Measurement Of Pressure Distribution Research Articles

Characterizing and predicting the partial slip subjected to variable gradients of velocity and pressure in eccentric micro-scale Taylor–Couette flows

In the context of eccentric micro-scale Taylor–Couette flow, variations in localized flow scales result in a non-uniform fluid–solid interface slip state, distinct from the typically studied uniform slip velocity distribution. This study introduces a boundary condition definition method aimed at characterizing partial slip states, complemented by a coupled iterative analysis system tailored to address this complexity. Key contributions include the development of a method for calculating the limiting shear stress, which considers local velocity gradients and pressures. Validation demonstrates that the locally derived slip state aligns more closely with Knudsen number distributions of local flow scales compared to traditional uniform slip models, and exhibits greater consistency with experimentally measured pressure distributions. Additionally, the study reveals that eccentric Taylor–Couette flow, characterized by significant variations in local flow scales and strong self-induced pressure effects, leads to complex distributions of local pressure, velocity gradients, and differences in local slip velocities. Specifically, the non-uniform distribution of local pressure gradients due to eccentricity results in partial slip occurring predominantly on the rotor in regions with positive pressure gradients, and on the stator in regions with negative pressure gradients. Furthermore, the variation in gap height exerts a greater influence on local slip compared to rotational speed and eccentricity ratio. Under certain conditions influenced by pressure gradients, the slip velocity on the rotor may exceed its tangential speed.

A METHOD OF SIMULATING SEAT LOAD FOR NUMERICAL ANALYSIS OF WOOD CHAIR STRUCTURE

This study aimed to investigate the characteristic values of the human-seat interface in a normal sitting posture, and to numerically mode the load on the chair seat for the structural design of chairs. The stress distributions and the characteristic values of seat were measured under normal sitting posture by using a human body pressure distribution measurement system considering the effects of gender and body mass index (BMI). The stress distribution on the seat was then numerically modeled using three modeling methods. The observed results and the numerical analysisresults were compared. The results showed that an inverted U-shaped pressure distribution was observed in normal sitting posture. The stress was concentrated on the ischial tuberosity with a maximum value of 0.066 MPa. The ratio of the load on the seat to the gravity of the human body weight was about 65.3%. The numerical model established using the body pressure mapping method was superior to those of the uniform load method and the standard loading pad method in terms of stress distribution, maximum stress, and contact area.

Interference effect on super large twin cooling towers exposed to stationary tornado-like vortices

A comprehensive investigation was conducted aiming at the interference effects on wind pressure distribution, aerodynamics characteristics, structural stability and reinforcement areas of super large twin cooling towers exposed to tornado-like vortices, and the effects of swirl ratios of tornados, grouped tower layouts, and relative central distances between the towers and the tornado were analysed based on a tornado-like vortex simulator. Two types of rigid model wind tunnel experiments were constructed for base forces and wind pressure distribution measurements. The experimental results demonstrate that the interference effects on base forces and local wind pressures are significantly influenced by the swirl ratios, central distances, and grouped tower layouts, etc. Moreover, the layout with a tornado located on the side of tandem twin cooling towers (along with the tornado translation direction being perpendicular to the central axis of the tandem combined twin cooling towers) is the most unfavourable, resulting in obvious amplification effects on base forces and local wind pressures compared with an isolated tower, and the maximum of interference factors (IFs) is 1.68 and 1.41 for the along-wind total wind force coefficient and minimal net mean pressure coefficient respectively. Subsequently, local stability indices and time-variant dynamic reinforcement envelopes were selected as the other evaluation criteria for estimating the interference effects on the cooling towers exposed to the tornado-like vortices, and the interference effects result in enlargements of the structural responses with the maximal IF of 1.36 for the inside meridional reinforcement. Finally, the various interference criteria at aerodynamic loading and structural reinforcement aspects were contrastive analysed, showing that the criterion of time-variant dynamic reinforcement area envelopes is a more reasonable criterion for evaluating the interference effects on the super large cooling towers exposed to the tornado-like vortices. This investigation aims to contribute to a better understanding of the wind-related effects of the cooling towers exposed to extreme non-synoptic winds, particularly tornadic vortex impacts.

