Analysis Of Pressure Distribution Research Articles

Characteristics of Wind Load on Spatial Structures with Typical Shapes due to Aerodynamic Geometrical Parameters and Terrain Type

The characteristics of wind load on large‐span roofs are complicated by their unique geometrical configurations and strong dependence on aerodynamic geometrical parameters and terrain type. However, there is rarely comprehensive research for characteristics of wind load on spatial structures due to aerodynamic geometrical parameters of roofs and terrain type. In this study, first, the effects of geometrical parameters of roofs and terrain type on the wind pressure distribution based on the data obtained from the existing wind tunnel tests were summarized. Then, the wind loads of full‐scale structures were predicted by CFD, and the efficiency of numerical results was further verified by the available wind tunnel tests on spatial structures. Finally, with comparative analyses of the wind pressure distribution of the roofs predicted by CFD under different cases, the effects of shape ratios, especially rise‐span ratio, height‐span ratio, length‐span ratio, and so on, and terrain type on the wind pressure field of typical spatial structures were presented. It can be beneficial to wind‐resistant design of structures and can be provided as reference for aerodynamic design optimum of span spatial structures.

Effects of various inlet/outlet positions and header forms on flow distribution and thermal performance in microchannel heat sink

Three-dimensional simulations are performed numerically to investigate the influence of inlet/outlet positions (Z-, I-, and C-type) and header forms (rectangular, symmetric trapezoidal, and triangular) on the flow and thermal performance in microchannel heat sinks. The conjugated heat transfer model is solved based on finite element method. A good agreement is found between the numerical results and theoretical data. A detailed analysis of flow and pressure distributions is proposed to explain the flow or heat transfer performance of different geometric structures. Results indicate that the performance of I-type with a rectangular header in terms of flow velocity uniformity and heat transfer is better than others under the same pumping power consumption.

Measurement of Tank Cooling Airflow Based on Array Sensors

Researching on the cooling airflow characters of tank will be helpful for optimizing the design of cooling system, and will be of great importance to improve the performance of armoured vehicles. According to the test requirements of tank under the actual working conditions, we studied and designed the proposed cooling airflow measurement system. The most important thing was that we finished the assembly of array sensors without any damage to tank. In addition, according to national standard we set the quantity and locations of the sensors, which was on the premise of avoiding the influence to airway. In this paper, there was description of cooling airflow signal processing; and there was analysis of air pressure distribution which was presented simultaneously by three-dimensional surface graph and plane graph at the exhaust port of tank engine compartment according to fitting algorithm.

Estimating CoP Trajectories and Kinematic Gait Parameters in Walking and Running Using Instrumented Insoles

Quantitative analysis of the plantar pressure distribution during dynamic tasks can facilitate diagnosis of foot and ankle dysfunctions and prevent potential injuries by providing detailed information about weight bearing and weight shifting patterns. Traditional laboratory measurements are currently limited by high operating costs and lack of portability. The use of instrumented insoles capable of capturing kinematic and kinetic gait parameters as subjects perform out-of-the-lab dynamic activities is a promising approach to overcome these limitations. This letter introduces SportSole , a fully portable system that can measure spatiotemporal gait parameters and center of pressure (CoP) trajectories. Wearing the SportSole , nine able-bodied subjects completed a walking session followed by a running session, each consisting of 10 full laps along a 16-meter straight-line path. Accuracy and precision of CoP trajectories and kinematic parameters were assessed using an electronic walkway as the reference system. After calibration, mean deviations in the CoP were 0.61 $\pm$ 0.05 cm (RMSE $\pm$ SD) for walking and 0.72 $\pm$ 0.08 cm for running. Deviations in stride length, stride time, and velocity were 1.66 $\pm$ 0.18 cm, 0.006 $\pm$ 0.003 s, and 1.65 $\pm$ 0.10 cm/s for walking, 1.91 $\pm$ 0.19 cm, 0.01 $\pm$ 0.03 s, and 2.67 $\pm$ 0.38 cm/s for running. These promising results indicate that the proposed system has the potential to be used for out-of-the-lab gait analysis of walking and running.

