Calculation Of Pressure Gradient Research Articles

SENSITIVITY ASSESSMENT OF A GRADIENT-BASED LEAK LOCALIZATION PROCEDURE FOR PRESSURE SENSOR FAULTS USING A LABORATORY MODEL OF A TRANSMISSION PIPELINE

This research addresses the topic of leakage localization in liquid transmission pipelines. Particularly, it deals with the standard gradient-based procedure used for performing such a task. The procedure relies on pressure gradient calculations based on pressure data collected from measurement points distributed along the pipeline. This study aimed to verify this procedure regarding its sensitivity to typical systematic errors related to pressure transducers. The primary measure evaluated was the accuracy of the calculated coordinate of a leak spot. The uncertainty of the leak localization result was also estimated following the Guide to the Expression of Uncertainty in Measurement convention. A laboratory model of the pipeline was used to practically implement and test the procedure. During experiments, low-intensity leakages with a level of 0.25–2.00% were simulated. Regarding typical systematic errors, the bias (zero moving) type and the proportional ratio type were considered, which were numerically simulated in the measurement data. The findings reveal how sensitive the examined procedure is in relation to these errors, considering their different levels and scenarios related to used pressure transducers.

Gender differences in coronary artery disease patterns

Abstract Background Gender differences in clinical presentation, natural history, and prognosis of coronary artery disease (CAD) have been reported. Fractional flow reserve (FFR) has also been shown to yield higher values in women than men. However, the gender differences in CAD patterns (focal vs diffuse) defined by coronary physiology remain to be studied. Methods This prospective study was performed at 23 sites and enrolled patients with at least one epicardial lesion with an FFR ≤ 0.80 intended to be treated by PCI. All patients underwent a standardized physiological protocol that mandated FFR pullbacks with pullback pressure gradient (PPG) calculation. The aim was to compare CAD patterns, defined by PPG, between genders. Results Overall, 1004 patients were included in the analysis, 236 females (250 vessels) and 768 males (794 vessels). Women were older (69.8 ± 10.3 vs. 67.0 ± 10.1, p <0.001), less frequently smokers (9.7% vs. 18.6%, p = 0.002), had less prior PCI in a non-target vessel (19.1% vs. 30.6%, p = 0.001) and had less prior MIs (14.4% vs. 21.5%, p = 0.021). On the baseline seven-item Seattle Angina Questionnaire (SAQ-7), females reported more physical limitation (70.9 ± 29.5 vs. 80.9 ± 25.1, p < 0.001), more frequent angina (76.7 ± 22.9 vs. 81.5 ± 20.3, p = 0.002) and a lower quality of life (51.8 ± 29.4 vs. 57.8 ± 29.1, p = 0.006) than men for the same degree of flow reduction (FFR 0.69 ± 0.12 vs. 0.67 ± 0.11, p=0.098). In women, the pattern of CAD demonstrated a more focal nature compared to men (PPG 0.65 ± 0.16 vs. 0.61 ± 0.16, p = 0.001). Also, women achieved higher post-PCI FFR (0.88 ± 0.07 vs. 0.87 ± 0.07, p = 0.02). The rate of periprocedural MI was not statistically different between genders (5.1% vs. 5.8%, p = 0.79) Conclusion Among patients with hemodynamically significant CAD, women report more symptoms and lower quality of life. Despite sharing a similar degree of flow impairment, women exhibited a more focal CAD phenotype than men, leading to superior physiological outcomes after PCI.Study flowchartPRO and Phisiology by gender

Impact of the pullback pressure gradient (PPG) on PCI planning and decision-making

