Through-thickness permeability of woven fabric under increasing air pressure: Theoretical framework and simulation

2016 ◽  
Vol 87 (13) ◽  
pp. 1631-1642 ◽  
Author(s):  
Xueliang Xiao ◽  
Andrew Long ◽  
Kun Qian ◽  
Xuesen Zeng ◽  
Tao Hua
Keyword(s):  
Analytical Model ◽  
Cfd Simulation ◽  
Cell Model ◽  
Rectangular Cross Section ◽  
Air Flow ◽  
Sensitivity Study ◽  
Unit Cell ◽  
Air Pressure ◽  
Woven Fabric ◽  
Duct Wall

Many technical applications of woven fabric are subject to increasing high pressure from air transport through the fabric. The through-thickness permeability (TP) of woven materials exhibits a dynamic response to increased air pressure. This paper presents an analytical model for predicting the steady TP of woven fabric. The approach was based on Darcy’s law and the Poiseuille equation, using the flow boundary of an idealized plain-weave unit cell. The unit cell model consists of a gradual converging-diverging (GCD) duct with a rectangular cross-section. Further, the dynamic TP of the GCD duct was established analytically as a function of increasing pressure, which correlates to the separation of air flow from the GCD duct wall. Air flow separation from the duct wall led to a quadratic relationship between the increasing pressure and air flow velocities. This dynamic TP and air flow nonlinearity were simulated numerically in the computational fluid dynamics solver CFX. Five GCD ducts under increasing air pressure were analyzed numerically and analytically. The comparison showed good agreement between the proposed analytical model and the CFD simulation, with a maximum error up to 12%. A sensitivity study showed that an increase in porosity or a decrease in the thickness of weave materials could result in a larger dynamic TP value.

An Intelligent Prediction System for Tensile Damage of Woven Fabric Based on Geometrical Modeling

2013 ◽  
Vol 339 ◽  
pp. 670-676
Author(s):  
Jeng Jong Lin
Keyword(s):  
Geometric Modeling ◽  
Cell Model ◽  
Tensile Load ◽  
Unit Cell ◽  
Woven Fabric ◽  
Prediction System ◽  
Surface Shear ◽  
Plain Weave ◽  
Modeling Approach ◽  
Static Conditions

An intelligent prediction system theory-based on geometric modeling is developed in the study. The damage behaviors of woven fabric can be predicted by using the developed prediction system, which is theory-based on finite element analyses (FEAs) approach. A unit cell model based on slice array model (SAM) for plain weave fabric is employed to predict the elastic properties. An unit cell is divided into slices either along or across the loading direction in the SAM to predict the mechanical properties of the fabric. The results show the geometric modeling approach based on SAM is pretty promising in predicting the mechanic properties (e.g., initial Young's modulus, surface shear modulus and Poisson's ratio) of the woven fabric. In the experimental approach, the damage behaviors of plain weave woven fabric are tested under quasi-static conditions and the tensile load-displacement curves of the fabric are obtained and the damage morphologies are also observed. The design of composite can become easier and more efficient by using geometric modeling approach to predict the probable damage due to tensile given to the woven fabric as such an enhancement material.

scholarly journals Unit Cell Model of Woven Fabric Textile Composite for Multiscale Analysis

2013 ◽  
Vol 68 ◽  
pp. 352-358 ◽  
Author(s):  
Anurag Dixit ◽  
Harlal Singh Mali ◽  
R.K. Misra
Keyword(s):  
Multiscale Analysis ◽  
Cell Model ◽  
Unit Cell ◽  
Woven Fabric ◽  
Unit Cell Model ◽  
Textile Composite

Large Deformation Modelling of Tight Woven Fabric under High Air Pressure

2015 ◽  
Vol 10 (1) ◽  
pp. 155892501501000
Author(s):  
Xueliang Xiao ◽  
Andrew Long ◽  
Hua Lin ◽  
Xuesen Zeng
Keyword(s):  
Plane Deformation ◽  
Sensitivity Study ◽  
Air Pressure ◽  
Woven Fabric ◽  
Maximum Displacement ◽  
External Work ◽  
Technical Textiles ◽  
Out Of Plane ◽  
Fabric Deformation ◽  
Work Done

Technical textiles used in airbag are usually in tight structure and subject to high air pressure in through-thickness direction. The pressure can deform fabric with changing its properties such as porosity and air permeability. This paper proposes an analytical approach to predict the out-of-plane deformation of tight fabric by analogy with membrane deformation. The model integrates the energies happened on the deformed fabric, that is, fabric strain energy, bending energy, and external work done. The fabric deformation can be predicted by minimizing the total fabric energy. The prediction was validated by experiment for fabric profile and the maximum displacement, and a good agreement was found for the cases of two typical fabrics. A sensitivity study shows that Young's modulus and Poisson's ratio can affect the fabric deformation significantly.