Ultrasound coupled with supercritical carbon dioxide for exfoliation of graphene: Simulation and experiment

Ultrasound coupled with supercritical CO2 has become an important method for exfoliation of graphene, but behind which a peeling mechanism is unclear. In this work, CFD simulation and experiment were both investigated to elucidate the mechanism and the effects of the process parameters on the exfoliation yield. The experiments and the CFD simulation were conducted under pressure ranging from 8MPa to 16MPa, the ultrasonic power ranging from 12W to 240W and the frequency of 20kHz. The numerical analysis of fluid flow patterns and pressure distributions revealed that the fluid shear stress and the periodical pressure fluctuation generated by ultrasound were primary factors in exfoliating graphene. The distribution of the fluid shear stress decided the effective exfoliation area, which, in turn, affected the yield. The effective area increased from 5.339cm3 to 8.074cm3 with increasing ultrasonic power from 12W to 240W, corresponding to the yield increasing from 5.2% to 21.5%. The pressure fluctuation would cause the expansion of the interlayers of graphite. The degree of the expansion increased with the increase of the operating pressure but decreased beyond 12MPa. Thus, the maximum yield was obtained at 12MPa. The cavitation might be generated by ultrasound in supercritical CO2. But it is too weak to exfoliate graphite into graphene. These results provide a strategy in optimizing and scaling up the ultrasound-assisted supercritical CO2 technique for producing graphene.

Analysis of plantar pressure distribution on pediatric subjects: A pilot study

Analysis of plantar pressure distribution on pediatric subjects: A pilot study

Design and implementation of a BSN-based system for plantar health evaluation with exercise load quantification

BackgroundPlantar pressure measurement has become increasingly useful in the evaluation of plantar health conditions thanks to the recent progression in sensing technology. Due to the large volume and high energy consumption of monitoring devices, traditional systems for plantar pressure measurement are only focused on static or short-term dynamic monitoring. It makes them inappropriate for early detections of plantar symptoms usually presented in long-term activities.MethodsA prototype of monitoring system based on body sensor network (BSN) is proposed for quantitative assessment of plantar conditions. To further assess the severity of plantar symptoms which can be reflected from the pressure distribution in motion status, an approach to conjoint analysis of pressure distribution and exercise load quantification based on the strike frequency (SF) and heart rate (HR) is also proposed.ResultsAn examination was tested on 30 subjects to verify the capabilities of the proposed system. The estimated correlation rate with reference devices (r>0.9) and error rate on the average (R_{AE}<0.08) of HR and SF indicated equal measuring capabilities as the existing commercial products . Comprised of the conjoint analysis based on HR and SF, the proposed method of exercise load quantification was examined on all subjects’ recordings.Conclusions A prototype of an innovative BSN-based bio-physiological measurement system has been implemented for the long-term monitoring and early evaluation of plantar condition. The experimental results indicated that the proposed system has a great potential value in the applications of long-term plantar health monitoring and evaluation.

Analysis of Pressure Distribution During Direct Microlaryngoscopy

This study aimed to investigate the pressure distribution during direct microlaryngoscopy and its relation with the positioning of the patient. This is a prospective study in cadavers. The pressure distribution during direct microlaryngoscopy was investigated in five adult fresh cadavers by using matrix-based piezoresistive thin-film sensors. The pressure among three head and neck positions (extension-extension, neutral, and flexion-extension) was studied. The real-time pressure and its distribution were recorded as 3-D contours. The map commonly showed two peak pressure points, with one focused on the middle of the laryngoscope (peak pressure 1) and the other one focused on the distal part of the laryngoscope (peak pressure 2). The mean average pressure in this study was 38 ± 13 kPa, and the flexion-extension position had the lowest average pressure and peak pressure. However, the average pressure and peak pressure 1 showed no significant difference among the three positions (P > 0.05); peak pressure 2 in the flexion-extension position was significantly lower than that in the extension-extension position (P = 0.024) and the neutral position (P = 0.020). The results of this study indicate that the flexion-extension position induced lower pressure exerted on the laryngoscope and is an optimal position for direct microlaryngoscopy. Hyoid bone may play an important role in the pressure exerted.

Novel design for PIG to eliminate the effect of hydraulic transients in oil and gas pipelines

Hydraulic Transient is one of the most destructive effects in oil and gas pipelines. Currently existing pigs are one of the main sources for this phenomena due to their physical characteristics and function. In this study, by implementation of a new design to the system of pigs, which utilizes the free spaces surrounding the robot, the effect of hydraulic transient is fully eliminated. To demonstrate the practicality and significance of this study, several various simulation experiments such as laminar flow, pressure distribution, velocity variations and stress analysis are conducted on the new design with adjustable arms as well as the former design utilizing sealing disks. The benefit of using adjustable arms exceeds the goal of this research and makes the design extremely versatile by giving it the ability of multi-diameter pipeline inspection and speed maintenance to derive highest resolution for inspection sensors.

