Pressure Distribution Curve Research Articles

Study of Pressure Fields in a Water Well during its Cleaning from Salt Deposits

The paper deals with the pressure fields in a water well during its cleaning from salt deposits using electric discharge equipment with the location of the charging and discharging device on the Earth surface. The curves of the spatial pressure distribution in a water well were obtained. Those graphs could be used to determine the processing modes, namely the number of processing points per 1 linear meter of the well. The results obtained showed a strong influence on the cleaning efficiency of the parameters of the high-voltage cable that connects the surface and submersible parts (electrical characteristics of the cable and its length). Methods to increase the efficiency of the impact are proposed.

Tirzepatide and blood pressure reduction: stratified analyses of the SURMOUNT-1 randomised controlled trial

BackgroundTreating obesity may be a pathway to prevent and control hypertension. In the SURMOUNT-1 trial in people with obesity or overweight with weight-related complications, 72-week tirzepatide treatment led to clinically...

Numerical investigation of flow around the injector of a Pelton turbine due to eroded needle

Abstract Injectors of Pelton turbines are prone to both sediment erosion and cavitation. This causes degradation of the surface morphology, which aggravates the quality of the jet, lowering the turbine’s performance. The study focuses on CFD analysis of a groove-shaped erosion pattern on the needle and analyses its influence on the quality of the jet at the three stages of erosion. The numerical model comprises of a nozzle with a cylindrical passage for modelling the jet. The research used the SST turbulence model and boundary conditions defined according to the turbine’s data, from which the model was obtained. This study explores the impact of silt erosion on pressure signals around the injector of a Pelton turbine. Needle pressure distribution curves were plotted at various erosion levels and openings, revealing that pressure deviation increases with increase in erosion. The effect turns out to be minimal during high opening levels but becomes substantial as opening levels decrease. Operating in part load conditions leads to a significant pressure drop due to the reduction in flow rate. The pressure distribution tends to become more uniform at full load, achieving optimal flow rates. However, a noticeable pressure drop is observed in the eroded region, reaching a minimum at the deepest eroded area. The pressure drop is further amplified with an increase in the level of erosion, indicating erosion’s disruptive impact on fluid flow. The findings highlight the complex interplay between erosion, needle pressure distribution, and jet diffusion.

Influence of Permeability and Shear-Thinning Behavior on the Hydrodynamics Flow Features Around Porous Square Cylinders

Abstract This article investigates the laminar flow of power-law fluids through two porous square cylinders in a side-by-side configuration. The effects of power-law index (n), Darcy number (Da), and gap ratio (g/W) are examined within ranges of g/W = 0.5–5, n = 0.4–0.8, and Da = 10−6–10−2, respectively. Two flow conditions are considered: first, for a creeping flow (unseparated flow) at Re = 1 where Darcy's law is applicable; second, for a viscous dominant flow at Re = 100, where Darcy–Forchheimer-extended model is exercised. Flow patterns behind the porous cylinders are analyzed using streamlines, velocity profiles, pressure distribution curves, and vorticity structural parameters (Г). In low permeability levels, the flow exhibits an irregular nonperiodic vortex shedding characterized by a single large vortex street far off the downstream for g/W = 0.5. However, synchronized wake patterns were observed in either antiphase or in-phase modes for higher gap ratios. Leading-edge separation with two-side recirculation induces quasi-periodicity in the flow for all g/W. It was found that increasing the permeability can prevent the leading edge separation. Additionally, a transition from antiphase to in-phase mode occurs when the permeability is altered while maintaining constant flow-time. The presence of a jet-like flow between cylinders significantly impacts unsteady wake patterns. The impact of g/W, power-law index, and permeability on drag is also examined. A jump in some flow parameters was observed at higher Re for the midrange Darcy number, but no such increase was noted for the high shear-thinning behavior. These findings provide a potential approach for improving the design of fluidic systems involving porous cylinders.

