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Wojnicki, Mirosław, Stanisław Biały, Jerzy Kuśnierczyk, Sławomir Szuflita, and Marcin Warnecki. "Pomiary mikroprzepuszczalności oparte na zjawisku zanikania impulsu ciśnienia (pressure pulse decay)." Nafta-Gaz 74, no. 5 (May 2018): 356–64. http://dx.doi.org/10.18668/ng.2018.05.02.
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Han, Guofeng, Yang Chen, and Xiaoli Liu. "Investigation of Analysis Methods for Pulse Decay Tests Considering Gas Adsorption." Energies 12, no. 13 (July 3, 2019): 2562. http://dx.doi.org/10.3390/en12132562.
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The pulse decay test is the main method employed to determine permeability for tight rocks, and is widely used. The testing gas can be strongly adsorbed on the pore surface of unconventional reservoir cores, such as shale and coal rock. However, gas adsorption has not been well considered in analysis pulse decay tests. In this study, the conventional flow model of adsorbed gas in porous media was modified by considering the volume of the adsorbed phase. Then, pulse decay tests of equilibrium sorption, unsteady state and pseudo-steady-state non-equilibrium sorption models, were analyzed by simulations. For equilibrium sorption, it is found that the Cui-correction method is excessive when the adsorbed phase volume is considered. This method is good at very low pressure, and is worse than the non-correction method at high pressure. When the testing pressure and Langmuir volume are large and the vessel volumes are small, a non-negligible error exists when using the Cui-correction method. If the vessel volumes are very large, gas adsorption can be ignored. For non-equilibrium sorption, the pulse decay characteristics of unsteady state and pseudo-steady-state non-equilibrium sorption models are similar to those of unsteady state and pseudo-steady-state dual-porosity models, respectively. When the upstream and downstream pressures become equal, they continue to decay until all of the pressures reach equilibrium. The Langmuir volume and pressure, the testing pressure and the porosity, affect the pseudo-storativity ratio and the pseudo-interporosity flow coefficient. Their impacts on non-equilibrium sorption models are similar to those of the storativity ratio and the interporosity flow coefficient in dual-porosity models. Like dual-porosity models, the pseudo-pressure derivative can be used to identify equilibrium and non-equilibrium sorption models at the early stage, and also the unsteady state and pseudo-steady-state non-equilibrium sorption models at the late stage. To identify models using the pseudo-pressure derivative at the early stage, the suitable vessel volumes should be chosen according to the core adsorption property, porosity and the testing pressure. Finally, experimental data are analyzed using the method proposed in this study, and the results are sufficient.
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Zhao, Yu, Chaolin Wang, Yongfa Zhang, and Qiang Liu. "A Method of Differentiating the Early-Time and Late-Time Behavior in Pressure-Pulse Decay Permeametry." Geofluids 2019 (April 9, 2019): 1–9. http://dx.doi.org/10.1155/2019/1309042.
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The pressure-pulse decay is a preferred technique for determining permeability of unconventional gas reservoir rocks. The pressure-pulse decay often shows quite different characteristics during the early time and the later time. Most approaches for estimating the permeability proposed in the literature are required to use the later-time pressure-pulse decay measurements. However, the later-time data are often selected subjectively, lacking a universal criterion. In this paper, a method of differentiating the early-time and late-time behavior for pressure-pulse decay test is proposed. The analytical results show that the critical time (dimensionless time) of early-/late-time decay characteristics mainly depends on the volume ratios, and it increases first and then decreases with the volume ratios. The critical time for cases with same chamber sizes is much less than that for cases with unequal chamber sizes. Applicability of the proposed methods is examined using a numerical simulator, TOUGH+REALGASBRINE. The numerical results show that the pressure gradient along the sample varies nonlinearly at the early time and becomes a constant at the late time. Then, the proposed method is applied to real data for permeability estimation. It is found that the early-time behavior is negligible as the volume ratio takes on small values. As the volume ratios increase, the deviation becomes significant and considerable permeability errors will be produced if these early-time data are used.
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Han, Guofeng, Xiaoli Liu, and Jin Huang. "Theoretical Comparison of Test Performance of Different Pulse Decay Methods for Unconventional Cores." Energies 13, no. 17 (September 2, 2020): 4557. http://dx.doi.org/10.3390/en13174557.
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Various pulse decay methods are proposed to test tight cores. These methods can be divided into three types. This study compares the performance of these methods to test the permeability of unconventional cores in terms of homogeneous cores, dual-medium cores, and gas adsorption, including the pressure equilibrium time, possible errors caused by conventional analysis methods, and reflections on the characteristics of dual-media. Studies shows that the two test methods with an antisymmetric relationship in the boundary conditions have basically identical test performance. When testing homogeneous cores, regardless of whether the gas is adsorptive or not, the pressure equilibrium time of the first type of method is approximately half of that of the second type of method. The dual-medium parameters seriously affect the pressure equilibrium time of different methods, which may cause the difference of order of magnitude. For homogeneous cores, the permeability errors of the first and second types of methods caused by porosity errors are similar and larger than that of the third type of method. For dual media, the fracture permeability obtained by the third type of method using the conventional analysis method may differ from the actual value by tens of times. No method can significantly eliminate the sorption effect. When the core is a dual-medium, only the pressure curves of the upstream positive-pulse method, downstream negative-pulse method and one-chamber method can reflect the characteristics of dual media. The pressure derivative of the one-chamber method cannot reflect the characteristics of dual media at the early time. The pressure derivative of the second type and the upstream positive-pulse downstream negative-pulse method can reflect the complete characteristics of dual media, but their pressure derivative of the constant-slope segment is small, and the interporosity flow parameter may not be identified.
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Shen, Shaicheng, Xiaochun Li, Zhiming Fang, and Nao Shen. "Effect of Gas Adsorption on the Application of the Pulse-Decay Technique." Geofluids 2020 (October 2, 2020): 1–11. http://dx.doi.org/10.1155/2020/8872888.
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The permeability of coal is an indispensable parameter for predicting the coalbed methane (CBM) and enhanced CBM (ECBM) production. Considering the low permeability characteristics of coal, the permeability is usually measured by the transient technique in the laboratory. Normally, it is assumed that the calculated permeability will not greatly vary if the pulse pressure applied in the experiment is small (less than 10% of pore pressure) and previous studies have not focused on the effect of the pulse pressure on the measurement permeability. However, for sorptive rock, such as coals and shales, the sorption effect may cause different measurement results under different pulse pressures. In this study, both nonadsorbing gas (helium) and adsorbing gas (carbon dioxide) were used to investigate the adsorption effect on the gas permeability of coal measurement with the pulse-decay technique. A series of experiments under different pore pressures and pulse pressures was performed, and the carbon dioxide permeability was calculated by both Cui et al.’s and Jones’ methods. The results show that the carbon dioxide permeability calculated by Jones’ method was underestimated because the adsorption effect was not considered. In addition, by comparing the helium and carbon dioxide permeabilities under different pulse pressures, we found that the carbon dioxide permeability of coal was more sensitive to the pulse pressure due to the adsorption effect. Thus, to obtain the accurate permeability of coal, the effect of adsorption should be considered when measuring the permeability of adsorptive media with adsorbing gas by the transient technique, and more effort is required to eliminate the effect of the pulse pressure on the measured permeability.
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Yang, Zehao, Qian Sang, Mingzhe Dong, Shaojie Zhang, Yajun Li, and Houjian Gong. "A modified pressure-pulse decay method for determining permeabilities of tight reservoir cores." Journal of Natural Gas Science and Engineering 27 (November 2015): 236–46. http://dx.doi.org/10.1016/j.jngse.2015.08.058.