Foot use during vertical climbing in chimpanzees (Pan troglodytes)

Upright bipedalism is a hallmark of hominin locomotion, however debates continue regarding the extent of arboreal locomotion and the nature of bipedalism practiced by early hominins. Pedal form and function play a prominent role in these debates, as the foot is the element that directly interacts with the locomotor substrate. Recent finds have substantially increased the availability of associated foot remains of early hominins and emphasized the enigmatic nature of the early evolution of human bipedalism. New discoveries of associated forefoot remains have afforded the opportunity to assess relative proportions across the forefoot of fossil hominins and illuminated the need for data on relative loading across the forefoot in extant hominoids. In order to provide functional data with which to examine the relationship between bony features and load distribution across the forefoot during climbing, we present the first analysis of plantar pressure distribution across the forefoot of chimpanzees climbing a vertical support. Chimpanzees load the medial metatarsals and first toe disproportionately during vertical climbing. Peak pressures on these elements occur at the end of stance phase during climbing and are higher than on any other elements of the foot. Toe pressures are considerably higher during vertical climbing than during knuckle-walking or movement on horizontal poles, supporting the notion that the plantarly-broad and dorsally-narrow metatarsal heads in chimpanzees and some early hominins are associated with close-packing of the metatarsophalangeal joint during climbing.

Association of CYP17A1 Genetic Polymorphisms and Susceptibility to Essential Hypertension in the Southwest Han Chinese Population

BackgroundThe CYP17A1 gene encodes for cytochrome P450 enzyme CYP17A1, which is involved with the steroidogenic pathway including mineralocorticoids. The CYP17A1 polymorphisms might affect enzyme activity, then leading to a state of mineralocorticoid 11-deoxycorticosterone excess characterized by hypertension, suppressed plasma renin activity, and low aldosterone concentrations. The aim of this study was to investigate the contribution of CYP17A1 polymorphisms in inducing the susceptibility to essential hypertension among the Southwest Han Chinese population.Material/MethodsEight single nucleotide polymorphisms of CYP17A1 were genotyped in a case-control study for samples by polymerase chain reaction-restriction fragment length polymorphism analysis.ResultsThe polymorphisms rs11191548 and rs4919687 were significantly associated with hypertension risk, which was confirmed by systolic and diastolic blood pressure distribution analyses between different genotype groups, and these two polymorphisms were found in linkage disequilibrium. The rs4919687 polymorphism was estimated to cause the destruction of exonic splicing silencer (ESR and Motif 3) sites and to transform the transcription factor AREB6 binding site, respectively, in the bioinformatics analyses. The haplotypes rs4919686A-rs3740397G -rs4919687C-rs743572C-rs11191548C and rs4919686A-rs3740397G-rs4919687T-rs743572C- rs11191548T were found to be susceptible to essential hypertension.ConclusionsOur findings suggest that the CYP17A1 polymorphisms could be a genetic risk factor for essential hypertension among the Yunnan Han Chinese population, which would have implications for the treatment of this complex disorder.

The Effect of the Addition of Inlet Disturbance Body (IDB) to Flow Resistance Through the Square Cylinders Arranged in Tandem

Flow resistance through the square cylinders arranged in tandem, with the addition of Inlet Disturbance Body (IDB) in the form of circular cylinder, was analyzed by computational fluid dynamics (CFD) simulation using FLUENT 6.3.26 software as well as by experiments on resistance force and pressure distribution analysis. There were 5 (five) Reynolds numbers (ReD) employed for the entire samples. Reynolds numbers were calculated based on condition of square cylinders arranged in tandem with diameter (D) of 70 mm. ReD values gained range from 30,625 to 96,250. The ratios of diameter of IDB circular cylinder and diameter of square cylinders diameter (d/D) were varied in three (3) levels, d/D = 0.08; 0.14 and 0.20, while the ratios of the distance between the cylinders and square cylinder diameter (L/D) were varied in 8 (eight) levels of L/D = 0.0 to 1.0. The experimental results showed the pattern of the value of drag coefficient (CD) and pressure coefficient (CP) decreasing with an increase in L/D and d/D. Lowest values of CD and CP obtained were 1.67 and 0.87 respectively for L/D = 0.43 and d/D = 0.14 for all values of the Reynolds number. It was caused by flow separation absorbed by the addition of IDB circular cylinder prior to the square cylinder arranged in tandem. For the value of L/D larger or smaller than 0.43, the values of CD and CP escalate because the vortex flow was pushed upward the flow, hence causing the boundary layer on top of the square cylinder to increase. This phenomenon is validated with CFD simulation. Placement of a circular cylinder as IDB mounted prior to square cylinders arranged in tandem is resulting in the reduction of resistance of square cylinder from CD = 2.13 to CD= 1.67 or as many as 21.5962% and reduction of the pressure distribution of CP = 1.02 to CP = 0.87 or at 14.7059%. Based on these results, the optimal values of L/D and d/D due to the addition of IDB were L/D = 0.43 and d/D = 0.14 with values of CD = 1.67 and CP = 0.87.