Optimal design of silver-loaded zeolite filter structure based on porous media model

Silver zeolite filters have potential applications in nuclear power plant filtration and emission systems due to their high-efficiency adsorption properties for radioactive methyl iodide. The adsorption performance of the filter is closely related to the flow distribution characteristics. To analyze the flow distribution characteristics of the filter element, we established a reasonable numerical calculation model and verified the model through experiments. Then based on the model, the advantages and disadvantages of different filter unit structures are analyzed. We proposed two new structural forms of filters and evaluated the performance of the filters based on the pressure distribution and flow increment curve, considering the difficulty of processing and space utilization. Comparative analysis and characteristic research have been carried out under different sizes, from the cylindrical filter to the round table filter and, finally, to the square filter. Our results show that round table and square filters have significantly improved flow distribution compared to traditional cylindrical filters. However, the structure of the round table filter is irregular, and the space utilization rate is low. Finally, through optimization design, the square filter with channel spacing L of 250 mm has the best performance. Our research results have a certain guiding significance for the design of the silver zeolite filter prototype.

Feature-Based Gait Pattern Modeling on a Treadmill

In this paper, we present a method of gait analysis on a treadmill based on pressure distribution. We aimed to model the gait patterns of a subject walking at a constant speed on a treadmill based on differences in current consumption. The changes in current consumption were converted into pressure distribution curves, and then specific features were extracted. The extracted features were used to model the walking pattern on a treadmill. To verify the validity of our proposed feature-based gait pattern modeling, we conducted experiments by gender, age, BMI (body mass index), and step-to-step symmetry. The experimental results showed that the heavier the subject, the higher the value of each feature. In particular, our feature point-based gait modeling provides an index that can help determine whether a subject’s gait is abnormal, depending on the difference between the features.

A Study of the Non-Linear Seepage Problem in Porous Media via the Homotopy Analysis Method

A non-Darcy flow with moving boundary conditions in a low-permeability reservoir was solved using the homotopy analysis method (HAM), which was converted into a fixed-boundary mathematical model via similarity transformation. Approximate analytical solutions based on the HAM are guaranteed to be more accurate than exact analytical solutions, with relative errors between 0.0089% and 2.64%. When λ = 0, the pressure drop of the Darcy seepage model could be instantaneously transmitted to infinity. When λ > 0, the pressure drop curve of the non-Darcy seepage model exhibited the characteristics of tight support, which was clearly different from the Darcy seepage model’s formation pressure distribution curve. According to the results of the HAM, a moving boundary is more influenced by threshold pressure gradients with a longer time. When the threshold pressure gradients were smaller, the moving boundaries move more quickly and are more sensitive to external influences. One-dimensional, low-permeability porous media with a non-Darcy flow with moving boundary conditions can be reduced to a Darcy seepage model if the threshold pressure gradient values tend to zero.

The Squeeze Film Effect with a High-Pressure Boundary in Aerostatic Bearings

The squeeze film effect was discussed in several fields, but mostly under the same pressure boundary conditions. However, pressures at the inlet and outlet are different for aerostatic bearings. In this paper, the dynamic Reynolds equation group, with the stiffness and damping pressure written separately, is deducted and numerically solved with a high-pressure boundary for a parallel flat and circular thin film. The circular thin film considers the two results of the supply pressure boundary inside and outside. All dynamic pressure distribution and stiffness curves are given in a dimensionless form, and a comparative analysis of squeeze film characteristics with and without external pressure is conducted. From the calculation results, it can be concluded that the squeeze effect shows damping for zero-frequency and stiffness for infinite-frequency for compressible lubricants. The dynamic pressure in the static high pressure region is also high at high frequencies affected by gas compressibility. Based on these analytical results, the transfer functions of the thin film are given to further analyze the dynamic performance of aerostatic bearings, and the shape of the response curve approximates an exponential decay form, even when the amplitude increases to 10% of the gas film thickness.

Study on the one-dimensional governing equations of aerostatic circular thrust bearing with a single air supply inlet

PurposeThe purpose of this paper is to derive the one-dimensional governing equations to describe the pressure distribution, load capacity and stiffness of aerostatic circular thrust bearing with a single air supply inlet.Design/methodology/approachThe film flow field is divided into four regions: supply pressure region, pressure dropping region, pressure rising region and laminar flow region. The influences of bearing clearance and supply pressure on the pressure distribution, load capacity and stiffness of the bearing are presented.FindingsWith the large film clearance and large supply pressure, the oblique shock wave occurs near the entrance of gas film, which greatly increases the pressure drop region. Hence, it is not appropriate to consider the oblique shock as a normal shock.Originality/valueThis paper introduces the invariants at the entrance of gas film, employs the functional relationships between density and pressure, and provides the empirical formulas for the pressure dropping and rising regions. The pressure distribution curves are therefore illustrated through a considerably simplified computational process.