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Stergiopulos, N., P. Segers, and N. Westerhof. "Use of pulse pressure method for estimating total arterial compliance in vivo." American Journal of Physiology-Heart and Circulatory Physiology 276, no. 2 (February 1, 1999): H424—H428. http://dx.doi.org/10.1152/ajpheart.1999.276.2.h424.
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We determined total arterial compliance from pressure and flow in the ascending aorta of seven anesthetized dogs using the pulse pressure method (PPM) and the decay time method (DTM). Compliance was determined under control and during occlusion of the aorta at four different locations (iliac, renal, diaphragm, and proximal descending thoracic aorta). Compliance of PPM gave consistently lower values (0.893 ± 0.015) compared with the compliance of DTM (means ± SE; r = 0.989). The lower compliance estimates by the PPM can be attributed to the difference in mean pressures at which compliance is determined (mean pressure, 81.0 ± 3.6 mmHg; mean diastolic pressure, over which the DTM applies, 67.0 ± 3.6 mmHg). Total arterial compliance under control conditions was 0.169 ± 0.007 ml/mmHg. Compliance of the proximal aorta, obtained during occlusion of the proximal descending aorta, was 0.100 ± 0.007 ml/mmHg. Mean aortic pressure was 80.4 ± 3.6 mmHg during control and 102 ± 7.7 mmHg during proximal descending aortic occlusion. From these results and assuming that upper limbs and the head contribute as little as the lower limbs, we conclude that 60% of total arterial compliance resides in the proximal aorta. When we take into account the inverse relationship between pressure and compliance, the contribution of the proximal aorta to the total arterial compliance is even more significant.
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Vanden Eynden, Frédéric, Thierry Bové, Marie-Luce Chirade, Guido Van Nooten, and Patrick Segers. "Measuring pulmonary arterial compliance: mission impossible? Insights from a novel in vivo continuous-flow based experimental model." Pulmonary Circulation 8, no. 2 (April 2018): 204589401877688. http://dx.doi.org/10.1177/2045894018776882.
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Arterial compliance (C) is related to the elasticity, size, and geometrical distribution of arteries. Compliance is a determinant of the load that impedes ventricular ejection. Measuring compliance is difficult, particularly in the pulmonary circulation in which resistive and compliant vessels overlap. Comparing different methods for quantification of compliance to a method that involves a continuous flow might help to identify the optimal method. Pulmonary arterial compliance was computed in six pigs based on the stroke volume to pulse pressure ratio, diastolic decay exponential fitting, area method, and the pulse pressure method (PPM). Compliance measurements were compared to those obtained under continuous flow conditions through a right ventricular bypass (Heartware Inc., Miami Lakes, FL, USA). Compliance was computed for various flows using diastolic decay exponential fitting after an abrupt interruption of the pump. Under the continuous flow conditions, resistance (R) was a decreasing function of the flow, and the fitting to P = e-t/RC yielded a pulmonary time constant (RC) of 2.06 s ( ± 0.48). Compliance was an increasing function of flow. Steady flow inter-method comparisons of compliance under pulsatile flow conditions showed large discrepancies and values (7.23 ± 4.47 mL/mmHg) which were lower than those obtained under continuous flow conditions (10.19 ± 1 0.31 mL/mmHg). Best agreement with steady flow measurements is obtained with the diastolic decay method. Resistance and compliance are both flow-dependent and are inversely related in the pulmonary circulation. The dynamic nature of the pulsatile flow may induce a non-uniformly distributed compliance, with an influence on the methods of measurement.
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Yang, Zehao, Mingzhe Dong, Shaojie Zhang, Houjian Gong, Yajun Li, and Feifei Long. "A method for determining transverse permeability of tight reservoir cores by radial pressure pulse decay measurement." Journal of Geophysical Research: Solid Earth 121, no. 10 (October 2016): 7054–70. http://dx.doi.org/10.1002/2016jb013173.
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Srikrishnan, S., P. K. Dash, and V. Jayakumar. "Evaluation of critical blockage ratio and pulse length in a pulse detonation engine using CFD and MATLAB." MATEC Web of Conferences 172 (2018): 02006. http://dx.doi.org/10.1051/matecconf/201817202006.
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A Pulse Detonation Engine (PDE) is a new invented propulsion device that takes advantage of the pressure rise inherent to the efficient burning of fuel-air mixtures via detonations. Detonation initiation is a critical process that occurs in the cycle of a PDE. A practical method of detonation initiation is Deflagration-to-Detonation Transition (DDT), which describes the acceleration of a subsonic deflagration created using low initiation energies to a supersonic detonation. The DDT process is not well understood due to a wide range of time and length scales involving complex chemistry, turbulence and unsteady pressure waves. This paper discuss about the effects of blocking ratio in the augmentation of detonation pressure and velocity inside a cylindrical tube of diameter 0.0254m and a length of 1 m. The blockages are rectangular in shape placed at 2/3rd distances of the length of the tube and the heights of the blockages are varied in terms of the diameter of the tube as 1/4th, 1/3rd, ½, 2/3rd and 3/4th the diameter of the tube. The setup is then analyzed in MATLAB using the physics of Friedlander’s equation, which formulate the decay time duration of pressure across the tube length, with and without the blockage. Further, a 2D CFD analysis through ANSYS Workbench is conducted which gave the effective blocking ratio in a rectangular type of blockage placed at the 2/3rd position of the length of the tube and the results are compared. For variable pressures ranging from 1 MPa to 100 MPa input, the effective pulse length is around 0.25 seconds after which the decay of pressure and temperature attain the critical limit. Also it is found that the maximum feasible velocity occurs for an inlet pressure of 10 MPa and 2/3rd height of the blockage where the corresponding outlet velocity is 4692m/s and outlet total pressure being 10.542 MPa.
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Vennin, Samuel, Alexia Mayer, Ye Li, Henry Fok, Brian Clapp, Jordi Alastruey, and Phil Chowienczyk. "Noninvasive calculation of the aortic blood pressure waveform from the flow velocity waveform: a proof of concept." American Journal of Physiology-Heart and Circulatory Physiology 309, no. 5 (September 2015): H969—H976. http://dx.doi.org/10.1152/ajpheart.00152.2015.
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Estimation of aortic and left ventricular (LV) pressure usually requires measurements that are difficult to acquire during the imaging required to obtain concurrent LV dimensions essential for determination of LV mechanical properties. We describe a novel method for deriving aortic pressure from the aortic flow velocity. The target pressure waveform is divided into an early systolic upstroke, determined by the water hammer equation, and a diastolic decay equal to that in the peripheral arterial tree, interposed by a late systolic portion described by a second-order polynomial constrained by conditions of continuity and conservation of mean arterial pressure. Pulse wave velocity (PWV, which can be obtained through imaging), mean arterial pressure, diastolic pressure, and diastolic decay are required inputs for the algorithm. The algorithm was tested using 1) pressure data derived theoretically from prespecified flow waveforms and properties of the arterial tree using a single-tube 1-D model of the arterial tree, and 2) experimental data acquired from a pressure/Doppler flow velocity transducer placed in the ascending aorta in 18 patients (mean ± SD: age 63 ± 11 yr, aortic BP 136 ± 23/73 ± 13 mmHg) at the time of cardiac catheterization. For experimental data, PWV was calculated from measured pressures/flows, and mean and diastolic pressures and diastolic decay were taken from measured pressure (i.e., were assumed to be known). Pressure reconstructed from measured flow agreed well with theoretical pressure: mean ± SD root mean square (RMS) error 0.7 ± 0.1 mmHg. Similarly, for experimental data, pressure reconstructed from measured flow agreed well with measured pressure (mean RMS error 2.4 ± 1.0 mmHg). First systolic shoulder and systolic peak pressures were also accurately rendered (mean ± SD difference 1.4 ± 2.0 mmHg for peak systolic pressure). This is the first noninvasive derivation of aortic pressure based on fluid dynamics (flow and wave speed) in the aorta itself.
