Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Modelling the filtration efficiency of a woven fabric: The role of
  multiple lengthscales   During the COVID-19 pandemic, many millions have worn masks made of woven
fabric, to reduce the risk of transmission of COVID-19. Masks are essentially
air filters worn on the face, that should filter out as many of the dangerous
particles as possible. Here the dangerous particles are the droplets containing
virus that are exhaled by an infected person. Woven fabric is unlike the
material used in standard air filters. Woven fabric consists of fibres twisted
together into yarns that are then woven into fabric. There are therefore two
lengthscales: the diameters of: (i) the fibre and (ii) the yarn. Standard air
filters have only (i). To understand how woven fabrics filter, we have used
confocal microscopy to take three dimensional images of woven fabric. We then
used the image to perform Lattice Boltzmann simulations of the air flow through
fabric. With this flow field we calculated the filtration efficiency for
particles a micrometre and larger in diameter. In agreement with experimental
measurements by others, we find that for particles in this size range,
filtration efficiency is low. For particles with a diameter of 1.5 micrometres
our estimated efficiency is in the range 2.5 to 10%. The low efficiency is due
to most of the air flow being channelled through relatively large (tens of
micrometres across) inter-yarn pores. So we conclude that fabric is expected to
filter poorly due to the hierarchical structure of woven fabrics.

16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph