The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform

Dongdong Gui - One of the best experts on this subject based on the ideXlab platform.

  • A Study about Solving the Nonlinear Spherical Seepage Model of Three-Area Composite Reservoir
    American Journal of Applied Mathematics and Statistics, 2015
    Co-Authors: Mei Luo, Dongdong Gui
    Abstract:

    This paper studies the nonlinear spherical seepage model of three-area composite reservoir under three kinds of outer Boundary conditions (infinite Boundary, Constant Pressure Boundary and closed Boundary) which not considering well-bore storage and skin factor. On the basis of similar structure of solution for differential equation’s Boundary value problem, this paper obtains the solution of the nonlinear spherical seepage model of three-area composite reservoir. The study not only benefits to understand the inherent laws of the solution, but also provides the convenience to compile corresponding test software.

  • A study on solving the nonlinear seepage flow model of three-region composite reservoir
    Proceedings of the 2015 International Conference on Power Electronics and Energy Engineering, 2015
    Co-Authors: Y. Wang, Xiao Xu Dong, Dongdong Gui
    Abstract:

    This paper builds a seepage model of three-region composite reservoir, in which quadratic-gradient effect, well-bore storage, effective radius and three kinds of outer Boundary conditions (Constant Pressure Boundary, closed Boundary and infinity Boundary) are considered. With Laplace transformation, the seepage flow model is transformed into a Boundary value problem of three-region composite zero-order modified Bessel equation by the substitution of variables and introduction of dimensionless variables. Based on the similar structure of the solution of the Boundary value problem of differential equation, this paper obtains solutions of dimensionless reservoir Pressure and dimensionless bottom-hole Pressure of three-region composite reservoir in Laplace space. This research not only contributes to further analyse the inherent law of the solution and compile corresponding well test analysis software, but also solves corresponding mathematical model of reservoir and supplements the study on composite reservoir. Keywords-composite reservoir; non-linear seepage; quadratic-gradient term; well-bore storage; effective radius; similar structure of solution; similar kernel function

  • A Study on Solving the Seepage Flow Model of Three-Area Composite Reservoir
    Applied Mechanics and Materials, 2014
    Co-Authors: Xiao Xu Dong, Dongdong Gui, Feng Jiu Zhang
    Abstract:

    This paper studies the seepage flow mathematical model of three-area composite reservoir under three kinds of outer Boundary conditions (infinite Boundary, Constant Pressure Boundary and closed Boundary), in which influences of well-bore storage and skin factor are not taken into consideration. On the basic of theory of similar structure of solution of Boundary value problem of differential equation, this paper obtain the solution of the seepage flow model of three-area composite reservoir. The study is not only conducive to further analyze the inherent law of the solution and solve corresponding application problems, but also easy to compile corresponding analysis software.

  • Similar Constructive Method of Solution for the Nonlinear Percolation Model in Composite Reservoir
    Applied Mechanics and Materials, 2014
    Co-Authors: Feng Jiu Zhang, Dongdong Gui, Xi Tao Bao, Xiao Xu Dong
    Abstract:

    This paper presents a percolation model for the composite reservoir, in which quadratic-gradient effect, well-bore storage, effective radius and three types of outer Boundary conditions: Constant Pressure Boundary, closed Boundary and infinity Boundary are considered. With Laplace transformation, the percolation model was linearized by the substitution of variables and obtained a Boundary value problem of the composite modified zero-order Bessel equation. Using the Similar Constructive Method this method, we can gain the distributions of dimensionless reservoir Pressure for the composite reservoirs in Laplace space. The similar structures of the solutions are convenient for analyzing the influence of reservoir parameters on Pressure and providing significant convenience to the programming of well-test analysis software.

  • Similar Constructive Method for Solving the Nonlinear Spherical Percolation Model in Dual-Porosity Media
    Advanced Materials Research, 2013
    Co-Authors: Xi Tao Bao, Dongdong Gui
    Abstract:

    This paper presents a spherical percolation model for dual-porosity media reservoir, where the quadratic-gradient term, wellbore storage and three types of outer Boundary conditions: Constant Pressure Boundary, closed Boundary and infinity Boundary were considered. Then a new method: Similar Constructive Method was put forward for solving this type of percolation model. And solutions of the dimensionless reservoir Pressure and the dimensionless bottomhole Pressure in Laplace space were obtained. It was proved that these solutions had a similar structure. The Similar Constructive Method is an elementary and algebraic method, simple and practical. And the similar structure of solutions can simplify the well test analysis software programming and analyze the reservoir parameter’s affection on Pressure conveniently. The present research has a great academic significance and application value in oil-gas field development.

