance of stable vortices and a better distribution of the Weibel dead zones at an oscillation cycle (t/T) of 0.5. During the course of the study, the pressure distribution within the OCBR and its dependence on oscillation amplitude were shown, which significantly impacted the pressure drop from 8.8 to 123 Pa as Re0 was raised. In order to alleviate the endpoints for high resistance of sharp edged baffles, two modified baffle designs (semi-central and smooth- edge central baffles) were used. The findings showed that the performance of the semi-central baffle design in terms of dead zone reduction and shear stress was superior to those of the other designs for both upward and downward flows, indicating its suitability for enhancing the performance of the OCBR. This research offers important developments in the efficient mixing processes needed in industrial applications and indicates some areas for effective testing and validation of the models developed. [ABSTRACT FROM AUTHOR]

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Abstract In this study, wind flow around a telecommunication tower (Milad Tower) model was numerically simulated. Several computational fluid dynamics (CFD) simulations were performed using the Reynolds Averaged Navier–Stokes (RANS) and the Delayed Detached Eddy Simulation (DDES) models. Two cases resembling the tower head with different inlet turbulence intensity profiles were considered, and computational results for wind flow and pressure distributions on various sections around the tower head and structure were presented and compared with the available wind tunnel data. Good agreement of the simulated pressure coefficient distributions around the head section in the windward and leeward sides of the tower with the wind tunnel data was observed. The regions with positive and negative pressures on the tower surface were identified based on the pressure coefficient distributions. In addition, the airflow characteristics around a model of the entire Milad Tower were studied. The simulation results for the airflow and the drag and lift coefficients acting on the tower for the high and low-intensity winds were evaluated and discussed. It was demonstrated that the DDES model was preferred for the simulation of mean pressure coefficients over the tower; however, the RNG k–ε model results, which were obtained at lower computational costs, were also satisfactory. In addition, the DDES showed better performance in simulating the maximum and minimum pressure coefficients on different tower levels and predicting the mean aerodynamics drag and lift coefficients. The results of the DDES model illustrated the higher power spectral density of velocity fluctuations on the leeward side of the tower compared with the windward side.

The design of vehicle cabin seats is crucial in transportation, as it directly affects the safety and comfort of both drivers and passengers. To design seat parameters that enhance sitting comfort, a quantitative evaluation of sitting comfort involving an understanding of users' physiological responses is necessary. This study aimed to assess users' physiological responses to relaxation induced by changes in seat parameters using electroencephalography and electrocardiography. We examined the physiological responses and subjective evaluations of relaxation in fifteen participants, focusing on the effects of reclining, ottoman, and slab. The results demonstrated an improvement in the subjective level of relaxation with changes in all seat parameters set here. However, central nervous system responses and autonomic nervous system reactions varied based on alterations in posture angles and seat pressure distributions. This underscores the importance of physiological markers, encompassing indicators of autonomic and central nervous system responses, in evaluating relaxation in relation to changes in posture angles and seat pressure distribution. [ABSTRACT FROM AUTHOR]

As the foundation of marine infrastructure, pile groups are subjected to extreme wave loads. Existing research primarily focuses on regular waves and wave forces. There is limited research on the pressure distribution of pile bodies under extreme waves. This paper describes a wave flume experiment where waves of a self-proposed extreme wave type were generated. The experiment considers three water depths (25/35/45 cm), three wave-pushing velocities (20/30/40 cm/s), and two clear distances (D, 2D). A total of 216 measuring points equipped with digital pressure sensors captured the vertical and circumferential pressure distribution and wave positive force. The results show that (1) the vertical and circumferential pressure distribution patterns of each component pile and the single pile are similar in various loading scenarios and clear distances. (2) The measuring point pressure, pressure after circumferential integration, and wave positive force are positively correlated with wave-pushing velocity. (3) The wave pressure is positively correlated with the water depth, while the pressure after circumferential integration is negatively correlated with the water depth. (4) When the clear distance is D, the wave positive force coefficient of each component pile is less than 1.0. [ABSTRACT FROM AUTHOR]

