Pressure Characteristics Research Articles

Research on the Balance Axial Force of the Back Blade of Centrifugal Pump Impeller based on CFD

Abstract One popular way to decrease the pump’s axial force is by utilizing the back blade. In this paper, by changing the number and width of back blades and using CFD 3D simulation technology, the influence law of back blades on pump performance, pump chamber liquid pressure characteristics and axial force characteristics is obtained. By changing the number of the back blade and width of the back blade, this paper adopt CFD 3D simulation technology to study, get pump performance, pump cavity liquid pressure characteristic and the influence law of axial force characteristics. The results show that the pump head and power increase with the increase of the width and number of back blades. However, the efficiency of the pump gradually decreases with the increase of the width and number of back blades. The impeller mounted back blade can change the pressure distribution of liquid of the pump chamber, and affect the axial force of the pump. The size and direction of the axial force change with the number and width of the back blades.

Effects of branched tube on pressure waves in the hyperloop system: An experimental study

In this study, we experimentally investigated the aerodynamic characteristics of the Hyperloop with branch tube, an important applicational situation. Experiments were performed considering two velocities (258.6 and 295.8 m/s) and five branched angles (θ = 30°–150°) using 8.75 cm of scaled pod model (blockage ratio = 0.34). The leading shock waves LSW1 and LSW2 generated in front of the pod model were measured, and their intensity was analyzed before, on, and after the branching. The intensity of LSW1 and LSW2 at the straight tube before branching was the same as that without branching. LSW1 and LSW2 were divided by branching and propagated to the branched tube, where their intensity decreased to branched shock waves BSW1 and BSW2, respectively. The degree of decrease in BSW1 was linear as θ increased, whereas BSW2 decreased as θ and speed of the pod model increased when θ ≤ 90° and was nearly constant at 0.80 when θ ≥ 120°. The pressure characteristics near the branching were non-axisymmetric and became axisymmetric as it moved forward through the branching when x/lt ≥ 0.66. When LSW1 and LSW2 passed through the branching and were propagated as transmitted shock waves TSW1 and TSW2 after branching, their intensity decreased to approximately 86% and 91%, respectively, and was not significantly affected by the pod speed and θ.

Unraveling the impact of infodemic stress on information and health behaviors: a double effect perspective

PurposeThis paper aims to explore the underlying mechanism whereby information-induced stress, resulting from the burdensome nature, questionable information reliability, misleading content and diffuse characteristics of infodemic pressure, impacts individuals’ online information-related behavior and health-related preventive behavior.Design/methodology/approachWe conducted a cross-sectional survey organized with social media users during the post-pandemic period. Based on the 342 valid responses, structural equation modeling was employed to validate the research model.FindingsThe results substantiate our multidimensional view of infodemic stress, which encompasses dimensions including information overload, uncertainty, diffusivity and insecurity. We found that the infodemic stress contributes to pandemic fatigue, then engenders both negative information behavior and reduced engagement in preventive behavior. Furthermore, infodemic stress has also been found to have a direct positive effect on individuals’ engagement in preventive behavior.Originality/valueThis study introduces the concept of “infodemic stress” and presents a comprehensive framework to capture its various dimensions. This study offers novel insights into the psychological and behavioral repercussions of the infodemic stress transmitted through social media.

Analysis of dynamic characteristics and influencing factors of CO2 low-permeability coal reservoir sequestration

