Environmental Engineering Reference
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Fig. 9 a Scheme of a bin
with staggered holes of
different size D ; b To p v i ew
of the bin showing the four
different thicknesses of the
face walls
cm 3 and angle of repose
27 .
diameter d
=
2
.
2mm, bulk density
ˁ =
0
.
57 gr
/
ʸ r
=
1 C and 45
Experiments were done in a temperature controlled room (25
±
±
10%
R.H.), upon a transparent, acrylic box, 10
×
10 cm inner cross-section and 50 cm
height.
As it is sketched in Fig. 9 , in the acrylic-made bin circular orifices of diameters
D
=
2
,
2
.
5 and 3 cm were drilled. The wall thicknesses were w
=
0
.
3
,
0
.
4
,
0
.
6 and
0.9 cm.
In Fig. 10 we show the corresponding particle size distributions which were deter-
mined by using a microscope software (Steindorff digital microscope) which allowed
to find the surface area of each particle and its surface diameter. This method yields
the average (median) particle sizes which were d
=
1
.
85mm for mustard and 2.2mm
for tapioca pearls.
Insets in each plot correspond to pictures of the respective granular materials.
In agreement with the experimental procedure established elsewhere (Medina
et al. 2013 , 2014 ) we need to measure the mass flow rate for exit holes at the bottom,
Fig. 10 Micrographs of the particle shapes of samples of mustard ( left-hand side ) and tapioca
( right-hand side ) used in our experiments
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