Abstract Background Coronary physiology using a distal measurement of fractional flow reserve (FFR) informs about the severity of coronary artery disease (CAD) and, when used for clinical decision-making about revascularisation, is associated with improved outcomes in patients considered for PCI. A second dimension of coronary physiology is available by performing a pullback maneuver, which aids in assessing the presence and location of focal pressure gradients. Yet, the impact of intracoronary physiology guidance with FFR pullbacks on real-time physician decision-making during PCI is not fully known. Methods This prospective study was performed at 25 sites and enrolled patients with at least one epicardial lesion with FFR ≤ 0.80 planned to be treated by PCI. A standardized physiological assessment with FFR pullbacks and Pullback Pressure Gradient (PPG) calculation was performed. Treatment plans were recorded for each lesion based on angiography alone and following FFR pullbacks. The goal of this study was to assess the procedural impact of physiology guidance in stable patients scheduled for PCI. Results Overall, 993 patients (1044 vessels) underwent complete physiological assessment with FFR and PPG. Decision-making during PCI changed in 47.5% (443/1044) after FFR pullbacks. Decision-making during PCI changed in 32.4% (289/890) after FFR pullbacks. PPG use changed revascularisation decisions in 13.9% (138/993) from PCI to CABG (5%; 50/993), from PCI to CABG in 5% (50/993) and to medical management in 8.9% ( 88/993). The frequency of decision changes was significantly higher in patients with diffuse CAD compared to focal cases (24.8% vs. 44.2%, p < 0.001). Among the subset of 855 patients (involving 880 vessels) who underwent PCI, operators modified decision-making regarding stent length in 22.1% of cases (197 out of 880), with these alterations being more prevalent in patients with diffuse CAD (57.2% vs. 46.3%, p = 0.002). Suboptimal Post-PCI result (FFR < 0.88) was more frequent in cases in which PCI strategy was not adapted based on PPG (55.5% vs. 45.6%, p= 0.016) Importantly, there was no significant change in the overall number of stents per patient after FFR pullbacks. Conclusion A standardized coronary physiological assessment impacted PCI decision-making in one-third of the vessels, with a predominant effect in vessels diffusely diseased. The assessment of the distribution of pressure losses along the coronaries modifies the treatment decision and influences PCI strategy in a significant proportion of patients. These findings provide insights into mechanisms by which coronary physiology might improve PCI outcomes.PCI strategy change based on PPGCumulative change of PCI strategy

Assessing boundary conditions in CFD for transvalvular pressure gradient calculation in cardiac hemodynamics

Abstract Background Computational fluid dynamics (CFD), which has the advantages of providing detailed pressure distribution, has been widely used for cardiac function assessment and heart disease diagnosis. However, the results are usually influenced by the boundary conditions. Particularly, the transvalvular pressure gradient, which serves as a crucial indicator for mitral stenosis and the efficacy of mitral valve surgery, can easily be miscalculated. Here, we assess the effects of widely used boundary conditions on the transvalvular pressure gradient computed based on the Bernoulli equation and the line probe, respectively. Purpose This study aims to determine the effects of boundary conditions on the transvalvular pressure gradient in CFD. Methods We constructed cardiac models including left atrium, left ventricle, aorta from CT and mitral valve from transesophageal echocardiography data (Figure 1). The intraventricular flow fields were computed using CFD tool with four different boundary conditions (BC) at the same cardiac output. BC1 involved specifying the total flow rate of the aorta, with zero pressure at the entrance of the pulmonary veins. BC2 maintained equal flow rates at the entrances of the pulmonary veins. BC3 followed Murray's law, where the flow rate ratio in the pulmonary veins is proportional to the 1.5 power of the area ratio. BC4 followed Poiseuille's law, where the flow rate ratio is proportional to the square of the area ratio. The results encompassed the mean transvalvular pressure gradient and peak transvalvular pressure gradient obtained through the Bernoulli equation and the line probe methods, respectively. Results Figures 2(A-D) present the contours of transvalvular pressure under peak flow velocity conditions and the isosurfaces of vorticity within the ventricle. The results show that the pressure within the atrium is notably lower in the BC2, leading to a 63% underestimation in the mean transvalvular pressure gradient and a 22.9% deviation in the peak transvalvular pressure gradient (Figure 2 F). The transvalvular pressure gradient for BC1, BC3, and BC4 do not exceed 10%. The results reveal that the pressure distribution and vorticity within the ventricle are consistent, primarily due to the influence of the mitral valve. Conclusion When evaluating transvalvular pressure gradient using CFD, it is crucial to specify appropriate boundary conditions. Using inappropriate boundary conditions may lead to underestimation of the transvalvular pressure gradient, thereby affecting further diagnostic decisions. In research studies, it is recommended to allocate flow in different branch vessels according to Murray's law, where the flow in different branch vessels is proportional to the 1.5 power of the vessel cross-sectional area.Modelling flow chartTransvalvular pressure gradient

