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A novel micro-slip friction modeling approach based on real pressure distribution is presented for simulating the interface friction behavior of blades with dovetail joints in aircraft engines. Considering the influence of rotational speed and stagger angle on the true pressure distribution of the dovetail joint, an asymmetric pressure density function was established and applied to the Iwan friction model. The pressure distribution at the tenon joint interface is obtained through finite element modeling. And the pressure distribution function is obtained through dimensionality reduction and data fitting. Under the framework of the Iwan model, a new tangential friction displacement relationship at the tenon interface was obtained by changing the critical slip force density function. On this basis, a dynamic model of the dovetail blade was established and the contact characteristics of the interface were analyzed. The results indicate that under the influence of uneven pressure distribution, the width and length directions of the contact interface exhibit different friction behaviors, and the nonlinear response of the blades is affected. [ABSTRACT FROM AUTHOR]

A new boundary treatment considering uniform particle distribution using additive boundary particles for the incompressible smoothed particle hydrodynamics (ISPH) method is proposed. With this new boundary treatment, the solid boundary can be easily modeled just following the geometry configuration and consequently the simulations of fluid–structure interaction problems can be simplified. The efficiency of this new boundary treatment is analyzed, and the implementations are compared with other exiting boundary treatments such as repulsive force and ghost particles. Simulations of the 2D dam-breaking case, static tank, and 2D u-tube test are carried out as examples to demonstrate the performance of this new boundary treatment. It is shown that better predictions can be gained with the new boundary treatment for the pressure distribution in these cases than those obtained from other boundary treatments. [ABSTRACT FROM AUTHOR]

The maneuverability of fighter aircraft designed using double delta wing configuration at low subsonic speed in addition to under high angle of attacks are highly appealing and fascinating to comprehend. Flow pattern formed by double delta wing help to facilitate lifting force under high angle of attack and at such low subsonic speed. In comparison to delta wing, vortex formations by strake part of wing play an important role to create a persistent vortex core capable of delaying stalling. In this investigation, force coefficients of 75°/45° double delta wing configuration is extracted both from wing tunnel experiment and numerical calculation between 0° to 30° angles of attack at Reynolds number of 1.4× 105 based on root chord length. It has also been attempted to investigate the flow pattern formation over wing leeward surface, interaction between vortices formed by strake/wing based on Q-criterion and pressure distribution along propagation path of vortices obtained from CFD (Computational Fluid Dynamics) calculations. Implications of interplay between vortices and pressure distribution in lift generation have also been analyzed. It has been found that around 15° angle of attack strake and wing vortices merge and gets more intensified. With higher angle of attack the lift generation significantly diminishes because of vortex bursting. [ABSTRACT FROM AUTHOR]

Nowadays, the reduction of petroleum products has been aggressively studied due to their environmental concerns and for finding alternative synthetic materials for sustainable development. Thus, naturally derived biocomposites have great potential for creating a sustainable economy with reduced environmental pollution. The present study deals in two major parts; first, the fabrication of the knee prosthetic socket from different laminate biocomposites (FFF, KKK, and RRR) and examined their mechanical performance, thermal stability and degradation behaviour. The interface pressure between the developed socket and residual limb has been examined using the F-socket sensor. Second, the output data of experiential tests and measured interface pressure have been used for numerical analysis to examine the equivalent stress, deformation and safety factor of the sockets at different loading conditions (500 N, 700 N and 900 N). The results observed that FFF biocomposites have maximum compressive strength (121.0 6MPa), impact strength (36.86 kJ/m2), and shear strength (28.51 MPa) which is 8.15%, 49.53%, and 58.88% higher than RRR biocomposites and 2.74%, 34.62%, and 39.28% higher compared to KKK biocomposites, respectively. RRR biocomposites recorded higher hardness (68.42) and fatigue endurance stress (82.86 MPa) due to higher brittleness properties. The thermogravimetric analysis and degradation behaviour have been analyzed to examine thermal stability, degradation temperature, and degradation weight loss behaviour of biocomposites. Finally, the stress generation on the developed socket during the gait cycle is much lower than its calculated strength that did not affect the performance of the socket. Therefore, laminated biocomposites can be an alternative biomaterial to plastics and conventional materials due to their lighter weight, higher flexibility, and economical to provide greater comfort to the users for knee prosthesis applications. [ABSTRACT FROM AUTHOR]

Underground hydrogen storage represents an innovative approach to energy storage. To ensure the secure operation of subterranean hydrogen storage strings, a computational fluid dynamics (CFD) methodology was employed to devise an erosion assessment model tailored for high-velocity conditions. The research delved into the erosion and abrasion dynamics of these storage strings when subjected to high-speed gas flows. This study further examined the impacts of gas velocity, particle size, pipe material, and pipe wall corrosion imperfections on flow patterns and erosion wear rates across the column. The outcomes revealed several noteworthy trends. As fluid velocity increased, the flow field's maximum pressure augmented, while it decreased alongside enlarging pipe diameter and particle size. P110 pipe material exhibited higher maximum pressure in comparison to N80. The effect of centrifugal force induced pressure to surge from the inner to the outer portion of the column. In the curved pipe section's outer wall, the frequent occurrence of high-angle collisions engendered elevated rates of erosion wear over time. Particularly noteworthy was the observation of the highest erosion rate in curved pipes showcasing three corrosion defects, attributed to the backflow effects of erosion pits. [ABSTRACT FROM AUTHOR]

