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Understanding the fluid flow through rock masses, which commonly consist of rock matrix and fractures, is a fundamental issue in many application areas of rock engineering. As the equivalent porous medium approach is the dominant approach for engineering applications, it is of great significance to estimate the equivalent permeability tensor of rock masses. This study aims to develop a novel numerical approach to estimate the equivalent permeability tensor for fractured porous rock masses.

The radial point interpolation method (RPIM) and finite element method (FEM) are coupled to simulate the seepage flow in fractured porous rock masses. The rock matrix is modeled by the RPIM, and the fractures are modeled explicitly by the FEM. A procedure for numerical experiments is then designed to determinate the equivalent permeability tensor directly on the basis of Darcy’s law.

The coupled RPIM-FEM method is a reliable numerical method to analyze the seepage flow in fractured porous rock masses, which can consider simultaneously the influences of fractures and rock matrix. As the meshes of rock matrix and fracture network are generated separately without considering the topology relationship between them, the mesh generation process can be greatly facilitated. Using the proposed procedure for numerical experiments, which is designed directly on the basis of Darcy’s law, the representative elementary volume and equivalent permeability tensor of fractured porous rock masses can be identified conveniently.

A novel numerical approach to estimate the equivalent permeability tensor for fractured porous rock masses is proposed. In the approach, the RPIM and FEM are coupled to simulate the seepage flow in fractured porous rock masses, and then a numerical experiment procedure directly based on Darcy’s law is introduced to estimate the equivalent permeability tensor.

The purpose of this paper is to investigate the evolution of the permeability of spherical packing during cold compaction by pore-scale modeling.

The discrete element method (DEM) is used to generate spherical packing structure under different compressive pressures and the Lattice Boltzmann method (LBM) is adopted to calculate the permeability of each spherical assembly.

It is found that the decrease of the porosity is the main reason of the reduction in permeability in the initial compression stage, but its influence becomes insufficient in the late compression stages. Besides, two empirical formulas are obtained, which describe the relation between the permeability and the equivalent mean diameter and the variation of normalized permeability with compressive pressure, respectively.

In this study, the authors study the spherical particles and ignore the non-spherical effects. Besides, the classical contact model, the linear-spring-damping model, is used in DEM, so the plastic deformation cannot be considered.

The DEM and the LBM are well combined to study the compaction effects on permeability of spherical packing. Two simple expressions of the spherical packing structure with uniform diameter distribution are given for the first time.

Gas permeability through damage networks in composite laminates is the key issue for the applicability of high‐performance composites to the cryogenic propellant tanks of space launch vehicles. A simple model for the gas permeability induced by multilayer matrix cracks in composite laminates is proposed based on the leak conductance at crack intersections, which is an extension of the model by Kumazawa et al (AIAA J. 41, 2037‐ ‐2044, 2003). Experimental evidence on the gas permeability mechanisms is summarized and reflected in the present model. In order to include the effects of applied loadings and damage sizes on the gas permeability, the leak conductance is assumed to be a function of the average crack opening displacements of the matrix cracks and the crack intersection angles. The leak conductance factor was empirically obtained as a function of the crack intersection angle, and the comparison of the gas permeability between the predictions based on the developed model and the experimental results is presented for the validity of this model.

This research study aims to develop regular cylindrical pore network models (RCPNMs) to calculate topology and geometry properties of explosively created fractures along with their resulting hydraulic permeability. The focus of the investigation is to define a method that generates a valid geometric and topologic representation from a computational modelling point of view for explosion-generated fractures in rocks. In particular, extraction of geometries from experimentally validated Eulerian smoothed particle hydrodynamics (ESPH) approach, to avoid restrictions for image-based computational methods.

Three-dimensional stabilized ESPH solution is required to model explosively created fracture networks, and the accuracy of developed ESPH is qualitatively and quantitatively examined against experimental observations for both peak detonation pressures and crack density estimations. SPH simulation domain is segmented to void and solid spaces using a graphical user interface, and the void space of blasted rocks is represented by a regular lattice of spherical pores connected by cylindrical throats. Results produced by the RCPNMs are compared to three pore network extraction algorithms. Thereby, once the accuracy of RCPNMs is confirmed, the absolute permeability of fracture networks is calculated.

The results obtained with RCPNMs method were compared with three pore network extraction algorithms and computational fluid dynamics method, achieving a more computational efficiency regarding to CPU cost and a better geometry and topology relationship identification, in all the cases studied. Furthermore, a reliable topology data that does not have image-based pore network limitations, and the effect of topological disorder on the computed absolute permeability is minor. However, further research is necessary to improve the interpretation of real pore systems for explosively created fracture networks.

Although only laboratory cylindrical rock specimens were tested in the computational examples, the developed approaches are applicable for field scale and complex pore network grids with arbitrary shapes.

It is often desirable to develop an integrated computational method for hydraulic conductivity of explosively created fracture networks which segmentation of fracture networks is not restricted to X-ray images, particularly when topologic and geometric modellings are the crucial parts. This research study provides insight to the reliable computational methods and pore network extraction algorithm selection processes, as well as defining a practical framework for generating reliable topological and geometrical data in a Eulerian SPH setting.