ARM Processor Based Wireless Data Acquisition System for Pressure Distribution Analysis

ARM Processor Based Wireless Data Acquisition System for Pressure Distribution Analysis

Pore pressure and stress distribution analysis around an inclined wellbore in a transversely isotropic formation based on the fully coupled chemo-thermo-poroelastic theory

Wellbore instability is a widespread problem when drilling in shale formations, particularly with water-based drilling fluid. The main reason for the occurrence of wellbore instability is that stress concentration and pore pressure redistribution occur around the wellbore once a hole is drilled; current studies show that the drilling fluid temperature and solute mass fraction play important roles during the process. In this work, a non-linear fully coupled chemo-thermo-poroelastic finite element model is developed to quantitatively access thermal and chemical effects on time-dependent pore pressure and effective stresses; in addition, material constant sensitivity analysis of an inclined well drilled in a transversely isotropic formation is presented. The results reveal the following: fluid transfer is greatly affected by thermal and chemical osmosis, the lower temperature and higher solute mass fraction of the drilling fluid contribute to decreasing the pore pressure and are beneficial for wellbore stability, and thermal parameters (such as thermal osmosis coefficient and thermal diffusivity) and chemical parameters (such as reflection coefficient and solute diffusion coefficient) have high effects on the pore pressure and effective stresses. Anisotropy ratio analysis of the material constants indicates that the pore pressure and effective stresses are very sensitive to Young's modulus and the permeability ratio, but are not sensitive to Poisson's ratio. Therefore, the developed coupled chemo-thermo-poroelastic theory illustrates that optimization of the reduction of the drilling fluid temperature while maintaining a high solute mass fraction could enhance wellbore stability.

Role and significance of wetting pressures during droplet impact on structured superhydrophobic surfaces.

The impact dynamics and spreading behavior of droplets impinging on structured superhydrophobic surfaces are dependent on both the droplet initial conditions and the surface texture. The equivalence of wetting and dewetting pressures is classically known to be a critical factor in determining the state of a droplet during the contact and spreading phases. The present study extensively examines the underlying physics behind this pressure balance during the impact process and its direct role in determining the wetting process. Extensive three-dimensional simulations employing droplet impact on a structured superhydrophobic surface has been performed to reveal the intricacies of the interactivities of the fluid with the microstructure. Insight onto the acute role of wetting pressures and the implications of the same on determining the wetting dynamics, with internal fluidics of the droplet during the impact process, has been discussed. The phenomenon of state transition from the Cassie-Baxter to the Wenzel up on impact is also investigated and the intricate flow mechanics at play within the posts has been presented. Knowledge of pressure distribution and internal flow structures within the droplet during its interaction with the surface at different instances of time reveals the root mechanism behind the impalement of the droplet to a fully wetting state. Analysis of the internal pressure and flow distribution also presents necessary justification for the existence of a partially impaled state. The time evolution of spread for different scenarios is in agreement with experimental results and the article provides insight onto the role of wetting pressure in determining fluidic interactions on such surfaces.

Dynamic plantar pressure distribution, strength capacity and postural control after Lisfranc fracture-dislocation

Substantial progress has been made in the operative treatment of Lisfranc fractures, however, the prognosis remains poor. We hypothesized that Lisfranc injuries change the postural control and muscle strength of the lower limb. Both are suggested to correlate with the clinical outcome and quality of life.17 consecutive patients suffering from a Lisfranc fracture dislocation were registered, underwent open reduction and internal fixation and were followed-up for 50.5±25.7months (Mean±SDM). Biomechanical analysis of muscle strength capacities, postural control and plantar pressure distribution was assessed >6 month postoperatively. Results were correlated to clinical outcome (AOFAS, FFI, Pain, SF-36).The isokinetic assessment revealed a significant reduction in plantar flexor and dorsal extensor peak torque of the injured limb compared to the uninjured limb. The dorsal extensor peak torque thereby correlated well with clinical outcome. Altered postural control was evident by a significant reduction in unilateral stance time, from which we calculated a strong correlation between stance time and the isokinetic strength measurement. Plantar pressure measurements revealed a significant reduction in peak pressure under the midfoot and of Force-Time Integral beneath the second metatarsal.Sufficient rehabilitation is crucial to the clinical outcome following anatomical open reduction of Lisfranc fracture-dislocation. The present study supports a rehabilitation approach focussing on restoring proprioception and calf muscular strength including isometric exercises of the dorsal extensors.