Evaluation of the performance of horizontal wells is an important aspect in the enhancement of their productivity. This study provides mathematical computations, and analysis for theoretical well and reservoir considerations. The study investigates how well design and reservoirs geometry affect the overall performance of a horizontal well in a completely bounded reservoir throughout its productive life. A horizontal well in a rectangular reservoir with completely sealed boundaries is considered and the effect of dimensionless well length LD\hspace{.25em}{L}_{\text{D}}, dimensionless reservoir length xeD\hspace{.25em}{x}_{\text{eD}}, and dimensionless reservoir width yeD{y}_{\text{eD}} on the pressure response over a given period of production using dimensionless time tD{t}_{\text{D}} is studied. The mathematical model used was derived using source and Green’s functions presented in part I of this study. Appropriate well and reservoir parameters are considered and the respective dimensionless parameters are computed which are then used in computing dimensionless pressure PD{P}_{\text{D}} and its dimensionless pressure derivative PD′\hspace{.25em}{P}_{\text{D}}^{^{\prime} }. From the computations, the results obtained are analysed in diagnostic log–log plots with a discussion of the flow periods. The results obtained indicate that an increase in dimensionless well length decreases pressure response during the infinite-acting flow at early times and during transition flows at middle time but increases the pressure response during the pseudosteady state flow at late times. The dimensionless reservoir width and length are observed not to influence dimensionless pressure response during the infinite-acting flow at early times and during the transition flows at middle time, only affecting the prevalence time of the flow periods. However it is observed that during the pseudosteady state flow at late times, dimensionless pressure response reduces with increased dimensionless reservoir length and width.

Ground configurations are an essential part of rail vehicles during wind tunnel tests. Reasonable reproductions of the infrastructures are of significance for experimental accuracy. In this work, the effects of ballast length were numerically studied via improved delayed detached eddy simulation (IDDES). Three extension lengths of the ballast accompanied by a 1/8th three-unit train model were proposed, with a pseudo infinite scenario as the benchmark. The numerical algorithm was firstly validated through a wind tunnel test in terms of aerodynamic loads and pressure distribution. The results revealed that the extended length of ballast had a significant impact on the leading and tail cars while less affected the middle car, due to the relatively farther distance from ballast ends. Ignored the drag coefficient, the influence of the ballast length on the separate cars was that the aerodynamic coefficients predicted by much longer ballast got closer to the benchmark. The ballast-edge-induced unrealistic flow and the train-nose-tip-induced realistic flow could easily be merged and interacted with each other and reinforced, thus causing a noticeable low-velocity zone at the leeward side. With the increasing ballast length, those two separations gradually moved away from each other, decoupled, and receded. A minimum length of E/H = 2 is recommended considering the aerodynamic performance and practical constraints of wind tunnel width. This study provides potential guidance for the arrangement of ground configurations for rail vehicles during wind tunnel tests.

In this study, the ogee spillway flow pattern under the influence of the spillway curve shape and upstream slope changes was evaluated using Flow-3D numerical simulator software. Thus, two ogee spillways with elliptical crest and USBR pattern were simulated in two vertical and oblique upstream modes with a slope of 3H:3V and three different heads, and the results of changes in effective parameters such as flow, velocity and pressure in the length of each spillway was examined. Validation of the results of the numerical model with the results of the Maynord experimental model showed that the Flow-3D numerical model has a high ability to simulate the flow field on the ogee spillway. Comparison of flow rate from numerical model with experimental data showed that the average computational error was less than 3% of the numerical model. Examination of the pressure field showed that at the height of the head equal to the design head, the pressures are close to atmospheric pressure and no negative pressure is created on the spillway crest, but at the head higher than the design head, negative pressure will be created on the spillway. The amount of negative pressure created at the beginning of the USBR spillway crest is higher than the negative pressure value of the elliptical spillway crest due to the lack of continuity in the crest and further separation of the flow lines from it. The results also showed that the ogee spillway with oval crest has a relatively better performance in the flow over the spillway and in these spillways it is possible to pass more discharge with higher safety and sloping the upstream side of the spillway causes a change in the discharge coefficient and finally the flow rate of the spillways.

Taking gob-side entry retaining in Sichuan Coal Group Xuyong No.1 mine as an engineering background, the displacement inverse analysis method is used to calibrate the physical and mechanical parameters test results of coal and rock, and the numerical simulation method is used to analyze the mine pressure distribution law of gob-side entry retaining roadway. Field observation shows that during the working face mining, the maximum relative displacement of roadway roof and floor is 743 mm. Roof subsidence is the main displacement mode of roadway roof and floor. The average roof subsidence is 3.6 times of floor heave, and the numerical simulation result is 3.5 times. The parameter calibration results show that the reduction of elastic modulus and cohesion has a significant impact on the roof and floor approach. At the same calculation step, the roof and floor approach increases with the decrease of elastic modulus and cohesion. When the elastic modulus is reduced to 20%, the maximum value of roof and floor approach increases to 800 mm. The numerical simulation results show that the abutment pressure at the high wall of gob-side entry retaining roadway at the rear of mining face increases significantly, and the abutment pressure distribution is low on both sides and “convex” with the middle height, and the peak value of abutment pressure increases with the advance of working face. The influence range of the average leading abutment pressure of the working face is 77 m.

