Static Fluid Pressure Research Articles

Experimental study on the influence of roadway shape on the evolution of outburst fluid static pressure

To explore the static pressure dynamic disaster mechanism of coal-and-gas outburst (CGO) fluid, the self-developed multi-field coupling large-scale physical simulation test system of coal mine dynamic disaster was used to carry out gas outburst and CGO physical simulation tests in straight, L-shaped and T-shaped roadways. The influence of roadway shape on the evolution of static pressure was explored, and the role of pulverized coal in the process of static pressure dynamic disaster was clarified. The results indicated that the static pressure showed a fluctuating downward trend during the outburst process. When gas outburst, the middle and front parts of the roadway in the straight section roadway were the most serious areas of static pressure disasters in the three shapes of roadways. The duration and range of high static pressure disaster in L-shaped roadway were larger than those in T-shaped and straight roadways in turn. When CGO, the most serious area of static pressure disaster in L-shaped and T-shaped roadways moved backward to the middle of the straight section roadway, and there was a rebound phenomenon in the process of static pressure fluctuation decline, which showed the pulse characteristics of CGO. During the outburst, the static pressure dynamic disaster hazard of L-shaped roadway was higher than that of T-shaped roadway, and the static pressure at the bifurcation structure decayed faster than that at the turning structure, which indicated that T-shaped roadway was more conducive to the release of static pressure in roadway, thus reduced the risk of static pressure disaster. When gas outburst, the static pressure attenuation of the fluid in the roadway before and after the turning and bifurcation structure was greater than that of CGO. The peak static pressure and impulse of the fluid during gas outburst were 2 times and 4–5 times that of CGO respectively. The presence of pulverized coal reduced the attenuation of static pressure and the hazard of dynamic disaster, prolonged the release time of energy, and led to the change of the maximum static pressure disaster area.

The Effect of PhET Simulation in Science Learning of Static Fluid Pressure Topics towards Students’ Creative Thinking Skill

This study aims to see is there a significant effect of the use of PhET simulations in science learning of static liquid pressure topics towards creative thinking skill of middle school students. This research was conducted at SMPIT Al-Ghozali Jember in 8th grade of C class and D class where each class consisted of 21 female students. The design of this research is Control Group Pretest-Posttest in which the learning in experimental class uses the PhET simulation while in control class uses the experimental video. The results of Wilcoxon Signed-Rank Test on students' creative thinking skill test scores are differed significantly both in the experimental class and the control class. The results of Mann-Whitney test are the students' student worksheets in the experimental class differed significantly from the control class. It can be concluded that there is a significant effect of the use of PhET simulations in this study.

A Momentum-Based Method for the Mass Concentration Measurement of Pneumatically Conveyed Solid: Computational Verification

A momentum-based method is proposed to measure the mass concentration of solids in pneumatic pipelines. The mechanism relies on the fact that particles flowing with the fluid will exert drag force and thus induce pressure increase on the fluid phase when they decelerate as approaching a static object or space in the flow domain. The pressure increase is expected to increase with the mass concentration of particles and the fluid velocity, and is also affected by the particles size and density. A conversion factor that indicates the extent to which particle momentum is converted to the fluid static pressure increase was defined. Computational verification of the mechanism was carried out with pulverized coal flow around a one-end closed tube with its opening facing towards the incoming flow. The pressure increase was quantitatively comparable to the fluid dynamic pressure when the solid-to-fluid mass ratio was of the same order of magnitude. The conversion factor was found insensitive to particle size over a wide range, which is advantageous since particle size distribution are usually not known in advance. Compared to most existing techniques, current mechanism is more robust and economic in industry field measurements.

