scholarly journals Effect of Shear Displacement on the Directivity of Permeability in 3D Self-Affine Fractal Fractures

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Richeng Liu ◽  
Na Huang ◽  
Yujing Jiang ◽  
Hongwen Jing ◽  
Bo Li ◽  
...  
Keyword(s):  
Flow Direction ◽  
Shear Displacement ◽  
Shear Direction ◽  
Flow Paths ◽  
Direction Parallel ◽  
Equivalent Permeability ◽  
Shear Process ◽  
Directional Permeability ◽  
Channeling Flow ◽  
Aperture Distribution

The effect of shear displacement on the directivity of permeability in fractures is studied in this paper. The studied fracture surface has 3D self-affine fractal characteristics that are created using the modified successive random addition (SRA) method. Fluid flow through the fracture is simulated using the COMSOL Multiphysics code based on the finite element method (FEM) by changing the angle between the shear direction and macroscopic flow direction. The evolutions of the aperture distribution and flow paths with changes in shear displacement are investigated, and the change in the equivalent permeability is evaluated. The results show that the mean aperture and its deviation for rough fractures increase as the shear displacement increases, and this change is accompanied by an increase in void spaces and decreasing contact areas between the upper and lower fracture surfaces. The flow paths become more tortuous, and the channeling flow effect occurs during the shear process. The equivalent permeability of the fractures varies as the inclination between the shear direction and macroscopic flow direction changes. The permeability with the largest magnitude exists in the direction perpendicular to the shear direction, and the permeability with the smallest magnitude exists in the direction parallel to the shear direction. The equivalent permeability of the fractures at other inclinations varies between the smallest and greatest values. Notably, larger inclinations correspond to higher permeability magnitudes. The ratio of the directional permeability to the permeability in the direction parallel to the shear direction varies between 1.03 and 2.71. This ratio tends to decrease as the shear displacement and JRC increase, which indicates that the directivity of the permeability is more obvious for fractures with smaller JRCs and smaller shear displacement.

scholarly journals A Fractal Model for Predicting the Relative Permeability of Rough-Walled Fractures

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zuyang Ye ◽  
Wang Luo ◽  
Shibing Huang ◽  
Yuting Chen ◽  
Aiping Cheng
Keyword(s):  
Porous Media ◽  
Multiphase Flow ◽  
Relative Permeability ◽  
Fractal Model ◽  
Numerical Results ◽  
Flow Paths ◽  
Capillary Model ◽  
Lognormal Distributions ◽  
Fractal Characteristics ◽  
Aperture Distribution

The relative permeability and saturation relationships through fractures are fundamental for modeling multiphase flow in underground geological fractured formations. In contrast to the traditional straight capillary model from porous media, the realistic flow paths in rough-walled fractures are tortuous. In this study, a fractal relationship between relative permeability and saturation of rough-walled fractures is proposed associated with the fractal characteristics of tortuous parallel capillary plates, which can be generalized to several existing models. Based on the consideration that the aperture distribution of rough-walled fracture can be represented by Gaussian and lognormal distributions, aperture-based expressions between relative permeability and saturation are explicitly derived. The developed relationships are validated by the experimental observations on Gaussian distributed fractures and numerical results on lognormal distributed fractures, respectively.

scholarly journals SIZE EFFECT ON THE PERMEABILITY AND SHEAR INDUCED FLOW ANISOTROPY OF FRACTAL ROCK FRACTURES

Fractals ◽  
2018 ◽  
Vol 26 (02) ◽  
pp. 1840001 ◽  
Author(s):  
NA HUANG ◽  
YUJING JIANG ◽  
RICHENG LIU ◽  
YUXUAN XIA
Keyword(s):  
Fluid Flow ◽  
Stable State ◽  
Simulation Method ◽  
Shear Direction ◽  
Direction Parallel ◽  
Flow Channels ◽  
Fracture Size ◽  
Flow Through ◽  
Model Size ◽  
Induced Flow

The effect of model size on fluid flow through fractal rough fractures under shearing is investigated using a numerical simulation method. The shear behavior of rough fractures with self-affine properties was described using the analytical model, and the aperture fields with sizes varying from 25 to 200[Formula: see text]mm were extracted under shear displacements up to 20[Formula: see text]mm. Fluid flow through fractures in the directions both parallel and perpendicular to the shear directions was simulated by solving the Reynolds equation using a finite element code. The results show that fluid flow tends to converge into a few main flow channels as shear displacement increases, while the shapes of flow channels change significantly as the fracture size increases. As the model size increases, the permeability in the directions both parallel and perpendicular to the shear direction changes significantly first and then tends to move to a stable state. The size effects on the permeability in the direction parallel to the shear direction are more obvious than that in the direction perpendicular to the shear direction, due to the formation of contact ridges and connected channels perpendicular to the shear direction. The variances of the ratio between permeability in both directions become smaller as the model size increases and then this ratio tends to maintain constant after a certain size, with the value mainly ranging from 1.0 to 3.0.