A novel strategy and characteristics of PVA/citric acid cross-linked hydrophilic elastic sponge of cellulose based on medicinal herb residue

A new ultra-hydrophilic elastic sponge composite has been proposed. Medicinal herbs, commonly used in herbal medicine and subsequently discarded, are rich in natural polymer substances, making them promising candidates for various material industries. TEMPO-oxidized cellulose was extracted from medicinal herb residue, and the physicochemical properties of an ultra-hydrophilic elastic sponge, prepared through a PVA and CA impregnate cross-linking process, were investigated. The fabricated composite sponge exhibited an increase in compressive stress-strain proportional to the PVA cross-linking concentration, and its water retention capability was assessed through retention tests. Swelling tests for various solvents were conducted to evaluate the potential use of the sponge in diverse industries, revealing the highest swelling ratio in water. Pressure distribution measurements using prescale film indicated that the sponge's shock absorption capacity was enhanced by PVA cross-linking, leading to improved pressure dispersion.

On the static performance of aerostatic elements

Porous aerostatic bearings and seals offer several advantages in precision engineering applications. The static performance of aerostatic elements, i.e., bearings and seals, is investigated both experimentally and numerically. This study presents a method, a test setup, and a measurement of the air gap pressure distribution with high spatial and temporal resolution. This study presents experimental and numerical results of the load capacity, air gap height, static stiffness, air consumption, and air gap pressure distribution. The experimental results are compared to a numerical model based on the modified Reynolds equation. Furthermore, boundaries for the operating parameter space of the investigated seal are determined by stiffness and leakage. The experimental results and the numerical model showed good correlation, providing corroborative evidence for the accuracy of the measurement setup and the feasibility of the pressure measurement method.

Development of aids to relieve vulvodynia during the postpartum period.

Postpartum women live with a low quality of life due to pain caused by episiotomy and perineal laceration. In particular, they endure pain when sitting for long periods of time to breastfeed. The purpose of this study is to develop a sitting aid to alleviate postpartum vulvodynia. This study was conducted in the following four phases from July 2017 to May 2019. They are: material selection and molding, cleaning and disinfection testing, pressure distribution measurement testing, and trial testing by postpartum women. The main material was a 100% polypropylene object with a three-dimensional reticular fiber spring structure and fiber density of 3.8 kg/m2. As a result, a sitting aid that withstands washing and disinfection well in the medical field and is breathable. It had moderate resilience and elasticity and reduced pressure on the seating surface for women weighing approximately 45 kg and 55 kg, but we were skeptical about its use for women weighing more than that. The completed sitting aid is noninvasively effective in improving the quality of life of many postpartum women, but the density and thickness of the main material should be reexamined to meet the needs of women in a wider weight range. In addition, a self-administered questionnaire survey of trial users revealed that some women did not experience relief from vulvodynia even after using the sitting aid. Such women also had physical problems such as discomfort in the lower back, difficulty breastfeeding, and difficulty standing up. For women with multiple physical problems, individual causes should be addressed.

A laboratory investigation into tyre-pavement contact behaviour of passenger car

ABSTRACT Understanding tyre-pavement contact behaviour helps to address pavement skid resistance which is highly related to traffic safety. In this study, a pressure distribution measurement system was employed to investigate the tyre-pavement contact behaviour of a passenger car in laboratory. The pavement macrotexture was characterised by a 3D scanner and the sand patch method. It was shown that the asphalt pavement gradation, the vertical force, the tyre inclination angle and the tyre pressure significantly have effects on tyre-pavement contact behaviour. The cumulative frequency curve of tyre-pavement contact stress can be well fitted by the Boltzmann model. Under the vertical force of 4 kN, the average contact stress increases significantly when the inclination angle exceeds 3.2°, while an inclination angle within 3.2° has almost no effect. The force on the rib on the side that the tyre leans to changes the most with the inclination angle. As the tyre pressure increases, the average contact stress increases linearly and the contact area decreases linearly. With the increase of tyre pressure, the contact region gradually shrinks towards the middle and the contact force slightly increases in the middle and decreases at the edges.

