The number of mesh increased as a result of applying the grid overlay boundary condition to the entrance of the bottom outlet, rather than to the upstream reservoir, in the investigated scenarios. Half of the flow was simulated due to the longitudinal symmetry of the conduit, which boosted the accuracy of flow simulation in the region. The grid size, ranging from 2 to 25 cm, decreased from the upstream toward the downstream of the conduit. This method generates a higher resolution for the transition regions. Table 2 indicates the numerical model sensitivity under various conditions.
Sensitivity of numerical model under various boundary conditions, simulated areas, amd mesh sizes
| Row . | Inlet boundary condition . | Simulated area . | The size of cubic meshes (m) (from upstream block to downstream of conduit) . | Total cells . | The computational time (s) . | R2 . | |||
|---|---|---|---|---|---|---|---|---|---|
| 10% . | 30% . | 70% . | 100% . | ||||||
| 1 | Flow Pressure (Entrance of reserviour) | Whole bottom outlet conduit | 0.5–0.4–0.3 | 1,506,304 | 25 | 0.921 | 0.902 | 0.895 | 0.912 |
| 2 | Volume Flow Rate (Entrance of the bottom outlet) | Whole bottom outlet conduit | 0.4–0.3–0.25 | 1,556,654 | 25 | 0.881 | 0.876 | 0.861 | 0.862 |
| 3 | Flow Velosity (Entrance of the bottom outlet) | Whole bottom outlet conduit | 0.4–0.3–0.25 | 1,586,718 | 25 | 0.862 | 0.854 | 0.839 | 0.842 |
| 4 | Flow Pressure (Entrance of the reserviour) | Half of the bottom outlet conduit | 0.5–0.35–0.2–0.1 | 1,706,546 | 25 | 0.941 | 0.902 | 0.915 | 0.927 |
| 5 | Flow Pressure (Entrance of the reserviour) | Half of the bottom outlet conduit | 0.5–0.30–0.2–0.1–0.05 | 1,680,255 | 25 | 0.971 | 0.956 | 0.946 | 0.941 |
| 6 | Applying Grid Overally bondary condition instead of the reserviour | Half of the bottom outlet conduit | 0.25–0.10–0.05–0.02 | 1,806,546 | 25 | 0.991 | 0.968 | 0.966 | 0.962 |
| Row . | Inlet boundary condition . | Simulated area . | The size of cubic meshes (m) (from upstream block to downstream of conduit) . | Total cells . | The computational time (s) . | R2 . | |||
|---|---|---|---|---|---|---|---|---|---|
| 10% . | 30% . | 70% . | 100% . | ||||||
| 1 | Flow Pressure (Entrance of reserviour) | Whole bottom outlet conduit | 0.5–0.4–0.3 | 1,506,304 | 25 | 0.921 | 0.902 | 0.895 | 0.912 |
| 2 | Volume Flow Rate (Entrance of the bottom outlet) | Whole bottom outlet conduit | 0.4–0.3–0.25 | 1,556,654 | 25 | 0.881 | 0.876 | 0.861 | 0.862 |
| 3 | Flow Velosity (Entrance of the bottom outlet) | Whole bottom outlet conduit | 0.4–0.3–0.25 | 1,586,718 | 25 | 0.862 | 0.854 | 0.839 | 0.842 |
| 4 | Flow Pressure (Entrance of the reserviour) | Half of the bottom outlet conduit | 0.5–0.35–0.2–0.1 | 1,706,546 | 25 | 0.941 | 0.902 | 0.915 | 0.927 |
| 5 | Flow Pressure (Entrance of the reserviour) | Half of the bottom outlet conduit | 0.5–0.30–0.2–0.1–0.05 | 1,680,255 | 25 | 0.971 | 0.956 | 0.946 | 0.941 |
| 6 | Applying Grid Overally bondary condition instead of the reserviour | Half of the bottom outlet conduit | 0.25–0.10–0.05–0.02 | 1,806,546 | 25 | 0.991 | 0.968 | 0.966 | 0.962 |