Yubo Wang^1,2,*, Yanan Yu^1,2, Qiming Wang³, Anxun Liu³

FDMP-Fluid Dynamics & Materials Processing, Vol.20, No.9, pp. 1993-2006, 2024, DOI:10.32604/fdmp.2024.049510 - 23 August 2024

Abstract A model is proposed for liquid film profile prediction in gas-liquid two-phase flow, which is able to provide the film thickness along the circumferential direction and the pressure gradient in the flow direction. A two-fluid model is used to calculate both gas and liquid phases’ flow characteristics. The secondary flow occurring in the gas phase is taken into account and a sailing boat mechanism is introduced. Moreover, energy conservation is applied for obtaining the liquid film thickness distribution along the circumference. Liquid film thickness distribution is calculated accordingly for different cases; its values are compared More >

Fang Li^1,*, Juan Wu¹, Haiyong Yi², Lihong Wu², Lingyun Du¹, Yuan Zeng¹

FDMP-Fluid Dynamics & Materials Processing, Vol.20, No.5, pp. 1015-1030, 2024, DOI:10.32604/fdmp.2023.043256 - 07 June 2024

Abstract Methods for horizontal well spacing calculation in tight gas reservoirs are still adversely affected by the complexity of related control factors, such as strong reservoir heterogeneity and seepage mechanisms. In this study, the stress sensitivity and threshold pressure gradient of various types of reservoirs are quantitatively evaluated through reservoir seepage experiments. On the basis of these experiments, a numerical simulation model (based on the special seepage mechanism) and an inverse dynamic reserve algorithm (with different equivalent drainage areas) were developed. The well spacing ranges of Classes I, II, and III wells in the Q gas More > Graphic Abstract

Xin Huang^1,*, Yunpeng Jiang¹, Daowu Huang¹, Xianke He¹, Xianguo Zhang², Ping Guo³

FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.6, pp. 1679-1691, 2023, DOI:10.32604/fdmp.2023.025312 - 30 January 2023

Abstract

The seepage mechanism plays a crucial role in low-permeability gas reservoirs. Compared with conventional gas reservoirs, low-permeability sandstone gas reservoirs are characterized by low porosity, low permeability, strong heterogeneity, and high water saturation. Moreover, their percolation mechanisms are more complex. The present work describes a series of experiments conducted considering low-permeability sandstone cores under pressure-depletion conditions (from the Xihu Depression in the East China Sea Basin). It is shown that the threshold pressure gradient of a low-permeability gas reservoir in thick layers is positively correlated with water saturation and negatively correlated with permeability and porosity. The

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Xuanyu Dong^1,*, Jingyao Yang²

FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.1, pp. 175-185, 2023, DOI:10.32604/fdmp.2022.021345 - 02 August 2022

Abstract A new numerical model for low-permeability reservoirs is developed. The model incorporates the nonlinear characteristics of oil-water two-phase flows while taking into account the initiation pressure gradient. Related numerical solutions are obtained using a finite difference method. The correctness of the method is demonstrated using a two-dimensional inhomogeneous low permeability example. Then, the differences in the cumulative oil and water production are investigated for different starting water saturations. It is shown that when the initial water saturation grows, the water content of the block continues to rise and the cumulative oil production gradually decreases. More >

T. Vu-Huu^{1, 2}, C. Le-Thanh³, H. Nguyen-Xuan⁴, M. Abdel-Wahab^{5, 6, *}

CMC-Computers, Materials & Continua, Vol.62, No.3, pp. 1109-1123, 2020, DOI:10.32604/cmc.2020.07989

Abstract This paper presents an adapted stabilisation method for the equal-order mixed scheme of finite elements on convex polygonal meshes to analyse the high velocity and pressure gradient of incompressible fluid flows that are governed by Stokes equations system. This technique is constructed by a local pressure projection which is extremely simple, yet effective, to eliminate the poor or even non-convergence as well as the instability of equal-order mixed polygonal technique. In this research, some numerical examples of incompressible Stokes fluid flow that is coded and programmed by MATLAB will be presented to examine the effectiveness More >

