# Influence of Fractal Disc Filter Flow Channel Parameters on Filtration Performance
## 3 Results and Discussion
### Influence of Single Flow Passage Parameter on Filtration Performance
#### 3.1.4 The Taper  
With the increase in taper, the cross-sectional area outside the lamination gradually increases. With the increase in taper, the head loss showed a trend of great decline at first and then a slow decline. When the flow passage taper is 0.0020, the stack head loss is the largest, reaching 3.08 m. When the flow passage taper is 0.0080, the lamina head loss is the smallest (1.62 m). Figure 13: Velocity cloud image and velocity vector image of 1–0 section of flow passage with different base size. Cut off the flow passage along the section and observe the flow state of the water body in the flow passage of different sections (the section position is the same as Figure 11). The velocity cloud image and velocity vector cloud image of the 1-1\({}^{\prime}\) section with different taper are shown in Figure 14. The velocity cloud image and velocity vector cloud image of the 1-0 section with different tapers are shown in Figure 15.  
Based on the presented color distribution in Figure 14, a comparative analysis between Figure 14a,b reveals that at the section before entering the buffer slot, the flow velocity in the main stream zone of the stack with a taper of 0.0020 can reach the maximum of 0.72 m/s, followed by those with a taper of 0.0040 and 0.0080, and the flow velocity in the main stream zone of the stack with a taper of 0.0060 is the smallest, only 0.51 m/s. By comparing the area of the low-speed zone near the wall, it is found that the flow passage with the taper of 0.0080 and 0.0060 has the largest area of the low-speed zone, accounting for 19.8% and 19.0% of the section area, respectively, while the flow passage with the taper of 0.0020 has the smallest area of the low-speed zone near the wall, accounting for only 15.4% of the section area. Therefore, it is determined that the laminate with a taper of 0.0020 is not conducive to sediment deposition, and the flow passage with a taper of 0.0060  
Figure 14: Velocity cloud image and velocity vector image of 1–1\({}^{\prime}\) section of flow passage with different taper. makes it easy to block sediment in the main stream area before entering the buffer slot, which is not conducive to the stable operation of the disc filter. As far as the velocity cloud map of the 1-1\({}^{\prime}\) section is concerned, the lamination with 0.0080 taper is better. In the flow velocity vector diagram of the 1-1\({}^{\prime}\) section, there are more flow velocity vectors in the parallel section of the laminations with a taper of 0.0080 except for the laminations with a taper of 0.0080, so the spiral flow formed will dissipate part of the energy. However, only a small part of the lamella with a taper of 0.0080 is parallel to the flow velocity of the section, which proves that the flow velocity of the section is mostly in the same direction as the flow velocity of the mainstream area without excessive energy consumption. Macroscopically, it shows that the head loss of the section of the taper is smaller than that of other sections. Therefore, the cross-section with a taper of 0.0080 is excellent. Based on the presented color distribution in Figure 15, a comparative analysis between Figure 15a,b reveals that except for the mainstream of the flow passage with a taper of 0.0080, the rest of the flow passage is dumbbell-shaped or rectangular. This indicates that the flow passage with a taper of 0.0080 has a wider water exchange space than the flow passage with other tapers. Therefore, a cross section with a taper of 0.0080 has a greater  
Figure 15: Velocity cloud image and velocity vector image of 1-0 section of flow passage with different taper. advantage. In the flow velocity vector diagram of the 1-0 section, the section with the taper of 0.0080 and 0.0060, the velocity vector is basically perpendicular to the section when it is near the wall, so there will be no phenomenon of rotating movement of the fluid near the wall. On the contrary, the velocity vector of the section with a taper of 0.0040 to 0.0020 near the wall still has a part parallel to the section.