Abstract The paper investigates the heat transfer in the exploitation of offshore argillaceous‐silt natural gas hydrate reservoirs considering sand control. The temperature prediction model is established in this investigation. The coupled pressure‐temperature model of the flowing fluid inside the wellbore is also presented. The sand control for argillaceous‐silt natural gas hydrate reservoirs mainly brings two effects into the temperature and pressure profiles simulation, including the moderate sand control and the Joule–Thompson effect. The moderate sand control is reflected by the volume and particle size of produced sand into the wellbore in the mathematical derivation. The Joule–Thompson is considered in the model due to the small diameter of sand control screens. The experiment is designed to measure the pressure drop caused by various mesh diameters of sand control screens. Subsequently, the regression relationship between the pressure drop and the mesh diameter is concluded to calculate the temperature change at the sand control screen. The simulation of heat transfer helps to analyze secondary hydrate formation risk in the wellbore. The proposed model identifies the high‐risk location of the secondary hydrate formation. The sand control effect and well geometry effect are discussed quantitatively. The strict sand control in the argillaceous‐silt natural gas hydrate (NGH) sediment exploitation reduces the risk of secondary hydrate formation significantly; however, it also has a negative effect on natural gas production. To balance the sand control and the prevention of secondary hydrate formation risk, it is suggested to install the heating electrode in the high‐risk location to ensure flow safety with acceptable sand control precision. The heat provided by heat electrodes is calculated by the model presented in this paper. The model can be used to determine the proper arrangement of heat electrodes. The paper also describes the secondary hydrate formation by adjusting the well geometry. The formation depth of the NGH reservoir and the sea interval should be considered in the risk analysis of the secondary hydrate formation. Additionally, the effects of wall thickness and wall thermal properties are evaluated and discussed. It is recommended to optimize the riser thickness with a small thermal conductivity value to minimize the secondary hydrate formation risk, which is more efficient compared to adjusting the cement sheath.

This paper is presented to compare various wavy leading-edge protuberances on oscillating hydrofoil performance and power efficiency. The unsteady turbulent 3D flow simulations were carried out by using the StarCCM+ software. The 3D hydrofoil with a straight at the leading-edge is a NACA0015 section with a chord of 0.24 m and an aspect ratio of 7. Four new types of hydrofoils are proposed with wavy leading-edge protuberance. The RANS equations with the realizable k–ε turbulence model are used to predict the turbulent flow around the hydrofoil under different conditions. In order to validate, a comparison of the numerical results of the forces coefficients and power efficiency of non-protuberance oscillating hydrofoil are shown in good agreement with experimental data. Then, four new profiles on the leading-edge of the hydrofoils are simulated and many results of the pressure distribution, vorticity contour, streamline velocity, and power coefficient for five hydrofoil types are presented and discussed. It is concluded that the hydrofoil of Type-M can achieve constantly higher efficiency of over 46% by employing appropriate heave and pitch amplitudes.

The grout pressure in the shield tunnel tail void during synchronous grouting is the key to controlling ground settlement and restraining the segment. However, the circumferential, longitudinal, and radial distribution of grout pressure considering the temporal variation in grout viscosity has not been well explored yet. In this study, a theoretical model of grout pressure distribution and dissipation considering the temporal variation in Bingham grout viscosity was established. The simulation results of the pressure model were verified by field-measured data. The results showed that the radial and longitudinal distributions of grout pressure considering the temporal variation in grout viscosity were closer to the field-measured data. The impacts of the main parameters on the pressure distribution and dissipation were analyzed. Compared with the effect of the shield tail void thickness, tunnel radius and yield shear stress have greater effects on grout pressure during the circumferential filling phase. During the longitudinal and radial diffusion phases, the increase in soil porosity and permeability coefficient was conducive to grout diffusion. The increase in the grout viscosity reduces the pressure loss during the grout flow process. The results of this research can provide a theoretical basis for the grout design process in shield tunnels. [ABSTRACT FROM AUTHOR]

The external heat exchanger (EHE) can solve the problem of the insufficient heating surface due to the large‐scale circulating fluidized bed (CFB) boiler effectively; furnace temperature and bed temperature can be regulated quickly and accurately with the adjustment of the solids circulation rate (SCR). The ash differs from coal‐fired boilers in particle size, density, and other physical parameters, so the circulation and heat transfer characteristics are not identical. The results of SCR and pressure distribution in a cold CFB experimental system with an EHE in which the height of the partition (HP) could be adjusted were analyzed. Experiments studied the effect of fluidized air velocity in the riser (Ug), HP of the EHE, and the pressure of the supply air chamber (PSA) in the EHE on SCR using quartz sand with an average size of 0.239 mm. It was noted that SCR increased with Ug and PSA in the range of 7.01–28.37 g/s with the increase in Ug, and the maximum value of SCR was obtained when PSA was 750 Pa and the HP was 80 mm. The experiments also noted that the increase in SCR significantly affected the pressure distribution in the region of high solids content (EHE and the region above 600 mm in the riser). A reference to the above characteristics of SCR and pressure distribution variations can be considered for operating commercial CFB waste incinerators. [ABSTRACT FROM AUTHOR]

The article considers the development of a near-wall separation vortex arising at a supersonic flow around the external dihedral corner due to the pressure drop between its faces, in the range of angles of attack α = 0.5°–6°. The processes of the origin and development of separation and secondary vortices at the angle increase are investigated in detail. Particular attention is paid to the flow structure change in the vortex location zone. A clear violation of the flow self-similarity in the front part of the model in the zone of vortex system formation is shown. [ABSTRACT FROM AUTHOR]

