FRACTAL ANALYSIS OF STRESS SENSITIVITY OF PERMEABILITY IN POROUS MEDIA

Fractals ◽  
2015 ◽  
Vol 23 (02) ◽  
pp. 1550001 ◽  
Author(s):  
XIAO-HUA TAN ◽  
XIAO-PING LI ◽  
JIAN-YI LIU ◽  
LIE-HUI ZHANG ◽  
JIANCHAO CAI
Keyword(s):  
Porous Media ◽  
Stress Sensitivity ◽  
Maximum Diameter ◽  
Permeability Model ◽  
Minimum Diameter ◽  
Mechanics Of Materials ◽  
Proposed Model ◽  
Fractal Characteristics ◽  
Experimental Expression ◽  
Good Agreement

A permeability model for porous media considering the stress sensitivity is derived based on mechanics of materials and the fractal characteristics of solid cluster size distribution. The permeability of porous media considering the stress sensitivity is related to solid cluster fractal dimension, solid cluster fractal tortuosity dimension, solid cluster minimum diameter and solid cluster maximum diameter, Young's modulus, Poisson's ratio, as well as power index. Every parameter has clear physical meaning without the use of empirical constants. The model predictions of permeability show good agreement with those obtained by the available experimental expression. The proposed model may be conducible to a better understanding of the mechanism for flow in elastic porous media.

A stress sensitivity model for the permeability of porous media based on bi-dispersed fractal theory

2018 ◽  
Vol 29 (02) ◽  
pp. 1850019 ◽  
Author(s):  
X.-H. Tan ◽  
C.-Y. Liu ◽  
X.-P. Li ◽  
H.-Q. Wang ◽  
H. Deng
Keyword(s):  
Porous Media ◽  
Fractal Dimension ◽  
Fractal Theory ◽  
Stress Sensitivity ◽  
Maximum Diameter ◽  
Proposed Model ◽  
Fractal Parameters ◽  
Stress Changes ◽  
Capillary Bundle ◽  
Definition Of

A stress sensitivity model for the permeability of porous media based on bidispersed fractal theory is established, considering the change of the flow path, the fractal geometry approach and the mechanics of porous media. It is noted that the two fractal parameters of the porous media construction perform differently when the stress changes. The tortuosity fractal dimension of solid cluster [Formula: see text] become bigger with an increase of stress. However, the pore fractal dimension of solid cluster [Formula: see text] and capillary bundle [Formula: see text] remains the same with an increase of stress. The definition of normalized permeability is introduced for the analyzation of the impacts of stress sensitivity on permeability. The normalized permeability is related to solid cluster tortuosity dimension, pore fractal dimension, solid cluster maximum diameter, Young’s modulus and Poisson’s ratio. Every parameter has clear physical meaning without the use of empirical constants. Predictions of permeability of the model is accordant with the obtained experimental data. Thus, the proposed model can precisely depict the flow of fluid in porous media under stress.

A model for transient flow in porous media embedded with randomly distributed tree-shaped fractal networks

2015 ◽  
Vol 29 (19) ◽  
pp. 1550135 ◽  
Author(s):  
Xiao-Hua Tan ◽  
Xiao-Ping Li ◽  
Jian-Yi Liu ◽  
Lie-Hui Zhang ◽  
Jianchao Cai
Keyword(s):  
Porous Media ◽  
Transient Flow ◽  
Heterogeneous Porous Media ◽  
Flow In Porous Media ◽  
Inversion Method ◽  
Type Curves ◽  
Fractal Properties ◽  
Proposed Model ◽  
The Laplace Transform ◽  
Fractal Characteristics

A model for transient flow in porous media embedded with randomly distributed tree-shaped fractal networks was presented based on the fractal properties of tree-shaped capillaries and generalized Darcy's law. The dimensionless expression of flowing pressure was developed using the Laplace transform and Stehfest numerical inversion method. The bilogarithmic type curves were illustrated and the influences of different fractal factors on dimensionless flowing pressure were also discussed. The presented study indicated that the fractal characteristics for the tree-shaped fractal networks should be considered in analysis of transient flow in the heterogeneous porous media. The proposed model may be conducible to a better understanding of the mechanism for transient flow in the multi-porosity porous media.

