scholarly journals Modelling of Permeation Grouting Through Soils

2020 ◽  
Vol 10 (1) ◽  
pp. 11-16
Author(s):  
S. B. Coskun ◽  
T. Tokdemir
Keyword(s):  
Mathematical Modeling ◽  
Numerical Simulation ◽  
Finite Element ◽  
Porous Medium ◽  
Capillary Pressure ◽  
Immiscible Fluids ◽  
Saturated Soils ◽  
Governing Equations ◽  
Permeation Grouting ◽  
Element Technique

AbstractIn this study, mathematical modeling of permeation grouting through fully saturated soil is proposed based on immiscible multiphase flow theory. Grout flow in the medium is modeled together with the existing water as the simultaneous flow of two immiscible fluids. In the model, the porous medium is assumed as isotropic and rigid, fluids are assumed as incompressible and capillary pressure is assumed as negligible. Governing equations are discretized using upstream weighted finite element technique and results show that, proposed models give good results and may be used in the numerical simulation of grouting through fully saturated soils.

Numerical Simulation of Two-Phase Flow in Severely Damaged Core Geometries

2006 ◽  
Author(s):  
Phongsan Meekunnasombat ◽  
Florian Fichot ◽  
Michel Quintard
Keyword(s):  
Numerical Simulation ◽  
Porous Medium ◽  
Two Phase Flow ◽  
Immiscible Fluids ◽  
Macroscopic Model ◽  
Phase Flow ◽  
Two Phase ◽  
Fuel Rods ◽  
The Core ◽  
The Impact

In the event of a severe accident in a nuclear reactor, the oxidation, dissolution and collapse of fuel rods is likely to change dramatically the geometry of the core. A large part of the core would be damaged and would look like porous medium made of randomly distributed pellet fragments, broken claddings and relocated melts. Such a complex medium must be cooled in order to stop the accident progression. IRSN investigates the effectiveness of the water re-flooding mechanism in cooling this medium where complex two-phase flows are likely to exist. A macroscopic model for the prediction of the cooling sequence was developed for the ICARE/CATHARE code (IRSN mechanistic code for severe accidents). It still needs to be improved and assessed. It appears that a better understanding of the flow at the pore scale is necessary. As a result, a direct numerical simulation (DNS) code was developed to investigate the local features of a two-phase flow in complex geometries. In this paper, the Cahn-Hilliard model is used to simulate flows of two immiscible fluids in geometries representing a damaged core. These geometries are synthesized from experimental tomography images (PHEBUS-FP project) in order to study the effects of each degradation feature, such as displacement and fragmentation of the fuel rods and claddings, on the two-phase flow. For example, the presence of fragmented fuel claddings is likely to enhance the trapping of the residual phase (either steam or water) within the medium which leads to less flow fluctuations in the other phase. Such features are clearly shown by DNS calculations. From a series of calculations where the geometry of the porous medium is changed, conclusions are drawn for the impact of rods damage level on the characteristics of two-phase flow in the core.

Numerical Simulation of Polymeric Gels

2015 ◽  
Author(s):  
Shawn A. Chester
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Steady State ◽  
Large Deformation ◽  
Governing Equations ◽  
Numerical Examples ◽  
Polymeric Gels ◽  
Finite Element Package ◽  
Fluid Diffusion ◽  
Transient And Steady State

Following [1], a theory for coupled fluid diffusion and large deformation is implemented as a user-element subroutine in the commercial finite element package ABAQUS. The governing equations are summarized along with details of the constitutive theory. A few numerical examples are provided to show the robustness of this methodology in both transient and steady state conditions.

Numerical Simulation of the Lubrication of the Head-Disk Interface Using a Non-Newtonian Fluid

1994 ◽  
Vol 116 (3) ◽  
pp. 541-548 ◽  
Author(s):  
Frank A. De Bruyne ◽  
D. B. Bogy
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Shear Rates ◽  
Dry Contact ◽  
Low Head ◽  
Magnetic Hard Disk ◽  
Element Technique ◽  
Contact Recording

The prospect of contact and near-contact recording in magnetic hard disk files naturally leads to reduced flying heights of the read-write head over the rigid disk. To avoid dry contact at these low head-to-disk spacings, a lubricant should be used to minimize wear and maximize reliability. Since fluids generally have a much greater viscosity than air and very large shear rates develop under the slider, it is believed that a fully flooded interface can only be practically possible if the fluid possesses a non-Newtonian character with a significant amount of shear-thinning. In this paper, we present results from extensive numerical simulations of the fully flooded head-disk interface using the finite element technique. This approach has proven very successful in calculating a wide variation of slider geometries for various fluid nonlinearities.