The Impact of Fatigue Testing and Surface Processing on Nickel Release in Nitinol Stents

Immersion testing of medical implants is typically performed under non-loaded conditions to assess susceptibility of metal ion release from a device. However, many implants are subjected to repetitive forces in vivo, which may increase ion release into surrounding tissues. Therefore, the objective of this study was to determine whether fatigue loading of stents with different surface finishes accelerates nickel release. Nitinol stents with an electropolished (EP) oxide or blue oxide (BO) were assigned to the following groups: (1) static immersion without loading, (2) static fluid pressure and bend, (3) dynamic pressure on a static bend, and (4) dynamic bending with static pressure. Immersion fluid was collected periodically and analyzed for nickel concentration using ICP-MS. Results indicated nickel release under dynamic bending was greater by up to 280× for EP and 190× for BO finishes compared to all other groups (p 0.27), nickel release under dynamic pressure conditions was up to 50× higher compared to static groups. In addition, BO stents released up to 6× greater levels of nickel compared to EP stents for static immersion, dynamic pressure, and dynamic bending groups (p < 0.05). These findings highlight the impact of fatigue loading on uniform corrosion for different nitinol stent surfaces.

Prototype design, fabrication, and testing of a 5-m large mirror support structure for the TALE experiment

To extend the detector measurement range to above 1016 eV so as to encompass for ultra-highenergy cosmic rays (UHECRs), Korean collaborators have contributed to the design, development, and structural evaluation of the telescope array (TA) experimental fluorescence detector (FD).With a 5-m diameter, this is the world’s largest interferometer. This new design requires stability; i.e., it must be constructed on a sturdy, reinforced foundation so as to provide reliability, suitability, and serviceability. Thus, fundamental analyses considering all environment-related factors have been conducted to test and evaluate the components of our large detection system. These analyses include a static stress analysis with ~80-kg loads for ~1 day, a static fluid stress analysis under a moderately heavy wind at 16-27 m/s, a thermal stress analysis at high temperatures of 47-58 °C, and an optical reflectivity test. There by, we determined a static pressure of 380 MPa (static fluid pressure: 0.1 MPa) and a thermal pressure of 10 MPa. The optical spot size was 30-40 mm with a very high peak (estimated value: 34.5 mm). Note that a brief description of the design and the production results for the Telescope Array Low-Energy Extension (TALE)-FD Mirror Support Structure prototype were presented at the December 13, 2013, TA collaborative meeting in Japan (ICRR).

Calculation and analysis of complex fluid flow in the multistage fan of a large turbogenerator end region

In order to study the distributions of complex fluid velocity and fluid pressure in the multistage fan of a large turbogenerator end region, the multistage fan in the 1407 MVA turbogenerator is analyzed. Characteristic curve of pressure and fluid rate of the multistage fan is determined. Static pressure distribution of dynamic and static fan blade surfaces and fluid velocity distribution around dynamic and static fan blade surfaces in the multistage fan are researched. The distribution laws of radial velocity, tangential velocity, and axial velocity between dynamic fan blade and static fan blade are given. The change laws of fluid static pressure and fluid total pressure are analyzed after fluid passes through dynamic and static fan blades. The calculated results match well with measured data. This research can provide an important reference for the optimal design and research of multistage fan in a large turbogenerator.

Continuity equation-derived valve area using CMR phase-contrast provides flow-independent assessment of valve stenosis

Background Assessing aortic valve stenosis (AVS) by cardiac magnetic resonance (CMR) remains challenging, largely due to effects of accelerated flow and resulting pressure recovery, or the phenomena of kinetic energy transmuting to static fluid pressure distally. Effective orifice area (EOA) is a technique used in echocardiography and has been shown to improve AVS assessment. The potential of phasecontrast velocity mapping (PC-MRI) to improve the accuracy of EOA rests on the ability to resolve high peak velocities; previous studies have shown systematic underestimation compared to echocardiography. We used in vitro experiments to assess the accuracy of EOA using the continuity equation with PC-MRI derived peak velocities and flows.

Theoretical Computation and Verification for Fluid Static Pressure in Centrifugal Pump Side Chamber

Theoretical Computation and Verification for Fluid Static Pressure in Centrifugal Pump Side Chamber

Remarks on the notion of “pressure”

In addition to understanding the various meanings attached to the word “pressure” one also has to comprehend the meanings of the phrases in which the term “pressure” appears. For instance one comes across the following combinations: “static-fluid pressure”, “thermodynamic pressure”, “mechanical pressure”, “contact pressure”, “stagnation pressure”, “vapor pressure”, “electro-osmotic pressure”, etc., One also often comes across the comment that “pressure is the Lagrange multiplier that enforces the constraint of incompressibility” and that “pressure is the mean normal stress”. In general the word “pressure” with different significations, is used with gay abandon without paying proper attention to its usage11The author is also guilty of following this slovenly and unmeticulous usage of the term “pressure”.. The distinction in the meanings of the above terms assumes paramount significance when discussing properties of materials, which could possibly depend on “pressure”. In this short note we discuss the distinction between various significations of the word “pressure”, and their implications with regard to response relations for bodies.