Streamlining multi-hole probe calibration using artificial neural networks

Accurately measuring the three-dimensional flow field characteristics in complex flow fields, particularly in turbomachines, is of utmost importance and is commonly achieved through experimental methods. Multi-hole pressure probes are a proven measuring technique to provide precise readings of flow characteristics in both two-dimensional (2D) and three-dimensional (3D) flow fields. However, manufacturing imperfections have an impact on their measuring accuracy so each probe has a slightly different measuring behavior. In order to take these specific characteristics into account a thorough calibration process prior to utilization has to be applied. This calibration process involves positioning the probe in various flow conditions in a wind tunnel and collecting all relevant data. A model is then established to correlate the measured pressure distribution across the probe holes with known flow conditions. Unfortunately, this calibration process is time-consuming and requires costly equipment.To address these challenges, this study introduces a novel calibration technique that leverages advanced machine learning methods, specifically artificial neural networks (ANNs), to significantly streamline the process. ANNs are renowned for their ability to model diverse systems and adapt and generalize well, making them a promising solution for simplifying the calibration of multi-hole probes. In this research, an ANN calibration model was developed specifically for a 5-hole probe, and its configuration was optimized through an automated hyperparameter optimization process. The performance of the ANN model was then compared to that of a conventional polynomial model. After confirming its accuracy, the ANN model was successfully re-adapted and applied to new probes, requiring minimal calibration data collection. The results highlight the potential of ANNs in probe calibration, as they enable a simplified process that demands fewer calibration data points.

An innovative EFD using FBG pressure sensors for ship seakeeping

AbstractThis paper examines the acquisition of the measurement data of the spatial distribution of unsteady pressure on a ship advancing in waves. The purpose of the study is to investigate the reliability of the pressure data obtained by the unprecedented experiment and to provide experimental data of unsteady pressure which can be used for validation of arbitrary computation methods. The optical fiber sensing technology, so-called FBG (fiber Bragg gratings) sensing, is employed as the pressure sensors. In the experiment, 379 FBG pressure sensors (version 7; the latest version) in total are attached to the port side surface of ship model and also ordinary strain-type pressure sensors are embedded in the starboard side for validating reliability of FBG pressure sensors by comparing both results. In addition to the pressure distribution, measurement is made for unsteady hydrodynamic forces such as added mass, damping coefficients, and wave exciting forces, and also for ship motions and added resistance. Most of the measurement is repeated at least five times for each condition, and results of measured pressures are evaluated with mean value and standard deviation. Regarding the added resistance, the distribution for estimating added resistance is also extracted from obtained pressure distribution and its pressure contour is illustrated to show visually which hull region affects the added resistance significantly. Validation of the measured pressure with FBG pressure sensors is carried out also by integrating measured pressures over the ship model surface and comparing it with forces directly measured with load cells. The measured pressure distribution is compared with typical calculation results with the Rankine panel method in frequency domain to demonstrate usefulness of the spatial pressure data for validating the calculation method. Through these studies, it is confirmed that the measured unsteady pressures with FBG pressure sensors are accurate enough and valuable as the validation data for any calculation method.