The influence of different inter-carriage gap configurations, including end wall geometries (3 cases) and gap spacings (0, 5, 8, 10, 15, 20, and 30 mm), on the aerodynamic characteristics of a wind-tunnel train was investigated. The shear stress transport (SST) k - ω turbulence model was employed to determine the airflow features of the train at Re = 2.25 × 106. For validation, the numerical drag force and pressure distributions on the streamlined heads were compared with the experimental benchmark of wind tunnel experiment. The numerical data show that substantial variations in the flow fields, pressure distributions and aerodynamic forces are observed between the trains with and without gap spacings, no matter which configuration is employed. As the gap spacing increases, the airflow along train body rushes into the gap easily, causing the formation of vortices at the gap between the internal and external windshields. The decreasing restriction of flow in the gap also contributes to the pressure differences on the end walls. With the increase of gap spacings, the pressure on both of the first and second inter-carriage gaps is decreased, and it on the first one is a little higher than that on the second at each gap spacing. The end wall geometry affects the flow structures around the train, especially in the region below half-height of the train. This results in a difference in the boundary layer thicknesses and drag contribution in all cases. The discrepancy of end wall geometry causes a substantial variation in the aerodynamic drag between different cases. As gap spacing increases, the aerodynamic drag of the head car decreases, while those of the middle and rear cars increase significantly. When the three cases are compared, the discrepancy of the total aerodynamic drag of Case 1 is the smallest when compared to the base case with a minimum of 0.03% at 10 mm gap spacing and followed by 0.05% at 8 mm. Therefore, to determine the aerodynamic forces for high-speed trains with fully enclosed inter-carriage configuration in wind tunnel test, having a high comparative value as the actual trains, the end wall geometry in Case 1 is recommended with a gap spacing of 10 mm or 8 mm. [ABSTRACT FROM AUTHOR]

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

Copyright of Journal of Central South University is the property of Springer Nature 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.)

A higher order lubrication model between slip walls is proposed for predicting the flow fields that cannot be described by the standard lubrication models based on the thin-gap approximation. The analysis shows that when considering the non-negligible pressure gradient in the surface-normal direction, the local pressure can be separated into (i) the base contribution by the modified Reynolds lubrication equation and (ii) the higher order component varying in both longitudinal and wall-normal directions, which takes the form proportional to the longitudinal derivative of the local velocity of the Couette–Poiseuille flow. For both (i) and (ii), the effect of the slip boundaries appears as the apparent displacements of the no-slip solid walls, and for (i) additional terms (to the no-slip case) also appear. The validity of the higher order slip-wall lubrication model is established by comparing the analytical prediction of the pressure with the fully resolved numerical results in a relatively wide region between a no-slip corrugated wall and a flat plate with varying slip length: the contribution of the higher order term is identified as the decreased lubrication pressure due to velocity slip. The model also successfully predicts the trend of pressure change between the varying slip case and a more realistic system with constant slip length for a channel, where the thin-gap approximation does not hold. [ABSTRACT FROM AUTHOR]

In this work, two new profiles at the leading-edge tubercles of the tidal turbine have been proposed to predict the hydrodynamic performance and obtain more power production than the original blade with a smooth leading edge. A computational method based on the Reynolds-Averaged Navier-Stokes (RANS) is employed for predicting the hydrodynamic performance of the tidal turbine. The turbulent model of the k − ω S S T (shear stress transport) has been used. A three-bladed tidal turbine with the NREL's S814 foil section is selected. The numerical results of the power coefficient against tip speed ratio (TSR) show a good agreement in comparison with the experimental data. Then, two new profiles of tubercles, namely zigzag (ZZ) and absolute sinus (AS), at the leading-edge with 0.1 chord length height at each section, are proposed. The results of the power and torque coefficients are significantly increased, especially at higher TSRs. [ABSTRACT FROM AUTHOR]

The aerodynamic performance of four train models with different windshield configurations (i.e., internal and/or external) in three train marshalling modes (i.e., 3, 6 and 8-car groups) was numerically investigated in this study. The train's airflow characteristics at Re=2.25×106 were determined using the shear stress transport (SST) k- turbulence model. The results were validated by comparing the pressure distributions and drag forces on the streamlined heads with experimental data. The difference in windshield configuration and train length has a substantial influence on the train’s flow field and surface pressure distribution. For the trains with internal windshields, due to non-uniform geometry, the flow is separated and vortices are formed at the windshield area. The boundary layer profile increases with the increased train length, and its thickness varies with windshield configurations. Asymmetric vortices are formed in the wake at a distance close to the tail car’s nose, except for trains with external windshields. The reduction of the flow velocity as the train length increases causes a reduction of the low pressure near the tail car’s streamline transition, thus causing a decrease in the tail car’s drag and lift forces. Consequently, for trains with external windshields, the head car’s drag increases, whereas the total train drag reduces significantly as the train length increases. Therefore, employing external windshields in all the inter-carriage gap sections, irrespective of the train length, demonstrates a good ability to reduce future train’s aerodynamic drag.

