Measurement Of Pressure Distribution Research Articles

ショットピーニングにおける衝突面圧分布の計測と関数近似

ショットピーニングにおける衝突面圧分布の計測と関数近似

Turbulence investigation in the VTI’s experimental aerodynamics laboratory

Wind tunnels are the aerodynamic laboratories which task is to enable high quality and stabile airflow in controlled volume, a test section, during run time, in order to study the effects of streaming around various aeronautical or nonaeronautical models (airfoils and bluff bodies with complex motorized or robotic constructions). The main requirement that leads to quality and reliable measurement results is a high flow quality in the test section: uniformity of the velocity and pressure fields along and across the test section, low turbulence level and low flow direction angularities or swirling. The knowledge of low parameters enables the exchange of the scientific and technical information, comparison of the experimental results from different wind tunnels and data scaling of the model to the real scale. The turbulence intensity TI significantly affects the wind tunnel results and reduction of turbulence is of the highest importance for the quality measurements. This paper presents the Experimental Aerodynamics Laboratory of the VTI in Belgrade, the equipment and methods of turbulence measurements in the test section stream and around different test models. Wind tunnel facilities maintain equipment and devices for sampling, acquisition and data reduction for various test types, from forces and moment measurements, over the pressure distribution measurements to the advanced measurements, followed with the appropriate flow visualization techniques. The modern instrumentation enables determine flow quality and its influence on tests and measurement results of static and dynamic model characteristics.

Optimization of Wind Tower Cooling Performance: A Wind Tunnel Study of Indoor Air Movement and Thermal Comfort

Wind tunnel testing and thermal comfort simulations were conducted to explore the performance of a wind-tower in a typical, medium-density apartment building located in subtropical Sydney. The research design consisted of three phases; first, wind tunnel experiments measured pressure distributions over the surface of a four-storey apartment building model scaled at 1:100. Secondly, hourly indoor air velocities were predicted for the six warmest months in Sydney using the Typical Meteorological Year 2013. Finally, thermal comfort simulations evaluated the comfort cooling potential of the wind towers. Results indicate that, during Sydney's warm hours (≥23°C), elevated air speeds resulting from the wind-tower improved in indoor comfort by 1725.8 degree hours (SET*) compared to the default design relying on through-window cross ventilation under the same conditions.

Pressure measurement in a microchannel

The present paper proposes a method to directly measure pressure distribution in a microchannel. A polyvinylidene fluoride (PVDF) piezoelectric film was packaged on the inside wall of a microchannel and connected to an external signal filtering amplifier to the oscilloscope to observe the voltage response when the flow through the microchannel and then the voltage response of the PVDF film converted into the pressure response. The experimental results demonstrated that the obtained data were quite consistent with the numerical calculations, and the pressure distribution in the microchannel presents a nonlinear function in which pressure increased with decreasing distance from the entrance.

Pore Water Pressure Distribution and Dissipation During Thaw Consolidation

A novel apparatus was developed for measurement of pore water pressure distribution and dissipation during thaw consolidation. Thaw consolidation tests were conducted to verify the applicability of nonlinear stress–strain relationship in 3-D large strain thaw consolidation theory. During thawing process, the measured pore pressure at different layers of soil samples increased sharply at first; when a certain value was approached, it stepped into dissipation stage. It was proved that the calculated results have a good agreement with tested results on both pore pressure distribution and dissipation. Further analysis indicated that nonlinearity of pore pressure distribution was proportionally related to thaw consolidation ratio (R), while it was opposite for thaw consolidation degree.

Characteristics of welding and arc pressure in TIG narrow gap welding using novel magnetic arc oscillation

Tungsten inert gas (TIG) narrow gap welding using magnetic arc oscillation is one of the most important methods for joining thick components. Today’s developments are aimed at increasing a sophisticated process understanding, especially concerning the physical effect of arc behavior, which can provide many strategies to enhance weld prediction and joint quality. In this article, the arc behaviors studied by its arc pressure, static characteristic, and arc profile in terms of arc force are presented. With the help of the forces acting on the welding arc, arc profile can be considered separately to allow an improved investigation of narrow gap welding involved. Measurements of arc pressure distribution are used to validate the weld formation and the final welding result. Under the same conditions, the uniformity of arc pressure distribution in both the bottom and sidewall improved with the increase in magnetic flux density. Furthermore, a comparative study of arc static characteristic with magnetic field and non-magnetic field has also been carried out. The reduction in the difference of arc static characteristic is attributed to the inverse effect between electromagnetic pinch force and Lorentz force with the increasing welding current.

Application of ideal pressure distribution indevelopment process of automobile seats.