FRACTAL ANALYSIS OF THE PENETRATION FLOW THROUGH MICRO-NANO POROUS GASKETS WITH EFFECTS OF SLIPPAGE AND STRESS-SENSITIVITY

Fractals ◽  
2019 ◽  
Vol 27 (03) ◽  
pp. 1950031
Author(s):  
XIAOMING HUANG ◽  
JIAWEI SUN ◽  
CHUNYU SHI ◽  
YANG DU ◽  
GUOLIANG XU
Keyword(s):  
Porous Media ◽  
Pore Size ◽  
Transport Theory ◽  
Stress Sensitivity ◽  
Sealing Material ◽  
Proposed Model ◽  
Slippage Effect ◽  
Flow Through ◽  
Gas Penetration ◽  
Flexible Graphite

The airtightness of non-metallic sealing structures undergoing harsh conditions is very crucial to the reliability of equipment in many industrial fields. In this study, the gas penetration through a non-metallic sealing material (NSM) with micro-nano porous structure under stress was investigated in detail based on the transport theory of fractal porous media. A complete theoretical model for predicting the stress sensitivity of the gasket permeability was developed, in which the slippage effect was of concern due to very fine pore size. The permeability of a flexible graphite gasket under different stresses was numerically predicted via scanning electron microscopy (SEM) and image processing. The influencing factors on the permeability of the NSM were analyzed quantitatively and good agreements with existing experimental results demonstrate the validity of the proposed model. Since the effects of the pore-size distribution and flow pattern regime were taken into account, the parameters of the model had a clear physical meaning and the model was suitable for determining the mechanism of penetration leakage through the NSM. In addition, the model could also be used for the analysis of other tight porous media with complex microstructure under stress deformation.

PERMEABILITY PREDICTION IN ROUGHENED FRACTURES UNDER STRESS CONDITION USING FRACTAL MODEL

Fractals ◽  
2019 ◽  
Vol 27 (03) ◽  
pp. 1950030 ◽  
Author(s):  
GANG LEI ◽  
NAI CAO ◽  
QINGZHI WEN
Keyword(s):  
Stress Condition ◽  
Fractal Model ◽  
Coupled Flow ◽  
Permeability Model ◽  
Microstructural Parameters ◽  
Rough Fracture ◽  
Proposed Model ◽  
Stress Dependent ◽  
Rock Lithology ◽  
Good Agreement

The prediction of permeability in rough fracture under stress condition presents ever more of a challenge in various scientific and engineering fields. However, up to now, the essential controls on stress-dependent permeability of rough fracture are not determined. In order to find a relationship between the microstructure and the permeability of rough fracture, an analytical method for the permeability of roughened fracture under stress condition is proposed based on the fractal model. The validity of the proposed model is obtained by the good agreement between the simulated results and the experimental data. Compared with the previous models, our model takes into account more factors, including the influence of the microstructural parameters of rough fracture and rock lithology. This paper presents that (1) the rock with soft lithology can yield smaller normalized permeability, (2) normalized permeability decreases with the increases of percent of smaller rough elements. The fractal permeability model can reveal more mechanisms that affect the coupled flow deformation behavior in the fractured porous media.

scholarly journals Examination of the fractal model for streaming potential coefficient in porous media

2019 ◽  
Vol 35 (1) ◽  
Author(s):  
Luong Duy Thanh
Keyword(s):  
Experimental Data ◽  
Porous Media ◽  
Zeta Potential ◽  
Streaming Potential ◽  
Fractal Model ◽  
Potential Coefficient ◽  
Proposed Model ◽  
Alternative Approach ◽  
High Fluid ◽  
Good Agreement