ABSTRACT Abandoned coal seams can be an important carrier for CO2 geological storage. Considering the gas seepage-diffusion and physical adsorption coupling characteristics in the process of CO2 adsorption and storage in coal and rock, a two-dimensional model of coupled flow-solidity for geological storage of CO2 in low-permeability reservoir with double voids was established by introducing the Zhang Hongbin model algorithm and adding the Klinkenberg effect and the compression effect of the rock skeleton in coal reservoirs in the controlling equation for rock deformation. The coupled flow-solid model was solved by using the PDE equation of COMSOL Multiphics program, and the simulation results difference between the new model and the traditional model in terms of sequestration dynamics were compared. The dynamic characteristic of reservoir gas pressure, formation stress, permeability and sequestration density in the process of CO2 geologic sequestration and injection were analyzed, and the influences of injection pressure and injection well diameter on the amount of CO2 sequestration were explored. The results show that the new model is more reasonable for calculating reservoir gas pressure and permeability compared with the Palmer-Mansoori model (PM model), and can simulate the free-state seepage movement of CO2 in the fracture system as well as its physical adsorption process compared with the single-heavy pore medium model. With continuous CO2 injection, the maximum sequestration density was raised to a limit value of about 1000 kg/m3 after 1 year. The date of reaching the limit of the sequestration volume was advanced by about 45 d when the positive pressure of the injected gas was increased from 10 kPa to 50 kPa. This model can reproduce the main parameters including, when affecting the effect, and realize the calculation of parameters such as CO2 density reaching the limit value, sealing limit day, sealing limit amount, which can provide a theoretical basis for further deep understanding of CO2 geological sealing law and scientific development of gas injection scheme.

The influence of fluid pressure, redox potential and crystal growth characteristics in Mississippi-Valley-Type (MVT) ore formation - lessons from a modern geothermal scale

The influence of fluid pressure, redox potential and crystal growth characteristics in Mississippi-Valley-Type (MVT) ore formation - lessons from a modern geothermal scale

Plantar Pressure Characteristics with Foot Postures and Balance Abilities in Indigenous Taiwanese: A Preliminary Exploration.

BACKGROUND Although Indigenous Taiwanese are generally known for having excellent athleticism and balance abilities, the correlation between foot characteristics and balance abilities has rarely been discussed. This study aimed to explore the characteristics of plantar pressure profiles associated with foot posture and balance abilities among Indigenous Taiwanese. MATERIAL AND METHODS We recruited 165 Indigenous college students and 183 healthy age-matched students. Bipedal static plantar pressure distributions (PPDs) with arch index (AI) and centers of gravity balance were examined using the JC Mat. Foot posture was determined by estimating the rearfoot postural alignment. RESULTS Indigenous Taiwanese in the study generally had low-arched feet with increased plantar loads at the medial (left: 1.21±0.43%; right: 1.20±0.46%) and lateral longitudinal arches (left: 24.51±5.26%; right: 24.45±6.64) (P<0.01) and the medial metatarsals (left: 21.78±3.81%; right: 22.19±3.91) (P<0.01). Footprint images illustrated pronounced cuboid and navicular collapses. Performances of balance abilities (left: 49.53±4.38%; right: 50.47±4.38) (P<0.01) and rearfoot postural angles (left: 1.37±1.25°; right: 1.32±1.17°) (P<0.05) were better than those of controls. CONCLUSIONS The feet in Indigenous Taiwanese had low arches and higher plantar loads at the medial and lateral longitudinal arches and medial metatarsals, while their centers of gravity were symmetrical and rearfoot posture was normal. These results may facilitate further studies on the relationship between foot characteristics, potential athleticism, and musculoskeletal injuries in Indigenous Taiwanese.

Catastrophe Information Characteristics and Prevention Measures of Water Inrush in Tunnel Approaching Fault with Different Water Pressure

In order to ensure the safety of the tunnel approaching the fault and prevent water inrush disasters, and then take reasonable protective measures, a fault-tunnel-surrounding rock is established by using a three-dimensional (3D) discrete element numerical analysis method, which takes into account the fluid-structure coupling effect. Based on the method of control variables, the catastrophe information characteristics of displacement and water pressure of the surrounding rock of the tunnel face and the corresponding characteristics of changes before the occurrence of water inrush disasters were studied under different fault water pressures during the excavation of the tunnel approaching the water-rich fault. The results show that, during excavation at the same step, displacement and its magnitude in the surrounding rock escalate as fault water pressure increases. The maximum pressure of the water in the surrounding rock is also constantly increasing. As tunnel excavation progresses, at constant fault water pressure, longer excavation distances result in greater axial displacement of the surrounding rock mass and increased water pressure at corresponding positions within the surrounding rock, leading to higher magnitude increases. As excavation proceeds, the displacement and water pressure in the surrounding rock and the increase of its amplitude continue to increase. Pre-reinforcement grouting techniques and pipe umbrella support systems that are very effective protective measures can be determined by a comprehensive approach integrating advanced geological forecasting methods, real-time water pressure detection, and the analysis of stress-strain and seepage pressure field variations in the surrounding rock mass.