The flat surface of a thin LiTaO3 substrate, exhibiting excellent electro-optical and piezoelectric properties, is required to enhance surface acoustic wave energy. A high-quality surface of a thin LiTaO3 substrate can be obtained through ultra-thinning processes, such as grinding and chemical mechanical polishing. However, during the ultra-thinning process, the grinding wheel gradually wears, leading to an uneven pressure distribution on its surface, which results in machining errors, such as cracks, subsurface damage, and chatter. Hence, the uneven pressure distribution must be examined to maintain and improve machining accuracy. In this study, reciprocating tests and simulations were performed on the grinding wheel of a LiTaO3 wafer using Archard's wear model in the commercial software ANSYS Transient Structural. In addition, a grinding simulation was performed, considering the grinding conditions and wear rate, to examine the pressure distribution on the surface of the grinding wheel. In the grinding simulations, the periodic pressure distribution changed at a high frequency of 12,987 Hz on the surface of the grinding wheel, with a maximum pressure of 1.7 MPa. Additionally, modal analysis was conducted to examine the occurrence of resonance, thereby confirming the risk of resonance. [ABSTRACT FROM AUTHOR]

Customised orthotic insoles play a critical role in addressing foot pathologies and improving comfort and biomechanical alignment for patients with specific needs. The use of 3D printing technology for the manufacturing of orthotic insoles has received considerable attention in recent years due to its potential for customisation, rapid prototyping, and cost-effectiveness. This paper presents the implementation of an algorithm purposely developed to generate an Additive Manufacturing File (AMF) containing the geometry of a patient-specific insole and the stiffness distribution based on pressure analysis from a baropodometric board. The generated file is used to 3D print via Fused Deposition Modelling an insole with a variable infill percentage depending on the pressure distribution on the patient's foot. Three inputs are used as source data for the AMF file coding: (i) the 3D model that defines the geometry of the insole designed by the orthopaedist; (ii) the pressure map of the patient's feet obtained with a baropodometric board; and (iii) the stiffness of the material that will be used to fabricate the insole. The proposed approach allows the fabrication of a patient-specific insole, capable of restoring the correct pressure distribution on the foot by varying the infill percentage. Two types of insoles were successfully fabricated using the implemented algorithm: the first was 3D printed, adding a top layer to be ready-to-use; the second was 3D printed without a top surface to be further customised with different coatings. The method described in this paper is robust for the fabrication of customised insoles and aims at overcoming the limitations of the traditional approach based on milling machining (e.g., time, costs, and path planning) since it can be easily integrated into any orthopaedic workshop. [ABSTRACT FROM AUTHOR]

This study delves into the characteristics of a water jet impacting a stationary target, employing Computational Fluid Dynamics (CFD) simulations conducted with ABAQUS/CFD 6.14. Inspired by an orthogonal cutting configuration of a Ti6AL4V alloy during high-pressure water jet-assisted machining, the paper investigates the effect of nozzle inclination angles ranging from 6° to 81°. Utilizing the Finite Volume (FV) method, the jet impacts the target with an initial velocity of 223 m/s through a 0.7 mm diameter nozzle, positioned 6 mm away from the target center. Additionally, simulations were conducted for a 23° inclined jet to analyze the influence of nozzle diameter 'D' across a range of 5 values from 0.3 mm to 1.1 mm, with a step of 0.2 mm. Turbulence phenomena are addressed using the K-ε model. Results indicate that a 23° inclination yields significant pressure values, enhancing chip fragmentation. Furthermore, recirculation phenomena intensify with inclination, highlighting the importance of nozzle diameter reduction for achieving a more laminar jet and precise injection, albeit with reduced cutting edge pressure. Moreover, the study introduces a novel approach to construct a new equivalent jet with modified boundary conditions to tackle fluid-structure coupling limitations, mitigating speed drops and turbulence phenomena. While thermal effects are excluded in this study, acknowledging the importance of sufficient cooling in machining operations, the findings provide valuable insights into the mechanical dynamics of machining processes. Additionally, the paper serves as a guideline for researchers, particularly those engaged in computational fluid dynamics within machining, shedding light on the underexplored area of numerical modeling of High-Pressure Lubrication (HPL) using software like Abaqus/CFD [ABSTRACT FROM AUTHOR]