Study on the Effect of Three-dimensional Reconstruction Technique Based on Human Gait Plantar Transient Data on Rehabilitation of Patients with Abnormal Foot Arch

This research employs non-contact plantar 3D data scanning and gait analysis methodologies to establish a rehabilitation assistance system tailored for foot arch anomalies. The system utilizes a non-contact plantar 3D data model to mitigate dysfunctions within the plantar skeletal-muscular system. Its objectives include facilitating personalized remote diagnosis of foot arch anomalies, enabling patients to monitor their rehabilitation progress, and supporting at-home rehabilitation efforts. A dataset comprising 124 cases of physiological foot arch anomalies in adults aged 18 and above was collected and analyzed. The findings demonstrate the system’s flexibility, high spatial resolution, personalization, and innovation. Notably, the system achieves real-time measurement of positive pressure and shear force distribution at the plantar interface, facilitates the construction of accurate geometric models, and yields high-quality plantar three-dimensional coordinate data. This research contributes theoretical and technical underpinnings for the application of footwork anomaly diagnosis and correction.

Stability in theory, in the laboratory and in the air: William Ellis Williams’ campaign for proof positive (1904–1914)

The equations that determine the stability of aircraft were formulated at Bangor, Wales, over the first two decades of the twentieth century, a formulation that was to prove as fit for purpose in characterizing the stability of aircraft today, as for the aeroplane allsorts that took to the sky in the wake of the Wrights' Flyer. While these equations are commonly identified with George Hartley Bryan, this does disservice to the contributions of others at Bangor. Not the least of these was William Ellis Williams, whose achievement in identifying photographically the modes predicted by theory is little recognized. Williams later went on to construct what was in all likelihood the first aeroplane designed solely for research to be built in a university department, making the first airborne measurement of pressure distribution across aircraft wings in his Bamboo Bird, in 1913, an achievement not hitherto afforded due credit in the literature.

Padding the seat of a wheelchair reduces ischial pressure and improves sitting comfort.

In this study, we aimed to examine whether a wheelchair cushion placed directly atop a sling seat or deflection of the sling seat compensated by a pad along with the placement of a wheelchair cushion changed sitting pressure. Additionally, we examined whether these additions changed sitting comfort. For twenty healthy adults who consented to participate, measurements were taken for three types of cushions, each with and without padding, under six conditions. The cushion types tested included air (cushion A), urethane foam (cushion U), and three-dimensional thermoplastic elastomer (cushion T). A pressure distribution measurement equipment was used for the measurements. Following the measurement, the comfort of the wheelchair cushion was measured. The ischial area pressure of the cushion A pad was significantly lower than that without the pad. Cushions U and T were for ischial area pressure with a pad, resulting in a decreasing trend in ischial area pressure with a pad compared to that without a pad; however, the difference was insignificant. For all cushions, sitting comfort was significantly better in all groups with padding than in those without. In conclusion, ischial pressure can be dispersed by placing a pad on the seat surface of a wheelchair cushion, and pads were suggested to improve sitting comfort for all cushions.

Establishment of the Interaction Simulation Model between Plug Seedlings and Soil

Currently, the simulation parameters for the model of the interaction between the transplanter, the plug seedlings, the soil, and the pot damage mechanism still need to be clarified. The optimization design of the planters and the improvement of planting quality are still urgent issues that need to be solved. In this paper, the simulation parameters of the pot and the soil were calibrated based on the pressure distribution measurement technology. With the actual collision impact force and matrix loss rate as the targets, a four-factor, three-level orthogonal test was designed to obtain the optimal parameters. Through the optimization analysis of the experimental results, it could be concluded that the pot–soil restitution coefficient, the pot–soil static friction coefficient, the pot–soil rolling friction coefficient, and the surface energy were 0.31, 0.88, 0.35, and 1.07 J/m2, respectively. The experimental verification of the optimal parameter combination showed that the relative error of the collision impact force was 1.65% and that the relative error of the matrix loss rate was 2.32%, which verified the model’s reliability. Based on the optimal parameters, the movement law of the hole tray seedlings was studied at different positions during the transplanting process. The plug seedlings collided not only with the planter but also with the soil, which led to the breakage and looseness of the pot structure. The relative error between the matrix loss rate of the transplanter inserting soil, the matrix loss rate of the transplanter that did not enter the soil, and the simulated matrix loss rate was less than 10%, which further proved the accuracy of the simulation model.