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Walder, J., and A. Nur. "Permeability measurement by the pulse-decay method: Effects of poroelastic phenomena and non-linear pore pressure diffusion." International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 23, no. 3 (June 1986): 225–32. http://dx.doi.org/10.1016/0148-9062(86)90968-x.
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Janiga, Damian, Robert Czarnota, Edyta Kuk, Jerzy Stopa, and Paweł Wojnarowski. "Measurement of Oil-CO2 diffusion coefficient using pulse-echo method for pressure-volume decay approach under reservoir conditions." Journal of Petroleum Science and Engineering 185 (February 2020): 106636. http://dx.doi.org/10.1016/j.petrol.2019.106636.
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Feng, Ruimin, Satya Harpalani, and Jun Liu. "Optimized pressure pulse-decay method for laboratory estimation of gas permeability of sorptive reservoirs: Part 2 - Experimental study." Fuel 191 (March 2017): 565–73. http://dx.doi.org/10.1016/j.fuel.2016.11.077.
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Darabi, Hamed, A. Ettehad, F. Javadpour, and K. Sepehrnoori. "Gas flow in ultra-tight shale strata." Journal of Fluid Mechanics 710 (September 27, 2012): 641–58. http://dx.doi.org/10.1017/jfm.2012.424.
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AbstractWe study the gas flow processes in ultra-tight porous media in which the matrix pore network is composed of nanometre- to micrometre-size pores. We formulate a pressure-dependent permeability function, referred to as the apparent permeability function (APF), assuming that Knudsen diffusion and slip flow (the Klinkenberg effect) are the main contributors to the overall flow in porous media. The APF predicts that in nanometre-size pores, gas permeability values are as much as 10 times greater than results obtained by continuum hydrodynamics predictions, and with increasing pore size (i.e. of the order of the micrometre), gas permeability converges to continuum hydrodynamics values. In addition, the APF predicts that an increase in the fractal dimension of the pore surface leads to a decrease in Knudsen diffusion. Using the homogenization method, a rigorous analysis is performed to examine whether the APF is preserved throughout the process of upscaling from local scale to large scale. We use the well-known pulse-decay experiment to estimate the main parameter of the APF, which is Darcy permeability. Our newly derived late-transient analytical solution and the late-transient numerical solution consistently match the pressure decay data and yield approximately the same estimated value for Darcy permeability at the typical core-sample initial pressure range and pressure difference. Other parameters of the APF may be determined from independent laboratory experiments; however, a pulse-decay experiment can be used to estimate the unknown parameters of the APF if multiple tests are performed and/or the parameters are strictly constrained by upper and lower bounds.
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Filogonio, Renato, Karina F. Orsolini, Gustavo M. Oda, Hans Malte, and Cléo A. C. Leite. "Baroreflex gain and time of pressure decay at different body temperatures in the tegu lizard, Salvator merianae." PLOS ONE 15, no. 11 (November 23, 2020): e0242346. http://dx.doi.org/10.1371/journal.pone.0242346.
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Ectotherms may experience large body temperature (Tb) variations. Higher Tb have been reported to increase baroreflex sensitivity in ectotherm tetrapods. At lower Tb, pulse interval (PI) increases and diastolic pressure decays for longer, possibly resulting in lower end-diastolic pressures and mean arterial pressures (Pm). Additionally, compensatory baroreflex-related heart rate modulation (i.e. the cardiac branch of the baroreflex response) is delayed due to increased PI. Thus, low Tb is potentially detrimental, leading to cardiovascular malfunctioning. This raises the question on how Pm is regulated in such an adverse condition. We investigated the baroreflex compensations that enables tegu lizards, Salvator merianae, to maintain blood pressure homeostasis in a wide Tb range. Lizards had their femoral artery cannulated and pressure signals recorded at 15°C, 25°C and 35°C. We used the sequence method to analyse the heart rate baroreflex-related corrections to spontaneous pressure fluctuations at each temperature. Vascular adjustments (i.e. the peripheral branch) were assessed by calculating the time constant for arterial pressure decay (τ)—resultant from the action of both vascular resistance and compliance—by fitting the diastolic pressure descent to the two-element Windkessel equation. We observed that at lower Tb, lizards increased baroreflex gain at the operating point (Gop) and τ, indicating that the diastolic pressure decays at a slower rate. Gop normalized to Pm and PI, as well as the ratio τ/PI, did not change, indicating that both baroreflex gain and rate of pressure decay are adjusted according to PI lengthening. Consequently, pressure parameters and the oscillatory power fraction (an index of wasted cardiac energy) were unaltered by Tb, indicating that both Gop and τ modulation are crucial for cardiovascular homeostasis.
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Liang, Yan, Jonathan D. Price, David A. Wark, and E. Bruce Watson. "Nonlinear pressure diffusion in a porous medium: Approximate solutions with applications to permeability measurements using transient pulse decay method." Journal of Geophysical Research: Solid Earth 106, B1 (January 10, 2001): 529–35. http://dx.doi.org/10.1029/2000jb900344.
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Chemla, Denis, Jean-Louis Hébert, Catherine Coirault, Karen Zamani, Isabelle Suard, Patrice Colin, and Yves Lecarpentier. "Total arterial compliance estimated by stroke volume-to-aortic pulse pressure ratio in humans." American Journal of Physiology-Heart and Circulatory Physiology 274, no. 2 (February 1, 1998): H500—H505. http://dx.doi.org/10.1152/ajpheart.1998.274.2.h500.
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On the basis of the windkessel model, the stroke volume-to-aortic pulse pressure ratio (SV/PP) has been proposed as an estimate of total arterial compliance, but recent studies have questioned this approximation. Aortic pressure was obtained at rest in 31 adults undergoing cardiac catheterization (47 ± 14 yr): controls ( n = 7), patients with dilated cardiomyopathy ( n = 10), and patients with other cardiac diseases ( n = 14). We calculated PP, mean aortic pressure (MAoP), heart period ( T), SV (thermodilution cardiac output/heart rate), total peripheral resistance ( R), total arterial compliance estimated by area method ( Carea), and the time constant of aortic pressure decay in diastole ( RCarea). In the overall population ( n = 31), there was no significant difference between SV/PP and Carea. SV/PP was linearly related to Carea(SV/PP = 0.99 Carea+ 0.05; r = 0.98; P < 0.001); the slope and intercept did not differ from unity and zero, respectively. Similar results were obtained in the three subgroups. These results implied that PP/MAoP and T/ RCareawere proportionally related ( T/ RCarea= 1.18PP/MAoP − 0.07; r = 0.96; P < 0.001). We conclude that for humans at rest 1) SV/PP gave a reliable estimate of Carea, and 2) T normalized by the time constant of aortic pressure decay in diastole was proportionally related to PP/MAoP. This last relationship could be considered an aspect of the coupling between the left ventricle and its load.
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Stergiopulos, N., J. J. Meister, and N. Westerhof. "Evaluation of methods for estimation of total arterial compliance." American Journal of Physiology-Heart and Circulatory Physiology 268, no. 4 (April 1, 1995): H1540—H1548. http://dx.doi.org/10.1152/ajpheart.1995.268.4.h1540.