The study of laminar incompressible fluid flow in the boundary layer revealed, even earlier, that the condition of complete adhesion of fluid particles to the surface (non-slip condition) of the moving body (half-plane) is not met in the flow development (formation) region. The assumption of constancy of the fluid velocity on the surface of a moving body, hence non-slip, leads, in the flow development region, to the complete absence of the normal component of the velocity field. And this contradicts the very concept of the flow development region, where there should be two velocity components - longitudinal (primary) and normal (secondary) ones. In the previous works of the authors, analytical solutions were obtained for the velocity field in the region of development of incompressible fluid flow in the boundary layer. Since the use of the incompressible fluid flow model is restricted by the Mach number, to further expand the speed range, the problem of the of slightly compressible fluid flow development region in the boundary layer was considered. It is analytically proven that all considerations regarding the impossibility of complete non-slip in the flow development region can be applied to a slightly compressible flow. Slight compressibility at the same time means the subsonic nature of the flow and the neglect of temperature effects due to friction. On the basis of a critical analysis of the existing approaches, which consider the flow of a fluid around a immobile plate in the framework of non-gradient flow (which is just impossible due to the lack of a mechanism for creating the motion of the fluid), it is shown that the system of equations is actually non-closed. For the region of flow development, where the longitudinal pressure gradient is not a constant value, one equation is missing. This equation, as in previous works, is obtained from the necessary condition for the extreme of the fluid rate functional. And although the complete solution for the longitudinal component of the velocity contains four constants of integration, to obtain the asymptotics near the solid surface it is sufficient to know only two quantities - the velocity and its first derivative (gradient). These values, as it turns out from the asymptotic solution, coincide with the case of incompressible flow, which allows us to expand the scope of the previously obtained results for a wider domain of Mach numbers, for example . And such values already correspond to the speeds of modern civil aircraft. The dimensionless distribution of pressure in the slightly compressible flow development region is presented and its significant heterogeneity is shown, which, in turn, indicates the importance of the obtained results. [ABSTRACT FROM AUTHOR]

Pressure ulcers are a common problem among individuals who, for medical reasons, must spend most of their day in bed. Manually turning a person's body is labor intensive and can easily cause occupational injuries. To compare the effectiveness of a new assisted turning mattress in pressure management with that of a conventional air mattress. This is a single-session crossover trial study. Twenty-four participants confined to bed were transferred onto the selected mattress (assisted turning or conventional air mattresses) in the selected position. Average interface pressures of bony prominences were measured after the participants laid on the mattress in different positions. After the data collection, they were transferred to the second mattress, and the process was repeated. Subjective feedback from participants and caregivers was also acquired immediately following a one-week trial period of assisted turning mattresses. The mean interface pressures were comparable for most body parts between two mattresses. Subjective feedback showed that assisted turning mattresses could relieve caregivers' workload but at the cost of patients' decreased feelings of safety. Assisted turning mattresses are equal to conventional air mattresses in pressure distribution. Proper pressure management through scheduled positional changes is required in assisted turning mattresses. [ABSTRACT FROM AUTHOR]

This study proposes to study the sliding and slippage mesoscopic defects that appear during the preforming phase of dry reinforcements to produce complex composite shapes. For this purpose, experimental preforming tests were conducted on a plain weave fabric with low cohesion using a specific punch developed specifically for this purpose, and which combines the geometric facets of a square and a tetrahedron. The tests were conducted under several configurations varying the blank holder pressure intensity as well as its distribution, through the number and springs position that generate normal forces on the blank holders. The results showed that the corners of the geometry formed by orthogonal faces favor the appearance of mesoscopic defects and specifically slippage because of its severity. Sliding has shown itself to be very sensitive both to the singularities of the geometry where it appears, and to the heterogeneity of the pressure distribution of the blank holders. On the other hand, the sliding, which appears in the vicinity of the slippage on flat faces, is rather sensitive to the distribution of the pressure. The increase in the blank holder pressure, regardless of the conditions of its application, leads to an almost linear increase in the extent and number of these mesoscopic defects. [ABSTRACT FROM AUTHOR]

ABSTRACT3D-printing enables fabricating insoles with locally variable mechanical properties that can better redistribute plantar pressure by altering the mechanical structure. However, current approaches have limitations in terms of speed, strand thickness, and gradual stiffness transitions. To address this, our research proposes utilising the 3D-printed Spacer technique. Our approach involves 3D-printing the insole on their lateral side, with gradual stiffness transitions achieved by modulating the feed speed and material extrusion, enabling strands thinner than the nozzle diameter, while eliminating travel movements. We present a workflow for customisation and fabrication of insole geometry utilising 3D foot scans and automatic g-code generation directly from our design tool. Additionally, we introduce a novel automated support removal process using a hot-wire cutter mounted on a 6-axis robotic arm. We evaluated the printed structures’ mechanical properties and durability through compression tests and assessed the insoles’ performance using a user wear test that included pressure distribution analysis.