Experimental Research on Strength Characteristics of Bulky Rock Material with Different Coarse Grain Content in Waste Pile of Mine

2012 ◽  
Vol 170-173 ◽  
pp. 295-300 ◽  
Author(s):  
Jun Du ◽  
Ke Peng Hou ◽  
Wei Liang
Keyword(s):  
Shear Modulus ◽  
Normal Stress ◽  
Friction Angle ◽  
Rock Material ◽  
Shear Displacement ◽  
Coarse Grain ◽  
Horizontal Loading ◽  
Shear Process ◽  
Main Basis ◽  
Rock And Soil

Bulky rock material of waste pile was composed of discarded rock and soil which was blasted and stripped from stope. It was characterized by dispersibility, complexity and variability. Shear strength index of bulky rock material was the main basis for analyzing slope stability of the waste pile. After the study on bulky rock material with different coarse grain content by indoor direct shear test, the results indicated that there was no obvious peak strength during the shear process, and variation of the shear displacement was slight in initial horizontal loading stage. Horizontal loading increased slowly and shear displacement had obvious change when shear displacement exceeded 5mm. Under the same normal stress, shear modulus G0.01 increased with the increase of coarse grain content when shear strain of specimen is 1/100. Shear modulus G0.01 of the specimen with same coarse grain content increased with the increase of normal stress, varying sensitive of G0.01 reduced when coarse grain content was larger. When the specimens with same coarse grain content were under failure, the shear modulus Gfailure was smaller than G0.01. Cohesive force c of the bulky rock material began to increase and then decrease with the increase of coarse grain content, and reached its maximum of 31.25KPa when the coarse grain content was 70%, internal friction angle increased with the increase of coarse grain content.

scholarly journals Non-orthogonal elastoplastic constitutive model for sand with dilatancy

2021 ◽  
Author(s):  
Jingyu Liang ◽  
Dechun Lu ◽  
Xiuli Du ◽  
Wei Wu ◽  
Chao Ma
Keyword(s):  
Constitutive Model ◽  
Plastic Flow ◽  
Flow Direction ◽  
Model Performance ◽  
Yield Function ◽  
Flow Rule ◽  
Shear Process ◽  
Hardening Parameter ◽  
Elastoplastic Constitutive Model ◽  
Plastic Flow Rule

A non-orthogonal elastoplastic constitutive model for sand with dilatancy is presented in the characteristic stress space. Dilatancy of sand is represented by the direction of plastic flow, which can be directly determined by applying the non-orthogonal plastic flow rule to an improved elliptic yield function. A new hardening parameter is developed to describe the contractive and dilative volume change during the shear process, which is co-ordinated with the non-orthogonal plastic flow direction. The combination of the non-orthogonal plastic flow rule and the proposed hardening parameter renders the proposed model with the ability to reasonably describe the stress-strain relationship of sand with dilatancy. The model performance is evaluated by comparing with the experimental data of sand under triaxial stress conditions.

scholarly journals Assessing Redundancy in Stormwater Structures Under Hydraulic Design

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1003 ◽  
Author(s):  
Sina Hesarkazzazi ◽  
Mohsen Hajibabaei ◽  
Julian David Reyes-Silva ◽  
Peter Krebs ◽  
Robert Sitzenfrei
Keyword(s):  
Complex Network ◽  
Flow Direction ◽  
Water Discharge ◽  
Extreme Rainfall ◽  
Cost Effective ◽  
Negative Effects ◽  
Flow Paths ◽  
Extreme Rainfall Events ◽  
Extreme Precipitation Events ◽  
Hydraulic Design