The relevance. Diffusers, either as nozzles or constituent elements, are frequently used in many mechanisms and machines. In this regard, the study of viscous fluid flow in diffusers aims to discover patterns of changes in the flow's hydrodynamic parameters, allowing better understanding of the nature of flow as a function of Reynolds number. Following the results of the analysis of the study, conditions for the proper construction of the mechanism unit, ensuring its reliable and durable operation will be revealed. The main aim of this study is to determine the velocity profiles in the flat diffuser for a viscous incompressible fluid by integrating the simplified Navier–Stokes differential equations under the established initial and boundary conditions, as well as the bifurcation point's dependence on the opening angle and Reynolds number of the diffuser. Objects: a flat diffuser in which viscous incompressible fluid moves. At the same time, revealing the patterns of changes of the hydrodynamic parameters of the flow is of defining value when choosing the structural dimension of devices and mechanisms, the main part of which is the flat diffuser. Methods. To reveal the patterns of changes of the hydrodynamic parameters of the flow in a flat diffuser, the study is based on the fundamental nonlinear differential equations of viscous fluid mechanics, which in a general case are not subject to an exact mathematical solution. For integration in the nonlinear differential equations, due to the smallness, the nonlinear-convective terms are neglected, and the inertial terms are also partially simplified. Such a simplification is justified if the velocities are very small or if the dynamic coefficient of viscosity of the fluid is very large. A method for solving the boundary value problem was developed, and regularities for changing the flow parameters were obtained. According to the derived regularities, graphs of the change in velocity, pressure and shear stresses on the wall of the fixed channel were plotted and the coordinates of the separation point were determined. Results. Depending on the angle of the diffuser opening and the Reynolds number, a general solution of the approximating Navier–Stokes equations was given. In accordance with the nature of the motion, the boundary conditions of the problem were established and the boundary value problem was stated. A method for integrating a boundary value problem was developed, and regularities for the change in velocities along the length of the diffuser were obtained for a parabolic distribution of velocities in the inlet sections. Graphs of the change in radial velocities along the length and at a fixed value of the opening angle were constructed, a flow pattern and the transition of a single-mode flow to multimode operation were obtained. For a fixed opening angle and Reynolds number, the conditions for flow separation from a fixed wall were derived, where the flow velocity changes the sign.

Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering Editorial Office 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.)

In recent years, accidents of gantry cranes caused by strong winds have occurred from time to time. Therefore, it is of practical engineering significance to study the wind load of gantry cranes. Aiming at the two gantry cranes wind load characteristics, the computational fluid dynamics (CFD) method was adopted to carry out simulation research on two gantry cranes. Firstly, the Pro/E software was used to establish a three-dimensional model of the gantry crane; the ANSYS software was used to establish the outflow field of the crane; the grid division and grid independence of the computational domain were carried out by ANSYS. Then, the numerical simulation of a single gantry crane was carried out by Fluent software to analyze the aerodynamic coefficients of a single gantry crane under different wind direction angles. At the same time, the difference between the wind load in Design Rules for Cranes and the simulation was compared. Finally, considering only the influence of inflow wind load, the numerical simulation of two gantry cranes was carried out. Meanwhile, the influence of wind direction angles and two gantry cranes spacing S to the drag coefficient, the wind reduction factor of gantry crane, the velocity change cloud diagram and the pressure distribution of gantry crane were studied. The results show that the maximum wind load on the gantry crane appears in the 45° wind direction. In 90° wind direction, the wind proof effect is the best with about 52% wind reduction when the distance between the two gantry cranes S =15 m. Critical spacing of two gantry cranes S=35 m. When S ＞35 m, two gantry cranes shielding effect is weakened until it disappears. The maximum pressure on headwind of main girder of gantry crane is close to the both ends of the girder. [ABSTRACT FROM AUTHOR]

A modified drafting system, named the soft drafting system, based on the ring spinning frame, has been introduced in the previous paper. In order to compare with the conventional drafting system, this paper analyzed pressure distributions of the two drafting systems and compared apron slippages based on the condition of spinning 18.2 tex combed cotton yarns. The results show that the floating area of the soft drafting system is only 6 mm, much smaller than that of the conventional drafting system at 12 mm. In addition, the soft drafting system can provide a longer and more stable friction zone and the curved channel is more conducive to the separation of fiber bundles to reduce yarn imperfections. The soft drafting system does not have the problem of apron-to-apron slippage that may cause deterioration of yarn quality. The slip rate of the soft drafting system between the lattice apron and the middle bottom roller is 0.03%, while the slip rate of the conventional drafting system between the bottom apron and the middle bottom roller is 8.58%, resulting in a reduction in drafting efficiency and poor stability of yarn quality. The experimental results show that the soft drafting system can significantly improve yarn evenness with CVm% of the soft drafting system decreasing 10.2% over the conventional drafting system. Also, the soft drafting system can reduce yarn imperfections, especially thick places with þ35% thick places decreasing 71.9% and þ50% thick places decreasing 70.4%. [ABSTRACT FROM AUTHOR]

The needle valve is a critical control unit for high-pressure hydrogen systems such as hydrogen refueling stations, which is the infrastructure of hydrogen energy. As an important part of the needle valve, the valve spool affects the flow characteristics of hydrogen in the valve and then affects the working performance and safety of the high-pressure hydrogen valve. In this paper, based on the real hydrogen gas model and the finite volume method, a CFD model of the high-pressure hydrogen needle valve is constructed to find out the influence of the valve spool shape on the performance and flow characteristics of the high-pressure hydrogen needle valve. The results show that high-pressure hydrogen will produce a sudden change in pressure around the valve spool and there will be a local high-speed area, and the turbulent intensity will also increase. The arc cone spool can increase the flow by 2%–8% at different openings of the valve, and reduce the maximum speed at the spool by 15% at small openings. In addition, the sudden change of pressure and the eddy current have also been improved. Flat-bottomed cone spool reduces turbulence intensity and energy consumption. Therefore, it can be concluded that changing the shape of the valve spool to have a larger flow area at a small opening can make the high-pressure hydrogen valve have a better flow field distribution. Flattening the cone angle of the spool can improve the turbulent flow in the valve. The research in this paper can provide research accumulation and theoretical support for the optimization design of the needle valve of the high-pressure hydrogen system. • A large pressure gradient of hydrogen flow will be generated at the valve spool. • The valve with arc cone spool has a larger flow rate and a smaller pressure drop. • The arc cone spool can reduce the high-speed zone and the eddy current in the valve. [ABSTRACT FROM AUTHOR]