Influence of Pathophysiologic Patterns of Coronary Artery Disease on Immediate Percutaneous Coronary Intervention Outcomes.

Diffuse coronary artery disease affects the safety and efficacy of percutaneous coronary intervention (PCI). Pathophysiologic coronary artery disease patterns can be quantified using fractional flow reserve (FFR) pullbacks incorporating the pullback pressure gradient (PPG) calculation. This study aimed to establish the capacity of PPG to predict optimal revascularization and procedural outcomes. This prospective, investigator-initiated, single-arm, multicenter study enrolled patients with at least one epicardial lesion with an FFR ≤0.80 scheduled for PCI. Manual FFR pullbacks were used to calculate PPG. The primary outcome of optimal revascularization was defined as an FFR ≥0.88 after PCI. A total of 993 patients with 1044 vessels were included. The mean FFR was 0.68±0.12, PPG 0.62±0.17, and the post-PCI FFR was 0.87±0.07. PPG was significantly correlated with the change in FFR after PCI (r=0.65 [95% CI, 0.61-0.69]; P<0.001) and demonstrated excellent predictive capacity for optimal revascularization (area under the receiver operating characteristic curve, 0.82 [95% CI, 0.79-0.84]; P<0.001). FFR alone did not predict revascularization outcomes (area under the receiver operating characteristic curve, 0.54 [95% CI, 0.50-0.57]). PPG influenced treatment decisions in 14% of patients, redirecting them from PCI to alternative treatment modalities. Periprocedural myocardial infarction occurred more frequently in patients with low PPG (<0.62) compared with those with focal disease (odds ratio, 1.71 [95% CI, 1.00-2.97]). Pathophysiologic coronary artery disease patterns distinctly affect the safety and effectiveness of PCI. PPG showed an excellent predictive capacity for optimal revascularization and demonstrated added value compared with an FFR measurement. URL: https://www.clinicaltrials.gov; Unique identifier: NCT04789317.

Gas permeability and mechanical properties of dust grain aggregates at hyper- and zero-gravity

Abstract Particle-particle and particle-gas processes significantly impact planetary precursors such as dust aggregates and planetesimals. We investigate gas permeability (κ) in 12 granular samples, mimicking planetesimal dust regoliths. Using parabolic flights, this study assesses how gravitational compression – and lack thereof– influences gas permeation, impacting the equilibrium state of low-gravity objects. Transitioning between micro- and hyper-gravity induces granular sedimentation dynamics, revealing collective dust-grain aerodynamics. Our experiments measure κ across Knudsen number (Kn) ranges, reflecting transitional flow. Using mass and momentum conservation, we derive κ and calculate pressure gradients within the granular matrix. Key findings: 1. As confinement pressure increases with gravitational load and mass flow, κ and average pore space decrease. This implies that a planetesimal’s unique dust-compaction history limits sub-surface volatile outflows. 2. The derived pressure gradient enables tensile strength determination for asteroid regolith simulants with cohesion. This offers a unique approach to studying dust-layer properties when suspended in confinement pressures comparable to the equilibrium state on planetesimals surfaces, which will be valuable for modelling their collisional evolution. 3. We observe a dynamical flow symmetry breaking when granular material moves against the pressure gradient. This occurs even at low Reynolds numbers, suggesting that Stokes numbers for drifting dust aggregates near the Stokes-Epstein transition require a drag force modification based on permeability.