Calculation of Nonlimit Active Earth Pressure against Rigid Retaining Wall Rotating about Base

A retaining wall with sandy fill was considered as the research object in order to study the nonlimiting active earth pressure under the rotation about the base (RB mode). Rankine’s and Coulomb’s earth pressure theories are no longer applicable to the above conditions (RB mode and nonlimiting active earth pressure). In order to improve the traditional earth pressure calculation methods (Rankine and Coulomb), a calculation method using curvilinear thin layer elements is presented with overall considerations of wall displacement, soil arching effect, and friction angle exertion coefficient to deduce the nonlimit active earth pressure under RB. Additionally, the calculation results were in good agreement with model test data (from Fang and Smita). Moreover, a parametric analysis was carried out. It was revealed that the developed value of the shear strength decreased with the depth, and the active earth pressure distribution curve was linear and nonlinear in the upper and lower halves, respectively.

Active Earth Pressure for Sloping Finite Soil While Accounting for Shear Stress and Curved Slip Surface

Calculating the earth pressure of the sloping soil having finite width behind the retaining wall is difficult for stability calculation. Thus, a novel method to calculate the active pressure of cohesionless sloping finite soil behind a retaining wall was developed to investigate. Taking cohesionless soil as the research object and considering the principal stress rotation of soil, the resultant force for active earth pressure, action point position, and earth pressure distribution of sloping finite soil was obtained based on assumptions of the translational mode of the rigid retaining wall and cycloidal slip surface. The accuracy of the proposed method was verified by model tests. The influence of the slope height ratio l / H and slope angle α on earth pressure was analyzed in this study. The result revealed that the horizontal component of the active earth pressure distribution curve for sloping finite soil was linear in area I and nonlinear with a drum shape in area II. There was a noticeable change at the junction of the two areas. The resultant force of earth pressure and the height of action point of resultant force increased and tended to reach a certain value as the aspect ratio l / H increased. When l / H ≥ 0.4 , the height of the action point of resultant force tended to be two-fifths the height of the wall. The resultant force and the height of the action point decreased linearly as the slope bottom angle increased.

Semi-analytical modeling of transient pressure behaviour for a multifractured horizontal well in a gas reservoir with a complex fracture network by considering effects of slippage, stress-sensitivity, and gas adsorption/desorption

A semi-analytical technique has been developed, validated, and applied to quantify the pressure behaviour of a multifractured horizontal well (MFHW) in a gas reservoir with discrete fracture networks and an arbitrary boundary. Considering stress-sensitivity and the slippage effect in the matrix subsystem, a pseudo-pressure is incorporated into the gas flow equations. To weaken the strong nonlinearity from such a combined effect, the dual-reciprocity boundary element method (DRBEM) is applied to efficiently and effectively linearize the governing equations by replacing the nonlinear function with a series of particular solutions. Comparing with the boundary element method (BEM), not only can the DRBEM be used to obtain the accurate solution in any space and time domains, but also it is flexible to deal with the nonlinearity restriction in the governing equations. The finite volume method (FVM) is then adopted to simulate gas flow behaviour in the fracture subsystem with different fracture geometries. Not only can the proposed model be applied to a complex fracture network and operating schedules, but also capture complex gas flow behaviour including the Langmuir sorption, slippage effect, and stress-sensitive effect in a gas reservoir with a discrete fracture network and an arbitrary boundary. The mathematical formulations have been validated and then extended to field applications. A strong stress-sensitive effect is found to result in a large pressure drop and offset the permeability-enhancing effect from the slippage effect. In addition, a decrease in pressure drop derived from gas desorption would restrict the stress-sensitive effect. Furthermore, it can be found that each individual factor imposes a significant impact on the linear flow and boundary dominated flow regimes. On the basis of a mutual interference, the combined effect (i.e., stress-sensitivity, slippage effect, and gas adsorption/desorption) may be weaker than that of each individual factor. In the late boundary-dominated flow regime, the effect of boundary shape becomes more obvious on the pressure distribution curves since the pressure wave would reach the boundaries near fractures within a relatively short time.