In designing a car seat the ideal pressure distribution is important as it is the largest contact surface between the human and the car. Because of obstacles hindering a more general application of the ideal pressure distribution in seating design, multidimensional measuring techniques are necessary with extensive user tests. The objective of this study is to apply and integrate the knowledge about the ideal pressure distribution in the seat design process for a car manufacturer in an efficient way. Ideal pressure distribution was combined with pressure measurement, in this case pressure mats. In order to integrate this theoretical knowledge of seating comfort in the seat development process for a car manufacturer a special user interface was defined and developed. The mapping of the measured pressure distribution in real-time and accurately scaled to actual seats during test setups directly lead to design implications for seat design even during the test situation. Detailed analysis of the subject's feedback was correlated with objective measurements of the subject's pressure distribution in real time. Therefore existing seating characteristics were taken into account as well. A user interface can incorporate theoretical and validated 'state of the art' models of comfort. Consequently, this information can reduce extensive testing and lead to more detailed results in a shorter time period.

Slip and turbulence phenomena in journal bearings with application to implantable rotary blood pumps

This paper describes an investigation into journal bearings with geometries and working fluid similar to centrifugal blood pumps. The aim is to describe the phenomena that cause these journal bearings to deviate from classical predictions. Experimental, analytical and numerical methods are used to investigate the behaviour of a range of bearings with geometries and working fluid similar to blood pumps. It was found that the clearance had a significant effect on the force-eccentricity characteristic of the bearing, with smallest and largest clearances deviating from classical predictions. Experimentally measured pressure distributions show that slip occurs when the clearance is small and that turbulence occurs with the largest clearances. The effects of these phenomena on lubricant pressure and blood compatibility are discussed.

Pressure Gradient and Nonadiabatic Surface Effects on Boundary Layer Transition

The influence of the streamwise pressure gradient and a nonadiabatic surface on boundary layer transition was experimentally investigated at the Cryogenic Ludwieg-Tube Göttingen, Germany. Boundary layer transition was detected nonintrusively by means of the temperature-sensitive paint technique. The wind-tunnel model was designed to achieve a quasi-uniform streamwise pressure gradient over a large portion of the model chord length. This allowed the effects on boundary layer transition of the streamwise pressure gradient and wall temperature ratio to be decoupled. The model was tested at high Reynolds numbers and at a high subsonic Mach number. Favorable, almost-zero, and adverse streamwise pressure gradients were considered; and various temperature differences between the flow and the model surface were implemented. Stronger flow acceleration and lower wall temperature ratios led to an increase of the transition Reynolds number. Larger increases in the transition Reynolds number were obtained at more pronounced flow acceleration for the same reduction in the wall temperature ratio. The measured pressure distributions served as input for boundary layer stability computations, performed according to compressible, linear, local stability theory under the (quasi-) parallel-flow assumption. Amplification factors of the Tollmien–Schlichting waves were shown to be reduced by stronger favorable pressure gradients and lower wall temperature ratios, which was in agreement with the observed variation in the transition Reynolds number.

Pressure and Draw-In Maps for Stamping Process Monitoring

This paper presents two tooling-integrated sensing techniques for the in situ measurement and analyses of pressure distribution at the tool–workpiece interface and material draw-in during the stamping processes. Specifically, the contact pressure distribution is calculated from the measurements by an array of force sensors embedded in the punch, whereas sheet draw-in is measured by custom-designed thin film sensors integrated in the binder. Quantification of the pressure distribution from spatially distributed sensors has been investigated as a regularization problem and solved through energy minimization. Additionally, a Bayesian framework has been established for combining finite-element analysis (FEA) based estimates of the pressure distribution with experimentally measured evidence, to achieve improved spatiotemporal resolution. A new data visualization technique termed pressure and draw-in (PDI) map has been introduced, which combine spatiotemporal information from the two sensing techniques into an illustrative representation by capturing both the tool–workpiece interaction (dynamic information) and resulting workpiece motion (kinematic information) in a series of time-stamped snap shots. Together, the two separate yet complementary process-embedded sensing methods present an effective tool for quantifying process variations in sheet metal stamping and enable new insight into the underlying physics of the process.

Experimental investigation of flowfield over an iced aerofoil

ABSTRACTWind-tunnel measurements were used to study the characteristics of the unsteady separation bubbles on a NACA 0015 aerofoil with simulated two-dimensional leading-edge glaze ice accretions. The unsteadiness present in the iced-aerofoil flowfield was determined using measurements of the time-dependent aerofoil surface pressure distribution at Reynolds number of 1.0 × 106. Additionally, the unsteady flow features were investigated through the power spectrum of the stream-wise velocity fluctuations using a hot-wire anemometry. The results showed that the highest value of root-mean-square fluctuation of the surface pressure consistently occurred upstream of the mean shear-layer reattachment location. Spectral analysis of stream-wise velocity fluctuations near reattachment location revealed evidence of the regular frequency at Strouhal numbers of 0.5-0.63. Moreover, the low-frequency oscillations associated with shear-layer flapping was also identified in the wake velocity spectra on the order of 10 Hz that resulted in Strouhal numbers of 0.0186-021.