Parity of esteem between general and vocational education is a widely discussed topic in those countries which have established a system of vocational education and training (VET) beside the system of general education, leading to numerous qualifications and licenses. This paper aims to address this issue.

An explorative consideration of curricular basic structures of TVET and higher education will reveal the qualitative differences in the different study courses and entailing barriers for permeability between TVET and higher education. A deepening analysis compares the curricular structures and evaluates the differences with the aid of selected criteria.

The article clarifies the hidden obstacles of permeability between vocational and higher education, and points out ways to shape lateral and vertical permeability with a view to career paths to build up human capabilities. However, until now most of these do not entail permeability to learning pathways in higher education. This is especially true when vocational programmes do not prepare for higher education at the same time, i.e. do not include a university entrance qualification. This discussion has gained a new momentum with the adoption of the European Qualifications Framework by the European Parliament and the Council in 2008, motivating member states to reconsider this context. Since then there is an intensive debate about opening universities for learners with vocational qualifications.

Due to the traditionally clear‐cut division between vocational and academic education and a separate dealing with the different concepts, organizations and institutions, a comparative research with methods and instruments has not yet developed. With regard to a comparison of vocational and academic education, research is still at the very beginning. There are currently no confirmed reliable answers to the question how the transitions between vocational and academic education could be shaped in order to ensure their success.

European initiatives and the implementation of instruments such as the Qualifications Framework to support permeability call for ways to offer academic education with degrees to persons with a qualified vocational background. The curricular structures of the universities are currently not geared to these requirements.

The relevant social dimension aims at an equivalence of vocational and academic education that has been discussed in some European countries since the 1960s. Some European initiatives (EQF, ECVET, etc) over recent years have led to the opening of universities for persons with a qualified vocational background. This helps to overcome social barriers.

The value added is a frame for comparison of curricular structures. The findings can then be thoroughly discussed in connection with the European Qualification Framework. In addition the article offers options for overcoming the obstacles for comparative research on vocational and academically qualified persons.

The purpose of this paper is to evaluate the air permeability of knitted fabrics containing elastane fibre and their seams applying both the new approach based on fabric thickness measurement at different pressures and standard method.

Investigations were performed with commercially available eight polyester knitted fabrics containing different elastane yarn proportion. Bonded seams were laminated applying the urethane thermoplastic adhesive film of 0.175 mm thickness. Bonds were laminated by heat at 5.6 kPa pressure applying pressing device GTK DEA 25 R at 140°C temperature for 40 s duration. Sewn seams were assembled with 607 covering chain stitch applying 5.0 stitches per cm density and 512 overedge chain stitch applying 5.0 stitches per cm density. Specimens without and with the seams were conditioned in standard atmosphere conditions according to the standard LST EN ISO 139 before air permeability testing according to the standard LST EN ISO 9237. Standard thickness of the investigated knitted fabric was determined according to the standard EN ISO 5084. It is known from literature that the porosity is dominant factor influencing the air permeability of knitted fabrics. Therefore, the assumption was made that due to fabric porosity knitted fabric thickness being measured at different pressures also may differ. Thus, the permeability property may also be related to the difference between fabric’s thicknesses being measured under different pressures which may be applied with different material thickness gauges.

There was shown that fabric assemblies make the significant influence on the textile permeability to air. The results obtained indicate that the air permeability of the investigated knitted fabrics depends not only on their structure parameters but also on the fabric seam type. Air permeability of the specimens with the seams was lower than one of specimens without the seams. The highest decrease in permeability which ranged from 19.9 per cent up to 60.0 per cent was determined for the bonds. Fabric specimens with 607 covering chain stitch seam were in the second place with regard to the previously considered parameter. And, their permeability was decreased from 0.6 per cent up to 52.6 per cent. Changes in the air permeability of the specimens with 512 overedge chain stitch seam were lowest in the range of investigated assemblies. Based on the determined results, it was concluded that the thickness difference of the specimens with and without seams measured at different pressures is related to fabric porosity which makes the significant influence on the air permeability.

The samples of investigated fabrics were taken from the two companies which manufactures leisure clothing and sportswear such as skiing or swimming costumes, etc. Thus, the obtained investigation results are significant not only for clothing science but also leads the improvement of clothing quality in fashion industry.

Assuring the comfort of the human body is one of the most important functions of clothing, especially of sportswear and leisure wear. Knitted fabrics should not only be elastic, but also have high air permeability for easily transmit of the perspiration from the skin to the atmosphere, thus making the wearer to feel comfortable. In this research, the air permeability of commercially available polyester knitted fabrics containing different amount of elastane was investigated and the influence of fabric assemblies on the air permeability property was evaluated. A new approach based on the fabric thickness measurement at different pressures and the standard methods for the evaluation of air permeability were used.

The objective of this paper is to provide a better understanding of the effect of irregular columnar jointed structure on the permeability and flow characteristics of rock masses.