Fractal study on the nonlinear seepage mechanism during low-permeability coal water injection

In the initial stage of coal seam water injection, due to the high density and low permeability of coal bodies, an obvious startup pressure gradient is observed in relation to water seepage; this phenomenon leads to low-velocity nonlinear seepage. In this paper, we study the nonlinear seepage law and the main influencing parameters of the water injection process. First, based on the startup pressure gradient, the nonlinear seepage equation, and the fractal theory, we formulated a nonlinear seepage model of coal seam water injection that considered the fractal characteristics of a complex coal structure. Subsequently, we carried out coal seam water injection and gas radial seepage experiments under a high overburden pressure, obtaining the startup pressure gradient according to the seepage characteristics and the changes of dynamic parameters. Then, the dynamic parameters of water injection, the structural parameters of the coal samples, the physical parameters, and the fractal dimension were substituted into the theoretical model to obtain the theoretically calculated value. Finally, through comparative analysis of theoretical and experimental startup pressure gradient calculation results, it is found that with the increase in the overburden pressure, the permeability of coal and the connectivity effect are reduced, while the fracture tortuosity and the startup pressure gradient increase. Moreover, coal seam permeability does not seem to be the single decisive factor for the nonlinear startup pressure gradient.

Measurements and Modeling of Pore‐Pressure Gradients in the Swash Zone Under Large‐Scale Laboratory Bichromatic Waves

AbstractThe present work presents physical laboratory measurements of surface elevation and pore water pressures in a fine sand bed under bichromatic waves in a large‐scale laboratory experiment. This was done at three cross‐shore locations in the swash zone, with pressures being measured at different depths in the bed. The measurements show that the pore pressure signal decays and shifts with increased depth. These measurements are used to validate a practical model, based on the theory of Yamamoto et al. (1978, https://doi.org/10.1017/S0022112078003006) and Guest and Hay (2017, https://doi.org/10.1002/2016JC012257). The model corresponds well with the measurements (nRMSE &lt; 0.2 and R2 &gt; 0.95 for most probes) and shows that a frequency‐based model can reproduce the pressures in the bed, despite the bed being exposed during dry periods. Furthermore, the model provides the opportunity to calculate pressure gradients, both throughout the bed and at the bed surface. These modeled pressure gradients at the bed surface show that the vertical pressure gradient can have an important impact on the Shields parameter, thereby influencing sediment transport.

Evolution of Echocardiography-Derived Hemodynamic Force Parameters After Cardiac Resynchronization Therapy

Echocardiography-derived hemodynamic forces (HDF) allow calculation of intraventricular pressure gradients from routine transthoracic echocardiographic images. The evolution of HDF after cardiac resynchronization therapy (CRT) has not been investigated in large cohorts. The aim was to assess HDF in patients with heart failure implanted with CRT versus healthy controls. HDF were assessed before and 6months after CRT. The following HDF parameters were calculated: (1) apical-basal strength, (2) lateral-septal strength, (3) the ratio of lateral-septal to apical-basal strength ratio, and (4) the force vector angle (1 and 2 representing the magnitude of HDF, 3 and 4 representing the orientation of HDF). In the propulsive phase of systole, the apical-basal impulse and the systolic force vector angle were measured. A total of 197 patients were included (age 64 ± 11years, 62% male), with left ventricular ejection fraction ≤35%, QRS duration ≥130ms and left bundle branch block. The magnitude of HDF was significantly lower and the orientation was significantly worse in patients with heart failure versus healthy controls. Immediately after CRT implantation, the apical-basal impulse and systolic force vector angle were significantly increased. Six months after CRT, improvement of apical-basal strength, lateral-septal to apical-basal strength ratio and the force vector angle occurred. When CRT was deactivated at 6months, the increase in the magnitude of apical-basal HDF remained unchanged while the systolic force vector angle worsened significantly. In conclusion, HDF in CRT recipients reflect the acute effect of CRT and the effect of left ventricular reverse remodeling on intraventricular pressure gradients. Whether HDF analysis provides incremental value over established echocardiographic parameters, remains to be determined.