Fuyou Liang^1,*, Tianqi Wang¹

Molecular & Cellular Biomechanics, Vol.16, Suppl.1, pp. 25-26, 2019, DOI:10.32604/mcb.2019.05710

Abstract Hepatic venous pressure gradient (HVPG) measurement has been increasingly accepted as a useful means for indirectly measuring portal venous pressure in patients with portal hypertension (PHT) caused by chronic liver diseases. Despite the existence of numerous studies addressing the clinical utility of HVPG measurement, it is as yet unclear how the accuracy of measured HVPG as a surrogate of portal pressure gradient (PPG) is influenced by the pathological status of the hepatic circulation that not only changes with the progression of liver disease but also differs considerably among patients. In addition, it remains unclear whether… More >

Witold Elsner^1,*, Artur Dróżdż¹, Paweł Niegodajew¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.21, No.2, pp. 41-41, 2019, DOI:10.32604/icces.2019.05114

Abstract Estimation of the wall skin friction in a turbulent boundary layer (TBL) is always challenging due to the large gradient of mean velocity in the near-wall region and requires precise measurements of mean velocity in viscous sublayer. This problem becomes even more serious for a flow with a strong positive pressure gradient where the low velocity closes the wall occurs. Hence, choosing an appropriate measuring technique for the wall skin friction measurement is an important issue. Most commonly used for this purpose is hot-wire technique, where determination of mean velocity gradient is strongly dependent on… More >

Adam B. Christopher¹, Abraham Apfel², Tao Sun², Jackie Kreutzer¹, David S. Ezon³

Congenital Heart Disease, Vol.13, No.5, pp. 713-720, 2018, DOI:10.1111/chd.12637

Abstract Objective: The most accurate noninvasive parameter to predict whether a patient with aortic coarctation will meet interventional criteria at catheterization remains elusive. We aim to determine the best independent echocardiographic predictors of a coarctation peak‐to‐peak pressure gradient ≥20 mm Hg at catheterization, the ac‐ cepted threshold for intervention.
Design: Retrospective query of our catheterization database from 1/2007 to 7/2016 for the diagnostic code of aortic coarctation was performed. Multiple echocardio‐ graphic measurements and blood pressure gradients prior to cardiac catheterization were collected. Univariate correlation of variables with the continuous catheteriza‐ tion peak were calculated using Spearman’s rho.… More >

Brian A. Boe¹, Mark D. Norris², Jeffrey D. Zampi², Albert P. Rocchini², Gregory J. Ensing²

Congenital Heart Disease, Vol.12, No.6, pp. 733-739, 2017, DOI:10.1111/chd.12514

Abstract Objective: We sought to identify a time during cardiac ejection when the instantaneous pressure gradient (IPG) correlated best, and near unity, with peak-to-peak systolic ejection gradient (PPSG) in patients with congenital aortic stenosis. Noninvasive echocardiographic measurement of IPG has limited correlation with cardiac catheterization measured PPSG across the spectrum of disease severity of congenital aortic stenosis. A major contributor is the observation that these measures are inherently different with a variable relationship dependent on the degree of stenosis.
Design: Hemodynamic data from cardiac catheterizations utilizing simultaneous pressure measurements from the left ventricle (LV) and ascending aorta (AAo)… More >

W. A. El-Askary¹

CMES-Computer Modeling in Engineering & Sciences, Vol.74, No.3&4, pp. 203-232, 2011, DOI:10.3970/cmes.2011.074.203

Abstract Large eddy simulation (LES) is a viable and powerful tool to analyze unsteady three- dimensional turbulent flows. In this paper, the method of LES is used to compute a plane turbulent supersonic boundary layer subjected to different pressure gradients. The pressure gradients are generated by allowing the flow to pass in the vicinity of an expansion-compression ramp (inclined backward-facing step with leeward-face angle of 25 degrees) for an upstream Mach number of 2.9. The inflow boundary condition is the main problem for all turbulent wall-bounded flows. An approach to solve this problem is to extract… More >