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Seven classic and recently proposed methods used for the estimation of total arterial compliance have been evaluated for their accuracy and applicability in different physiological conditions. The pressure and flow data are taken from a computer model that provides realistic simulations of the nonlinear-distributed systemic arterial tree. Besides the great flexibility in simulating different physiological or pathological cases, the major advantage of the computer model is that it allows precise knowledge of the pressure-dependent total arterial compliance, which is the variable of interest. The results show that the methods based on the two-element windkessel (WK) model are more accurate than those based on the three-element WK model. The classic exponential decay and the diastolic area method yield essentially similar results, and their compliance estimates are accurate within 10% except at high heart rates. The later part of diastole, i.e., from the time that the systolic pressure wave has reached all peripheral beds, gives the best results. The newly proposed two-area and pulse pressure methods, both based on the two-element WK model, are accurate (errors in general < 10%) and can be applied to other locations in the arterial tree where the decay time and area method cannot. Methods based on the three-element WK model consistently overestimate total arterial compliance (> or = 25%). The errors in the methods based on the three-element WK model arise from the fact that the input impedance in that model deviates significantly from the true input impedance at low frequencies. The strong dependence of compliance on pressure (elastic nonlinearity) does not invalidate the compliance estimates.(ABSTRACT TRUNCATED AT 250 WORDS)
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Feng, Ruimin, Jun Liu, and Satya Harpalani. "Optimized pressure pulse-decay method for laboratory estimation of gas permeability of sorptive reservoirs: Part 1 – Background and numerical analysis." Fuel 191 (March 2017): 555–64. http://dx.doi.org/10.1016/j.fuel.2016.11.079.
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Wang, H., G. H. Priestman, S. B. M. Beck, and R. F. Boucher. "Pressure wave attenuation in an air pipe flow." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, no. 4 (April 1, 2000): 619–32. http://dx.doi.org/10.1243/0954406001523957.
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Pressure wave transmission attenuation in an air pipe flow is investigated both theoretically and experimentally. This investigation is to ensure the viability of remote flow measurement in an air pipe flow using a new fluidic pressure-pulse-transmitting flowmeter. The novel flowmeter produces self-induced oscillations, whose frequency is proportional to the flowrate. These pressure waves are transmitted via the flowing fluid and can be detected far downstream of the device. Experimental work has been conducted to ascertain how much the pressure waves are attenuated in air flow in a pipeline. This was done by using pipes of 0.05m diameter and both 4.7 and 28.5m long installed downstream of the flowmeter. A method of network simulation known as transmission line modelling (TLM), which has been programmed as the Sheffield University Network Analysis Software (SUNAS) code, is described and utilized to predict the wave decay through the air pipe flow. The theoretical and experimental results were found to give good agreement, demonstrating both the value of the modelling software and the viability of the remote flow measurement concept.
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Schilden, Thomas, and Wolfgang Schröder. "Inclined slow acoustic waves incident to stagnation point probes in supersonic flow." Journal of Fluid Mechanics 866 (March 13, 2019): 567–97. http://dx.doi.org/10.1017/jfm.2019.121.
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Tunnel noise in supersonic testing facilities is known to be a decisive factor in boundary layer transition experiments. It defines initial conditions for the growth of modal instabilities by the receptivity mechanism. That is, to interpret experimental results, the determination of tunnel noise is of crucial importance. It is common to use stagnation point probes equipped with pressure transducers in supersonic flows, but since tunnel noise undergoes modulation during the measurement, the probes must be calibrated. The predominant component of tunnel noise is caused by the nozzle boundary layer which radiates highly inclined slow acoustic waves. Therefore, the calibration of stagnation point probes for these disturbances is essential. For quasi-steady deviations from the free stream, an analytic reduced-order method holds. A corresponding conflicting model derived by Stainback & Wagner (1972, AIAA Paper 72-1003) is revised and corrected. Inclined slow acoustic waves generate higher pressure perturbations at the probe than non-inclined waves. In general, costly three-dimensional direct numerical simulations can be used for calibration. In this study, however, new axisymmetric boundary conditions are proposed to reduce the problem to two dimensions to efficiently investigate the detection of incident inclined slow acoustic waves by stagnation point probes. A cylindrical probe with a rounded edge is investigated in supersonic flow at a Mach number $Ma=5.9$. For the inclination angle of radiated slow acoustic waves, stagnation point pressure fluctuations abruptly decay with increasing Strouhal number and a similar behaviour can be seen at constant Strouhal number with increasing inclination angle. Two simple criteria for the onset of decay based on the radial wavenumber are deduced. Furthermore, stagnation point pressure fluctuations were decomposed into an initial pulse impact and resonant amplification to separately investigate the effects. The initial pulse determines the overall pressure signal. At high inclination angles, a new mechanism for resonance caused by a surface pressure wave travelling at the phase speed of the incident wave was found to supersede resonance caused by oscillating acoustic waves prevailing at low inclination angles.
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Volkov, Vladimir Ya, Boris V. Sakharov, Nailia M. Khasanova, and Danis K. Nurgaliev. "Analysis of the composition and properties of heavy oils in situ by Low Field NMR relaxation method." Georesursy 20, no. 4 (November 30, 2018): 308–23. http://dx.doi.org/10.18599/grs.2018.4.308-323.
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For the analysis of heavy oils, the method of simultaneous measurement of the free induction decay (FID) together with the decay of the echo signal in the Carr-Purcell-Meiboom-Gill (CPMG) pulse program was used. The measurements were carried out on a «Chromatek-Proton 20M» NMR analyzer operating at a frequency of 20 MHz. A special control program was created on the NMR analyzer that automatically tunes and measures the full FID curve, then switches to measuring the decay of the echo amplitude by the CPMG pulse sequence, and then the investigation ends with a joint processing of all the experimental data. This method makes it possible to measure the amplitudes of NMR signals and the relaxation times T2 of protons of heavy oil components in situ, including asphaltenes, without any perturbations in the analyzed system. Under the influence of paramagnetic centers located in asphaltenes, the amplitude-relaxation characteristics of oil protons are divided into 7 groups associated with solid asphaltenes in crystalline and amorphous states, resins with high and low density, aromatic and saturated compounds. The NMR amplitudes of these fractions correlate well with the group composition of heavy oils as determined by gravitational-chromatographic SARA method. The combined FID + CPMG method can be recommended for determining the SARA composition and other properties of oil in situ. The behavior of fractions of heavy oil in the temperature range (-15оС ÷ +60оС) was investigated by SARA-NMR method. For the first time in situ, it has been shown that resins participate in the formation of asphaltenes in a closed volume when the oil is cooled from a stable state at room temperature, and vice versa, asphaltenes are disaggregated by heating with the release of resins. The SARA-NMR method is promising for the on-line monitoring of the production, transportation and processing of heavy oil in real conditions of temperature, pressure and dissolved gases. However, the design of the NMR sensor must be adapted to industrial applications. The possibilities of designing NMR probes on process pipelines of larger diameter than in laboratory instruments can be extended taking into account the procedure proposed for correcting the inhomogeneity of the magnetic field in the probed volume based on the FID signal of the liquid oil fraction.
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Wang, Chunguang, Yuxiao Zang, Linsen Wang, Zhongwei Chen, Guanglei Cui, Kunkun Fan, and Weitao Liu. "Interaction of Cleat-Matrix on Coal Permeability from Experimental Observations and Numerical Analysis." Geofluids 2019 (November 18, 2019): 1–15. http://dx.doi.org/10.1155/2019/7474587.
