7
truck going in and coming out of the mine without any fan
in the model domain. This was done to assess the impact
of just the movement of a truck on airflow inside the mine.
Later, a fan was added to the return side of the mine as
placing the fan at the entry did not provide space to cre-
ate a moving domain to model the movement of a truck.
Figure 9 shows the placement of the truck in the model
domain near the entry. Modeling of the moving object in
COMSOL Multiphysics has been discussed in detail by the
authors’ previous work [18]. However, in the current work,
the modeling is in three-dimension and the truck height
was at 3.9 m (13 ft) which is 3 m (10 ft) above surface level.
A moving domain for the truck movement was created,
which is 457-m (1,500-ft) long, 9-m (30-ft) wide and 6-m
(20-ft) high. This dimension allowed the truck to move in
and out of the mine to the Return 1.
Modeling a moving body in CFD is challenging as the
model needs to solve for both airflow and movement of the
body in the fluid domain. Apart from that, the most critical
aspect is the meshing of the moving domain as well as the
rest of the geometry. Figure 10 shows the mesh elements of
the moving domain and around the truck body. As from
shown in Figure 10, it can be seen that mesh around the
truck body is tetrahedron and in the moving path there
is structured rectangular mesh swept along the moving
domain. The mesh elements in the rest of the domain are
tetrahedron. The mapped mesh elements are all rectangular
block in a shape which is advantageous for moving body
simulation. As the moving body changes position, the mesh
element expands and contracts which usually changes the
mesh quality, but in the case of mapped mesh, their mesh
quality does not change due to its shape.
The speed of the truck in the simulation was assumed
to be 9 m/s, which is 20 miles per hour. The model was run
for 45 seconds for both cases when the truck is going in
and coming out of the mine. The velocity streamline of the
simulation result at 20 seconds of the truck moving in the
mine is shown in Figure 11. It can be seen from the figure
Figure 8. Sampling locations for comparing airflow quantity
Table 1. Comparison of the airflow at different locations (numbers shown are in m3/s and
cfm within parentheses)
Base Case
3.66-m diameter
fan
3.66-m and
2.44-m diameter
fans
3.66-m and 0.91-m
diameter fans
Location 1 0.087 (184) 21.250 (45,026) 17.426 (36,923) 30.334 (64,274)
Location 2 0.009 (919) 4.301 (9,113) 18.096 (38,343) 3.950 (8,369)
Location 3 0.068 (144) 6.085 (12,893) 57.543 (121,926) 10.472 (22,188)
Location 4 3.055 (6473) 56.181 (119,040) 51.950 (110,075) 51.035 (108,137)
truck going in and coming out of the mine without any fan
in the model domain. This was done to assess the impact
of just the movement of a truck on airflow inside the mine.
Later, a fan was added to the return side of the mine as
placing the fan at the entry did not provide space to cre-
ate a moving domain to model the movement of a truck.
Figure 9 shows the placement of the truck in the model
domain near the entry. Modeling of the moving object in
COMSOL Multiphysics has been discussed in detail by the
authors’ previous work [18]. However, in the current work,
the modeling is in three-dimension and the truck height
was at 3.9 m (13 ft) which is 3 m (10 ft) above surface level.
A moving domain for the truck movement was created,
which is 457-m (1,500-ft) long, 9-m (30-ft) wide and 6-m
(20-ft) high. This dimension allowed the truck to move in
and out of the mine to the Return 1.
Modeling a moving body in CFD is challenging as the
model needs to solve for both airflow and movement of the
body in the fluid domain. Apart from that, the most critical
aspect is the meshing of the moving domain as well as the
rest of the geometry. Figure 10 shows the mesh elements of
the moving domain and around the truck body. As from
shown in Figure 10, it can be seen that mesh around the
truck body is tetrahedron and in the moving path there
is structured rectangular mesh swept along the moving
domain. The mesh elements in the rest of the domain are
tetrahedron. The mapped mesh elements are all rectangular
block in a shape which is advantageous for moving body
simulation. As the moving body changes position, the mesh
element expands and contracts which usually changes the
mesh quality, but in the case of mapped mesh, their mesh
quality does not change due to its shape.
The speed of the truck in the simulation was assumed
to be 9 m/s, which is 20 miles per hour. The model was run
for 45 seconds for both cases when the truck is going in
and coming out of the mine. The velocity streamline of the
simulation result at 20 seconds of the truck moving in the
mine is shown in Figure 11. It can be seen from the figure
Figure 8. Sampling locations for comparing airflow quantity
Table 1. Comparison of the airflow at different locations (numbers shown are in m3/s and
cfm within parentheses)
Base Case
3.66-m diameter
fan
3.66-m and
2.44-m diameter
fans
3.66-m and 0.91-m
diameter fans
Location 1 0.087 (184) 21.250 (45,026) 17.426 (36,923) 30.334 (64,274)
Location 2 0.009 (919) 4.301 (9,113) 18.096 (38,343) 3.950 (8,369)
Location 3 0.068 (144) 6.085 (12,893) 57.543 (121,926) 10.472 (22,188)
Location 4 3.055 (6473) 56.181 (119,040) 51.950 (110,075) 51.035 (108,137)