A simple method for predicting pressure transients in high-speed subway tunnel based on train reflected waves

The aerodynamic pressure transients caused by high-speed subway trains entering the tunnel can usually be simulated with high accuracy using three-dimensional compressible numerical simulation methods. However, these methods often require high computer resources, complex pre-processing and post-processing processes. For practical engineering design, it is difficult to use these methods to achieve fast and simple calculation. In this paper, a train wave signature method (TWS method) proposed by previous scholars in high-speed railroad tunnels was introduced, the principles of the method were explained in detail and a generalized computational method for predicting the pressure time history was established. Additionally, an improved TWS method based on the reflected waves from trains was proposed by analyzing the reflection mechanism of pressure waves encountering trains during the trains passing through the tunnel, and the calculation results were verified by using field measurements and three-dimensional numerical simulations. The results show that the improved TWS method has better accuracy compared to the TWS method. Furthermore, this paper presents a smoothing method to enhance the optimization of the improved TWS method and extends its feasibility for pressure gradient calculation.

Noninvasive, patient-specific computational fluid dynamics simulations of dural venous sinus pressures in idiopathic intracranial hypertension

BackgroundThe pathophysiology of Idiopathic Intracranial Hypertension (IIH) is poorly understood, making the disease difficult to properly diagnose and treat. Endovascular venous stenting has emerged as an effective non-invasive treatment option for a select cohort of IIH patients with venous sinus stenosis and elevated venous sinus pressure gradient. Unfortunately, current methods of determining patient eligibility for stenting treatment depend on highly invasive and insufficient measurement methods such as venous manometry, which can only measure pressure gradients and not other components of the complex 3D hemodynamic environment. Thus, there is a need for a non-invasive methodology for determining the 3D flow environment of the dural venous sinuses. ObjectiveTo develop a novel method of non-invasive, patient-specific computational fluid dynamic (CFD) simulation of venous sinus hemodynamics for evaluating stenting eligibility. MethodA patient with IIH and elevated sinus pressure gradient underwent MR venography, phase-contrast MR venography, and venous manometry. Patient-specific dural venous anatomy was segmented from the MR venography to construct 3D models of the venous sinuses. 3D transient patient-specific computational fluid dynamic simulations were conducted using flow velocities measured with phase-contrast MR venography as boundary conditions. ResultsSuccessful computational simulations were completed, allowing for the calculation of the spatio-temporal evolution of blood flow through the dural venous sinuses, and the quantitative examination of pressure gradients. Calculated pressure gradients from CFD were validated against venous manometry with an error of only ∼5%. ConclusionsWe have successfully developed time-resolved, patient-specific 3D computational simulations of the dural venous sinuses without assumptions at the boundary conditions for the first time. The methodology can accurately and non-invasively measure venous pressure gradients. This preliminary study serves as a proof of concept for our method to be used as a diagnostic tool for determining venous stenting eligibility, as well as a tool for advancing the general understanding of IIH pathophysiology. Statement of SignificanceThe pathophysiology of Idiopathic Intracranial Hypertension (IIH) is poorly understood making the disease difficult to properly diagnose and treat. Endovascular venous stenting has emerged as an effective non-invasive treatment option for a select cohort of IIH patients with venous sinus stenosis and elevated venous sinus pressure gradient. Our work provides a method for noninvasively determining eligibility for venous sinus stenting, avoiding costly and invasive venous manometry.

Modelling and evaluating piston slap-induced cavitation of cylinder liners in heavy-duty diesel engines.