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Gas transport through porous coal contains gas laminar flow in the cleat network and gas adsorption/diffusion in the matrix block. Since permeable capacity of the cleat is greater than that of the matrix, change of the matrix pressure readily lags behind change in the cleat pressure. Such unsynchronized pressure changes can result in a complex compatible deformation of a cleat-matrix system, significantly affecting the coal permeability. In this paper, we investigated the cleat-matrix interaction on coal permeability by using a modified pressure pulse decay method integrated with numerical analysis. The experimental results indicate that the bulk volume of the coal sample rapidly expanded at the beginning of gas injection, and then the volume expansion rate of the coal sample slowed down as the downstream pressure of the coal sample gradually equilibrated with the upstream pressure. During this process, the coal permeability was observed to gradually decrease with time. Numerical analysis results indicate that gas transport from the cleat to the matrix can attenuate the differential pressure between the cleat and the matrix. A smaller ratio of initial matrix permeability to initial cleat permeability can prolong decay duration of the differential pressure inside the cleat-matrix system. Although the coal sample is subjected to a stress-controlled condition, the coal permeability response to gas diffusion is closer to the case using a constant volume boundary. The dynamic change of coal permeability is significantly affected by the cleat-matrix interaction, in cases where the short-term change is mainly attributable to the cleat network and the long-term change is controlled by matrix swelling/shrinkage.
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Dzuba, Jaroslav, Milan Držík, Gabriel Vanko, Ivan Rýger, Martin Vallo, Vladimír Kutiš, and Tibor Lalinský. "Modal Analysis of Gallium Nitride Membrane for Pressure Sensing Device." Key Engineering Materials 605 (April 2014): 404–7. http://dx.doi.org/10.4028/www.scientific.net/kem.605.404.
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A circular high electron mobility transistor (C-HEMT) prepared on the AlGaN/GaN membrane surface has been investigated and its potential for pressure sensing has been already demonstrated. The key issue in the design process of such heterostructure based MEMS sensors is the stress engineering. This way we can scale the sensor performance, measured pressure range and sensitivity. Especially, the knowledge of the exact value of the residual stress in membranes (caused by deposition process) helps us to optimize the sensing devices. In this work, the residual stress determination method in gallium nitride circular shaped membrane is reported. It is shown that resonant frequency method using Laser Doppler Vibrometry (LDV) for membrane vibration measurement seems to be an appropriate technique to determine the residual stress in micro-scale membranes. Circularly shaped AlGaN/GaN micro-membranes are excited by acoustic short time pulse. The decay oscillating motion of the membrane is recorded by oscilloscope. By FFT spectral analysis of the signals the resonance frequencies are obtained. For the sample studied, the natural frequency mode resonance peak is used to define the residual stress level. To verify the observed stress in investigated membranes, prestressed modal analysis in finite element method (FEM) code ANSYS is performed. The stress extracted from the measured frequency is taken as an initial stress state of the modelled membrane. Experimentally obtained shock spectra are compared with that computed by FEM simulation.
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Sarkar, Arnab, Raju V. Shah, D. Alamelu, and Suresh K. Aggarwal. "Studies on the ns-IR-Laser-Induced Plasma Parameters in the Vanadium Oxide." Journal of Atomic, Molecular, and Optical Physics 2011 (October 16, 2011): 1–7. http://dx.doi.org/10.1155/2011/504764.
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We report spectroscopic studies of laser-induced plasma (LIP) produced by ns-IR-Nd:YAG laser light pulses of different energies onto four different oxides of vanadium (VO, V2O3, VO2, and V2O5) in air under atmospheric pressure. For each oxide with a different oxidation state of vanadium, both electron density and plasma temperature were calculated for different time delays and laser pulse energies. The plasma temperature was determined from Boltzmann plot method, whereas the electron number density was estimated from the Saha equation. The decay rates for plasma temperature as well as electron density were observed to follow power law and were independent of the nature of vanadium oxide. These investigations provide an insight to optimize various parameters during LIBS analysis of vanadium-based matrices.
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Chen, Zeliang, Xinglin Wang, Guoqing Jian, Leilei Zhang, Pengfei Dong, Philip M. Singer, and George J. Hirasaki. "Fast Permeability Estimation of an Unconventional Formation Core by Transient-Pressure History Matching." SPE Journal 25, no. 06 (April 27, 2020): 2881–97. http://dx.doi.org/10.2118/201107-pa.
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Summary Unconventional resources are of great importance in the global energy supply. However, the ultralow permeability, which is an indicator of the producibility, makes the unconventional production challenging. Therefore, the permeability is one of the critical petrophysical properties for formation evaluation. There are many existing approaches to determine permeability in the laboratory using core analysis. The methods can be divided into two categories: steady-state and unsteady-state approaches. The steady-state approach is a direct measurement using Darcy's law. This approach has disadvantages because of the accuracy in the measurement of low flow rate and the long run time. The unsteady-state approach includes pulse decay, oscillating pressure, and Gas Research Institute methods. These approaches are complicated in terms of setups and interpretations. Both steady-state and unsteady-state approaches typically have a constraint on the maximum differential pressure. We propose a novel unsteady-state method to determine the permeability by transient-pressure history matching. This approach involves simulation and experiments. On the experiment side, the ultralow-permeability core undergoes 1D CO2-flooding experiments, during which the transient pressure is monitored for history matching. On the simulation side, the transient-pressure history is simulated using the finite-volume method incorporating real-gas pseudopressure and table lookup to deal with the nonlinearity in fluid properties and singularity during phase transition. The free parameter permeability in the simulation is adjusted for history matching to determine the rock permeability. Our new unsteady-state approach is developed for fast and convenient permeability estimation for unconventional formation cores. This approach is a valuable addition to existing permeability measurement methods.
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Ratnakar, Ram R., and Birol Dindoruk. "A New Technique for Simultaneous Measurement of Nanodarcy-Range Permeability and Adsorption Isotherms of Tight Rocks Using Magnetic Suspension Balance." SPE Journal 24, no. 06 (September 6, 2019): 2482–503. http://dx.doi.org/10.2118/191504-pa.
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Summary Flow and adsorptive characteristics of methane and other natural gases onto tight rock formations are of economic interest for proper engineering evaluation and reservoir performance management. This work presents a novel technique to enable the simultaneous determination of nanodarcy permeability and adsorption isotherms of gas in such formations through the transient analysis of experimental data from magnetic suspension balance (MSB). MSB has primarily been shown to be an effective tool for evaluating the amount of gases adsorbed onto tight shales/coals, especially when the adsorbed amount is small. In addition to the classical usage of the measured data using MSB, a new mathematical model based on volume averaging has been developed to describe the transient behavior of the adsorption phenomenon and to obtain the nominal or apparent permeability of shale samples from experimental data. Historically, the permeability of nanoporous materials is measured using two leading methods: the Gas Research Institute method and the pressure–pulse–decay method; however, neither of these methods yields information about the adsorptive behavior of the porous medium or considers such phenomena. In this study, we developed a simple theoretical framework to obtain the isotherm of gas adsorption onto a tight shale (or other tight materials such as coal) sample and the permeability of the sample, simultaneously. The results show that the permeability vs. pressure plot follows the Klinkenberg effect at lower pressures, as expected. The overall methodology developed here can be applied to any type of adsorbing gases and shale/coal samples. The utility and validity of the methodology are demonstrated by applying the developed methodology in experiments performed on three tight shale samples (unconventionals) using two different gases: methane and CO2.
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Krakowska-Madejska, Paulina, Edyta Puskarczyk, Magdalena Habrat, Paweł Madejski, Marek Dohnalik, and Mariusz Jędrychowski. "Development of a Permeability Formula for Tight and Shale Gas Reservoirs Based on Advanced High-Precision Lab Measurement Techniques." Energies 14, no. 9 (May 4, 2021): 2628. http://dx.doi.org/10.3390/en14092628.