Microscale Permeability Predictions of Porous Fibrous Media

1999 ◽  
Author(s):  
Nam D. Ngo ◽  
Kumar K. Tamma
Keyword(s):  
Cell Model ◽  
Three Dimensional ◽  
Unit Cell ◽  
Woven Fabric ◽  
Fiber Preform ◽  
Fibrous Media ◽  
Design And Optimization ◽  
Realistic Representation ◽  
Brinkman’S Equation ◽  
Fabric Structures

Abstract A good understanding of woven fiber preform permeabilities is critical in the design and optimization of the composite molding processes, yet these issues remain unresolved in the literature. Many have attempted to address permeability predictions for flat undeformed fiber preform, but few have investigated permeability variations for complex three-dimensional molds. In this study, the objectives are to: (i) first provide a brief review of existing methods for the prediction of the fiber mat permeability; (ii) postulate a more realistic representation of a unit cell to account for such fabric structures as crimp, tow spacing and the like; and (iii) apply computational approximations for predicting effective permeabilities for use in the modeling of structural composites processes. The Stokes equation is used to model the flow in the inter-tow region of the unit cell, and in the intra-tow region, the Brinkman’s equation is used. Preliminary permeability prediction calculations are performed for a three-dimensional unit cell model representative of PET 61 woven fabric. The results showed good agreement with experimental data published in literature.

scholarly journals Model of thermal buoyancy in cavity-ventilated roof constructions

2021 ◽  
pp. 174425912098418
Author(s):  
Toivo Säwén ◽  
Martina Stockhaus ◽  
Carl-Eric Hagentoft ◽  
Nora Schjøth Bunkholt ◽  
Paula Wahlgren
Keyword(s):  
Analytical Model ◽  
Flow Rate ◽  
Numerical Study ◽  
Air Flow ◽  
Wind Pressure ◽  
Air Flow Rate ◽  
Test Set ◽  
Air Cavity ◽  
Thermal Buoyancy ◽  
The Impact

Timber roof constructions are commonly ventilated through an air cavity beneath the roof sheathing in order to remove heat and moisture from the construction. The driving forces for this ventilation are wind pressure and thermal buoyancy. The wind driven ventilation has been studied extensively, while models for predicting buoyant flow are less developed. In the present study, a novel analytical model is presented to predict the air flow caused by thermal buoyancy in a ventilated roof construction. The model provides means to calculate the cavity Rayleigh number for the roof construction, which is then correlated with the air flow rate. The model predictions are compared to the results of an experimental and a numerical study examining the effect of different cavity designs and inclinations on the air flow rate in a ventilated roof subjected to varying heat loads. Over 80 different test set-ups, the analytical model was found to replicate both experimental and numerical results within an acceptable margin. The effect of an increased total roof height, air cavity height and solar heat load for a given construction is an increased air flow rate through the air cavity. On average, the analytical model predicts a 3% higher air flow rate than found in the numerical study, and a 20% lower air flow rate than found in the experimental study, for comparable test set-ups. The model provided can be used to predict the air flow rate in cavities of varying design, and to quantify the impact of suggested roof design changes. The result can be used as a basis for estimating the moisture safety of a roof construction.

scholarly journals Thermo-Viscoelastic Response of 3D Braided Composites Based on a Novel FsMsFE Method

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 271
Author(s):  
Jun-Jun Zhai ◽  
Xiang-Xia Kong ◽  
Lu-Chen Wang
Keyword(s):  
Finite Element ◽  
Cell Model ◽  
Structural Parameters ◽  
Thermal Relaxation ◽  
Viscoelastic Behavior ◽  
Unit Cell ◽  
Time Dependent ◽  
3D Braided Composites ◽  
Equivalent Time ◽  
Representative Unit Cell

A homogenization-based five-step multi-scale finite element (FsMsFE) simulation framework is developed to describe the time-temperature-dependent viscoelastic behavior of 3D braided four-directional composites. The current analysis was performed via three-scale finite element models, the fiber/matrix (microscopic) representative unit cell (RUC) model, the yarn/matrix (mesoscopic) representative unit cell model, and the macroscopic solid model with homogeneous property. Coupling the time-temperature equivalence principle, multi-phase finite element approach, Laplace transformation and Prony series fitting technology, the character of the stress relaxation behaviors at three scales subject to variation in temperature is investigated, and the equivalent time-dependent thermal expansion coefficients (TTEC), the equivalent time-dependent thermal relaxation modulus (TTRM) under micro-scale and meso-scale were predicted. Furthermore, the impacts of temperature, structural parameters and relaxation time on the time-dependent thermo-viscoelastic properties of 3D braided four-directional composites were studied.

scholarly journals Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Dillon Alexander Wilson ◽  
Kul Pun ◽  
Poo Balan Ganesan ◽  
Faik Hamad
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Bubble Diameter ◽  
Diameter Ratio ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Flow Rates ◽  
Throat Diameter

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

scholarly journals Extension of Pin-Based Point-Wise Energy Slowing-Down Method for VHTR Fuel with Double Heterogeneity

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2179
Author(s):  
Tae-Young Han ◽  
Jin-Young Cho ◽  
Chang-Keun Jo ◽  
Hyun-Chul Lee
Keyword(s):  
Cross Sections ◽  
Cell Model ◽  
Unit Cell ◽  
Moderation Effect ◽  
Slowing Down ◽  
Matrix Layer ◽  
The Mean ◽  
Dancoff Factor ◽  
Double Heterogeneity ◽  
Very High

For the resonance treatment of a very high temperature reactors (VHTR) fuel with the double heterogeneity, an extension of the pin-based pointwise energy slowing-down method (PSM) was developed and implemented into DeCART. The proposed method, PSM-double heterogeneity (DH), has an improved spherical unit cell model with an explicit tri-structural isotropic (TRISO) model, a matrix layer, and a moderator for reflecting the moderation effect. The moderator volume was analytically derived using the relation of the Dancoff factor and the mean chord length. In the first step, the pointwise homogenized cross-sections for the compact was obtained after solving the slowing down equation for the spherical unit cell. Then, the shielded cross-section for the homogenized fuel compact was generated using the original PSM. The verification calculations were performed for the fuel pins with various packing fractions, compact sizes, TRISO sizes, and fuel temperatures. Additionally, two fuel block problems with very different sizes were examined and the depletion calculation was carried out for investigating the accuracy of the proposed method. They revealed that the PSM-DH has a good performance in the VHTR problems.

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