The problem of fluid withdrawal from a reservoir into a well or injection of fluid from a well into a reservoir in the presence of a hydraulic fracture perpendicular to the wellbore is considered in the constant flow rate regime. Analytical solutions that describe the evolution of pressure in the fracture at a constant reservoir-to-well fluid flow rate are obtained. Approximate solutions are constructed using the method of successive change of stationary states (SCSS). A comparison of the numerical results of the exact and approximate solutions shows that these solutions are almost identical. The influence of the reservoir features of the stratum and fracture on the evolution of pressure in the fracture and well is analyzed. [ABSTRACT FROM AUTHOR]

The effects of bump control on shock aerodynamic characteristics have been investigated by simulations. A bump control that based on the changes of local upper surface of two-dimensional (2D) airfoil or three-dimensional (3D) wing model has been applied to affect the shock intensity and position. The simulation results are close of other experiment when the calculate parameters are same with each other. The simulations show that the drag and lift characteristics can be improved with the bump control, and the results of improvement strongly depend on control parameters. For the 2D RAE2822 airfoil, the optimal control position of the bump control must keep close to the position of the shock wave. The 3D local bump that located on 80% wing span wise and closed to the tip can acquire a batter control results for the 3D RAE2822 wing model. [ABSTRACT FROM AUTHOR]

Introduction: Daily volume loss of residual limb is a condition that most prosthetic users face, negatively affecting their life. One of the consequences is the loss of contact between the residual limb and the socket, which modifies internal pressures. Objective: The aim of this study was to study how the loss of volume of the residual limb affects socket adjustment through measuring pressures inside the socket. Study design: The study design is prospective longitudinal. Materials and Methods: Four subjects with unilateral transtibial amputation, with at least 1 year of prosthetic use, and walking with a comfortable prosthesis participated in this study. The pressure between the socket and the subject's residual limb was measured with an FSocket System (Tekscan). Residual limb volume was measured before and after each test with two different methods: optical scanning (Structure Sensor, Occipital) and conical frustum model. Sanders' protocol for volume loss was followed (Sanders et al. J Rehabil Res Dev. 2012;49:1467–1478). Volume changes in the residual limb and socket internal pressures were analyzed. Results/Discussion: The pressure graph obtained is consistent with Sanders' volume graphs. The pressure distribution inside the socket is lost after 5 hours of use of the prosthetic device; this can be related to volume loss and alignment. The only area where the pressure increases is in the distal zone, given that once the prosthetic fit is lost, weight bearing is transferred to the socket's distal section (mean volume loss, intrasession −3%; mean pressure loss, intrasession −39%). Conclusions: The study suggests that a small change in the volume can cause a change in the distribution of pressures inside the socket, indicating that the prosthetic fit may be compromised. For patient follow-up, measuring pressure inside the socket could be a useful indicator of socket misfit. Clinical Relevance: Daily volume changes in the prosthesis can produce pressures that lead to pain, injuries, an inefficient gait, and prosthesis abandonment. Consequently, it is important to understand the behavior of the pressures inside the socket and the influence of the daily changes of volume on the socket adjustment to design better strategies and techniques of daily volume changes management. [ABSTRACT FROM AUTHOR]

This paper is presented to compare various wavy leading-edge protuberances on oscillating hydrofoil performance and power efficiency. The unsteady turbulent 3D flow simulations were carried out by using the StarCCM+ software. The 3D hydrofoil with a straight at the leading-edge is a NACA0015 section with a chord of 0.24 m and an aspect ratio of 7. Four new types of hydrofoils are proposed with wavy leading-edge protuberance. The RANS equations with the realizable k-e turbulence model are used to predict the turbulent flow around the hydrofoil under different conditions. In order to validate, a comparison of the numerical results of the forces coefficients and power efficiency of non-protuberance oscillating hydrofoil are shown in good agreement with experimental data. Then, four new profiles on the leading-edge of the hydrofoils are simulated and many results of the pressure distribution, vorticity contour, streamline velocity, and power coefficient for five hydrofoil types are presented and discussed. It is concluded that the hydrofoil of Type-M can achieve constantly higher efficiency of over 46% by employing appropriate heave and pitch amplitudes. [ABSTRACT FROM AUTHOR]

The safety of lithium-ion batteries has to be guaranteed over the complete lifetime considering geometry changes caused by reversible and irreversible swellings and degradation mechanisms. An understanding of the pressure distribution and gradients is necessary to optimize battery modules and avoid local degradation bearing the risk of safety-relevant battery changes. In this study, the pressure distribution of two fresh lithium-ion pouch cells was measured with an initial preload force of 300 or 4000  N. Four identical cells were electrochemically aged with a 300 or 4000  N  preload force. The irreversible thickness change was measured during aging. After aging, the reversible swelling behavior was investigated to draw conclusions on how the pressure distribution affected the aging behavior. A novel test setup was developed to measure the local cell thickness without contact and with high precision. The results suggested that the applied preload force affected the pressure distribution and pressure gradients on the cell surface. The pressure gradients were found to affect the locality of the irreversible swelling. Positions suffering from large pressure variations and gradients increased strongly in thickness and were affected in terms of their reversible swelling behavior. In particular, the edges of the investigated cells showed a strong thickness increase caused by pressure peaks. [ABSTRACT FROM AUTHOR]

Bolted joints widely exist in the field of the national defense industry. However, its nonlinear stiffness degradation will occur under tangential load which may lead to the reliability reduction. According to Coulomb friction theory, the pressure distribution is the key in the tangential degradation of bolted joints. Therefore, this paper aims to analyze the pressure distribution of bolted joints. Firstly, we established a threaded bolt model and two simplified models. Secondly, the accuracy of the three models describing the contact area is verified, and the influence of preload and material properties on the contact radius is analyzed. Thirdly, we compared the pressure distribution of the three models, and results show that the smooth bolt model is more suitable for pressure analysis. Finally, the accuracy of several different functions to characterize the pressure distribution of bolted joints is analyzed, and results indicated that the Fernlund function is optimal. This paper provides a feasible simplified bolt model for finite element analysis, and the optimal pressure distribution function can be applied in the tangential stiffness degradation modeling. [ABSTRACT FROM AUTHOR]