An efficient numerical procedure is proposed to investigate the permeability and fluid flow in columnar jointed rock masses (CJRMs), of which the columnar jointed networks are generated by a modified constrained centroid Voronoi algorithm according to the field statistical results. The fractures are represented explicitly by using the lower-dimensional zero thickness elements. And the modeling scheme is validated by a benchmark test for flow in fractured porous media. The effective permeability and representative elementary volume (REV) size of CJRMs are estimated using finite element method (FEM). The influences of joint density and variation coefficient of columnar joint structure on the permeability of the rock mass are discussed.

The simulation results indicate that the permeability is scale-dependent and tends to be stable with increase of model size. The hydraulic REV size is determined as 3.5 m for CJRMs in the present study. Moreover, the joint density is a dominant factor affecting the permeability of CJRMs. The average permeability of columnar jointed structures increases linearly with the joint density under the same REV size, while the influence from the coefficient of variation can be neglected.

The present paper investigates the REV size of the CJRMs and the effect of joint parameters on the permeability. The proposed method and the results obtained are useful on understanding the hydraulic characteristic of the irregular CJRMs in engineering projects.

Air permeability of knitted fabrics is normally measured for the samples in their unstretched state. But, this air permeability values indicate the ability of these garments to allow air through them when they are not in use. But, the real-time condition is different and certainly the knitted garments mentioned above will subject to a degree of stretch during their usage. So, the measurement of air permeability under stretch and the fabric properties which would influence the air permeability of weft-knitted fabrics in their stretched state is of paramount importance. The paper aims to discuss these issues.

The aim of this research work is to investigate the change in air permeability values under the incremental extension of cotton tubular weft-knitted fabrics produced from the yarns of different spinning systems.

From the results, it is evident that the pique fabric samples of compact spun yarn displayed the highest air permeability values during the incremental stretch at all the three relaxation states. It is followed by the pique samples of ring spun yarn. Next to pique samples, the jersey samples made from the compact yarn and ring spun yarn revealed more air permeability, respectively. The core spun pique samples and core spun jersey samples displayed the least air permeability values, respectively. But, the pique and jersey samples made up of ring yarn and compact yarn showed gradual reduction in their air permeability towards the incremental stretch and the core spun pique samples and core spun jersey samples were uniformly seen with gradual increase in their air permeability during the incremental stretch.

Very limited quantity of research has been carried out in this area. So, a novel attempt has been made in this research work to investigate the influence of incremental stretch on air permeability of single knit structures.

Parachutes are equipment that is repeatedly used as and when needed. Some of them are used for as many as 60 jumps. The property of the canopy fabric gets deteriorated with use. It is evaluated by destructive tensile and bursting strength. This study aims to focus on the nondestructive evaluation of the canopy fabric's fitness by testing air permeability and relating it with bursting strength. Predictor equations were developed to determine bursting strength from air permeability values.

ANOVA techniques and statistical regression equations were formed.

A series of samples containing five parachutes fabrics was used seven times, and their air permeability and bursting strength were determined to find the extent to the effect of reuse of parachute fabrics on their bursting strength and air permeability determination. It was found that there was a progressive drop in bursting strength and an increase in air permeability. An investigation of the extent of determination in terms of bursting strength and an increase in air permeability following the sense of five different types of parachute fabrics is reported.

The work focuses on the prediction of bursting strength to textile materials only and may not apply to other materials like membranes and sheets. The process of determining air permeability is relatively simpler and faster.

The bursting strength can be predicted for used parachutes, which are otherwise subjected to destructive testing.

The men using the parachutes can be assured of the superior flawless performance of the parachute as equipment and also contribute to the saving of resources due to nondestructive testing, 100% evaluation of all parachutes is possible.

This article describes the nature of the test procedure and discusses the means of introducing it to users of parachutes. It is accepted that the method must undergo field evaluation and possible modification before it can become a routine tool of parachute using organizations.

The purpose of this paper is to form a numerical simulation method for permeability coefficient that can consider the characteristics of gravel gradation and further explore the effects of indoor test factors and gradation characteristics on the permeability coefficient of gravel.

The random point method is used to establish the polyhedral gravel particle model, the discrete element method (DEM) is used to construct the gravel permeability test sample with gradation characteristics and the finite element method is used to calculate the permeability coefficient to form a DEM-computational fluid dynamics combined method to simulate the gravel seepage characteristics. Then, verified by the indoor test results. Based on this method, the influence of sample size, treatment method of oversize particles and the content of fine particles on the permeability coefficient of gravel is studied.

For the gravel containing large particles, the larger size permeameter should be used as far as possible. When the permeameter size is limited, the equal weight substitution method is recommended for the treatment method of oversized particles. Compared with the porosity, the pore connectivity has a higher correlation with the permeability coefficient of the sample.

Insufficient consideration of the movement of gravel particles in the seepage process is also an issue for further study.

The simulation method described in this paper is helpful for qualitative analysis, quantitative expression of pore size and makes up for the defect that the seepage characteristics in pores cannot be observed in laboratory tests.