scholarly journals Progress in Experimental and Theoretical Evaluation Methods for Textile Permeability

2019 ◽  
Vol 3 (3) ◽  
pp. 73 ◽  
Author(s):  
Mohamad Karaki ◽  
Rafic Younes ◽  
Francois Trochu ◽  
Pascal Lafon
Keyword(s):  
Numerical Simulation ◽  
Analytical Methods ◽  
Measurement Techniques ◽  
Analytical Models ◽  
Theoretical Evaluation ◽  
Unidirectional Fiber ◽  
Simulation Tools ◽  
Performance Preparation ◽  
Personal Performance ◽  
Methods Numerical

A great amount of attention has been given to the evaluation of the permeability tensor and several methods have been implemented for this purpose: experimental methods, as well as numerical and analytical methods. Numerical simulation tools are being seriously developed to cover the evaluation of permeability. However, the results are still far from matching reality. On the other hand, many problems still intervene in the experimental measurement of permeability, since it depends on several parameters including personal performance, preparation of specimens, equipment accuracy, and measurement techniques. Errors encountered in these parameters may explain why inconsistent measurements are obtained which result in unreliable experimental evaluation of permeability. However, good progress was done in the second international Benchmark, wherein a method to measure the in-plane permeability was agreed on by 12 institutes and universities. Critical researchers’ work was done in the field of analytical methods, and thus different empirical and analytical models have emerged, but most of those models need to be improved. Some of which are based on Cozeny-Karman equation. Others depend on numerical simulation or experiment to predict the macroscopic permeability. Also, the modeling of permeability of unidirectional fiber beds have taken the greater load of concern, whereas that of fiber bundle permeability prediction remain limited. This paper presents a review on available methods for evaluating unidirectional fiber bundles and engineering fabric permeability. The progress of each method is shown in order to clear things up.

Numerical simulation and experimental investigation of multiphase mass transfer process for industrial applications in China

2019 ◽  
Vol 36 (1) ◽  
pp. 187-214
Author(s):  
Chao Yang ◽  
Guangsheng Luo ◽  
Xigang Yuan ◽  
Jie Chen ◽  
Yangcheng Lu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Transfer Process ◽  
Transport Phenomena ◽  
Measurement Techniques ◽  
Mass Transfer Process ◽  
Industrial Applications ◽  
Economic Benefits ◽  
Distillation Columns ◽  
Stirred Reactors

Abstract This paper presents a comprehensive review of the remarkable achievements by Chinese scientists and engineers who have contributed to the multiscale process design, with emphasis on the transport mechanisms in stirred reactors, extractors, and rectification columns. After a brief review of the classical theory of transport phenomena, this paper summarizes the domestic developments regarding the relevant experiments and numerical techniques for the interphase mass transfer on the drop/bubble scale and the micromixing in the single-phase or multiphase stirred tanks in China. To improve the design and scale-up of liquid-liquid extraction columns, new measurement techniques with the combination of both particle image velocimetry and computational fluid dynamics have been developed and advanced modeling methods have been used to determine the axial mixing and mass transfer performance in extraction columns. Detailed investigations on the mass transfer process in distillation columns are also summarized. The numerical and experimental approaches modeling transport phenomena at the vicinity of the vapor-liquid interface, the point efficiency for trays/packings regarding the mixing behavior of fluids, and the computational mass transfer approach for the simulation of distillation columns are thoroughly analyzed. Recent industrial applications of mathematical models, numerical simulation, and experimental methods for the design and analysis of multiphase stirred reactors/crystallizers, extractors, and distillation columns are seen to garnish economic benefits. The current problems and future prospects are pinpointed at last.

Effect of Solar Brightness Profiles on the Performance of Parabolic Concentrating Collectors

2009 ◽  
Author(s):  
Daniel J. Chapman ◽  
Diego A. Arias
Keyword(s):  
Analytical Methods ◽  
Meteorological Data ◽  
Uncertainty Propagation ◽  
Gaussian Function ◽  
Analytical Models ◽  
The Sun ◽  
Solar Concentrator ◽  
Optical Performance ◽  
Optical Surface ◽  
Solar Brightness

Solar brightness profiles were used to model the optical performance of a parabolic linear solar concentrator. A sensitivity analysis of the sun size on collector performance was completed using analytical methods. Ray traces were created for solar brightness profiles having circumsolar ratios from 0–40%, slope errors of the optical surface from 2–5 mrads, and angles of incidence varying from 0–60 degrees. Using typical meteorological data for two locations, the optical performance was calculated and averaged over a year. Intercept factors of these simulations were compared to simpler analytical models that cast the sun shape as a Gaussian function. Results showed that collector performance is relatively insensitive to solar profile, and that using a representative Gaussian solar profile will tend to underestimate collector performance compared to using exact weighted solar profiles by about 1%. This difference is within the uncertainty propagation of the intercept factor calculated with analytical methods.

scholarly journals A review of methods for addressing components of interventions in meta-analysis

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0246631
Author(s):  
Maria Petropoulou ◽  
Orestis Efthimiou ◽  
Gerta Rücker ◽  
Guido Schwarzer ◽  
Toshi A. Furukawa ◽  
...  
Keyword(s):  
Panic Disorder ◽  
Analytical Methods ◽  
Meta Analysis ◽  
Complex Interventions ◽  
Software Tools ◽  
Analytical Models ◽  
New Developments ◽  
Healthcare Interventions ◽  
Multicomponent Interventions ◽  
Interacting Components