Abstract Background This study analysed changes in gait and pedobarography and subjective and functional outcomes after isolated Chopart joint injury. Methods The results of 14 patients were reviewed. Kinematic 3D gait analysis, comparative bilateral electromyography (EMG) and pedobarography were performed. Results On the injured side, the 3D gait analysis showed a significantly increased internal rotation and decreased external rotation of the hip and significantly decreased adduction and decreased range of motion (ROM) for the ankle. On the healthy side, the pedobarography revealed a significantly increased mean force in the forefoot, an increased peak maximum force and an increased maximum pressure in the metatarsal. When standing, significantly more weight was placed on the healthy side. The EMG measurements showed no significant differences between the healthy and injured legs. Conclusions After isolated Chopart injuries, significant changes in gait and pedobarography can be seen over the long term.

Although numerous experimental studies on a hybrid thruster have been recently executed, a fuel port pressure was rarely measured because a gap between a fuel and a fuel case is complicated to be sealed due to a fuel port pressure sensor hole. Therefore, the hybrid thruster with an exposed solid fuel was applied to install a fuel port pressure sensor without the fuel case. An exposed solid fuel hydrogen peroxide catalytic decomposition hybrid thruster with PE (PolyEthylene) and PMMA (PolyMethyl MethAcrylate) as fuels, H 2 O 2 as an oxidizer, MnO 2 /Al 2 O 3 as a catalyst for the oxidizer, 20 bar as a combustion chamber pressure, and 5 s as a burning time was organized. Combustion tests without fuel port pressure sensors to discern an effect of them and with PMMA to visualize a combustion were performed. A fuel port pressure distribution was satisfactorily measured. Three phenomena of four fuel port pressures and a post-combustion chamber pressure in a steady state included an increase at the beginning, a maintenance at the middle, and a decrease at the end induced by a variable oxidizer mass flow rate, a flame generation, and a fuel regression respectively. • Application of exposed solid fuel to install fuel port pressure sensor on fuel. • Combustion visualization to explain occasional error solved by hydraulic fluid. • Increase of fuel port pressure at beginning due to variable oxidizer mass flow rate. • Maintenance of fuel port pressure at middle due to flame generation. • Decrease of fuel port pressure at end due to fuel regression. [ABSTRACT FROM AUTHOR]

To investigate flow uniformity within individual unit cells in internal manifold-type solid oxide fuel cell stacks with respect to electrical capacity and stack height variations, numerical analyses using computational fluid dynamics techniques were conducted on SOFC stack models with capacities of 1 kWe, 2 kWe, and 3 kWe. The results of these calculations reveal that while the inlet flow rate increases with an increase in the number of unit cells, the flow rate supplied to each unit cell remains largely consistent, resulting in a nearly uniform pressure drop in the core region. Nonetheless, the flow rate in the pipe and manifold regions increases proportionally to the inlet flow rate for 1 kWe, 2 kWe, and 3 kWe models, leading to a corresponding increase in pressure drop. Furthermore, the patterns of mass flow rate and pressure drop within unit cells are comparable. Particularly, the pressure drop within unit cell channels is primarily influenced by the pressure distributions in the outlet manifold regions. In summary, as the stack height increases, the uniformity of pressure and flow rate distributions among unit cells decreases. This effect is more pronounced in the cathode with a higher flow rate than the anode, and it has implications for achieving uniform flow rates while minimizing flow rates in individual unit cells. [ABSTRACT FROM AUTHOR]

The operation of marine vessels with high efficiency provides a great contribution within the scope of the International Maritime Organization and the sustainable development goals. In terms of the propulsion system, selecting the appropriate propeller is critical to effectively use the engine power installed in marine vessels because the biggest energy losses during transmission occur on the propeller and ship hull. Increasing propeller efficiencies above a certain level is quite a challenge by simply changing the number of blades, pitch, or propeller type. Therefore, various energy-saving device applications, such as propeller boss cap fins (PBCFs), are performed on the ship propeller. The effects of National Advisory Committee for Aeronautics 4415 profile PBCFs which have a different position and pitch angle integrated into the E698 model propeller have been investigated to describe efficiency, vortex, and pressure distributions based on the KRISO very large crude carrier 2 designed hull in this study. The E698 model propeller has been created by the 3D software and the validation has been performed by the computational fluid dynamic solver software based on the reference values of the propeller. The effect of four PBCF applications which have different pitches and positions on the model propeller has been revealed in terms of the efficiency, pressure distributions, and vortexes. Although P45-R45 and P45-R90 PBCF applications are quite close to the E698 propeller in terms of efficiency, no significant efficiency increase has been observed. In addition, the efficiency has decreased considerably in P90-R45 and P90-R90 applications. PBCFs application with P45-R90 has provided superiority to the base model in terms of pressure distributions and vortex formation. However, any improvement has not been achieved in the remaining three designs. Therefore, PBCF applications should be applied quite elaborately based on propeller types. [ABSTRACT FROM AUTHOR]

