# Influence of Fractal Disc Filter Flow Channel Parameters on Filtration Performance
## 3 Results and Discussion  
### Influence of Single Flow Passage Parameter on Filtration Performance  
#### 3.1.1 The Number and Position of Buffer Slot  
In order to facilitate the observation of the laminated pressure changes, the pressure of the radial section was analyzed, and the flow passage pressure distribution diagram of the radial section is shown in Figure 6. The presence or absence of buffer grooves has a certain influence on the overall pressure distribution of laminate. The pressure distribution of the stack with a buffer groove is more uniform than that of the stack without a buffer groove. The pressure distribution at 1-1' is more uniform than that at 1-0. In order to further study the change of velocity in the flow passage, the flow passage is cut into different sections along the flow direction (as shown in Figure 2). The fractal flow passage without buffer groove, the flow passage before optimization (the buffer groove is located at 1-0 position), and the simulated optimized buffer groove flow passage (the buffer groove is located at 1-1' position) are respectively shown. The internal flow velocity changes are shown in Figure 7.  
Figure 6: Pressure distribution of flow passage in radial section.  
In Figures 6 and 7, The red series means high pressure and fast flow velocity, and the blue series means low pressure and slow flow velocity. According to the color distribution presented in this figure, the velocity of each section of flow passage is high in the center and low at the edge. The flow velocity of each section of the stack with a buffer groove is lower  
Figure 7: Cross-section flow velocity cloud picture of buffer slot at different positions.  
than that of the stack without a buffer groove, and the flow velocity changes relatively slowly. Because the buffer groove increases the flow area of the section, the flow velocity of the section decreases and the low-speed area increases. Water flow enters the inner flow passage after flowing through the buffer slot. The decrease in flow area results in an increase in velocity in the main flow area. However, compared with the flow passage without a buffer slot, the low-speed zone near the flow passage wall is larger, indicating that the design is more conducive to sediment interception. The low flow velocity of the buffer trough reduces its sand-carrying capacity, resulting in large particle-size sediment being deposited in the low-speed area of the buffer trough and small-particle sediment flowing out with the flow. When the buffer slot is located at the 1-1\({}^{\prime}\) section, the velocity area of the 1-2\({}^{\prime}\) section in the low-speed zone and the main flow zone account for 16.4% and 15.9% of the section area, respectively. When the buffer slot is located at 1-0 section, the velocity area of 1-2\({}^{\prime}\) section in the low-speed zone and the main flow zone account for 14.8% and 3.6% of the section area, respectively. The main stream area is large; the laminated flow passage is not easy to plug, while the low-speed area is large, which makes it easy to deposit sediment. Therefore, the optimized lamination effectively avoids the condition that the first half of the filter flow passage is prone to depositing most of the sediment and exiting the working state prematurely, thereby extending the running time of the filter and reducing the number of backwashes.  
The above results show that the existence of buffer slots can not only reduce the loss of water head but also facilitate the interception of sediment. As the position of the buffer slot moves from the flow passage inlet to the flow passage outlet, the head loss decreases first and then increases, and the head loss reaches its lowest when the buffer slot is located at 1-1\({}^{\prime}\). The filtration performance of a disc filter is better when the position of the flow passage buffer slot is 1-1\({}^{\prime}\).