Prof Andrew Long Dr Xuesen Zeng Modelling the StructurePermeability Relationship for Woven Fabrics Division of Materials Mechanics and Structures Faculty of Engineering What degree did I do before my PhD What made I choose this topic ID: 390021
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Slide1
Xueliang XiaoProf. Andrew LongDr. Xuesen Zeng
Modelling the Structure-Permeability Relationship for Woven Fabrics
Division of Materials, Mechanics and Structures
Faculty of EngineeringSlide2
What degree did I do before my PhD? What made I choose this topic? Four years, Bachelor's degree on Textile Science and Engineering(China) Two years, Masters study on Surface Coating and Nano Technique(China)PhD, come to a new field, original topic “Modelling impact performance of wearable airbag for fall protection”. (UK)
Where to start? How to start? What methodology? Keywords in the topic? Challenging……
Requirement: Low gas permeability
Main jobs on: woven fabric, permeability, fabric structure, analytical modelling2
Division of Materials, Mechanics and Structures
Faculty of EngineeringSlide3
Summary of main work (discoveries, contributions) during PhD studyAn analytical static permeability model developed without fitting factor for woven fabric in through-thickness, excellent accuracy!Studied fabric dynamic permeability experimentally, compared it with corresponding fabric static permeability and found their difference;
Modelled fabric deformation under high pressure load and its effect on the fabric through-thickness permeability;Studied the nonlinear relationship of pressure and flow velocity when high speed flow through the ‘fabric’ structure;
Tried to understand which effect has more contribution on the fabric permeability? fabric deformation or nonlinear flow;
3
Division of Materials, Mechanics and Structures
Faculty of EngineeringSlide4
4
Fabric static through-thickness permeability (unit cell level)
∆P
Ohm’s Law
K is similar with R
Laminar Flow
Darcy’s law for low Re values
The
Forchheimer
equation for high Re values
Where ,
Kg ? &
Ky
?Slide5
5
Previous model
The
Gebart
model
The
Kulichenko
model
Current model
Yarn permeability
Gap permeability
Fabric static through-thickness permeability (unit cell level)Slide6
6
Yarn permeability model
Yarn permeability
θ
Flow parallel and perpendicular to filaments
Fabric static through-thickness permeability (unit cell level)
Matrix transposeSlide7
7
Fabric static through-thickness permeability (unit cell level)
Gap permeability model
x
y
Parabola fitted gap cross section
Hagen-
Poiseuille
flow
Gap flow
(Gradual converging-diverging flow channel)
(straight flow channel)Slide8
8
3
D woven f
abric--- static through-thickness permeability
K
1
h
1
∆P
1
K
i
h
i
∆P
i
K
n
h
n
∆
P
n
∆P, H
μ
, v
μ
, v
homogenization
Real 3D fabric by CT scanningSlide9
9
Fabric dynamic through-thickness permeability
High initial pressure impact + fabric deformation
Transient pressureSlide10
10
Fabric deformation under high pressure load
Dial gauge
Vernier
caliper
Deformed fabric under high pressure loadSlide11
11
Fabric deformation under high pressure load
r
z
a’
a’
D:bending rigidity
E: Young’s modulusSlide12
12
Effect of fabric deformation on its permeability
Ly
2a’
Input new predicted geometric parameters into yarn and gap permeability models to get deformed fabric permeability values
Assume all yarns have the same
ε
value
Slide13
13
Modelling nonlinear flow in gaps of woven fabric
Without fabric deformation, both increased pressure and flow velocity display a nonlinear relationship.
∆P
V
Nonlinear flow based on the
Navier
-Stokes Equation
(body force is 0)
x
ySlide14
14
Modelling nonlinear flow in gaps of woven fabric
A
1
V
1
P
1
A
2
V
2
P
2
BC
BC
BC
If C=8, the equation is for a circular tube;
If , the equation is for gradual converging-diverging flow channel.
The
Forchheimer
Eq.
A
B
C
CFD simulation
Forchheimer
style Eq. for woven fabricSlide15
15
Nonlinear flow model with fabric deformation
Fabric U
2
Future research based on current models
R
d
, a
d
and
λ
d
can be predicted by the deformation model in Chapter 5.
To develop rectangular gap permeability model.
To study fluid flow in twisted yarns (staple fibres).
To simulate flow behaviour in real woven fabric by CFD.
To understand why
Forchheimer
factors varying under high Re values
To develop a nonlinear flow model for yarns or tight fabrics.Slide16
16
Division of Materials, Mechanics and Structures
Faculty of Engineering
Thank you very much!