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Computed X-ray tomography (CT), together with pulse and pressure decay permeability methods were used to evaluate a formula for absolute reservoir permeability. For this reason, 62 core samples representing geological material of tight, gas-bearing sandstones, mudstones, limestones, and dolostones were studied. Samples were divided into two groups with lower and higher permeability values. Images of the pore space were processed and interpreted to obtain geometrical parameters of the objects (pores, microfractures) with 0.5 × 0.5 × 0.5 µm3 voxel size. Statistical methods, which included basic statistical analysis, linear regression, and multiple linear regression analysis, were combined to evaluate the formula for absolute permeability. It appeared that the following parameters: Feret Breadth/Volume, Flatness/Anisotropy, Feret Max/Flatness, moments of inertia around middle principal axis I2/around longest principal axis I3, Anisotropy/Flatness, Flatness/Anisotropy provided the best results. The presented formula was obtained for a large set of data and is based only on the geometric parameters of the pore space. The novelty of the work is connected with the estimation of absolute permeability using only data from the CT method for tight rocks.
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Guerci, Philippe, Yasin Ince, Paul Heeman, Dirk Faber, Bulent Ergin, and Can Ince. "A LED-based phosphorimeter for measurement of microcirculatory oxygen pressure." Journal of Applied Physiology 122, no. 2 (February 1, 2017): 307–16. http://dx.doi.org/10.1152/japplphysiol.00316.2016.
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Quantitative measurements of microcirculatory and tissue oxygenation are of prime importance in experimental research. The noninvasive phosphorescence quenching method has given further insight into the fundamental mechanisms of oxygen transport to healthy tissues and in models of disease. Phosphorimeters are devices dedicated to the study of phosphorescence quenching. The experimental applications of phosphorimeters range from measuring a specific oxygen partial pressure (Po2) in cellular organelles such as mitochondria, finding values of Po2 distributed over an organ or capillaries, to measuring microcirculatory Po2 changes simultaneously in several organ systems. Most of the current phosphorimeters use flash lamps as a light excitation source. However, a major drawback of flash lamps is their inherent plasma glow that persists for tens of microseconds after the primary discharge. This complex distributed excitation pattern generated by the flash lamp can lead to inaccurate Po2 readings unless a deconvolution analysis is performed. Using light-emitting diode (LED), a rectangular shaped light pulse can be generated that provides a more uniformly distributed excitation signal. This study presents the design and calibration process of an LED-based phosphorimeter (LED-P). The in vitro calibration of the LED-P using palladium(II)-meso-tetra(4-carboxyphenyl)-porphyrin (Pd-TCCP) as a phosphorescent dye is presented. The pH and temperature were altered to assess whether the decay times of the Pd-TCCP measured by the LED-P were significantly influenced. An in vivo validation experiment was undertaken to measure renal cortical Po2 in a rat subjected to hypoxic ventilation conditions and ischemia/reperfusion. The benefits of using LEDs as a light excitation source are presented.
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Matsukawa, S., and T. Wada. "Vector autoregressive modeling for analyzing feedback regulation between heart rate and blood pressure." American Journal of Physiology-Heart and Circulatory Physiology 273, no. 1 (July 1, 1997): H478—H486. http://dx.doi.org/10.1152/ajpheart.1997.273.1.h478.
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We present a noninvasive technique for analyzing the feedback relationship between short-term fluctuations in blood pressure (BP) and heart rate (HR) in humans. Beat-to-beat BP was monitored for several minutes with a noninvasive BP measuring device, i.e., arterial tonometry, in 16 healthy subjects and 15 patients on hemodialysis (HD), and the recorded systolic BP (SBP) and the pulse wave interval (R-R interval) were fitted to vector autoregressive models according to Akaike's method. The impulse-response function was then simulated to determine the contribution of changes in R-R interval or SBP to the fluctuation of SBP or R-R interval along a time scale. In healthy subjects, when a simulated 1-mmHg impulse was applied to SBP, the R-R interval increased to approximately 3.5 ms with a delay of several beats. In HD patients the same impulse caused essentially no response in the R-R interval. A 1-ms impulse applied to the R-R interval decreased SBP, and the response was not different in healthy subjects and HD patients. In the R-R interval-to-R-R interval response and the SBP-to-SBP response, the exponential-like decay after the initial jump was more rapid in the HD patients than in the healthy subjects. The results demonstrated that this technique can provide information on the feedback regulation between fluctuations in BP and HR in patients with or without autonomic nervous system dysfunction. This technique provides a simple and practical way to estimate autonomic function in clinical medicine.
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Murawski, K., K. Murawski, and H. Y. Schive. "Numerical simulations of acoustic waves with the graphic acceleration GAMER code." Bulletin of the Polish Academy of Sciences: Technical Sciences 60, no. 4 (December 1, 2012): 787–92. http://dx.doi.org/10.2478/v10175-012-0091-9.
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Abstract We present results of numerical simulations of acoustic waves with the use of the Graphics Processing Unit (GPU) acceleration GAMER code which implements a second-order Godunov-type numerical scheme and adaptive mesh refinement (AMR). The AMR implementation is based on constructing a hierarchy of grid patches with an octree data structure. In this code a hybrid model is adopted, in which the time-consuming solvers are dealt with GPUs and the complex AMR data structure is manipulated by Central Processing Units (CPUs). The code is highly parallelized with the Hilbert space-filling curve method. These implementations allow us to resolve well desperate spatial scales that are associated with acoustic waves. We show that a localized velocity (gas pressure) pulse that is initially launched within a uniform and still medium triggers acoustic waves simultaneously with a vortex (an entropy mode). In a flowing medium, acoustic waves experience amplitude growth or decay, a scenario which depends on a location of the flow and relative direction of wave propagation. The amplitude growth results from instabilities which are associated with negative energy waves.
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Hou, Xiaowei, Yanming Zhu, Shangbin Chen, and Yang Wang. "Gas flow mechanisms under the effects of pore structures and permeability characteristics in source rocks of coal measures in Qinshui Basin, China." Energy Exploration & Exploitation 35, no. 3 (March 28, 2017): 338–55. http://dx.doi.org/10.1177/0144598717700080.
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The gas flow mechanisms in source rocks of coal measures under the effects of the pore structures and permeability characteristics were investigated by field-emission scanning electron microscopy, low-pressure nitrogen gas adsorption, high-pressure mercury intrusion, and pressure pulse decay permeability method. Various flow regimes were distinguished in the pores and fractures of differing scales, and the mass fluxes through the same were calculated using the data obtained by the numerical and experimental investigations. Results indicated that mesopores predominated in shale, while coal contained well-developed mesopores and macropores. In addition, the permeabilities of coal and shale were observed to be significantly anisotropic and highly stress dependent. The cross-sectional area proportions of the pores per unit cross-sectional area of the matrix in the free molecular, transition, and slip flow regimes in shale and coal were determined to be, respectively, 0.2:0.7:0.1 and 0.15:0.6:0.25. In the free molecular and transition flow regimes, the mass flux decreased with increasing reservoir depth, while the reverse was the case in the slip flow regime. Further, in the continuum flow regime, the mass flux was unimodally distributed with respect to the reservoir depth. The total mass flux in coal was greater in the direction perpendicular to the bedding compared to the direction parallel to the bedding, while the reverse was the case in shale. In addition, the continuum flow regime predominated in coal in both the directions perpendicular and parallel to the bedding, but only in the direction parallel to the bedding in shale. This work presents a comprehensive model for the analysis of all the flow regimes in pores and fractures of differing scales, as well as the anisotropy. Findings of the study are meaningful for establishing the coupling accumulation mechanism of the Three Coal Gases and developing a unified exploration and exploitation program.
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Mukhametdinova, Aliya, Andrey Kazak, Tagir Karamov, Natalia Bogdanovich, Maksim Serkin, Sergey Melekhin, and Alexey Cheremisin. "Reservoir Properties of Low-Permeable Carbonate Rocks: Experimental Features." Energies 13, no. 9 (May 3, 2020): 2233. http://dx.doi.org/10.3390/en13092233.