Sex Differences in Metatarsal Bone Density and In-Shoe Load Distribution in Recreational Runners

Runners are at an increased risk of stress fractures compared to other athletes; with female runners sustaining greater metatarsal stress fractures compared to male runners. PURPOSE: To examine sex differences between the bone mineral density (BMD) of the second and fifth metatarsal and in-shoe loading of the foot during running. METHODS: Fifteen recreational runners (7 males, 8 females: height 168.3±9.3 cm, 68.2±11.8 kg, age 20.7±0.8 years), who run at least 10 miles per week, volunteered to participate. A dual x-ray absorptiometry (DXA) method was used to scan the second and fifth metatarsals. BMD was calculated for the total area of each metatarsal. Pressure distribution measurement insoles were used to calculate relative load (force-time integral of medial, central, lateral forefoot divided by total force time integral) while participants ran on a treadmill at a self-selected speed with three different step rate conditions in a randomized order. Subjects were instructed to adjust their cadence using feedback from an audible metronome set to preferred step rate, as well as ten percent higher and ten percent lower step rates. One-way ANCOVAs were used to examine sex differences between BMD controlling for height and mass. Repeated measures ANCOVAs were used to examine sex differences in forefoot loading across step rates while controlling for treadmill velocity. RESULTS: Total fifth metatarsal BMD was greater in males (0.466 g/cm2 [95% CI: 0.43, 0.50]) compared to females (0.409 g/cm2 [95% CI: 0.37, 0.44], p=0.04). Sex differences were not found in second metatarsal BMD (p=0.8). After controlling for treadmill velocity, a main effect (p=0.04) of sex on central forefoot relative loading was found, such that females (16.0% [95% CI: 14.4, 17.7]) exhibited greater loading compared to males (13.2% [95% CI: 11.4, 14.9]). Relative loading of the lateral and medial forefoot was not statistically different between sexes (p>0.05). CONCLUSIONS: A difference in BMD of the fifth metatarsals was found between males and females. Interestingly, sex differences did not exist in second metatarsal BMD but females had greater relative loading under the central forefoot compared to males. The relationship between biomechanical loading, BMD and stress fracture risk should be examined longitudinally.

Male sex, height, weight, and body mass index can increase external pressure to calf region using knee-crutch-type leg holder system in lithotomy position.

BackgroundWell-leg compartment syndrome (WLCS) is one of the catastrophic complications related to prolonged surgical procedures performed in the lithotomy position, using a knee-crutch-type leg holder (KCLH) system, to support the popliteal fossae and calf regions. Obesity has been implicated as a risk factor in the lithotomy position-related WLCS during surgery. In the present study, we investigated the relationship between the external pressure (EP) applied to the calf region using a KCLH system in the lithotomy position and selected physical characteristics.MethodsTwenty-one young, healthy volunteers (21.4±0.5 years of age, eleven males and ten females) participated in this study. The KCLH system used was Knee Crutch®. We assessed four types of EPs applied to the calf region: box pressure, peak box pressure, contact pressure, and peak contact pressure, using pressure-distribution measurement system (BIG-MAT®). Relationships between these four EPs to the calf regions of both lower legs and a series of physical characteristics (sex, height, weight, and body mass index [BMI]) were analyzed.ResultsAll four EPs applied to the bilateral calf regions were higher in males than in females. For all subjects, significant positive correlations were observed between all four EPs and height, weight, and BMI.ConclusionEP applied to the calf region is higher in males than in females when the subject is supported by a KCLH system in the lithotomy position. In addition, EP increases with the increase in height, weight, and BMI. Therefore, male sex, height, weight, and BMI may contribute to the risk of inducing WLCS.

感圧塗料を用いたターボ機械内壁面における圧力分布計測

感圧塗料を用いたターボ機械内壁面における圧力分布計測

213 感圧塗料を用いた静圧気体スラスト軸受内圧力分布の可視化と計測 : 慣性力が軸受内流動に及ぼす影響(GS2-3 感温塗料・感圧塗料)

213 感圧塗料を用いた静圧気体スラスト軸受内圧力分布の可視化と計測 : 慣性力が軸受内流動に及ぼす影響(GS2-3 感温塗料・感圧塗料)

Pressure Distribution Measurement in Knee Arthoplasty

The paper describes and evaluates the measurement procedure of pressure distribution in knee arthoplasty, which represents an artificial replacement of a human knee joint. First we briefly present the knee arthoplasty and its composition. Further we describe in detail the measurement procedure, i.e. the measuring machine, which simulates a human step cycle, and the layout and type of used sensors. Finally, we compare the measured pressure distribution data with those from a mathematical model to evaluate the accuracy of the model and we also check any unpredictable pressure deviations in the joint replacement.