Use of a novel pressure distribution system for severely ill neonates: a clinical pilot study carried out by the PREPICare consortium

BackgroundPressure Injuries are not exclusively an adult phenomenon; various risk factors contribute to a high prevalence rate of 43% in the neonatal and pediatric intensive care population. Effective preventive measures in this population are limited.MethodsWe performed a pilot study to analyze the distribution and localization of support surface interface pressures in neonates in a pediatric intensive care unit (PICU). The hypothesis was that pressure redistribution by a novel air mattress would reduce pressure peaks in critical neonates. The measurements were conducted in a 27-bed level III PICU between November and December 2020. This included measuring pressure distribution and pressure peaks for five neonates positioned on either a state-of-the-art foam mattress or a new prototype air mattress.ResultsWe confirmed that the pressure peaks were significantly reduced using the prototype air mattress, compared with the state-of-the-art foam mattress. The reduction of mean pressure values was 9–29%, while the reduction of the highest 10% of pressure values was 23–41%.ConclusionsThe journey to an effective, optimal, and approved product for severely ill neonates to reduce Pressure Injuries is challenging. However, a crucial step was completed by this pilot study with the first pressure measurements in a real-world setting and the successful realization of a decrease in pressure peaks obtained using a prototype air mattress.

A design based on centrifugal inertia of rotational oil film for reducing pressure at shaft hole

Shaft seal covers a very wide range of machinery and applications. Lip seals, which are used for sealing shafts against the exit or ingress of liquids, are a type of shaft seal. Reducing the wear of the sealing ring and extending its service life can increase the time interval for machine maintenance and inspection. In this paper, a disk structure for reducing the pressure difference between the inside and outside of the lip seals is proposed. The disk structure forms a layer of rotating oil film on the seal ring, so the oil pressure near the seal ring is less than in a sealing chamber. First, based on the similarity principle and the hypothesis of von Kármán, a theoretical model of the rotating oil film was established, and the dominant influence of inertia of circumferential velocity and viscosity of radial velocity on pressure distribution was expounded. Then, an experimental device that can measure pressure distribution and temperature was constructed, and a pressure distribution measurement experiment was conducted. Based on theoretical models and experiments, it was proved that the rotating disk could generate a pressure drop and the pressure drop was a function of the square of the rotating speed. The influence of temperature and oil film thickness was studied, and it was found that the increase in the temperature and oil film thickness weakened rotational flow inertia and enhanced radial flow viscosity, increasing pressure within the oil film. Additionally, it was observed that the oil in the sealing chamber produced a sunken liquid level due to the stirring of the rotating disk, which would reduce the boundary pressure at the periphery of the oil film and produce a greater pressure drop inside the oil film.

Lifetime based pressure and temperature sensitive paint measurement on a civil aircraft wing under conditions near the onset of shock-induced separation

Lifetime-based pressure- and temperature-sensitive paint (PSP and TSP) measurements were conducted in a large-scale industrial transonic wind tunnel to obtain high-quality pressure data for validation of computational fluid dynamics (CFD) simulations. A wind tunnel test was performed using the NASA common research model in the JAXA 2 m × 2 m transonic wind tunnel. The freestream Mach number was varied in the range of 0.70–0.89, and aerodynamic forces and moments were acquired in order to obtain the pitch break condition related to the onset of shock-induced separation. Polymer-based PSP was coated on a main wing of the model, and TSP was used in tandem with PSP to correct the temperature dependence of PSP. The two-gate lifetime-based method was applied to obtain the PSP and TSP emissions. An a-priori/in-situ hybrid calibration was conducted to convert ratio-of-ratios to pressure, and measured pressure distributions were mapped onto a three-dimensional (3D) model grid. The root-mean-square error for the pressure measurements was evaluated by pressure tap data and was approximated to be 0.8 kPa for all Mach numbers tested. The obtained pressure distributions exhibited a significantly high signal-to-noise ratio and were used for comparison with CFD results on a 3D grid. The high-spatial-resolution PSP measurements helped to accurately localize the differences from the CFD simulation results and showed that the prediction of the shock location along the main wing is still a relevant challenge.