Elastic Distortion Calculation of a Controlled-Clearance Piston-Cylinder Assembly up to 1500 MPa Using Finite Element Method

Abstract A controlled-clearance piston-cylinder assembly is modelled using finite element method (FEM). Elastic distortion of the piston-cylinder engagement gap is calculated by the FEM model and then is input to a fluid dynamics model to solving the pressure distribution which works as load in the FEM model. Accurate distortion-pressure solutions are obtained for measurement pressure of (100~1500) MPa by iterative calculations until a convergence of interest is reached. Results are generated for various jacket pressures maintaining balance. Dramatic rapid decent are found near the gap exit after a steady profile for both distortion and pressure distribution curves. Gap exit width can be two orders of magnitude smaller than the nominal gap clearance, and comparable to the irregularity of the piston and cylinder, introducing risks of inaccuracy or potential damage.

Effect of the variations of the gap flow guides geometry on the savonius wind turbine performance: 2D and 3D studies

The Savonius wind turbine has been identified to have low power and torque coefficients. Numerous blade shapes and modifications have been proposed to improve its performance. In the present study, double gap flow guides of different lengths of 25–100 mm were introduced at different angular positions of 45–90° in a 0.5 m diameter blade Savonius turbine. The unsteady Reynolds Averaged Navier Stokes equations and the turbulence equations corresponding to SST k−ω were solved using the commercial software ANSYS FLUENT. Simulations were conducted in 2D and validated with 3D simulations at key points. The extracted results of the coefficient of performance and torque were compared with the available experimental data for the purpose of validation. A maximum increase of 12.24% in the coefficient of performance was observed for model 75 (degree angle) - 75 (mm length) at a tip speed ratio 1. Despite the high performance of model 75-75, model 60–75 showed a higher average of coefficient of performance across the considered range of tip speed ratios. The advantage of gap flow guides was explained in light of streamline plots, velocity vector plots and pressure distribution curves.

Effects of operating parameters on flow force characteristics in a conical throttle valve

PurposeFlow force is one of the crucial factors affecting the performance of conical throttle valves. The purpose of this paper is to determine the relationship between the flow force and operating parameters of the conical throttle valve.Design/methodology/approachThe flow force of the throttle valve can be obtained by the difference between the axial force and static pressure on the valve spool. In this paper, the internal fluid is divided into two regions and the axial force and static pressure are obtained, respectively. In addition, a two-dimensional axisymmetric simulation model and experimental test are carried out to validate the results of the flow force.FindingsIt can be seen that the theoretical, simulation and experimental results exhibit high agreement with each other and the error between them decreases with the increase in the size of the opening. The curves of pressure distribution reveal that the pressure on the spool first decreases then increases when it reaches the minimum pressure at the orifice. Additionally, the minimum pressure decreases with the increase of opening and pressure difference. The results also indicate that the increase in the size of the opening and inlet pressure has a positive effect on the flow force. However, the increase in outlet pressure has a negative effect on the flow force.Originality/valueIn this paper, the flow force calculation model of conical throttle valve is established and the influence of operating parameters on the flow force of conical throttle valve is studied.

Numerical simulation of formation damage by drilling fluid in low permeability sandstone reservoirs

Understanding the formation damage surrounding the well during the drilling operation is the key to predict damage degree and protect the formation in oil/gas reserviors. Based on the core drainage results, we obtained an empirical relationship between the invasion volume of drilling fluid and permeability reduction of formation. Furthermore, the equation is incorporated into a commercial reservior numerical simulation simulator to characterize the behaviors of drilling fluid invasion process. The results show that, although the invasion depth in low permeability reservoirs is short with the range of 1.7–2.5 m, the effect on recovery factor is significant due to the narrow seepage area in the near fracture region. When considering the formation damage, the pressure in the near-fracture damage region drops sharply, leading to a three-stage shape in pressure distribution curve. In addition, we found that high viscosity and low density oil-based slurry and shorter soaking period are conducive to decrease the formation damage during drilling operation. This work reveals the fundamental mechanisms of formation damage in low permeability reservoirs, which is a theoretical basis in formulation drilling fluids and optimization operation parameters.

