4.3 Three-Dimensional Pebble Flow
217
4.3.2 3D Pebble Flow in HTR-PM
4.3.2.1 Simulation Configurations
The main body of the HTR-PM is a cylindrical container on a conical base, which
is then contracted into a central discharging silo (see Fig.4.32). The diameter of the
cylindrical part is about 3 m and the total height is about 10 m. The cylindrical part
is called the main body here, and the conical base is underneath the cylindrical part.
The conical base is used to contract the main body to a small silo with diameter
0.5 m. To study the effects of the base angle (the angle from the conical surface to
the horizon) on the pebble flow, three base angles θ = 30
◦ (Fig. 4.32a), 45
◦ (Fig.
4.32b), 60
◦ (Fig. 4.32c), are used here (termed as “A30”, “A45”, “A60” for short, see
in Table 4.13. Moreover, the effect of friction coefficients on the three-dimensional
pebble flows is also explored here where the friction coefficients are μ = 0.3, 0.5,
and 0.8, respectively.
Also, three kinds of recirculation patterns are studied (see in Table 4.13)
• Case “Star-Fa” in Fig. 4.32d: It has one loading hole in the center of the bed top and
six peripheral loading holes distributed equally and annularly around the central
hole. In this loading mode, the recirculation rate is set at 1 pebble per 0.3 ms, which
is the fastest recirculation mode in the current experiment. As the distribution at
the loading hole is star-like and the recirculation is the fastest, this case is termed
as the “Star-Fa” mode.
• Case “Cent-Me” in Fig. 4.32e: It has only one large loading hole in the bed center.
Its recirculation rate is intermediate (1 pebble per 1 ms). This case is termed as
“Cent-Me” mode.
• Case “Ring-Sl” in Fig. 4.32f: It has one small central loading hole and a ring-like
loading line in the periphery of the central hole. It is termed as “Ring-Sl” mode,
and its recirculation rate is the slowest (1 pebble per 2 ms).
Finally, the model validation issues have already been completed in some of the
earlier studies [67, 68].
4.3.2.2 Effects of Base Angles
On Discharge Flow Patterns and Pebble Spindle Structure
Figure 4.33 shows the snapshots of flow patterns within the beds of different base
angles (θ = 30
◦ (Fig. 4.33a), 45
◦ (b), 60
◦ (c)) when almost ∼ 0, 0.5N p , and N p pebbles are recirculated. Based on the overall view in Fig. 4.33a and the median sectional
view of the flow patterns in Fig. 4.33b, c, the pebble flow is almost horizontally uniform as a mass flow pattern. With N p pebbles are circulated, the resident pebbles
within the corner of the bed (the junction of the cylindrical body and the conical
base) become less within the bed of a larger base angle. Therefore, it is estimated
217
4.3.2 3D Pebble Flow in HTR-PM
4.3.2.1 Simulation Configurations
The main body of the HTR-PM is a cylindrical container on a conical base, which
is then contracted into a central discharging silo (see Fig.4.32). The diameter of the
cylindrical part is about 3 m and the total height is about 10 m. The cylindrical part
is called the main body here, and the conical base is underneath the cylindrical part.
The conical base is used to contract the main body to a small silo with diameter
0.5 m. To study the effects of the base angle (the angle from the conical surface to
the horizon) on the pebble flow, three base angles θ = 30
◦ (Fig. 4.32a), 45
◦ (Fig.
4.32b), 60
◦ (Fig. 4.32c), are used here (termed as “A30”, “A45”, “A60” for short, see
in Table 4.13. Moreover, the effect of friction coefficients on the three-dimensional
pebble flows is also explored here where the friction coefficients are μ = 0.3, 0.5,
and 0.8, respectively.
Also, three kinds of recirculation patterns are studied (see in Table 4.13)
• Case “Star-Fa” in Fig. 4.32d: It has one loading hole in the center of the bed top and
six peripheral loading holes distributed equally and annularly around the central
hole. In this loading mode, the recirculation rate is set at 1 pebble per 0.3 ms, which
is the fastest recirculation mode in the current experiment. As the distribution at
the loading hole is star-like and the recirculation is the fastest, this case is termed
as the “Star-Fa” mode.
• Case “Cent-Me” in Fig. 4.32e: It has only one large loading hole in the bed center.
Its recirculation rate is intermediate (1 pebble per 1 ms). This case is termed as
“Cent-Me” mode.
• Case “Ring-Sl” in Fig. 4.32f: It has one small central loading hole and a ring-like
loading line in the periphery of the central hole. It is termed as “Ring-Sl” mode,
and its recirculation rate is the slowest (1 pebble per 2 ms).
Finally, the model validation issues have already been completed in some of the
earlier studies [67, 68].
4.3.2.2 Effects of Base Angles
On Discharge Flow Patterns and Pebble Spindle Structure
Figure 4.33 shows the snapshots of flow patterns within the beds of different base
angles (θ = 30
◦ (Fig. 4.33a), 45
◦ (b), 60
◦ (c)) when almost ∼ 0, 0.5N p , and N p pebbles are recirculated. Based on the overall view in Fig. 4.33a and the median sectional
view of the flow patterns in Fig. 4.33b, c, the pebble flow is almost horizontally uniform as a mass flow pattern. With N p pebbles are circulated, the resident pebbles
within the corner of the bed (the junction of the cylindrical body and the conical
base) become less within the bed of a larger base angle. Therefore, it is estimated