Cavitation erosion of cylinder liner seriously affects the operational reliability and service life of heavy-duty diesel engines. The accuracy of the modeling-based cavitation risk evaluation is limited by the unclear correspondence between cylinder liner vibration and coolant cavitation. This report is intended to investigate the correspondence between cylinder liner vibration and coolant pressure by combining vibration cavitation test, pressure gradient calculation, and visualization observation. The cavitation risk of the cylinder liner under piston slap is also quantitatively analyzed based on the nonlinear structural dynamics model. The results show that the occurrence of cavitation will cause a nonlinear relationship between the cylinder liner acceleration and the coolant pressure. The difference in cavitation risk for each cylinder is related to the structural modal characteristics of the crankcase. In addition, the effect of piston-liner clearance and piston pin offset on the cavitation risk is investigated based on the dynamics model.

Drift-flux correlation based on coaxial line phase sensor in a horizontal slug flow

In two-phase flow, void fraction plays an important role in the pressure gradient calculation and the flow pattern analysis, while the distribution parameter C0 and drift velocity ugm are crucial parameters in the establishment of drift flux void fraction correlation. Since the distribution parameter and drift velocity in the constitutive equation cannot reflect the influence of gas–liquid velocity and pressure in most existing correlations, theoretical and experimental studies are carried out to solve these problems in this study. The electromagnetic wave coaxial line phase sensor is designed for void fraction measurement, and the horizontal slug flow experiments (63 data points) have been conducted in a stainless steel tubular test section with an inside diameter of 50.0 mm. A comparison of the performance of thirteen existing drift-flux predictive correlations based on current and literature data (with different pressures (0.1–0.6 MPa) and pipe diameters (19–101.6 mm)) is made. Based on comparative analysis, the L-M parameter X, the liquid mass quality ratio to gas mass quality (1-x)/x and superficial velocity um are chosen to optimize the structure of existing models. A new drift flux correlation that could handle different phase velocities and system pressure is proposed. Experimental results indicate that the mean absolute percentage error (MAPE) of the distribution parameter and drift velocity correlations are 5.88 % and 27.37 %. The MAPE of the drift flux void fraction is 6.98 % (current data) and 11.07 % (literature data), respectively.

Uncertainty of PIV/PTV based Eulerian pressure estimation using velocity uncertainty

This work introduces a method to estimate the uncertainty of the pressure fields reconstructed from particle image velocimetry / particle tracking velocimetry (PIV/PTV) measurements by propagating the instantaneous velocity vector uncertainty through the pressure reconstruction. The uncertainty propagations through the calculation and integration of pressure gradients are modelled as linear transformations. The autocorrelation coefficient was modelled and incorporated in the uncertainty estimation to reproduce the effect of the autocorrelation of velocity errors on the reconstructed pressure’s accuracy. The method was first tested on synthetic velocity fields contaminated with varying levels of artificial noise correlated in space, time, or between components. The error analysis shows that the proposed method could predict the spatiotemporal variations of the pressure errors. The estimated pressure uncertainty also captures the effects of the velocity noise level, the autocorrelation, and the different pressure-gradient integration methods, with more than 80% accuracy in most test cases. The method was applied to an experimental vortex ring flow with planar PIV and a laminar pipe flow with volumetric PTV. The error analysis shows that the obtained pressure uncertainty possessed similar spatial and statistical distributions as the pressure errors. The results also indicate that the performance of the proposed uncertainty estimation method depends on the accuracy of the velocity uncertainty. The proposed uncertainty estimation method exhibits reliability in obtaining the local and instantaneous pressure uncertainty from the PIV/PTV measurements.