Shahram Atabay - One of the best experts on this subject based on the ideXlab platform.

  • Shape factor in the drawdown solution for well testing of dual-porosity systems
    Advances in Water Resources, 2009
    Co-Authors: Hassan Hassanzadeh, Mehran Pooladi-darvish, Shahram Atabay
    Abstract:

    Abstract One of the important parameters in existing commercial dual-porosity reservoir simulators is matrix–fracture shape factor, which is customarily obtained by assuming a Constant Pressure at the matrix–fracture Boundary. In his work, Chang [1] , [2] addressed the impact of Boundary conditions at the matrix–fracture interface and presented analytical solutions for the transient shape factor and showed that for a slab-shaped matrix block a Constant Pressure Boundary condition leads to an asymptotic (long-time) shape factor of π2/L2, and that a Constant volumetric flux leads to an asymptotic shape factor of 12/L2. In a recent paper [3] , we reconfirmed Chang’s [1] , [2] results using a Laplace transform approach. In this study, we extend our previous analysis and use infinite-acting radial and linear dual-porosity models, where the Boundary condition is chosen at the wellbore, as opposed to at the matrix Boundary. The coupled equations for fracture and matrix are solved analytically, taking into account the transient exchange between matrix and fracture. The analytical solution that invokes the time dependency of fracture Boundary condition under Constant rate is then used to calculate the transient shape factors. It is shown that, for a well producing at Constant rate from a naturally fractured reservoir, the appropriate value of stabilized shape factor is 12/L2. This contrasts with the commonly used shape factor for a slab-shaped matrix block that is subject to a Constant Pressure Boundary condition, which is π2/L2. The errors in the matrix–fracture exchange term in a dual-porosity model associated with the use of a shape factor derived based on Constant Pressure Boundary condition at the matrix Boundary are then evaluated.

Yiannis Ventikos - One of the best experts on this subject based on the ideXlab platform.

  • Computational investigation of subject-specific cerebrospinal fluid flow in the third ventricle and aqueduct of Sylvius.
    J Biomech, 2007
    Co-Authors: Yiannis Ventikos
    Abstract:

    The cerebrospinal fluid flow in the third ventricle of the brain and the aqueduct of Sylvius was studied using computational fluid dynamics (CFD) based on subject-specific Boundary conditions derived from magnetic resonance imaging (MRI) scans. The flow domain geometry was reconstructed from anatomical MRI scans by manual image segmentation. The movement of the domain Boundary was derived from MRI brain motion scans. Velocimetric MRI scans were used to reconstruct the velocity field at the inferior end of the aqueduct of Sylvius based on the theory of pulsatile flow in pipes. A Constant Pressure Boundary condition was assigned at the foramina of Monro. Three main flow features were observed: a fluid jet emerging from the aqueduct of Sylvius, a moderately mobile recirculation zone above the jet and a mobile recirculation below the jet. The flow in the entire domain was laminar with a maximum Reynolds number of 340 in the aqueduct. The findings demonstrate that by combining MRI scans and CFD simulations, subject-specific detailed quantitative information of the flow field in the third ventricle and the aqueduct of Sylvius can be obtained.

  • MICCAI - Reconstruction of cerebrospinal fluid flow in the third ventricle based on MRI data
    Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Inte, 2005
    Co-Authors: Vartan Kurtcuoglu, Michaela Soellinger, Peter Boesiger, Dimos Poulikakos, Paul Summers, Kevin Boomsma, Yiannis Ventikos
    Abstract:

    A finite-volume model of the cerebrospinal fluid (CSF) system encompassing the third ventricle and the aqueduct of Sylvius was used to reconstruct CSF velocity and Pressure fields based on MRI data. The flow domain geometry was obtained through segmentation of MRI brain anatomy scans. The movement of the domain walls was interpolated from brain motion MRI scans. A Constant Pressure Boundary condition (BC) was specified at the foramina of Monro. A transient velocity BC reconstructed from velocimetric MRI scans was employed at the inferior end of the aqueduct of Sylvius. It could be shown that a combination of MRI scans and computational fluid dynamics (CFD) simulation can be used to reconstruct the flow field in the third ventricle. Pre-interventional knowledge of patient-specific CSF flow has the potential to improve neurosurgical interventions such as shunt placement in case of hydrocephalus.