Study on Contact Stress Distribution Characteristics and Damage of Plug Seedlings Based on Flexible Pressure Sensor.

At present, there is a problem that the growth quality is reduced due to damage to the plug seedling pot during the transplanting process. In this study, the pressure distribution measurement system was used to measure the contact area of plug seedlings when they collided with the ground. The effects of seedling age and forward speed on the characteristics of contact stress distribution and potting damage were investigated through a single-factor experiment. The results were comprehensively considered based on the single-factor test, and the Box-Behnken test was used to optimize the design. The matrix loss rate was used as the evaluation index to determine the optimal parameter combination for transplanting: the tray specification was 72, the seedling age was 30 d, and the forward speed was 1.25 km·h-1. This study can provide a reference and technical support for further research on pot damage in plug seedling transplanting. The optimized parameters can provide practical guidance for reducing pot damage and improving growth quality during transplanting plug seedlings.

A Novel Physical Human–Robot Interface With Pressure Distribution Measurement Based on Electrical Impedance Tomography

A Novel Physical Human–Robot Interface With Pressure Distribution Measurement Based on Electrical Impedance Tomography

Analysis of tyre-pavement contact behaviour of heavy truck in full-scale test

ABSTRACT Tyre-pavement contact behaviour is one of the core issues in pavement engineering. In this study, the tyre-pavement contact behaviour was investigated in full-scale tests. The pavement texture was characterised by a 3D scanner and the sand patch method. The data of tyre-pavement contact stress were collected by a pressure distribution measurement system. The characteristics of the tyre-pavement contact stress distribution were explored by introducing the Boltzmann model. The feasibility of the Hertz model in assessing the tyre-pavement contact behaviour was evaluated. The results showed that the tyre-pavement carries a larger load by extending the contact area in longitudinal direction and increasing the contact stress mainly at the lateral edges. The pavement texture has significant effects on the contact behavior. Under the regular tyre vertical force range, the value of contact stress is within 1000 kPa for about 80% of the tyre-pavement contact area, but the maximum contact stress can be up to 3000 kPa. The Boltzmann model can be used to fit the contact stress distribution, and some parameters of the model have linear relationships with pavement surface macrotexture. The Hertz model can reflect the average state of tyre-pavement contact behaviour.

Ultra-small high‐temperature pressure sensor chips fabricated in single‐layer (111) SOI wafers

This paper presents a 0.5 mm × 0.5 mm tiny-sized high-temperature piezoresistive pressure sensor fabricated with a thin-film under bulk single-sided micromachining process from the front-side of single-layer (111) silicon on insulator (SOI) wafer. The (111)-device layer of the SOI wafer is specifically selected to optimize the piezoresistor performance where the SiO2 buried layer isolates the piezoresistors from the handle substrate. And the (111)-handle layer is employed to subtly construct a single-crystalline-silicon beam-island combining with a very thin but uniform poly-silicon diaphragm for realization of both low nonlinearity and high sensitivity. Without double-sided micromachining process and wafer bonding used, a tiny sensor-chip size of 0.5 mm × 0.5 mm is achieved, which is required in wind-tunnel systems for measuring pressure distribution at high temperature. The testing results of the fabricated sensor show high sensitivity of 0.15 mV V−1 kPa−1 for 150 kPa measure range and satisfactory linearity of ±0.11% FS (full scale) at ambient temperature. At 350 °C, the overall accuracy is 0.17% FS and the thermal hysteresis is 0.22% FS. The temperature coefficient of zero-point offset of the sensor is tested as low as 0.01% °C−1 FS and the temperature coefficient of sensitivity is −0.07% °C−1 FS within the whole temperature range from −55 °C to 350 °C. Featuring the advantages of high accuracy and high-yield low-cost fabrication, the tiny-sized high-temperature pressure sensors exhibit promising perspectives in the field of aerospace industry including wind-tunnel applications.