A novel Godunov-type scheme for free-surface flows with artificial compressibility

Variable density incompressible flows are governed by parabolic equations. The artificial compressibility method makes these equations hyperbolic-type, which means that they can be solved using techniques developed for compressible flows, such as Godunov-type schemes. While the artificial compressibility method is well-established, its application to variable density flows has been largely neglected in the literature. This paper harnesses recent advances in the wider field by applying a more robust Riemann solver and a more easily parallelisable time discretisation to the variable density equations than previously. We also develop a new method for calculating the pressure gradient as part of the second-order reconstruction step. Based on a rearrangement of the momentum equation and an exploitation of the other gradients and source terms, the new pressure gradient calculation automatically captures the pressure gradient discontinuity at the free surface. Benchmark tests demonstrate the improvements gained by this robust Riemann solver and new pressure gradient calculation.

Void Fraction Measurement Using the Coaxial Line Phase Sensor in the Vertical Gas-Liquid Slug Flow

Void fraction is one of the most important parameters in gas-liquid two-phase flow, which plays a crucial role in the pressure gradient calculation and the flow pattern analysis. In this paper, a new coaxial line phase sensor based on the electromagnetic wave propagation is designed and phase shift principle is proposed for the void fraction measurement, and the function relationship between the void fraction and phase difference is derived. By the theoretical analysis and 56 static calibration experiments, the measurement model is proposed in this paper. Air-water two-phase flow experiments have been conducted in a vertical tube at 48 flow conditions in a stainless-steel tubular test section which has an inside diameter of 50.0mm. The dimensionless quantities related to the void fraction, e.g. dynamic viscosity ratio, gas-liquid density ratio, gas-phase Froud number (Frg) and Lockhart-Martinelli parameter ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {X}}_{{\mathrm {LM}}}$ </tex-math></inline-formula> ), are dimensional analyzed. According to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Pi $ </tex-math></inline-formula> theorem, a new void fraction correlation which could acceptably handle all the available data of different flow conditions (authors’ and literature) is proposed. Laboratory results indicate that the mean absolute error (MAE) of the correlation is 6.46% within an error band of ±10% and 8.03% (183 literature data points) within an error band of ±15%. The void fraction correlation has good prediction accuracy and a certain extrapolation for different flow regimes and fluid characteristic parameters.

Immediate results of surgical treatment of high and intermediate risk pulmonary embolism in elderly and senile patients

The aim of the study: is to analyze the immediate results of surgical treatment of high-and intermediate-risk PE in a group of elderly and senile patients. Material and methods. The study included 43 patients operated on for high-and intermediate-risk pulmonary embolism between 2008 and 2019. In the general group of patients, the number of women prevailed and amounted to 67.4%. The average age was 65.4 ± 4.23 years old. The Miller index in the general group was 29.1 ± 1.42. The Geneva Index was 8.4 ± 1.12. The average pressure in the pulmonary artery at the time of operation was 54 ± 1.4 mm Hg, and the peak pressure was 68 ± 3.43 mm Hg. Results. 5 patients died at the hospital stage. Thus, the hospital survival rate of patients was 88.4%. Among nonlethal complications, cardiovascular and respiratory failure prevailed. According to the statement, the calculated pressure gradient in the pulmonary artery was 29.0 ± 3.1 mm Hg. Conclusion. Surgical treatment is a highly eff ective and reliable method of treatment in the group of older patients.

Evaluation of Mud Weight Using Safe Mud Window Concept Based on Well Log Data: A Case Study of Well OP-002 in the North Sumatra Basin Area, Indonesia

In the drilling operation of well OP-002 which is located in the North Sumatra Basin at a depth interval of 2887 - 3186 m occurred partial loss, and caving at a depth interval of 500 - 1650 m, where the drilling problem is caused by the use of inappropriate mud weight. Safe mud window analysis is carried out by processing well log data to build PPFG (Pore Pressure Fracture Gradient) and 1D Geomechanics model using several calculation methods. Furthermore, the results of the calculation of pore pressure and fracture gradient are validated with well test data from the well OP-002, so the safe mud window can be determined, and can be used as a basis in the analysis of the drilling problems that occur. The optimum mud weight can minimize wellbore instability, with a limit value that must be greater than the collapse pressure, but not exceeding the minimum insitu stress limit. From the results of the mud safe window analysis, it can be concluded that at a depth interval of 500 - 1650 m caving occurs, because the density value used is smaller than the shear failure gradient, and at a depth interval of 1619 - 2829 m, the density value used is greater than Shmin. To overcome this problem, a mud wight with a safe mud window concept is recommended, namely the selection of the optimum mud weight to be used must be greater than the pore pressure and shear failure gradient and does not exceed the minimum horizontal stress and fracture gradient values.