Due to the characteristics of thin-walled curved surface, wall thickness variations, and cantilevered machining fixtures, the mechanical state of the different contact positions of aircraft engine blades varies significantly during the grinding process. The different contact interactions between the contact wheel and the blade lead to changes in material removal efficiency and surface quality. To achieve contact state control during the blade grinding process, a novel flexible abrasive belt grinding device was designed and developed, taking into account the compliance of the rubber wheel. The significant effect of compliance parameters on the grinding contact state was verified through simulation. The grinding contact pressure distribution and normal contact force at different positions in the blade width and length directions were studied, and a prediction model for the maximum contact pressure and normal contact force was established based on back propagation neural networks. The results showed that with the increase in contact wheel compliance, the effective contact range increased; the pressure distribution gradually became uniform, and showed a double-elliptical distribution. The maximum contact pressure was significantly reduced, with a reduction of up to 46.00%. As the grinding contact position moved towards the weak rigidity area of the blade, the contact pressure distribution became more uniform. The normal contact force was significantly reduced, with a maximum reduction of 68.49%. The mean average percentage error (MAPE) of the prediction model was small, verifying the effectiveness of the model. The research results of this manuscript laid a foundation for achieving consistent control of the blade grinding material removal rate through contact wheel compliance adjustment. [ABSTRACT FROM AUTHOR]

High temperature high pressure (HTHP) environment in deep wells plays an important role in mud rheology control; omitting its effects will lead to an inaccurate knowledge of hole pressures and a negative influence on safe drilling. Based on the principle of energy conservation, a borehole temperature computation model is established. In this model a method of computing borehole temperature by coupling the effects of temperature and pressure is built up taking into account the effects of the fluid flow state on temperature and pressure. The reliability of the model is verified using data acquired from field operations. The study results show that the effect of temperature on the density and rheology of a drilling fluid is more important than the effect of pressure. As a well becomes deeper, the density and yield point of the drilling fluid in the annulus are also increasing. As the circulation time increases, the bottom hole temperature is decreasing, the density, yield point and flow index of the drilling fluid in the annulus are increasing, while the thickening index is decreasing. The ECD of the drilling fluid in the annulus under coupled temperature and pressure condition is lower than the ECD of the fluid in the same annulus without considering the coupling of temperature and pressure, the difference between the two ECD is 0.067 g/cm3 . Hence, if the effects of temperature and pressure coupling on the density and rheology of a drilling fluid are not considered, a mud density lower than that is necessary to balance the formation pressure will be designed, and well kick and blowout may be induced. The results and understanding of this study provide a key theoretical base for precise evaluation of temperature and pressure in an ultra-deep well. [ABSTRACT FROM AUTHOR]

The guideway is deformed due to the clamp force of the bolt and the manufacturing error of the mounting surface. Deformation and manufacturing error constitute the guideway straightness error. In this paper, the pressure distribution of the bolt in the tightened state is simulated first, the relationship between the bolt clamp force and the tightening torque is calculated, and then the deformation of the guideway under different tightening torques is simulated. Finally, experiments are carried out on a guideway, and the results prove that the method proposed in this paper can accurately calculate the deformation of the guideway. [ABSTRACT FROM AUTHOR]

Nowadays, due to the complexity of water distribution systems and their large scale, their design, operation and maintenance require the use of optimal methods, which have become more important than in the past in improving their calibration. The most important issue in the simulation modeling of these systems is the consistency between the calculated and measured data. In the absence of the results of unaccounted water studies in the network, the use of statistical experimental methods is still needed as one of the main elements in model calibration. Based on this, the current research was conducted to investigate the effects of different patterns of unaccounted water based on the calculated water consumption patterns and to determine the optimal pattern of unaccounted water within the water distribution network covering the number of 6 ground reservoirs. The comparison of the statistical parameters showed that the use of the inverse model of the customers' consumption, which is not considered as a water model, for calibrating the hydraulic model of the distribution network, provides more acceptable limits for the closeness of the predicted values to the recorded values of the hourly output of the reservoirs, and therefore It is better to be used in studies related to planning and designs. [ABSTRACT FROM AUTHOR]