Regional pore-fluid pressures in the active western Taiwan thrust belt: A test of the classic Hubbert–Rubey fault-weakening hypothesis

We document regional pore-fluid pressures in the active Taiwan thrust belt using 55 deep boreholes to test the classic Hubbert–Rubey hypothesis that high static fluid pressures (depth normalized as λ = Pf/ρrgz) account for the extreme weakness of thrust faults, since effective friction μf∗=μf(1−λ). Taiwan fluid pressures are dominated by disequilibrium compaction, showing fully compacted sediments with hydrostatic fluid pressures at shallow depths until the fluid-retention depth zFRD ≈ 3 km, below which sediments are increasingly undercompacted and overpressured. The Hubbert–Rubey fault weakening coefficient is a simple function of depth (1 − λ) ≈ 0.6zFRD/z. We map present-day and pre-erosion fluid pressures and weakening (1 − λ) regionally and show that active thrusts are too shallow relative to zFRD for the classic Hubbert–Rubey mechanism to be important, which requires z ≥ ∼4zFRD ≈ 12 km to have the required order-of-magnitude Hubbert–Rubey fault weakening of (1 − λ) ≤ ∼0.15. The best-characterized thrust is the Chelungpu fault that slipped in the 1999 (Mw = 7.6) Chi-Chi earthquake, which has a low effective friction μf∗≈0.08–0.12, yet lies near the base of the hydrostatic zone at depths of 1–5 km with a modest Hubbert–Rubey weakening of (1 − λ) ≈ 0.4−0.6. Overpressured Miocene and Oligocene detachments at 5–7 km depth have (1 − λ) ≈ 0.3. Therefore, other mechanisms of fault weakening are required, such as the dynamical mechanisms documented for the Chi-Chi earthquake.

Hydrodynamic modeling of downward gas–solid flow. Part II: Co-current flow

The one-dimensional model of accelerating turbulent downward co-current gas–solid flow of coarse particles was formulated and experimentally verified by measuring the pressure distribution along the transport tube. The continuity and momentum equations were used in the model formulation and variational model was used for the prediction of the fluid–particle interphase drag coefficient.The experiments were performed by transporting spherical glass particles 1.94mm in diameter in a 16mm i.d. acrylic tube at constant solid mass flux of 392.8kg/m2s. Tube Reynolds number ranged from 880 to 11,300 and the slip Reynolds number from 32 to 670. At these conditions, the loading ratio Gp/Gf was in the range from 395 to 31. Experimental data for the static fluid pressure distribution along the transport tube agree quite well with the model predictions.The results measured at a distance of 1.51m from the transport tube inlet show that the particle velocity and the mean voidage increase with the increase in superficial gas velocity. The slip velocity changes from negative values at low gas superficial velocities to positive values at high gas superficial velocities. The same trend was observed for the change of the pressure gradient in the system.The values of the pressure gradient, porosity, particle velocity and slip velocity along the tube were calculated according to the formulated model. The distance from the transport tube inlet at which the slip velocity changes its sign from positive to negative is the function of the gas superficial velocity. At positive slip velocity both gravity and drag contribute to particle acceleration. At negative slip velocity the drag force acts in upward direction resisting the particle acceleration. In downward co-current gas–solid flow acceleration length is relatively long, about two times longer compared to the upward co-current gas–solid flow.