Numerical Investigation of Shell-Nozzle Diameter Effect on Thermal Performance of Shell-and-Tube Heat-Exchanger

The shell nozzle diameter plays a crucial role in determining heat transfer efficiency and pressure characteristics in shell and tube heat exchangers. In this study, we have conducted a numerical simulation to explore the effects of varying shell nozzle diameters on heat transfer performance, flow behavior, and pressure drop within a shell and tube heat exchanger. Ranging from 10 to 110 mm, we assessed how altering the shell nozzle diameter affected heat transfer, flow patterns, and pressure drop. Employing the k-ω shear stress transport turbulence model, we compared numerical Nusselt numbers to experimental data, observing a correlation. As the shell nozzle diameter decreased, inlet velocity surged, generating a stronger vortex. Shrinking from 110 to 10 mm, this reduction amplified vorticity by an average of 169%, notably intensifying heat exchange by 35%. Evaluating the overall heat transfer coefficient against pressure drop, we used the thermal enhancement factor, reaching a peak of 4.39 at a 70 mm shell nozzle diameter. This exploration lays groundwork for optimizing shell nozzle diameters in these heat exchangers.

CFD-FEM simulation of hydroelastic responses and slamming loads of a bow-flare ship advancing in head regular waves

ABSTRACT In this paper, the global motions and wave loads on a large bow-flare ship with the effect of hydro-elasticity, including whipping and springing, are numerically simulated by a CFD-FEM two-way coupled method. The simulation results of ship motions and wave loads by employing the numerical method are demonstrated by verification and validation studies including comparison with tank model experiment results. Additionally, the presented method is applied to study the motions, wave loads and slamming loads of the ship in different wave conditions. The vertical bending moment and vertical shearing force of different frequency components and their distribution along ship length are studied. The characteristics of slamming pressure and green water loads and their spatial distribution are studied. The simulation results indicate that the present numerical method well reproduces ship seakeeping and hydro-elasticity and has potential application values in the design and evaluation of ship wave loads.

The Quasistatic Pressure Characteristics of a Confined Cabin in a Water Mist Environment

To investigate the quasistatic pressure load characteristics of an explosion in a confined cabin in a water mist environment, explosion tests were conducted under different explosive and water mist masses. The concentration of water mist, droplet diameter, and quasistatic pressure inside the cabin were measured. On the basis of the theoretical model of quasistatic pressure in adiabatic ideal gas cabins, a theoretical model of the quasistatic pressure in a confined cabin in a water mist environment was established. On the basis of experimental data and theoretical models, an empirical formula was proposed for the peak quasistatic pressure of implosion in a water mist environment. A model for a cabin explosion in a water mist environment was established, and the load characteristics of a cabin explosion under high water mist concentrations were analyzed. The relevant research results contribute to the prediction of the quasistatic pressure of explosions in a confined cabin in a water mist environment.

Undrained triaxial tests of underconsolidated overlying sediments of hydrate deposits in the South China Sea

The South China Sea (SCS) is an important repository for natural gas hydrates (NGHs), where some NGH deposits and their overlying sediments (OSs) are in an underconsolidated state. During the exploitation of NGHs, the stability of the OSs of the NGH deposits is one of the key factors in ensuring mining safety. Especially under different consolidation degrees, the mechanical response and stability of the OSs will vary, which directly affects the safety and efficiency of the NGH mining. This research explores the influence of different consolidation degrees on the mechanical properties of the OSs of NGH deposits in the SCS. The strength and pore pressure characteristics were analyzed through undrained triaxial shear tests. The findings indicate that an increase in consolidation degree enhances the strain softening behavior, and an increase in initial effective stress enhance the strain hardening and shear contraction behaviors of the samples. The failure strength, modulus, and maximum excess pore pressure increase with the consolidation degree and initial effective stress, and there is an approximately linear correlation between failure strength and consolidation degree. Therefore, the exploitation of NGHs in the SCS must comprehensively consider the burial depth and consolidation degree of the OSs. The findings of this study will assist in optimizing mining plans and enhancing safety during the exploitation process.