Background: This study analysed changes in gait and pedobarography and subjective and functional outcomes after isolated Chopart joint injury. Methods: The results of 14 patients were reviewed. Kinematic 3D gait analysis, comparative bilateral electromyography (EMG) and pedobarography were performed. Results: On the injured side, the 3D gait analysis showed a significantly increased internal rotation and decreased external rotation of the hip and significantly decreased adduction and decreased range of motion (ROM) for the ankle. On the healthy side, the pedobarography revealed a significantly increased mean force in the forefoot, an increased peak maximum force and an increased maximum pressure in the metatarsal. When standing, significantly more weight was placed on the healthy side. The EMG measurements showed no significant differences between the healthy and injured legs. Conclusions: After isolated Chopart injuries, significant changes in gait and pedobarography can be seen over the long term. [ABSTRACT FROM AUTHOR]

In the heat insulation winding molding process of solid rocket motors, the pressure applied by the press roller directly affects the quality of the winding molding. Insufficient pressure can result in poor bonding quality and may cause defects. This paper aims to provide an optimal design of the press roller to improve the winding molding quality of the heat insulation. The effect of the cylindrical press roller on the pressure distribution was analyzed using the elastic foundation model and a finite element (FE) model, which was assessed by Hertz theory. Subsequently, the press roller was optimized to an elliptical concave design. The effect of the radius of the elliptical concave press roller on the pressure distribution was analyzed. A comparison of the effect of the elliptical concave press roller and the cylindrical press roller on the pressure distribution was conducted using the FE model. The results show pressure uniformity is significantly improved when the elliptical concave press roller is employed on the mandrel with the smallest radius. Additionally, the elliptical concave press roller increases the pressure at the edge of the tape, which reduces the risk of lifted edges and, thereby, improves the winding molding quality of the heat insulation. [ABSTRACT FROM AUTHOR]

Under the influence of crosswind, when high-speed trains (HSTs) meet on a bridge, they produce complex vortexes, strong aerodynamic loads, and other aerodynamic effects. The purpose of this paper is to reveal the influences of crosswind and windbreaks on the vortexes generated by HSTs, the pressure distributions on the surfaces of the trains, and the aerodynamic load coefficients of the trains when they meet on a bridge, as well as the influence of the pressure waves generated by the trains on the windbreaks. The three-dimensional incompressible improved delayed detached eddy simulation (IDDES) method based on the SST k-ω turbulence model is used for numerical calculation purposes, and the overset grid method is used to realize the relative motions of the trains. The results show that the windbreaks can reduce the negative pressure (NP) imposed on the train surface and effectively improve the pressure distribution; crosswinds have a significant impact on the vortexes generated by trains, and the vortexes generated by the upstream train affect the stability of the downstream train; windbreaks can reduce the aerodynamic load applied when trains meet and thus improve the safety of the trains; and the head and tail waves generated by trains impose pressure on the windbreaks, which affects the reliability of the windbreaks installations. The simulation results can provide a preliminary reference for future research. [ABSTRACT FROM AUTHOR]

How to achieve an effective balance between functionality and comfort is a key factor in the design of the top part of socks. In order to make the top part of socks more consistent with the characteristics of pressure distribution at the lower leg while improving pressure comfort, the lower leg and foot of the human body was taken as the research object, and Mimics software was used to establish a three-dimensional model of the lower leg and foot. ABAQUS software was applied to simulate the pressure distribution state of the lower leg at the top part of the socks and the stress trend in each region of the lower leg after wearing experimental socks. In order to further study the compression state of the lower leg section at the top part of the socks after wearing the socks, the section was divided into eight regions according to the angle, and the functional relationship between pressure and displacement was obtained through curve fitting. Meanwhile, the volume shrinkage of the eight regions of the lower leg section after compression was calculated, respectively. Results showed that the curvature radius of the lower leg, the thickness of the soft tissue and the position of the skeleton jointly affected the pressure and displacement values after wearing socks, and the distribution trend of volume shrinkage was different at each region of the lower leg section. The conclusion could provide the theoretical basis for the optimization design of the tightness degree of the top part of socks in different regions, and provide a data reference for the research and development of pressure socks that meet the required pressure comfort. [ABSTRACT FROM AUTHOR]