  • Reconstruction of cerebrospinal fluid flow in the third ventricle based on MRI data
    2005
    Co-Authors: Kurtcuoglu, Michaela Soellinger, Peter Boesiger, Dimos Poulikakos, Paul Summers, Kevin Boomsma, Yiannis Ventikos
    Abstract:

    A finite-volume model of the cerebrospinal fluid (CSF) system encompassing the third ventricle and the aqueduct of Sylvius was used to reconstruct CSF velocity and Pressure fields based on MRI data. The flow domain geometry was obtained through segmentation of MRI brain anatomy scans. The movement of the domain walls was interpolated from brain motion MRI scans. A Constant Pressure Boundary condition (BC) was specified at the foramina of Monro. A transient velocity BC reconstructed from velocimetric MRI scans was employed at the inferior end of the aqueduct of Sylvius. It could be shown that a combination of MRI scans and computational fluid dynamics (CFD) simulation can be used to reconstruct the flow field in the third ventricle. Pre-interventional knowledge of patient-specific CSF flow has the potential to improve neurosurgical interventions such as shunt placement in case of hydrocephalus. © Springer-Verlag Berlin Heidelberg 2005.

Kemal Hanjalic - One of the best experts on this subject based on the ideXlab platform.

  • a new approach to modelling near wall turbulence energy and stress dissipation
    Journal of Fluid Mechanics, 2002
    Co-Authors: Suad Jakirlic, Kemal Hanjalic
    Abstract:

    A new model for the transport equation for the turbulence energy dissipation rate e and for the anisotropy of the dissipation rate tensor e ij , consistent with the near-wall limits, is derived following the term-by-term approach and using results of direct numerical simulations (DNS) for several generic wall-bounded flows. Based on the two-point velocity covariance analysis of Jovanovic, Ye & Durst (1995) and reinterpretation of the viscous term, the transport equation is derived in terms of the ‘homogeneous’ part e h of the energy dissipation rate. The algebraic expression for the components of e ij was then reformulated in terms of e h , which makes it possible to satisfy the exact wall limits without using any wall-configuration parameters. Each term in the new equation is modelled separately using DNS information. The rational vorticity transport theory of Bernard (1990) was used to close the mean curvature term appearing in the dissipation equation. A priori evaluation of e ij , as well as solving the new dissipation equation as a whole using DNS data for quantities other than e ij , for flows in a pipe, plane channel, Constant-Pressure Boundary layer, behind a backward-facing step and in an axially rotating pipe, all show good near-wall behaviour of all terms. Computations of the same flows with the full model in conjunction with the low-Reynolds number transport equation for ( u i u i ) All Overbar, using e h instead of e, agree well with the direct numerical simulations.

Ole Jørgen Nydal - One of the best experts on this subject based on the ideXlab platform.

  • The effect of Boundary conditions and droplet entrainment on severe slugging using a Lagrangian slug tracking model
    International Journal of Multiphase Flow, 2016
    Co-Authors: Ivar Eskerud Smith, Ole Jørgen Nydal
    Abstract:

    Abstract This study presents a Lagrangian slug tracking model for prediction of slug flow in multiphase flow pipelines. Simulations are compared with severe slugging experiments from the SINTEF Large Scale Multiphase Laboratory with 0.189 m inner diameter and a length of about 1000 m. The fluids used in the experiments are nitrogen and naphtha, and the system Pressure is 25 bar. The model is shown to give fast and accurate results within the experimental accuracy without the need for a sub-grid model, as long as the grid size is not too large around the riser bottom where the liquid blockage occurs. It is also shown that simulations using a Constant Pressure Boundary condition at the outlet are not always adequate, as the Pressure fluctuations in the receiving facilities can significantly affect the flow. Furthermore, we show that the inclusion of a droplet field has a significant impact on the predicted slugging periods.