Many healthcare interventions are complex, consisting of multiple, possibly interacting, components. Several methodological articles addressing complex interventions in the meta-analytical context have been published. We hereby provide an overview of methods used to evaluate the effects of complex interventions with meta-analytical models. We summarized the methodology, highlighted new developments, and described the benefits, drawbacks, and potential challenges of each identified method. We expect meta-analytical methods focusing on components of several multicomponent interventions to become increasingly popular due to recently developed, easy-to-use, software tools that can be used to conduct the relevant analyses. The different meta-analytical methods are illustrated through two examples comparing psychotherapies for panic disorder.

scholarly journals Numerical simulation of minor losses coefficient on the example of elbows

2018 ◽  
Vol 180 ◽  
pp. 02093
Author(s):  
Smyk Emil ◽  
Mrozik Dariusz ◽  
Olszewski Łukasz ◽  
Peszyński Kazimierz
Keyword(s):  
Numerical Simulation ◽  
Numerical Methods ◽  
Numerical Method ◽  
Cross Section ◽  
Analytical Methods ◽  
Circular Cross Section ◽  
Experimental Methods ◽  
Loss Coefficient ◽  
Complicated Problem ◽  
Minor Losses

Determining of minor losses coefficient is very complicated problem. Analytical methods are often very difficult and experimental methods are very expensive and time-consuming. Consequently, the use of numerical methods seems to be a good solution, but there are no publications describing this issue. Therefore, the paper is describing the numerical method of determining the minor loss coefficient ξ on the example of elbows with circular cross-section.

A Comparative Analysis of Thermal Blood Perfusion Measurement Techniques

1987 ◽  
Vol 109 (3) ◽  
pp. 218-225 ◽  
Author(s):  
R. Kress ◽  
R. Roemer
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Time Window ◽  
Measurement Techniques ◽  
Temperature Response ◽  
Blood Perfusion ◽  
Analytical Models ◽  
Transient Temperature ◽  
Two Dimensional ◽  
Transient Heating

The object of this study was to devise a unified method for comparing different thermal techniques for the estimation of blood perfusion rates and to perform a comparison for several common techniques. The approach used was to develop analytical models for the temperature response for all combinations of five power deposition geometries (spherical, one- and two-dimensional cylindrical, and one- and two-dimensional Gaussian) and three transient heating techniques (temperature pulse-decay, temperature step function, and constant-power heat-up) plus one steady-state heating technique. The transient models were used to determine the range of times (the time window) when a significant portion of the transient temperature response was due to blood perfusion. This time window was defined to begin when the difference between the conduction-only and the conduction-plus-blood flow transient temperature (or power) responses exceeded a specified value, and to end when the conduction-plus-blood flow transient temperature (or power) reached a specified fraction of its steady-state value. The results are summarized in dimensionless plots showing the size of the time windows for each of the transient perfusion estimation techniques. Several conclusions were drawn, in particular: (a) low perfusions are difficult to estimate because of the dominance of conduction, (b) large heated regions are better suited for estimation of low perfusions, (c) noninvasive heating techniques are superior because they have the potential to minimize conduction effects, and (d) none of the transient techniques appears to be clearly superior to the others.

A Geomechanical Evaluation of Fault Reactivation Using Analytical Methods and Numerical Simulation

2020 ◽  
Author(s):  
Majid Taghipour ◽  
Mohammad Ghafoori ◽  
Gholam Reza Lashkaripour ◽  
Nasser Hafezi Moghaddas ◽  
Abdullah Molaghab
Keyword(s):  
Numerical Simulation ◽  
Analytical Methods ◽  
Fault Reactivation

scholarly journals Modelling of textile composite reinforcements on the micro-scale

2014 ◽  
Vol 14 (1) ◽  
pp. 28-33 ◽  
Author(s):  
Oliver Döbrich ◽  
Thomas Gereke ◽  
Chokri Cherif
Keyword(s):  
Numerical Simulation ◽  
Finite Element Analysis ◽  
Computational Cost ◽  
Textile Composite ◽  
Element Analysis ◽  
Simulation Tools ◽  
Micro Scale ◽  
Generating Method ◽  
Geometrical Effects ◽  
Composite Reinforcements

Abstract Numerical simulation tools are increasingly used for developing novel composites and composite reinforcements. The aim of this paper is the application of digital elements for the simulation of the mechanical behaviour of textile reinforcement structures by means of a finite element analysis. The beneficial computational cost of these elements makes them applicable for the use in large models with a solution on near micro-scale. The representation of multifilament yarn models by a large number of element-chains is highly suitable for the analysis of structural and geometrical effects. In this paper, a unit cell generating method for technical reinforcement textiles, using digital elements for the discretization, is introduced.

Analytical Computational Models for Relationship between Ultimate Bending Moment of Concrete Segments and Axial Force

2020 ◽  
Vol 853 ◽  
pp. 177-181
Author(s):  
Zhi Yun Wang ◽  
Shou Ju Li
Keyword(s):  
Numerical Simulation ◽  
Computational Model ◽  
Axial Force ◽  
Computational Models ◽  
Plane Deformation ◽  
Bending Moment ◽  
Analytical Models ◽  
Bending Moments ◽  
Axial Forces ◽  
Practical Engineering

Concrete segments are widely used to support soil and water loadings in shield-excavated tunnels. Concrete segments burden simultaneously to the loadings of bending moments and axial forces. Based on plane deformation assumption of material mechanics, in which plane section before bending remains plane after bending, ultimate bending moment model is proposed to compute ultimate bearing capacity of concrete segments. Ultimate bending moments of concrete segments computed by analytical models agree well with numerical simulation results by FEM. The accuracy of proposed analytical computational model for ultimate bending moment of concrete segments is numerically verified. The analytical computational model and numerical simulation for a practical engineering case indicate that the ultimate bending moment of concrete segments increases with increase of axial force on concrete segment in the case of large eccentricity compressive state.

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