Frictional force distribution in the drafting zone is a key factor to control the fiber movement during drafting, and hence to determine the quality of the drafted strands. The frictional force is usually expressed by pressure acting on the strand or fibers in the drafting zone. In order to investigate the pressure distribution in the drafting zone, a device was designed with a film pressure sensor, by which the pressure distribution in different drafting forms and drafting parameters was measured. The effects of drafting parameters, such as the linear density of the strand, roller settings, etc., on the pressure distribution were discussed. [ABSTRACT FROM AUTHOR]

This paper presents a numerical model of a four-pass supercritical steam superheater with a complex flow system. The specific heat of steam is a function of temperature and pressure, and the specific heat of flue gas is a function of temperature. Pressure and temperature changes along the length of the tubes were also determined. The modified Churchill equation was used to calculate the steam-side friction factor of Darcy–Weisbach. The flue gas temperature variations behind the individual superheater tube rows were calculated. The steam and wall temperature distributions were determined in each tube row along its length. Knowing the temperature of the tube walls and the steam along the flow direction enables the selection of the correct steel grade for the tubes. Thanks to this advantage of the proposed method, the investment can be reduced in superheater construction without the danger of overheating the tube material. The results of the superheater simulation were compared with the results of measurements on the actual object. The proposed numerical method can find application in steam superheaters' design and performance calculations. It can also be used to monitor superheater operating parameters, which are difficult to measure due to the high flue gas temperature. [ABSTRACT FROM AUTHOR]

(1) Objective: The objective of this study was to experimentally obtain the ideal pressure distribution model of buttock and thigh support for office workers in forward-leaning and upright sitting postures, reproduce the support provided by mesh materials with elastic materials, and propose an effective seat design scheme to improve the comfort of office workers. (2) Method: Based on the seven most popular mesh chairs on the market, pressure distribution experiments, and the fuzzy clustering algorithm, the relatively ideal body pressure distribution matrices were generated for office workers under two common sitting postures, and the corresponding partitioned sitting support surfaces were obtained. A prototype chair was created and validated by combining the ergonomics node coordinates and the physical properties of the materials. (3) Result: An ideal support model of four zones was constructed, and prototype pads were designed and produced according to this model. Subjects were recruited to test the ability of the prototypes to reproduce the ideal pressure distribution maps. (4) Conclusion: The four-zone ideal support model is capable of effectively representing the buttock and thigh support requirements in forward-leaning and upright sitting postures, and it is useful for the development of related products. Studying sitting postures and pressure values generated by different activities of office workers will help to refine the needs of office personnel and provide new ideas for the design of office chairs. [ABSTRACT FROM AUTHOR]

To predict the risk of pressure injuries in home‐care, it is important to quantify deformation of internal tissue. However, it is difficult for users in home‐care to use conventional modalities such as MRI because the modalities are expensive and not portable for the trunk. Therefore, we have developed a deformation estimation method in a sitting position with the use of machine learning and a low‐cost portable pressure mapping system. We defined the deformation as estimated soft tissue thickness values on each cell of pressure distribution. The thickness on a cell was estimated from measured pressure distribution and no‐load thickness. A no‐load thickness was prepared before estimation using a model. In this article, the estimation method was applied to two single‐layered phantoms which were constructed from wood as an ischial tuberosity and two gels as muscle and fat. The estimation errors were only 1.03% and 2.56% in the muscle and fat phantoms, respectively. We confirmed the estimation errors were adequately small values. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

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In this study, the ogee spillway flow pattern under the influence of the spillway curve shape and upstream slope changes was evaluated using Flow-3D numerical simulator software. Thus, two ogee spillways with elliptical crest and USBR pattern were simulated in two vertical and oblique upstream modes with a slope of 3H:3V and three different heads, and the results of changes in effective parameters such as flow, velocity and pressure in the length of each spillway was examined. Validation of the results of the numerical model with the results of the Maynord experimental model showed that the Flow-3D numerical model has a high ability to simulate the flow field on the ogee spillway. Comparison of flow rate from numerical model with experimental data showed that the average computational error was less than 3% of the numerical model. Examination of the pressure field showed that at the height of the head equal to the design head, the pressures are close to atmospheric pressure and no negative pressure is created on the spillway crest, but at the head higher than the design head, negative pressure will be created on the spillway. The amount of negative pressure created at the beginning of the USBR spillway crest is higher than the negative pressure value of the elliptical spillway crest due to the lack of continuity in the crest and further separation of the flow lines from it. The results also showed that the ogee spillway with oval crest has a relatively better performance in the flow over the spillway and in these spillways it is possible to pass more discharge with higher safety and sloping the upstream side of the spillway causes a change in the discharge coefficient and finally the flow rate of the spillways. [ABSTRACT FROM AUTHOR]