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ABSTRACT Cylindrical steel silos with flat bottoms are widely used in agriculture and industry for storing granular materials. While research has advanced our understanding of pressure on silo walls, accurate prediction, especially during the dynamic filling and discharge phases, remains a challenge. This study presents a finite element (FE) analysis of pressure distribution in a model cylindrical steel silo with a flat bottom, investigating the influence of the height-to-diameter (H/D) ratio. The numerical results were validated against experimental data from a pilot-scale test facility storing corn. Material properties were determined through laboratory experiments, with mechanical properties obtained from literature. An arbitrary Lagrangian formulation was employed for the FE calculations. The FE results showed good agreement with experimental data for static pressure distribution on the silo wall across all H/D ratios analyzed. While the patterns of dynamic pressure curves were similar, the FE-predicted magnitudes were lower than those observed experimentally. Notably, the simulations captured significant pressure fluctuations during silo discharge.

In this paper, the pressure distribution on the slippers of a mono-rail sled with vibration damping is investigated. Due to the many applications of sled testing in the aerospace industry, the study of system vibrations is highly noticeable. In this research, first, by mathematical modelling of the sled, the governing Equations are extracted and natural frequencies and vibration modes are obtained from the analytical method using the mass and stiffness matrix of the system. Then, using numerical simulation and validation methods with experimental results performed in wind tunnels, the modal analysis of the designed sled sample is performed. A difference of less than eight percent in both numerical and analytical methods proves the accuracy of the results. The results show that the role of the slipper in the vibrations created in the sled is very important due to the large torsional and transverse oscillations in different positions, and the highest static pressure occurs in the inner layer of the slipper.

As an important component of the deep tunnel drainage system for dealing with urban waterlogging, the rotating stepped dropshaft has been proposed due to its small air entrainment. However, the hydraulic characteristics inside the shaft still need to be fully studied. In this study, the flow patterns, water velocity, and pressure in the rotating stepped dropshaft under different flow rates and geometric parameters were studied using a three-dimensional numerical model. The results show that increasing the central angle of the step and reducing the step height can both reduce the terminal velocity. A theoretical formula for predicting the terminal velocity was established and well validated. The connection between the shaft and the outlet pipe poses a severe threat to the structural safety due to alternating positive and negative pressures. Wall-attached swirling flow generates a circular high-pressure zone at the bottom of the dropshaft and the larger the flow rate, the greater the pressure gradient at the center of the bottom. By using the momentum theorem and considering the impact pressure range of the swirling flow, the shaft bottom pressure can be predicted reasonably well. HIGHLIGHTS The hydraulic characteristics of rotating stepped dropshafts are analyzed and the terminal velocity is evaluated theoretically and well validated.; The pressure distribution inside rotating stepped dropshafts and the impact effect of the wall-attached swirling flow on the shaft bottom are determined.; A simplified theoretical model is established to predict the impact pressure of the shaft.;

Under the influence of crosswind, when high-speed trains (HSTs) meet on a bridge, they produce complex vortexes, strong aerodynamic loads, and other aerodynamic effects. The purpose of this paper is to reveal the influences of crosswind and windbreaks on the vortexes generated by HSTs, the pressure distributions on the surfaces of the trains, and the aerodynamic load coefficients of the trains when they meet on a bridge, as well as the influence of the pressure waves generated by the trains on the windbreaks. The three-dimensional incompressible improved delayed detached eddy simulation (IDDES) method based on the SST k-ω turbulence model is used for numerical calculation purposes, and the overset grid method is used to realize the relative motions of the trains. The results show that the windbreaks can reduce the negative pressure (NP) imposed on the train surface and effectively improve the pressure distribution; crosswinds have a significant impact on the vortexes generated by trains, and the vortexes generated by the upstream train affect the stability of the downstream train; windbreaks can reduce the aerodynamic load applied when trains meet and thus improve the safety of the trains; and the head and tail waves generated by trains impose pressure on the windbreaks, which affects the reliability of the windbreaks installations. The simulation results can provide a preliminary reference for future research.