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This paper presents an integrated petrophysical characterization of a representative set of complex carbonate reservoir rock samples with a porosity of less than 3% and permeability of less than 1 mD. Laboratory methods used in this study included both bulk measurements and multiscale void space characterization. Bulk techniques included gas volumetric nuclear magnetic resonance (NMR), liquid saturation (LS), porosity, pressure-pulse decay (PDP), and pseudo-steady-state permeability (PSS). Imaging consisted of thin-section petrography, computed X-ray macro- and microtomography, and scanning electron microscopy (SEM). Mercury injection capillary pressure (MICP) porosimetry was a proxy technique between bulk measurements and imaging. The target set of rock samples included whole cores, core plugs, mini cores, rock chips, and crushed rock. The research yielded several findings for the target rock samples. NMR was the most appropriate technique for total porosity determination. MICP porosity matched both NMR and imaging results and highlighted the different effects of solvent extraction on throat size distribution. PDP core-plug gas permeability measurements were consistent but overestimated in comparison to PSS results, with the difference reaching two orders of magnitude. SEM proved to be the only feasible method for void-scale imaging with a spatial resolution up to 5 nm. The results confirmed the presence of natural voids of two major types. The first type was organic matter (OM)-hosted pores, with dimensions of less than 500 nm. The second type was sporadic voids in the mineral matrix (biogenic clasts), rarely larger than 250 nm. Comparisons between whole-core and core-plug reservoir properties showed substantial differences in both porosity (by a factor of 2) and permeability (up to 4 orders of magnitude) caused by spatial heterogeneity and scaling.
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Kang, S. M. M., E. Fathi, R. J. J. Ambrose, I. Y. Y. Akkutlu, and R. F. F. Sigal. "Carbon Dioxide Storage Capacity of Organic-Rich Shales." SPE Journal 16, no. 04 (April 4, 2011): 842–55. http://dx.doi.org/10.2118/134583-pa.
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Summary This paper presents an experimental study on the ability of organic-rich-shale core samples to store carbon dioxide (CO2). An apparatus has been built for precise measurements of gas pressure and volumes at constant temperature. A new analytical methodology is developed allowing interpretation of the pressure/volume data in terms of measurements of total porosity and Langmuir parameters of core plugs. The method considers pore-volume compressibility and sorption effects and allows small gas-leakage adjustments at high pressures. Total gas-storage capacity for pure CO2 is measured at supercritical conditions as a function of pore pressure under constant reservoir-confining pressure. It is shown that, although widely known as an impermeable sedimentary rock with low porosity, organic shale has the ability to store significant amount of gas permanently because of trapping of the gas in an adsorbed state within its finely dispersed organic matter (i.e., kerogen). The latter is a nanoporous material with mainly micropores (< 2 nm) and mesopores (2-50 nm). Storage in organic-rich shale has added advantages because the organic matter acts as a molecular sieve, allowing CO2—with linear molecular geometry—to reside in small pores that the other naturally occurring gases cannot access. In addition, the molecular-interaction energy between the organics and CO2 molecules is different, which leads to enhanced adsorption of CO2. Hence, affinity of shale to CO2 is partly because of steric and thermodynamic effects similar to those of coals that are being considered for enhanced coalbed-methane recovery. Mass-transport paths and the mechanisms of gas uptake are unlike those of coals, however. Once at the fracture/matrix interface, the injected gas faces a geomechanically strong porous medium with a dual (organic/inorganic) pore system and, therefore, has choices of path for its flow and transport into the matrix: the gas molecules (1) dissolve into the organic material and diffuse through a nanopore network and (2) enter the inorganic material and flow through a network of irregularly shaped voids. Although gas could reach the organic pores deep in the shale formation following both paths, the application of the continua approximation requires that the gas-flow system be near or beyond the percolation threshold for a consistent theoretical framework. Here, using gas permeation experiments and history matching pressure-pulse decay, we show that a large portion of the injected gas reaches the organic pores through the inorganic matrix. This is consistent with scanning-electron-microscope (SEM) images that do not show connectivity of the organic material on scales larger than tens of microns. It indicates an in-series coupling of the dual continua in shale. The inorganic matrix permeability, therefore, is predicted to be less, typically on the order of 10 nd. More importantly, although transport in the inorganic matrix is viscous (Darcy) flow, transport in the organic pores is not due to flow but mainly to molecular transport mechanisms: pore and surface diffusion.
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Winhausen, Lisa, Alexandra Amann-Hildenbrand, Reinhard Fink, Mohammadreza Jalali, Kavan Khaledi, Pooya Hamdi, Janos L. Urai, Joyce Schmatz, and Florian Amann. "A comparative study on methods for determining the hydraulic properties of a clay shale." Geophysical Journal International 224, no. 3 (November 10, 2020): 1523–39. http://dx.doi.org/10.1093/gji/ggaa532.
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SUMMARY A comprehensive characterization of clay shale behavior requires quantifying both geomechanical and hydromechanical characteristics. This paper presents a comparative laboratory study of different methods to determine the water permeability of saturated Opalinus Clay: (i) pore pressure oscillation, (ii) pressure pulse decay and (iii) pore pressure equilibration. Based on a comprehensive data set obtained on one sample under well-defined temperature and isostatic effective stress conditions, we discuss the sensitivity of permeability and storativity on the experimental boundary conditions (oscillation frequency, pore pressure amplitudes and effective stress). The results show that permeability coefficients obtained by all three methods differ less than 15 per cent at a constant effective stress of 24 MPa (kmean = 6.6E-21 to 7.5E-21 m2). The pore pressure transmission technique tends towards lower permeability coefficients, whereas the pulse decay and pressure oscillation techniques result in slightly higher values. The discrepancies are considered minor and experimental times of the techniques are similar in the range of 1–2 d for this sample. We found that permeability coefficients determined by the pore pressure oscillation technique increase with higher frequencies, that is oscillation periods shorter than 2 hr. No dependence is found for the applied pressure amplitudes (5, 10 and 25 per cent of the mean pore pressure). By means of experimental handling and data density, the pore pressure oscillation technique appears to be the most efficient. Data can be recorded continuously over a user-defined period of time and yield information on both, permeability and storativity. Furthermore, effective stress conditions can be held constant during the test and pressure equilibration prior to testing is not necessary. Electron microscopic imaging of ion-beam polished surfaces before and after testing suggests that testing at effective stresses higher than in situ did not lead to pore significant collapse or other irreversible damage in the samples. The study also shows that unloading during the experiment did not result in a permeability increase, which is associated to the persistent closure of microcracks at effective stresses between 24 and 6 MPa.
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Gajda, D., S. Liu, and M. Lutyński. "The concept of hydrogen-methane blends storage in underground mine excavations – gas permeability of concrete." E3S Web of Conferences 266 (2021): 03007. http://dx.doi.org/10.1051/e3sconf/202126603007.
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Power–to–gas technology gives the possibility to store the excess power from renewable energy sources by converting electrical energy into gas such as eg. hydrogen. There is however a problem with accessibility of sites where pure hydrogen can be stored. Hence, the idea of blending hydrogen with methane and use underground mine excavations to increase the storage capacity, apart from salt caverns. However, hydrogen has strong capability to diffuse through different materials, including steel and some minerals. The paper proposes a concept of hydrogen/methane blends storage in abandoned underground mine excavations. Research is focused on permeability of concrete as a barrier for stored gases. Gas permeability from two methods: pulse – decay and steady – state, were compared. Gas permeability of investigated concrete and geopolymers depends on the composition and pressure conditions, including axial stress. A significant improvement of tightness of the concrete can be achieved, using a synthetic compounds.
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"Permeability measurement by the pulse-decay method: effects of poroelastic phenomena and non-linear pore pressure diffusion." International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 23, no. 6 (December 1986): 225. http://dx.doi.org/10.1016/0148-9062(86)92411-3.