Hydrodynamic modeling of downward gas–solids flow. Part I: Counter-current flow

The one-dimensional model of accelerating turbulent downward counter-current gas–solids flow of coarse particles was formulated and experimentally verified by measuring the pressure distribution along the transport tube. The continuity and momentum equations were used in the model formulation and variational model was used for the prediction of the fluid–particle interphase drag coefficient.Experiments were performed by transporting spherical glass particles 1.94mm in diameter in a 16mm i.d. acrylic tube at constant solids mass flux of 392.8kg/m2s. Tube Reynolds number ranged from 170 to 5300 and the slip Reynolds number from 650 to 1060. Under these conditions loading ratio (Gp/Gf) varied between 66 and 2089. Visual observations show that particles flow downward in apparently homogenous dispersion. Experimental data for the static fluid pressure distribution along the transport tube agree quite well with the model predictions. The mean voidage and the particle velocity decrease, while the slip velocity increases with the increase in gas superficial velocity.The values of the pressure gradient, porosity, particle velocity and slip velocity along the tube were calculated according to the formulated model. In these calculations, particle–wall friction coefficient was determined indirectly by adjusting the fp value to agree with the experimental data. The effect of the value of fp on the model calculations was significant.Calculations show that the acceleration length for the same particles (1.94mm) in downward counter-current gas–solids flow is about two times higher than the acceleration length in upward co-current gas–solids flow. In the system investigated, “choking” occurs at slip velocity which is about 73% of the single particle terminal velocity.

The Response of Rigid Plates to Deep Water Blast: Analytical Models and Finite Element Predictions

One-dimensional analytical models and finite element calculations are employed to predict the response of a rigid plate, supported by a linear spring, to loading by a planar pressure shock wave traveling in water or in a similar inviscid liquid. Two problems are considered: (i) a spring-supported rigid plate in contact with fluid on one side and (ii) a spring-supported rigid plate in contact with fluid on both sides; for both problems, plates are loaded by an exponentially decaying shock wave from one side. Cavitation phenomena in the liquid, as well as the effect of the initial static fluid pressure, are explicitly included in the analytical models and their predictions are found to be in excellent agreement with those from FE calculations. The validated analytical models are used to determine the sensitivity of the plate’s response to mass, spring stiffness and initial static pressure.

Performance characteristics of a novel tubular-shaped passive direct methanol fuel cell

The present work consists of a tubular-shaped direct methanol fuel cell (DMFC) that is operated completely passively with methanol solution stored in a central fuel reservoir. The benefit of a tubular-shaped DMFC over a planar-shaped DMFC is the higher instantaneous volumetric power energy density (power/volume) associated with the larger active area provided by the tubular geometry. Membrane electrode assemblies (MEAs) with identical compositions were installed in both tubular and planar-shaped, passive DMFCs and tested with 1, 2, and 3M methanol solutions at room temperature. The peak power density for the tubular DMFC was 19.0mWcm−2 and 24.5mWcm−2 while the peak power density for the planar DMFC was 20.0mWcm−2 and 23.0mWcm−2 with Nafion® 212 and 115 MEAs, respectively. Even though the performance of the fuel cell improved with each increase in methanol concentration, the fuel and energy efficiencies decreased for both the tubular and planar geometries due to increased methanol crossover. The tubular DMFC experienced higher methanol crossover potentially due to a higher static fluid pressure in the anode fuel reservoir (AFR) caused by the vertical orientation of the tubular fuel reservoir. The performance of the tubular DMFC in this work represents an 870% improvement in power density from the previous best, passive, tubular DMFC found in the literature.

VALIDATION OF THE STATIC PRESSURE AND WAVE PRESSURE BY MPS WITH NEW GRADIENT OPERATOR

Accuracy of a highly precised Moving-particle semi-implicit (MPS) method, proposed by the authors, is compared with that of the traditional MPS method on the static fluid pressure and water wave propagation. The MPS method is modified with a precise estimation of the gradient. In a static fluid analysis, a good accuracy is obtained in the modified MPS for static pressure than in the original MPS. In case of progressive water wave propagation analysis, the oscillation of wave pressure can also be simulated with high accuracy. The study suggests that the proposed method for the gradient operator can contribute to improve the accuracy of the MPS method.