Research on the Unsteady Flow Characteristics of Solid–Liquid Two-Phase Flow in a Deep-Sea Mining Lift Pump and Model Experimental Verification

The deep-sea mining lift pump is one of the pivotal components in deep-sea mineral transportation systems and its internal flow is very complex; consequently, unraveling its unsteady flow behavior pattern holds immense practical value. This study adopts numerical methods to analyze the time-averaged distribution characteristics of the internal flow field in mining lift pumps, as well as the flow field’s pulsation intensity distribution characteristics, the vortex’s spatiotemporal evolution process in both moving and static cascades, and the time- and frequency-domain pulsation characteristics of internal pressure in each flow passage component under four different flow conditions are also investigated. The hydraulic properties of mining lift pumps under these four different conditions are also evaluated, and the outcomes are benchmarked against those of numerical predictions. Our findings reveal that the interplay between impeller blades and guide vanes significantly influences the pump’s flow characteristics, with the pump’s unsteady flow influencing its hydraulic properties. Experimental validation of this system confirms that the pump under study is in line with design specifications in terms of hydraulic properties. The method validation test on the prototype pump shows that the SST k-ω model is capable of successfully forecasting instability in the flow features of deep-sea mining lift pumps. These results will serve as a theoretical reference for regulating the flow state inside deep-sea mining lift pumps.

Effects of rail models on aerodynamic characteristics of trains in crosswinds at a large yaw angle

Rail models may be simplified at different levels in wind tunnel tests and numerical simulations. This work used delayed detached eddy simulations to analyze and compare the aerodynamic loads (drag, side force, lift, and rolling moment), surface pressure, and flow characteristics around a train model placed on subgrades with three different rail models: no-rail, simplified rail, and realistic rail. The simulations were conducted at a large yaw angle of 60°. The mean aerodynamic characteristics of the car bodies and bogies were similar with the simplified rail model and realistic rail model, while those were completely different without the rail model. The difference in aerodynamic loads between the no-rail model and the realistic rail model was as high as 53.1%, whereas the difference between the simplified and realistic rail models was only 7.7%. And for fluctuating aerodynamic characteristics of the train, there was still differences between the cases with the simplified and realistic models. Further, the rail model significantly impacted the flow (such as the velocity, turbulent kinetic energy, and vorticity) around the train, especially under the train, resulting in significant differences in the aerodynamic loads in time and frequency domains. For accurate and precise measurements of mean aerodynamic loads, incorporating a rail model (with the simplified model being sufficient) can improve accuracy by 48.0% and precision by 66.9%. When focusing on fluctuating aerodynamic loads, using a realistic rail model is essential to accurately capture amplitude-frequency characteristics. The rail model setup recommendations outlined in this work aim to enhance the accuracy and reliability of various wind tunnel tests and numerical simulations related to train aerodynamics.

Basic characteristics of tongue pressure and electromyography generated by articulation of a syllable using the posterior part of the tongue

The basic function of the tongue in pronouncing diadochokinesis and other syllables is not fully understood. This study investigates the influence of sound pressure levels and syllables on tongue pressure and muscle activity in 19 healthy adults (mean age: 28.2 years; range: 22–33 years). Tongue pressure and activity of the posterior tongue were measured using electromyography (EMG) when the velar stops /ka/, /ko/, /ga/, and /go/ were pronounced at 70, 60, 50, and 40 dB. Spearman's rank correlation revealed a significant, yet weak, positive association between tongue pressure and EMG activity (ρ = 0.14, p < 0.05). Mixed-effects model analysis showed that tongue pressure and EMG activity significantly increased at 70 dB compared to other sound pressure levels. While syllables did not significantly affect tongue pressure, the syllable /ko/ significantly increased EMG activity (coefficient = 0.048, p = 0.013). Although no significant differences in tongue pressure were observed for the velar stops /ka/, /ko/, /ga/, and /go/, it is suggested that articulation is achieved by altering the activity of both extrinsic and intrinsic tongue muscles. These findings highlight the importance of considering both tongue pressure and muscle activity when examining the physiological factors contributing to sound pressure levels during speech.