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Sanmiguel-Rojas, E., P. Gutierrez-Castillo, C. del Pino, and J. A. Auñón-Hidalgo. "Cavitation in Transient Flows Through a Micro-Nozzle." Journal of Fluids Engineering 141, no. 9 (April 1, 2019). http://dx.doi.org/10.1115/1.4042887.
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High cavitating or supercavitating flows in fuel injector systems are crucial since they improve the mixing and the fuel atomization into combustion chambers, decreasing both fuel consumption and pollutant emissions. However, there is a lack of information regarding the required time to obtain high cavitating flows at the nozzle outlet, from the start of the injection pulse. In this work, a new method to quantify the time to get supercavitating flows at the nozzle outlet is developed. In particular, the delay in the inception of a supercavitating flow through a micronozzle is numerically analyzed for different pressure drops in a well-studied benchmark for fuel injectors. The three-dimensional simulations show that a delay higher than 100 μs is necessary for moderate pressure drops. Nevertheless, the delay tends to decay by rising amplitudes of the pressure pulse, reaching a saturation value of around 65 μs.
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Lasseux, Didier, Pascal Jolly, Yves Jannot, and Emmanuel Sauger Benoit Omnes. "Permeability Measurement of Graphite Compression Packings." Journal of Pressure Vessel Technology 133, no. 4 (May 16, 2011). http://dx.doi.org/10.1115/1.4002922.
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In this work, we address the issue of the sealing performance of ring-shape valve compression packings. Our analysis is focused on the characterization of the permeability of the rings made of die-formed exfoliated graphite. Because of the tight character of the material, significant Klinkenberg effects are expected. In addition, due to the manufacturing process, permeabilities kz and kr as well as Klinkenberg coefficients bz and br in the respective axial and radial directions are markedly different and strongly dependent upon the applied stress. A specific experimental device based on pressure pulse decay of nitrogen through the material was designed for the measurement in each direction under a controlled axial compression. Determination of kz and kr and bz and br is performed on the basis of a nonstationary gas flow model in the radial and axial directions using an inverse procedure applied to the pressure decay signal. Our results confirm the efficiency of the method developed here. They clearly show the anisotropic character of the material (kz is roughly one order of magnitude larger than kr) and the dependence upon axial compression. The present analysis is the key step before further quantification of the leak rate that may result from the permeation through the material as envisaged here as well as through interfaces between the housing, the packings, and the stem.
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Tang, Xiaojun, Hongqing Lv, Xiangnan Meng, Zhenqing Wang, and Qin Lv. "Stability characteristic of hypersonic flow over a blunt wedge under freestream pulse wave." Open Physics 12, no. 1 (January 1, 2014). http://dx.doi.org/10.2478/s11534-014-0421-7.
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AbstractTo investigate the stability characteristic of hypersonic flow under the action of a freestream pulse wave, a high-order finite difference method was employed to do direction numerical simulation (DNS) of hypersonic unsteady flow over an 8° half-wedge-angle blunt wedge with freestream slow acoustic wave. The evolution of disturbance wave modes in the boundary layer under a pulse wave and a continuous wave are compared, and the wall temperature effect on the hypersonic boundary layer stability for a pulse wave disturbance is discussed. Results show that, both for a pulse wave and a continuous wave in freestream, the disturbance waves inside the nose boundary layer are mainly a fundamental mode; the Fourier amplitude of pressure disturbance mode in the boundary layer for a pulse wave is far less than that for a continuous wave, and the band frequency of the former is wider than that of the latter. All disturbance modes decay rapidly along the streamwise in the nose boundary layer. In the non-nose boundary layer, the dominant mode is transferred from fundamental mode into second harmonic. The transformation of dominant mode for a pulse wave appears much earlier than that for a continuous wave. Different frequency disturbance modes present different changes along streamline in the boundary layer, and the frequency band narrows around the second harmonic mode along the streamwise. Keen competition and the transformation of energy exist among different modes in the boundary layer. Wall temperature modifies the stability characteristic of the hypersonic boundary layer, which presents little effect on the development of fundamental modes and cooling wall could accelerates the growth of the high frequency mode as well as the dominant mode transformation.
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Zhang, Zilai, Shusheng Zang, Bing Ge, and Peifeng Sun. "Acoustic Diagnostics Applications in the Study of the Oscillation Combustion in Lean Premixed Pre-Evaporation Combustor." Journal of Engineering for Gas Turbines and Power 140, no. 12 (November 28, 2018). http://dx.doi.org/10.1115/1.4039463.
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The paper presents an experimental investigation of the thermoacoustic oscillations detection in a lean premixed pre-evaporation (LPP) combustor using acoustic signals. The LPP model combustion chamber oscillation combustion test platform was designed and built; the thermal parameters signal, the acoustic signal, and the dynamic pressure signal were collected under the steady condition and the transition condition, and been analyzed comparatively. The experimental result shows that, at the same inlet air speed, the dominant frequency of the combustion chamber is proportional to the thermal load, while at the same fuel flow, the main frequency of the combustion chamber does not change with the changing of air speed. In addition, the doubling frequency of the acoustic signal is more obvious than the pressure signals, which show that the interference of the acoustic signal is less. In the transition condition, the pulse energy of the acoustic signal is obviously increased after ignition. The dominant frequency energy increases when the working condition begins to change in the stable to oscillation combustion condition. The dominant frequency energy decreases when the working condition begins to change in the oscillation to stable combustion condition. During the flameout condition, the oscillating energy begins to decay from the high frequency region. For the acoustic signal is less disturbed than the pressure signal and it can obtain the same result with the pressure signal in the oscillation condition and the transition condition, acoustic diagnostic is an auxiliary method for combustion oscillation in LPP combustor.
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Mayo, R. M., J. W. Newman, A. Sharma, Y. Yamagata, and J. Narayan. "Electrostatic Measurement of Plasma Plume Characteristics in Pulse Laser Ablated Carbon." MRS Proceedings 593 (1999). http://dx.doi.org/10.1557/proc-593-261.
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ABSTRACTA triple Langmuir probe measurement has been implemented to investigate plasma plume character in low fluence (∼ 3.0 J/cm2) pulsed laser evaporation (PLE) discharges and has been found to be an extremely valuable tool. Absolute plasma plume density estimates are found to reside in the range 1.0 × 1013–2.0 × 1014 cm−3 for vacuum pulses. A simple heavy particle streaming model for vacuum pulses allows estimates of the plume ionization fraction of ∼ 10%. This is consistent with typical deposition inventory suggesting that high kinetic energy ions play an important role in DLC film deposition. Electron temperature is found to consistently reside in the range 0.5-3.0 eV, and appears to be uninfluenced by operating conditions and large variations in Ar and N2 fill gas pressure. Consistent with strong plume ion and neutral particle coupling to the background fill, constancy of Te suggests expulsion of background gas by the energetic plume. The leading edge ion plume speed is measured via temporal displacement of spatially separated probe signals on consecutive PLE pulses. Flow speeds as high as 5.0 × 104 m/s are observed, corresponding to ∼ 156 eV in C+. The ion flow speed is found to be a strongly decreasing function of fill pressure from an average high of ∼ 126 eV in vacuum to ∼ 0.24 eV at 600 mTorr N2. Raman scattering spectroscopy indicates DLC film quality also degrades with fill pressure suggesting the importance of high ion kinetic energy in producing good quality films. Optical emission indicates an increase in C2 molecular light intensity with fill gas pressure implying a reduced, if any, role of these species in DLC production. Ion current signal anomalies in high pressure pulses indicate the formation of high mass carbon clusters during plume evolution in the presence of background gas. Mass diffusivity estimates, based on density decay, suggest the presence of under these conditions. Demonstration and control of such cluster formation may provide method(s) for controlling novel advanced materials properties.