Acoustoelastic effects on mode waves in a fluid-filled pressurized borehole in triaxially stressed formations

Based on the nonlinear theory of acoustoelasticity, considering the triaxial terrestrial stress, the fluid static pressure in the borehole and the fluid nonlinear effect jointly, the dispersion curves of the monopole Stoneley wave and dipole flexural wave propagating along the borehole axis in a homogeneous isotropic formation are investigated by using the perturbation method. The relation of the sensitivity coefficient and the velocity-stress coefficient to frequency are also analyzed. The results show that variations of the phase velocity dispersion curve are mainly affected by three sensitivity coefficients related to third-order elastic constant. The borehole stress concentration causes a split of the flexural waves and an intersection of the dispersion curves of the flexural waves polarized in directions parallel and normal to the uniaxial horizontal stress direction. The stress-induced formation anisotropy is only dependent on the horizontal deviatoric terrestrial stress and independent of the horizontal mean terrestrial stress, the superimposed stress and the fluid static pressure. The horizontal terrestrial stress ratio ranging from 0 to 1 reduces the stress-induced formation anisotropy. This makes the intersection of flexural wave dispersion curves not distinguishable. The effect of the fluid nonlinearity on the dispersion curve of the mode wave is small and can be ignored.

Prediction of the particle circulation rate in a draft tube spouted bed suspension dryer

A model for predicting the particle circulation rate in a draft tube spouted bed dryer with inert particles is proposed and verified. The calculation algorithm requires three input values: the gas velocity in the draft tube one data point for the static pressure in the draft tube, and the pressure gradient in the annulus. The particle circulation rate can be estimated by solving the continuity and momentum equations for turbulent accelerating two-phase flow. The numerical solution is based on an iterative procedure until the assumed value of the particle circulation rate produces the prescribed value of the fluid static pressure at a certain axial position. Experiments were performed in a cylindrical column of 215 mm diameter with a draft tube of 70 mm diameter and length of 900 mm. Polyetylene pellets were used as the inert particles with a diameter of 3.3 mm, a density of 921 kg/m3 and a sphericity of 0.873. The model predictions of the particle circulation rate are in good agreement with the experimental data.

A New Formulation for Buckling Analysis in Fluid-Structure Interaction Problem.

This paper presents the procedure of two dimensional buckling analysis considering fluid-structure interaction. In the formulation, the buckling of thin structures subjected to the pressure of viscous flow is modeled, where the geometrically nonlinear equation and the Navier-Stokes equation should be considered. These equations are solved by the strong coupling formulation and the Newton-Raphson method with the so-called arc-length technique. The buckling load and mode are determined by checking the determinant of stiffness and the scaled corrector method. In order to confirm the validity of the present formulation, the arch subjected to only the static pressure of fluid is analyzed. In the subsequent examples, the effect due to the fluid-structure interaction on the buckling of structure is investigated.

Experiments on steady and oscillatory flows at moderate Reynolds numbers in a quasi-two-dimensional channel with a throat.

The study of steady and unsteady oscillatory static fluid pressures acting on the internal wall of a collapsible tube is essential for investigation of the complicated behavior observed when a flow is conveyed inside a tube. To examine the validity of two one-dimensional nonsteady theoretical flow models, this paper presents basic experimental observations of flow separation and reattachment and measured data on the static pressure distributions of the flow in a quasi-two-dimensional channel with a throat, together with information on the corresponding shape of the wall deflection and motion. For combinations of moderate Reynolds numbers and angles of the divergent segment of the channel, a smooth flow is separated from the wall downstream of the minimum cross section and reattached to the wall farther downstream. The measured data are compared with numerical results calculated by the two flow models.

On the effect of pore pressure on the isotropic behavior of saturated porous media

This paper analyzes the small strain elasticity of fluid saturated porous media and the influence of the fluid static pressure, or pore pressure, on their isotropic constitutive properties. The porous medium is modelled as a lattice assembly of monodisperse spheres that interact through Hertz contacts. The size of the spheres and hence the matrix volume at zero solids stress are shown to be influenced by the pore pressure. Consequently, the structural pressure generated by elastic Hertzian contact deformations is shown to depend on both the volume occupied by the matrix and the pore pressure. This result is then generalized for random assemblies of spheres by using an isotropic constitutive law that is realistic for dry sands. The present findings suggest that the contributions of pore pressure and structural pressure to the total stress do not have a constant weighting as is often assumed, but one that is sensitive to the deformation state of the matrix. The theory also captures the characteristic loss of matrix stiffness during liquefaction at sufficiently elevated pore pressures.