In this work, the fractal model for the streaming potential coefficient in porous media recently published has been examined by calculating the zeta potential from the measured streaming potential coefficient. Obtained values of the zeta potential are then compared with experimental data. Additionally, the variation of the streaming potential coefficient with fluid electrical conductivity is predicted from the model. The results show that the model predictions are in good agreement with the experimental data available in literature. The comparison between the proposed model and the Helmholtz-Smoluchowski (HS) equation is also carried out. It is seen that that the prediction from the proposed model is quite close to what is expected from the HS equation, in particularly at the high fluid conductivity or large grain diameters. Therefore, the model can be an alternative approach to obtain the zeta potential from the streaming potential measurements.

scholarly journals STRESS SENSITIVITY ANALYSIS OF FRACTAL POROUS MEDIA BASED ON THE ELASTO-PLASTIC THICK-WALLED CYLINDER MODEL

Fractals ◽  
2021 ◽  
Vol 29 (03) ◽  
pp. 2150162
Author(s):  
ZHAOQIN HUANG ◽  
XIN SU ◽  
YANCHAO LI ◽  
KAI ZHANG ◽  
JUN YAO
Keyword(s):  
Porous Media ◽  
Fractal Theory ◽  
Fractal Model ◽  
Stress Sensitivity ◽  
Proposed Model ◽  
Cylinder Model ◽  
Stress Cycles ◽  
Dependent Flow ◽  
Stress Dependent ◽  
Walled Cylinder

The stress-dependent flow and transport behaviors of porous media are ubiquitous in various scientific and engineering applications. It has been shown that the change of effective stress has important effects on the permeability and porosity of porous media. In this paper, a new stress sensitivity model for porous media is developed based on the fractal theory and the elasto-plastic thick-walled cylinder model. The proposed model is able to predict the elasto-plastic deformation of the fractal porous media under loading–unloading stress cycles, which plays a crucial role on the permanent variations of the permeability and porosity. It is found that the permeability of stress-sensitivity porous media is related to the capillary fractal dimension, capillary fractal tortuosity dimension, minimum and maximum capillary diameters, Young’s modulus and Poisson’s ratio of capillary. Each parameter has a clear physical meaning. The validity of the developed fractal model is verified by comparing the model predictions with the available experimental data.

scholarly journals Compact Modelling of Electrical, Optical and Thermal Properties of Multi-Colour Power LEDs Operating on a Common PCB

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1286
Author(s):  
Krzysztof Górecki ◽  
Przemysław Ptak
Keyword(s):  
Integrated Circuits ◽  
Optical Model ◽  
Printed Circuit Board ◽  
Circuit Board ◽  
Junction Temperature ◽  
Optical Parameters ◽  
Spice Simulation ◽  
Light Emitting ◽  
Proposed Model ◽  
Good Agreement

This paper concerns the problem of modelling electrical, thermal and optical properties of multi-colour power light-emitting diodes (LEDs) situated on a common PCB (Printed Circuit Board). A new form of electro-thermo-optical model of such power LEDs is proposed in the form of a subcircuit for SPICE (Simulation Program with Integrated Circuits Emphasis). With the use of this model, the currents and voltages of the considered devices, their junction temperature and selected radiometric parameters can be calculated, taking into account self-heating phenomena in each LED and mutual thermal couplings between each pair of the considered devices. The form of the formulated model is described, and a manner of parameter estimation is also proposed. The correctness and usefulness of the proposed model are verified experimentally for six power LEDs emitting light of different colours and mounted on an experimental PCB prepared by the producer of the investigated devices. Verification was performed for the investigated diodes operating alone and together. Good agreement between the results of measurements and computations was obtained. It was also proved that the main thermal and optical parameters of the investigated LEDs depend on a dominant wavelength of the emitted light.