Study of Water Jet Collision of High Pressure Flat Jet Nozzles for Hydraulic Descaling

One of the most effective methods for descaling hot-rolled steel products is performed using highpressure flat jet nozzles. These descaling nozzles are arranged in rows in hot rolling mills and areset in such a way that each adjoining pair of nozzles creates an overlapping area of water jet streams.Good homogeneity of the pressure distribution over the width of the hot-rolled plate is often used as anindicator of quality of the homogeneity of descaling. The presented laboratory measurements examineone pair of adjoining nozzles with a particular focus on the pressure distribution in the overlappingarea. This paper deals with one particular setting of a pair of descaling nozzles with zero offset anglesfor the jet streams. A measured pressure distribution and an outcome of an erosion test on an aluminumplate are presented and discussed. The erosion test shows that spots with higher pressures do notnecessarily result in a higher amount of removed material during an erosion test. The erosion test differs from the expected outcome in such a way that a detailed discussion of this phenomenon is outlined with possible explanations.

感圧塗料を用いたターボ機械内部流れ場における圧力分布計測手法の構築

In this study, we measured pressure distribution of a casing wall surface of an axial compressor by using pressure sensitive paint (PSP) as a measurement technique of internal flows to analyze anomalous flow phenomena of internal flows of turbo machinery, and we investigated the validity and feasibility of this method. Consequently, we clarified that the luminescence intensity is enhanced by applying the white opaque coating composed of boron nitride (BN) nanoparticle on the PSP layer, and the qualitative pressure distribution showing pressure rises caused by rotor blades was obtained. Although uncompensated temperature influence is one of the other error sources, proper temperature compensation can improve the accuracy of the pressure measurement by PSP.

Accuracy of finite element analyses of CT scans in predictions of vertebral failure patterns under axial compression and anterior flexion

Finite element (FE) models built from quantitative computed tomography (QCT) scans can provide patient-specific estimates of bone strength and fracture risk in the spine. While prior studies demonstrate accurate QCT-based FE predictions of vertebral stiffness and strength, the accuracy of the predicted failure patterns, i.e., the locations where failure occurs within the vertebra and the way in which the vertebra deforms as failure progresses, is less clear. This study used digital volume correlation (DVC) analyses of time-lapse micro-computed tomography (μCT) images acquired during mechanical testing (compression and anterior flexion) of thoracic spine segments (T7–T9, n=28) to measure displacements occurring throughout the T8 vertebral body at the ultimate point. These displacements were compared to those simulated by QCT-based FE analyses of T8. We hypothesized that the FE predictions would be more accurate when the boundary conditions are based on measurements of pressure distributions within intervertebral discs of similar level of disc degeneration vs. boundary conditions representing rigid platens. The FE simulations captured some of the general, qualitative features of the failure patterns; however, displacement errors ranged 12–279%. Contrary to our hypothesis, no differences in displacement errors were found when using boundary conditions representing measurements of disc pressure vs. rigid platens. The smallest displacement errors were obtained using boundary conditions that were measured directly by DVC at the T8 endplates. These findings indicate that further work is needed to develop methods of identifying physiological loading conditions for the vertebral body, for the purpose of achieving robust, patient-specific FE analyses of failure mechanisms.

Analysis of structure of warp-knitted spacer fabric on pressure indices

Spacer fabrics are widely used as mattress materials of bed and wheelchair. It is due to the fact that the special sandwich structure is effective in evenly dispersing pressure to improve pressure concentration, which prevents ulcer disease of long-term seated/lying people. However, there are few investigations on relationship between structure of spacer fabric and pressure behaviour. So, the main content dealt with in the paper was to adopt pressure pad system to measure pressure distribution behaviour of spacer fabric compressed by seated people, and pressure indices with average gradient integral, pressure peak, average pressure and contacting area were featured based on pressure nephogram. Pressure tests of varying surface stitch density, spacer filaments arrangement density and layers of spacer fabric were conducted. Experimental results showed that mattress without spacer fabric existed serious pressure concentration effect, while mattress with spacer fabric obviously improved hip pressure concentration effect. Pressure concentration effect could be well improved by increasing surface stitch density, spacer filament arrangement density and thickness. Moreover, it was a good method to produce mattress with good pressure property by combining reasonable layers of spacer fabrics to meet the same pressure-relief requirements.