As environmental change is happening at an unprecedented pace, a reliable and proper urban drainage design is required to alleviate the negative effects of unexpected extreme rainfall events occurring due to the natural and anthropogenic variations such as climate change and urbanization. Since structure/configuration of a stormwater network plays an imperative role in the design and hydraulic behavior of the system, the goal of this paper is to elaborate upon the significance of possessing redundancy (e.g., alternative flow paths as in loops) under simultaneous hydraulic design in stormwater pipe networks. In this work, an innovative approach based on complex network properties is introduced to systematically and successively reduce the number of loops and, therefore, the level of redundancy, from a given grid-like (street) network. A methodology based on hydrodynamic modelling is utilized to find the optimal design costs for all created structures while satisfying a number of hydraulic design constraints. As a general implication, when structures are subject to extreme precipitation events, the overall capability of looped configurations for discharging runoff more efficiently is higher compared to more branched ones. The reason is due to prevailing (additional) storage volume in the system and existing more alternative water flow paths in looped structures, as opposed to the branched ones in which only unique pathways for discharging peak runoff exist. However, the question arises where to best introduce extra paths in the network? By systematically addressing this question with complex network analysis, the influence of downstream loops was identified to be more significant than that of upstream loops. Findings, additionally, indicated that possessing loop and introducing extra capacity without determining appropriate additional pipes positions in the system (flow direction) can even exacerbate the efficiency of water discharge. Considering a reasonable and cost-effective budget, it would, therefore, be worthwhile to install loop-tree-integrated stormwater collection systems with additional pipes at specific locations, especially downstream, to boost the hydraulic reliability and minimize the damage imposed by the surface flooding upon the metropolitan area.

Evidence of magmatic flow by 2-D image analysis of 3-D shape preferred orientation distributions

2004 ◽  
Vol 175 (4) ◽  
pp. 331-350 ◽  
Author(s):  
Patrick Launeau
Keyword(s):  
Image Analysis ◽  
Shear Flow ◽  
Simple Shear ◽  
Flow Direction ◽  
Preferred Orientation ◽  
Simple Shear Flow ◽  
Shear Direction ◽  
Thin Sections ◽  
Passive Deformation ◽  
Shape Ratio

Abstract The 3-D Shape Preferred Orientation (SPO) ellipsoid can be obtained by image analysis on a minimum of three perpendicular sections, when the 2-D measurements can be assimilated to ellipses. As numerous phenomenons can modify the SPO in magma (boundary condition effects, crystal interactions, joint migrations, etc.), the ellipsoid calculation is first tested on a set of digital models of simple shear flow. Those models, made of scattered shape ratio distribution, show that a suspension of crystals in a simple shear flow of the magma produces SPO parallel to the shear direction with an intensity given by the average shape ratio of the crystals, without any link with the amount of shear flow. This steady state SPO along the flow direction is particularly useful to study magma emplacement even if it is also shown that a critical shear rate γ between 4 and 8, for crystal shape ratio between 2 and 5 respectively, is sufficient to completely reorient a SPO. Therefore the SPO does not record magmatic strain as may do an enclave, which is an interface between two magmas with low viscosity contrast, that can record the whole strain of the magma by its passive deformation along the flow. An infinite strain is necessary here to parallelize the enclave on the shear flow direction. The application to a natural case (gabbronorite of the Bushveld, South Africa) shows that we must take care of the mineral chosen to describe a flow in a magma and that a careful classical study of the structures observed in thin sections is always required. To allow anyone to test the quality of the 2-D/3-D conversions, a web site is associated to this publication with a free access to all the image analysis and ellipsoid programs presented below.

The Interaction of the Wake from an Oscillating Blade with a Fixed Cascade

1971 ◽  
Vol 22 (1) ◽  
pp. 42-52
Author(s):  
D. S. Whitehead ◽  
V. G. Nabar
Keyword(s):  
Theoretical Investigation ◽  
Flow Direction ◽  
Mean Flow ◽  
Direction Parallel ◽  
The Mean

SummaryThe paper presents a theoretical investigation of the flow when the wake from a single vibrating aerofoil interacts with a fixed downstream cascade set normal to the mean flow direction. It is concluded that the effects of the cascade extend upstream by a distance of about one quarter of the wavelength of the fluctuations in the wake. It is also found that the wake passes through the cascade unchanged in strength, but that the cascade sheds vorticity of equal and opposite magnitude, so that, if an average is taken in the direction parallel to the cascade, the wake is annulled.

Sign in / Sign up

Export Citation Format

Share Document