Liquefaction behavior and shear strain-based pore pressure model of fiber reinforced calcareous sand

The generation mechanism of pore pressure plays an essential role in understanding the liquefaction behavior of sand under cyclic loading. Extensive undrained simple shear tests were undertaken to study the pore pressure and shear strain development characteristics of calcareous sand reinforced by fibers. The results show that the deformation patterns of the tested calcareous sand gradually shift from brittle to ductile failure as fiber content increases. The mechanism of pore pressure generation in calcareous sand subjected to cyclic loading is quite distinct from that of siliceous sand, exhibiting more pronounced accumulation in the initial stage of cyclic loading. Fiber reinforced calcareous sand exhibits reverse shear contraction behavior when liquefaction is imminent. A remarkable finding is the establishment of a unique correlation between pore pressure ratio and shear strain, irrespective of the fiber reinforcement. Consequently, a shear strain-based pore pressure generation model of reinforced calcareous sand is then developed to predict the pore pressure built-up trend under varying fiber content and length conditions. This model is also applicable to various testing conditions and soil types.

The effects of fiber load and frictional work on fatigue behavior of water hydraulic artificial muscles in underwater environment

Water Hydraulic Artificial Muscles (WHAMs) exhibit characteristics of high pressure and substantial load capacity. In previous work, the fatigue life of WHAMs under elastic load has been investigated, and experimental results have indicated that the fatigue life is related to both fiber load and frictional work. To individually investigate the impact of fiber load and frictional work on the fatigue life of WHAMs, an experimental scheme was designed to test the fatigue life under different levels of fiber load and frictional work. Meanwhile, the working pressure and contraction range were determined for various working conditions, in order to assess their effects on the fatigue life of WHAMs. The W-test confirms that the fatigue life of WHAMs under each working condition follows a normal distribution. Based on the experimental results, the influence of fiber load and frictional work on fatigue life was analyzed. And the experimental results indicate that the impact of fiber load on the fatigue life of WHAMs is approximately three times greater than that of frictional work. Furthermore, substituting aramid 1414 fiber with aramid 3 fiber in the fiber sleeve led to a substantial increase in fatigue life, elevating the average fatigue life to more than 4 times. Based on the power-law model, a fatigue model of WHAM is established with fiber load and frictional work as factors. The relative error between the fatigue model and experimental results in previously published work demonstrates that the new fatigue model can accurately predict the fatigue life of WHAMs.

Levitating Magnetic Insoles: A Novel Approach to Alleviating Plantar Fasciitis Through the Reduction and Redistribution of Plantar Pressures

Plantar fasciitis, a leading cause of foot pain, affects a significant portion of the population, with an estimated prevalence of 10% during an individual’s lifetime. This debilitating condition can result in substantial healthcare costs and decreased quality of life. The pain is attributed to the inflammation of the plantar fascia, which is crucial for supporting the foot's arch. Risk factors for plantar fasciitis include obesity, sedentary lifestyles, improper footwear, and biomechanical abnormalities. Current treatment options are primarily conservative, with varying levels of success. In response, an affordable, lightweight, and soft, magnetic insole was developed as a novel approach to alleviate plantar fasciitis by reducing and redistributing plantar pressures with neodymium magnets. The final prototype achieves a magnetic repulsion force of approximately 84.57 lbs. and incorporates sensor modules to monitor data. The device also facilitates real-time data visualization between Arduino and personal devices, providing valuable insights into plantar pressure and walking characteristics for various patients. Data analysis and structural optimization are further enhanced through the use of MATLAB and Excel, which generate heatmaps to visualize plantar pressure distribution. Future research should focus on increasing the magnetic intensity to improve pain relief effectiveness and incorporating personalized disease-specific adjustments to optimize the magnet placement within the sole. By addressing the prevalent issue of foot pain and offering a potential solution for plantar fasciitis, our levitating magnetic insoles demonstrate significant potential for enhancing the quality of life for a large portion of the population.

Plantar pressure in relation to hindfoot varus in people with unilateral upper motor neuron syndrome.