Numerical study of the effect of inlet geometry on combustion instabilities in a lean premixed swirl combustor

The effects of flow structure and flame dynamics on combustion instabilities in a lean premixed swirl combustor were numerically investigated using Large eddy simulation (LES) by varying the inlet geometry of combustor. The dynamic ksgs-equation and G-equation flamelet models were respectively employed as the LES subgrid models of turbulence and combustion. The divergent half angle (α) in the combustor inlet was varied systematically from 30° to 90° to quantify the effect of inlet geometry on the combustion instabilities. This variation caused considerable deformation in recirculation zones in terms of their size and location, leading to significant changes in flame dynamics. Analysis of unsteady pressure distributions in the combustor showed that the largest damping caused by combustion instabilities takes place at α = 45°, and the amplitude of acoustic pressure oscillation is largest at α = 30°. Examination of local Rayleigh parameters indicated that controlling flame-vortex interactions by modifying inlet geometry can change the local characteristics of combustion instabilities in terms of their amplification and suppression, and thus serve as a useful approach to reduce the instabilities in a lean premixed swirl combustor. These phenomena were studied in detail through unsteady analysis associated with flow and flame dynamics.

A Modeling Approach to Study the Fluid-Dynamic Forces Acting on the Spool of a Flow Control Valve

This paper introduces an approach to study a valve's internal fluid dynamics. During operation, the flow causes forces on the spool. These forces must be correctly balanced. Since these forces cannot be measured, a three-dimensional (3D) computational fluid dynamic (CFD) modeling approach is needed. A case study has been undertaken to verify the approach on a two-way pressure compensated flow control valve. Since forces vary during operation, the analysis must be transient. From the initial zero spool position, the flow goes through the valve causing a spool shift inside the valve's housing until the spool stops at its final position. Forces depend on the spring reaction, the inlet pressure force, the pressure force of the fluid inside the spool, and the spring holder volumes, and the balance of forces influences the outlet flow rate at the final spool position. First, the initial case geometry was modeled, prototyped, and tested, and this geometry was studied to verify the model accuracy compared to experimental data. The comparison shows good agreement with a maximum error of 3%. With the same approach, several other geometries were designed, but only the best geometry was prototyped and tested. The model was adopted to make several analyses of velocity contouring, streamlines trends, and pressure distribution in the fluid volume. The modeled and tested results achieved the expected performance confirming the effectiveness of the methodology.

Computational Fluid Dynamics Predictions of Control-Surface Effects for F-16XL Aircraft

Computational fluid dynamics methods play an increasingly important role in aircraft design and development. Some examples are conditions that cannot be tested before a flight test. To rely on these methods, it is essential that they are assessed and evaluated with a state-of-the-art wind tunnel test and/or in-flight data. In a previous project, Cranked-Arrow Wing Aerodynamics Project International, it was reported that all computational fluid dynamics methods failed to some degree in the transonic regime where shock–vortex interaction phenomena were present. Detailed analysis of surface pressure distribution showed that computational fluid dynamics was not able replicate the correct flowfield and produce acceptable results. This paper aims to restudy those transonic flight conditions for which computational fluid dynamics underperforms and to try to determine or shed light on the extent to which surface effects contribute to the computational fluid dynamics predictions.

A vortex force study for a flat plate at high angle of attack

The vortex force is studied for a flat plate at arbitrarily large angle of attack. A suitable vortex force approach, adapted from a previous work, is used to study the vortex force and to build a vortex force line map to identify the force effect of any potential vortex. This map can be used exactly for a potential point vortex and approximately for a concentrated leading-edge vortex (LEV) or trailing-edge vortex (TEV); the latter are shown to have a non-potential vortex core. By means of this map, we identify a force-producing critical region, due to pressure suction, above the front and rear parts of the plate for an LEV and a TEV, respectively. The impulsively started flow problem is used as an application, with validation by computational fluid dynamics. The force variation in time is decomposed into four repeatable stages (force release, force enhancement, stall and force recovery) in close relation to the individual and combined effect by an LEV and a TEV. A pressure distribution analysis shows that force enhancement is due to pressure suction by an LEV, while stall and force recovery are respectively due to the upwash effect (which reduces the pressure below the plate) of a new TEV right off the plate and the pressure suction of this TEV having now moved above the plate. A viscous effect causes a small-amplitude oscillation on the force curves by promoting multiple small-scale LEVs.