Accuracy and Uncertainty of Gradient Based Leak Localization Procedure for Liquid Transmission Pipelines.

This paper describes issues of leakage localization in liquid transmission pipelines. It focuses on the standard leak localization procedure, which is based on the calculation of pressure gradients using pressure measurements captured along a pipeline. The procedure was verified in terms of an accuracy and uncertainty assessment of the resultant coordinate of a leak spot. An important aim of the verification was to assess the effectiveness of the procedure in the case of localization of low intensity leakages with a level of 0.25–2.00% of the nominal flow rate. An uncertainty assessment was carried out according to the GUM convention. The assessment was based on the metrological characteristics of measuring devices and measurement data obtained from the laboratory model of the pipeline.

Analysis and Calculation of Threshold Pressure Gradient Based on Capillary Bundle

Oilfield water injection is one of the important means to supplement energy to the formation and enhance oil recovery in the process of oilfield development. The level of water injection technology determines the effect of oilfield development and also determines the length of oilfield development life. Research on seepage law of water injection development in low-permeability reservoir is the basis and important technical means of low-permeability reservoir development, and the key point of seepage law is to analyze the starting pressure gradient law. In previous studies, either static test or dynamic experimental value is used, so the error of pseudo starting pressure gradient derived from experimental value is too large, which makes people expand the starting pressure value in low-permeability reservoir in practical engineering application, and the starting pressure gradient obtained from laboratory test cannot be applied in actual reservoir. To accurately calculate the threshold pressure gradient for low-permeability reservoirs, the threshold permeability is proposed through the study of the seepage law and laboratory experiments. It is recognized that the threshold pressure gradient and the threshold permeability had been changing during the seepage. Through steady-state “flow rate-pressure difference” displacement experiment, with natural cores from a low-permeability reservoir, based on a capillary bundle model, the method for calculating the gradient is innovatively proposed. The experimental data show that the whole low-permeability seepage flow is nonlinear, divided into three stages according to the physical stages with obvious changes. Through processing and analyzing of the experimental results, first, it is showed that both threshold pressure gradient and threshold permeability increase with the rise of flow rate and the increasing amplitude is gradually decreasing. Second, the study proposes the permeability is the main controlling reason of the threshold pressure gradient, and the flow velocity is an important reason. Third, we obtain the formulas of the minimum threshold pressure gradient, the threshold pressure gradient, and the corresponding threshold permeability of different cores and the power function relationship between the threshold pressure gradient and the core permeability is obtained. And further, the one-dimensional experimental results are applied to the radial fluid flow, and the recognition that the threshold pressure gradient decreases with increasing distance and the ratio of the threshold pressure to the total displacement pressure difference are obtained. The ratio of starting pressure to total pressure drop is about 0.5, and the higher the permeability is, the lower the ratio is lower under 0.5. These findings significantly help in understanding how to effectively develop low-permeability reservoir by water injection. Through the dynamic macro experiment and microcapillary bundle principle, the experiment can be divided into several sections for analysis, which can be more accurate. The minimum start-up pressure gradient can not only guide the later development of the oilfield, but also enrich the theoretical study of non-Darcy low-velocity seepage. At the same time, the law of flow velocity and start-up pressure gradient indirectly proves the boundary layer theory of the generation mechanism of start-up pressure gradient and supports and guides the effective development of various development methods of low-permeability reservoir.