December 2013
Attachment C
Settling Velocity Calculations
113-82323
J:\11JOBS\113-82323 Bear Lodge Mine\Surface Water\November 2013\Pit Dewatering Pond\SedBasin_1.xls
1. Calculation of the settling velocity u of a single particle: natural sediment or spherical
input cel: yellow
calculation cel: blue
INPUT:
Acceleration of gravity g =
9.81 m/s
2
usually g = 9.81 m/s
2
Density of particle ρ
PARTICLE
= ρ
P
=
1100 kg/m
3
Diameter of particle d =
0.00025
meter
(
Be Aware
: 1 mm = 0.001 m)
Assume Fine sand
Density of fluid ρ
FLUID
= ρ
F
=
1000 kg/m
3
usually water ρ
F
= 1000 kg/m
3
Viscosity of fluid η
FLUID
= η
F
=
0.001 Pa s
usually water η
F
= 0.001 Pa s
"Dimensionless particle diameter d
*
"=
2.484065317
Natural particles (Song Zhiyao):
Settling velocity u = 0.002304019 m/s
Re = ρ
F
*u*d/η
F
=
5.76E-01
0.007559116 ft/s
Spherical particles (Guo):
Settling velocity u = 0.003026225 m/s
Re = ρ
F
*u*d/η
F
=
7.57E-01
0.009928559 ft/s
V
S
=
0.01
ft/s
Settling velocity for the design particle size chosen
Q =
1.11
cfs
500 gpm Discharge rate measured in cubic feet per second
A
S
=
177 sq. ft.
Minimum surface are for trapping soil particles of a certain size
S University of Applied Sciences; N