Hindfoot varus deformity is common in people with unilateral upper motor neuron syndrome (UMNS) and can be dynamic or persistent. The aims of this study were (1) to gain insight into plantar pressure characteristics of people with chronic UMNS in relation to hindfoot varus and (2) to propose a quantitative outcome measure, based on plantar pressure, for the scientific evaluation of surgical interventions. In this retrospective study, a cohort comprising plantar pressure data of 49 people with UMNS (22 "no hindfoot varus", 18 "dynamic hindfoot varus", and 9 "persistent hindfoot varus"), and 586 healthy controls was analyzed. As an indication of plantigrade foot contact, the ratio between the plantar contact area of the affected and the non-affected foot was calculated. To investigate spatial and temporal aspects of plantar pressure, normalized plantar pressure patterns and center of pressure trajectories were computed. People with UMNS had lower plantar pressure area ratios compared to healthy controls. Additionally, increased plantar pressure underneath the lateral foot was found in people with a persistent hindfoot varus. Center of pressure trajectories were more lateral during the first 26% of the stance phase in people with a dynamic hindfoot varus and during the first 82% of the stance phase in people with a persistent hindfoot varus compared to healthy controls. Spatial and temporal differences in plantar pressure were found in people with dynamic or persistent hindfoot varus deformity. We propose to primarily use the medio-lateral center of pressure trajectory as outcome measure for the scientific evaluation of surgical interventions targeting hindfoot varus.

Effect of impedance boundary-controlled casing treatment on performance of a fan subjected to inlet swirls

An experimental investigation is conducted to evaluate the performance and the stalling process of a fan subjected to inlet swirls, as well as the effectiveness of an Impedance Boundary-Controlled (IBC) Casing Treatment (CT) on the stall margin recovery. An operating cycle is proposed based on the hysteresis effect of harmonic flap oscillation of airfoils and parallel compressor theory to explain the pressure characteristic of the fan under twin swirl inlets. Twin swirls are observed to reduce the stall margin of the fan, and the circumferential location where the spike is detected turns to the intersection area of the twin swirl. The IBC CT is proven to extend the stall margin of the fan for 12.7%–22.3% when subjected to inlet swirls with an efficiency loss of around 1%. The IBC CT helps to reduce the size of the operating cycle of the fan by redistributing the blade loading and adding the system damping to dissipate the perturbation energy.

Effect of airflow velocity in vessel-pipelines on dust explosion during pneumatic conveying

In order to investigate the flame propagation and pressure characteristics of dust particles during airflow transportation, a dust explosion experimental apparatus simulating dust handling processes was designed. The system is supplied with a stable airflow by a high-pressure fan, capable of continuously transferring dust from the vessel to the pipeline at a controllable speed. Dust explosion experiments were meticulously executed by applying 1 kJ of ignition energy to the transported dust particles at airflow velocities of 5, 10, and 15 m/s. This study examines the effects of airflow velocity, pipe diameter, and ignition position on explosion characteristics and delves into the mechanisms of these effects through a detailed analysis of experimental results. For the maximum explosion pressure, an increase in airflow velocity causes the maximum explosion pressure to rise. As the pipe diameter increases, the maximum explosion pressure first rises and then falls. The maximum explosion pressure occurs in the case of bottom ignition. The range of maximum explosion pressure values is expected to provide a reference for explosion detection and explosion venting. For flame propagation, the flame undergoes five processes within the vessel, including ignition of dust particles, spherical flame development, flame stretching towards the mouth of the pipe, complete combustion of particles, and near exhaustion of particle combustion. The higher the airflow velocity and the larger the pipe diameter, the more pronounced the flame stretching and development towards the pipe opening become. Within the pipe, two distinct flame propagation behaviors were observed under conditions of high and low airflow velocities. Compared with the experimental results of high-pressure pneumatic powder spraying forming a dust cloud within a vessel-pipeline, this study measures the maximum explosion pressure at specific turbulence levels and establishes a quantitative relationship between airflow velocity and explosion characteristics. Utilizing this correlation can provide a reference for predicting industrial-grade dust explosion characteristics at different airflow velocity levels, thereby offering a more optimized design basis for the design and safety protection of industrial equipment.