Effects of mattress firmness on infant body pressure distribution

Infancy is a developmental stage in an individual's life. As an important part of infant development, sleep greatly influences the physiological and mental development of infants, and the health and comfort of infant sleep is a major public concern. From the viewpoint of ergonomics, this study investigated the effects of mattress firmness on the body pressure distribution of infants aged 0–3 years in the supine posture. Six types of mattresses with different firmness values were tested and 11 healthy infant subjects participated in the experiment. A Tekscan body pressure measurement system was used to record data. The body pressure distribution of infants was analysed using six pressure distribution indices including the maximum pressure, average pressure, contact area, maximum pressure gradient, average pressure gradient, and longitudinal pressure distribution curve. The results revealed that, in the supine posture, there is significant correlation between the body pressure indices and the mattress firmness. The average pressure has the strongest correlation with mattress firmness. The infants' buttocks zone had the highest pressure, while the pressure on the head and leg zones was relatively low. The recommended K value, which represents the mattress firmness, ranges from 267 to 669 mm2.

Design and control of precision work stage with air bearing for large size optical grating fabrication

Scanning Beam Interference Lithography (SBIL) is an advanced large-diameter and high-precision plane grating manufacturing solution, which has very high requirements for the positioning accuracy and running speed of the work stage carrying the substrate. In order to improve the size and accuracy of optical grating manufacturing in scanning interference lithography further, air bearing with high precision, high loading capacity and high stiffness is one of the key components for the work stage. In this paper, in order to design a large stroke work stage which meets the demand, firstly, the air bearing, the core part of the work stage, is analyzed and calculated by finite element method, and the pressure distribution curve of the air bearing of the work stage is obtained. On this basis, the linear air bearing with high bearing capacity and high stiffness is designed by using the omni-directional preloading analysis method of high-precision motion platform. Based on the high-precision position feedback of grating encoder, the high-precision closed-loop control of 20nm (3σ) is realized by using PID control and trap filter, which meets the design and requirements, and provides technical and engineering support for the manufacture of large-scale optical grating.

Physical simulation of the nonlinear transient flow behavior in closed high-pressure gas reservoirs. Part I: Pressure-depleted flow experiments on matrix cores

In this work, in order to physically simulate the transient flow process of gas in a closed high-pressure reservoir, a pressure-depleted flow experiment was newly designed. Then five short matrix cores were put into a long core holder with a closed end-face to conduct the experiment. Six pressure gauges were uniformly distributed at six different positions on the holder to monitor the flow pressures at the endpoints of each core, and a flow meter was located at the outlet of the holder to test the flow rate. Before the experiment, an initial pressure distribution was built along the holder. By using the experimental pressure data, a series of curves of pressure dynamics and pressure distribution were plotted and then matched by nonlinear regressions. It was found that the pressure dynamical curves and the pressure distribution curves could be described by a piecewise equation and a quadrinomial equation, respectively. By using the experimental flow rate data, the dynamical curves of flow rate were plotted and matched by a quadrinomial function of the semi-logarithm of time. In addition, it was also found that the relationship of pressure with flow rate could only be described by using a polynomial function, instead of the classic binomial and exponential functions. All the curves related to pressure and flow rate were of strong nonlinearity. Furthermore, an infinitesimal method was presented to deduce the calculation formula of gas recovery factor whose value at any experimental time was calculated. At the end, the nonlinear transient flow characteristics were thoroughly analyzed and summarized. This study can be a good reference for researchers in the related field to study the nonlinear transient flow behavior of geo-fluids.

Force Characteristics of Rotating Air Film and Flow Closed-Loop for Noncontact Adsorption

A rotating air film is used in a wide range of applications, such as rotating machines, filtering systems, and computer storage devices. In this article, the pressure distribution and force characteristic curve of a rotating air film were both theoretically and experimentally analyzed. First, based on von Karman's similarity transformation, a theoretical model of the pressure distribution and generation mechanism of suction force of a finite disk was developed by considering the distance of two disks and the edge conditions of the disk. The experimental results showed good agreement with theoretical results. This article also proposes a new application for the rotating air film, i.e., a noncontact adsorption device, based on the negative feedback closed-loop of force and distance between two disks. The method was investigated and verified theoretically and experimentally, and a force characteristic curve with positive stiffness could be formed. Finally, based on the proposed method, we designed and manufactured an apparatus that can exert suction force on a flat workpiece without contact.