Ground configurations are an essential part of rail vehicles during wind tunnel tests. Reasonable reproductions of the infrastructures are of significance for experimental accuracy. In this work, the effects of ballast length were numerically studied via improved delayed detached eddy simulation (IDDES). Three extension lengths of the ballast accompanied by a 1/8th three-unit train model were proposed, with a pseudo infinite scenario as the benchmark. The numerical algorithm was firstly validated through a wind tunnel test in terms of aerodynamic loads and pressure distribution. The results revealed that the extended length of ballast had a significant impact on the leading and tail cars while less affected the middle car, due to the relatively farther distance from ballast ends. Ignored the drag coefficient, the influence of the ballast length on the separate cars was that the aerodynamic coefficients predicted by much longer ballast got closer to the benchmark. The ballast-edge-induced unrealistic flow and the train-nose-tip-induced realistic flow could easily be merged and interacted with each other and reinforced, thus causing a noticeable low-velocity zone at the leeward side. With the increasing ballast length, those two separations gradually moved away from each other, decoupled, and receded. A minimum length of E/H = 2 is recommended considering the aerodynamic performance and practical constraints of wind tunnel width. This study provides potential guidance for the arrangement of ground configurations for rail vehicles during wind tunnel tests. [ABSTRACT FROM AUTHOR]

Wind loads on heliostats are often investigated through experimental wind tunnel studies or numerical simulations. However, these approaches cannot consider the full-scale conditions but require a reproduction and simulation of both the heliostat structure and the wind conditions. Complementary full-scale investigations are therefore crucial but are at the same time relatively costly, as it is cumbersome to set up large heliostats with measurement devices. This paper introduces a new pressure measurement system which is easy-to-apply to a real-scale heliostat and enables full-scale investigations with minimized effort. The results of a first field study are presented during which wind and pressure measurements were taken simultaneously over periods of 10 min at a 48.5 m2 pentagonal Stellio heliostat. The non-dimensional pressure distributions are investigated and it is shown that the mean c p -values are very consistent amongst the measurement periods and reach values between 2.2 and 2.6. These values, in turn, are found to agree well with results of a wind tunnel study. Moreover, the behavior of the load coefficients with varying angles of attack is studied and the aerodynamic admittance functions are evaluated which give in-depth insight into the generation of aerodynamic loads. The admittance functions are found to start decreasing at a non-dimensional frequency of approximately 0.2. This finding indicates that eddies which are about the size of the heliostat or larger are fully effective in generating aerodynamic loads while the effectiveness of smaller eddies is reduced. • New pressure measurement system developed with maximum sampling frequency of 50 Hz. • Full-scale wind and pressure measurements conducted over several 10-minute periods. • Mean pressure distributions found to reach consistent cp-values between 2.2 and 2.6. • Aerodynamic admittance gives insight into wind load generation. • Eddies smaller than the heliostat are not fully effective in generating loads. [ABSTRACT FROM AUTHOR]

The aerodynamic performance of four train models with different windshield configurations (i.e., internal and/or external) in three train marshalling modes (i.e., 3, 6 and 8-car groups) was numerically investigated in this study. The train's airflow characteristics at Re=2.25×106 were determined using the shear stress transport (SST) k-ω turbulence model. The results were validated by comparing the pressure distributions and drag forces on the streamlined heads with experimental data. The difference in windshield configuration and train length has a substantial influence on the train's flow field and surface pressure distribution. For the trains with internal windshields, due to non-uniform geometry, the flow is separated and vortices are formed at the windshield area. The boundary layer profile increases with the increased train length, and its thickness varies with windshield configurations. Asymmetric vortices are formed in the wake at a distance close to the tail car's nose, except for trains with external windshields. The reduction of the flow velocity as the train length increases causes a reduction of the low pressure near the tail car's streamline transition, thus causing a decrease in the tail car's drag and lift forces. Consequently, for trains with external windshields, the head car's drag increases, whereas the total train drag reduces significantly as the train length increases. Therefore, employing external windshields in all the inter-carriage gap sections, irrespective of the train length, demonstrates a good ability to reduce future train's aerodynamic drag. [ABSTRACT FROM AUTHOR]

Powder metallurgy is a popular method of making raw powders into specific shaped samples. However, the pressure distribution and the microhardness difference within the sample are nonnegligible and unclear when the sample is long or exceeds a specific size. In this study, the long magnesium blocks, with a ratio of about 2.8 between the sample height and the sample side length, are successfully synthesized under three uniaxial and two biaxial conditions. Then, the sample hardness values on the outer surface and the center plane are tested to study the microhardness distribution. The modified analytical expression indicates that the normal pressure exponentially decreases along the compression direction, which is consistent with the hardness distribution trend. Because higher pressure leads to a more compact arrangement of the powders, more metal bonds are formed after sintering. During the first pressing, the sidewall pressure makes the surface hardness higher. The secondary reverse compression mainly improves the bottom and core hardness due to the re-orientation and re-location of the powders. The obtained relationship between the applied pressure and the hardness distribution is instructive in predicting and improving the sample quality. [ABSTRACT FROM AUTHOR]

To clarify distribution characteristics of impact pressure induced by sloshing along the rectangular tank wall and predict the vertical position where the maximum pressure appears, this paper uses VOF method and dynamic mesh technique to simulate the sloshing in the rectangular tank and analyze the sloshing pressure under different conditions. The results show that the vertical position of the maximum sloshing pressure decreases with the increase of the impact strength when liquid does not impact the roof of the tank. The vertical position of the maximum sloshing pressure decreases with the increase of the excitation amplitude. The relationship between the vertical position of the maximum sloshing pressure and the excitation frequency presents parabola-like characteristics and the parabola opens up, which means the vertical position has the minimum value with the change of the excitation frequency, and the minimum of the vertical position occurs when the liquid in the tank near the resonance state. It also shows that the maximum sloshing pressure does not always appear at the static free surface corresponding to different filling levels. Instead, it is distributed regionally as the filling level changes. [ABSTRACT FROM AUTHOR]