scholarly journals Wave Equations of Porous Media Saturated With Two Immiscible Fluids Based on the Volume Averaging Method

2021 ◽  
Vol 9 ◽  
Author(s):  
Fansheng Xiong ◽  
Jiawei Liu ◽  
Zhenwei Guo ◽  
Jianxin Liu
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Wave Propagation ◽  
Wave Equations ◽  
Coefficient Matrix ◽  
Immiscible Fluids ◽  
Original Model ◽  
Governing Equations ◽  
Improved Model ◽  
Dispersion And Attenuation

Simulating and predicting wave propagation in porous media saturated with two fluids is an important issue in geophysical exploration studies. In this work, wave propagation in porous media with specified structures saturated with two immiscible fluids was studied, and the main objective was to establish a wave equation system with a relatively simple structure. The wave equations derived by Tuncay and Corapcioglu were analyzed first. It was found that the coefficient matrix of the equations tends to be singular due to the inclusion of a small parameter that characterizes the effect of capillary stiffening. Therefore, the previously established model consisting of three governing equations may be unstable under natural conditions. An improved model based on Tuncay and Corapcioglu’s work was proposed to ensure the nonsingularity of the coefficient matrix. By introducing an assumption in which one fluid was completely wrapped by the other, the governing equation of the wrapped fluid was degenerated. In this way, the coefficient matrix of wave equations became nonsingular. The dispersion and attenuation prediction resulting from the new model was compared with that of the original model. Numerical examples show that although the improved model consists of only two governing equations, it can obtain a result similar to that of the original model for the case of a porous medium containing gas and water, which simplifies the complexity of the calculations. However, in a porous medium with oil and water, the predictions of dispersion and attenuation produced by the original model obviously deviate from the normal trend. In contrast, the results of the improved model exhibit the correct trend with a smooth curve. This phenomenon shows the stability of the improved model and it could be used to describe wave propagation dispersions and attenuations of porous media containing two immiscible fluids in practical cases.

Progress in Collapse Analyses

1987 ◽  
Vol 109 (1) ◽  
pp. 33-41 ◽  
Author(s):  
E. Riks
Keyword(s):  
Finite Element ◽  
Structural Analysis ◽  
Limit Point ◽  
Nonlinear Deformation ◽  
General Purpose ◽  
Finite Element Code ◽  
Governing Equations ◽  
Collapse Analysis ◽  
Element Technique ◽  
Intractable Problem

In the field of finite element structural analysis, the computation of collapse states of structures prone to unstable behavior has long been considered a difficult if not intractable problem. Only recently have procedures that deal effectively with this difficulty found their way in general-purpose finite element codes. Although the explanation for the cause of the so-called limit point obstacle is actually simple—an inappropriate parameterization of the governing equations in the neighborhood of the limit point—this cause does not seem to have been widely understood in the period of development of the finite element technique. In this paper, some of the remedies that have been proposed to overcome the problems are reviewed, including the principle of adaptive parameterization which is now the basis of a new procedure for collapse analysis in the finite element code STAGS. The discussion also includes the treatment of simple bifurcation points because unstable bifurcation can be considered a special form of collapse. It can be concluded that collapse problems, in the sense discussed in this paper, no longer present difficulties that exceed those normally encountered during the solution of nonlinear deformation paths. Further developments, in particular those with respect to improved efficiency, are in progress. Some of the promising ventures in this direction are indicated.

Dynamic Finite Element Analysis of a Piezoelectric Bimorph Beam Deflector With Consideration of Hysteresis Effect

2003 ◽  
Author(s):  
Paul C. P. Chao ◽  
C. W. Chiu ◽  
J. S. Huang ◽  
H. C. Tseng
Keyword(s):  
Finite Element ◽  
Constitutive Equations ◽  
Hysteresis Effect ◽  
Piezoelectric Bimorph ◽  
Governing Equations ◽  
Element Analysis ◽  
Dynamic Finite Element Analysis ◽  
Polarization Term ◽  
Bimorph Beam ◽  
Element Technique

This study is devoted to propose a method of finite element technique to account for the hysteresis effect of a piezoelectric bimorph beam deflector. To this end, the constitutive equations of a general piezoelectric material are first modified to include the hysteresis effect by adding a polarization term in one of constitutive equations. Based on these modified constitutive equations and employment of Preisach model for hysteresis, the governing equations of the bimorph beam are derived through the utilization of Hamilton’s principle and calculus of variation. In addition, according to the common physical rules, boundary, transition and continuous conditions are next formulated to complement the governing equations. Simulations are finally conducted to show the effectiveness of the proposed modeling technique and decipher the dynamic behavior of the piezoelectric beam with consideration of hysteresis effect.

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