Artificial Intelligence (AI) can be used to model efficient processes. In this paper, AI and CFD are employed to maximize the wall pressure of the impinging jet, which has a wide range of industrial and technological applications. Firstly, the CFD model is validated with the experimental results for various geometrical and flow rate configurations (H/D= {1, 2, 3, 4, 5, 10, 20}, where H is nozzle to flat plate distance and D is nozzle diameter, and Reynolds Number (Re) ranges {Re= 15,000, 25,000, 30,000}. In explanatory data analysis, Pressure and D are slightly negatively correlated. Re and D show a negative relation of −0.2 whereas a slight negative relation appears for D vs H/D. Re vs H/D have a positive correlation of 0.2. Various activation functions were explored to find that tangent hyperbolic performed best model fit under AI. The Artificial Neural Networks (ANNs) are applied to train the model with minimized least squared error. Finally, the trained model is optimized for the maximum wall pressure over the distance. The maximum pressure obtained from the trained model is 383.83 KPa.

Numerical analysis of a U-type solid oxide fuel cell stack was performed using computational fluid dynamics to investigate the effects of stack capacities and fuel/air utilization rates on the internal flow uniformity. The results indicated that increasing the fuel/air utilization rate improved the gas flow uniformity within the stack for the same stack capacity. The uniformity in the anode fluid domain was better than that in the cathode fluid domain. Furthermore, the flow uniformity within the stack was associated with the percentage of pressure drop in the core region of the stack. The larger the percentage of pressure drop in the core region, the more uniform the flow inside the stack. Additionally, under a fuel utilization rate of 75%, the computational results exhibited excessively high fuel utilization rates in the top cell of a 3 kWe stack, indicating a potential risk of fuel depletion during actual stack operation.

Motivated by existing techniques for implementing roughness on cylinders to control flow disturbances, we performed delayed detached eddy simulations (DDES) at Re = 6×106 that generated unsteady turbulent flow around a rectangular cylinder with a controlled wrinkled surface and a 1:4 aspect ratio. A systematic study of the roughness effect was carried out by implementing different configurations of equally spaced grooves and bumps on the top-surface of the cylinder. Our results suggest that groove geometries reduce energy dissipation at higher rates than the smooth reference case, whereas bumped cylinders produce relative pressures characterized by a sawtooth pattern along the middle-upper part of the cylinder. Moreover, cylinders with triangular bumps increase mean drag and lift forces by up to 8% and 0.08 units, respectively, while circular bumps increase vorticity and pressure disturbances on the wrinkled surface. All of these effects impact energy dissipation, vorticity, pressure coefficients, and flow velocity along the wrinkled surface. Both the surface-manufactured cylinders and the proposed visualization techniques could be replicated in a variety of engineering developments involving flow characterization in the presence of roughness.

The flow characteristics of homogeneous gases in complex systems are an important issue in many areas, including underground mines. The flow in mine excavations and ventilation systems is described by known mathematical relationships that could be applied to various cases. In this paper, a flow in a duct with a local sink of mass and momentum for multiple variants of cooperation of a mechanical fan was analyzed. The relationships for the total and static pressure of air in the duct were derived. In the next stage, a calculation example of how the mass flow rate of air, and the total and static pressure of the flowing air will change in the tested sections for the duct with and without a sink, is presented. The derived formulas and calculated values for the considered calculation case allow the verification of the obtained relationships at the measurement station. Analyzing the results of the examples presented in the article, it can be concluded that the total and static pressure at the sink point differ depending on the equation of motion used. In the case of the classic equation, the value of total pressure is lower than the value calculated from the new equation of motion, and the difference between them is about 20 Pa. In the case of static pressure, this difference is about 46 Pa. Qualitative differences in the static pressure distribution at the release location were also demonstrated. Depending on the applied approach, positive or negative changes in the static pressure are noticed. The presented form of the equation of motion made it possible to determine the flow characteristics in the duct with a point mass and momentum sink in the case of the operation with and without a fan.

The efficient development and exploitation of shale oil depends on long-distance horizontal wells. As the degree of cleaning of the wellbore plays a key role in these processes, in this study, this problem is investigated experimentally by focusing on the dimensionless cuttings bed height. A method is proposed to calculate the horizontalwell hydraulic extension taking into account the influence of the wellbore cleaning degree on the wellbore pressure distribution and assess the effect of a variety of factors such as the bottom hole pressure, the circulating pressure drop, the drilling pump performance and the formation properties. The analysis shows that the hydraulic extension of horizontal wells decreases with an increase in the cuttings bed height, and the higher the displacement of drilling fluid, the faster the hydraulic extension declines. The annular pressure drop of the horizontal section increases with the increase of the cuttings bed height, resulting in a higher bottom-hole pressure. Several arguments are provided to guide the safe drilling of shale oil horizontal wells and overcome the limits of current technological approaches. [ABSTRACT FROM AUTHOR]