Static and Dynamic Structure of Molecular Monomers and Dimers of the Rare-earth Fluorides

2001 ◽  
Vol 56 (5) ◽  
pp. 381-385
Author(s):  
Z. Akdeniz ◽  
M . Gaune-Escard ◽  
M. P. Tosi
Keyword(s):  
Rare Earth ◽  
Bond Length ◽  
Geometrical Structure ◽  
Vibrational Mode ◽  
Dynamic Structure ◽  
Molecular Shape ◽  
Proposed Model ◽  
Infrared Studies ◽  
Charged Clusters ◽  
Good Agreement

Abstract We determine a model of the ionic interactions in RF3 compounds, where R is a rare-earth element in the series from La to Lu, by an analysis of data on the bond length and the vibrational mode frequencies of the PrF3, GdF3 and HoF3 molecular monomers. All RF3 monomers are predicted to have a pyramidal shape, displaying a progressive flattening of the molecular shape in parallel with the lanthanide contraction of the bond length. The vibrational frequencies of all monomers are calculated, the results being in good agreement with the data from infrared studies of matrix-isolated molecules. We also evaluate the geometrical structure and the vibrational spectrum of the La2F6 and Ce2F6 dimers, as a further test of the proposed model. -PACS 36.40.Wa (Charged clusters)

scholarly journals Physiological potential of stylosanthes cv. Campo Grande seeds coated with different materials

2015 ◽  
Vol 37 (2) ◽  
pp. 117-124 ◽  
Author(s):  
Priscilla Brites Xavier ◽  
Henrique Duarte Vieira ◽  
Cynthia Pires Guimarães
Keyword(s):  
Activated Carbon ◽  
Calcium Silicate ◽  
Dry Matter ◽  
Seed Quality ◽  
Maximum Diameter ◽  
Minimum Diameter ◽  
Germination Time ◽  
Germination Speed ◽  
Mean Germination Time ◽  
Limestone Sand

The aim of this study was to assess the effect of different coatings on the physiological potential of stylosanthes cv. Campo Grande seeds. The treatments were: uncoated seeds; limestone + PVA glue; limestone + sand + PVA glue; limestone + activated carbon + PVA glue; calcium silicate + PVA glue; calcium silicate + sand + PVA glue; calcium silicate + activated carbon + PVA glue. Posteriorly, the seeds were analyzed for water content (WC), maximum diameter (MAD) and minimum diameter (MID), thousand seed weight (TSW), germination test, germination speed index (GSI), mean germination time (MGT), emergence, emergence speed index (ESI), mean emergence time (MET), shoot and root length, fresh and dry matter of shoot and root. The coating increased the TSW, MAD and MID and decreased its WC. The treatments comprising limestone + PVA glue and limestone + sand + PVA glue increased the germination time, but none of the treatments negatively affected the physiological seed quality. Treatment with calcium silicate + PVA glue was outstanding for germination speed index and fresh and dry matter of shoot and root in the stylosanthes cv. Campo Grande seeds coating.

Distribution of diaphragmatic lymphatic stomata

1991 ◽  
Vol 70 (4) ◽  
pp. 1544-1549 ◽  
Author(s):  
D. Negrini ◽  
S. Mukenge ◽  
M. Del Fabbro ◽  
C. Gonano ◽  
G. Miserocchi
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Surface Area ◽  
Frequency Distribution ◽  
Maximum Diameter ◽  
Minimum Diameter ◽  
Average Value ◽  
Scanning Electron

In seven anesthetized rabbits we measured the size, shape, and density of lymphatic stomata on the peritoneal and pleural sides of the diaphragm. The diaphragm was fixed in situ and processed for scanning electron microscopy. Results are from 2,902 peritoneal and 3,086 pleural fields (each 1,620 microns 2) randomly chosen from the various specimens. Stomata were seen in 9% of the fields examined, and in 30% of the cases they appeared grouped in clusters with 2-14 stomata/field. Stoma density was 250 +/- 242 and 72 +/- 57 (SD) stomata/mm2 on peritoneal and pleural sides, respectively, and it was similar over the muscular and tendinous portion of the two surfaces. The maximum diameter ranged from less than 1 to approximately 30 microns, with an average value of 1.2 +/- 3.1 micron. The ratio of the maximum to the minimum diameter and the surface area averaged 2 +/- 1.4 and 0.7 +/- 2.4 micron 2, respectively. The maximum and minimum diameter and surface area values followed a lognormal frequency distribution, suggesting that stomata geometry is affected by diaphragmatic tension.

Sign in / Sign up

Export Citation Format

Share Document