## 4 Results and Discussion
### Analysis Results of Pressure Fluctuation with Division Pier  
From the results of numerical analysis, it can be seen that the different lengths of the division pier only had an impact on the hydraulic loss of the straight outlet conduit but had no obvious impact on the velocity distribution and pressure distribution near the wall of the straight outlet conduit; from the perspective of economy and construction difficulty, the length of the division pier should not be excessive. In order to explore the energy and power spectrum characteristics of the straight outlet conduit with the division pier, the pressure fluctuation signal of scheme 1 was analyzed. As shown in Figure 18, a division pier made of acrylic material was set in the test section of the straight outlet conduit; after setting the division pier in the test section of the straight outlet conduit, the original flow field structure of the water flow would inevitably change, and the change of the flow field would have a certain impact on the pressure pulsation near the wall of the straight outlet conduit. Thus, the difference in the energy and power spectrum of P1 and P3 in the test section of the straight outlet conduit with or without a division pier was analyzed. Figure 17: Power spectrum of each monitoring point in sub-band 0–31.25 Hz under different working conditions. The comparison results of the energy values of the two monitoring points with and without a division pier are shown in Figure 19. The results show that the energy values of the two monitoring points in the straight outlet conduit decreased with the decrease of the flow rate with or without the division pier, and the energy values of the two monitoring points in the straight outlet conduit with the division pier were less than those without the division pier. When the flow coefficient was less than 1.0, the smaller the flow coefficient, the more obvious the influence of the division pier on the energy value of the monitoring point in the straight outlet conduit test section. When the flow coefficient was greater than 1.0, the greater the flow coefficient, the smaller the influence of the division pier on the energy value of the monitoring point in the straight outlet conduit test section. The reasonable setting of the division pier is conducive to reducing the pressure pulsation in the straight outlet conduit and to the safe and stable operation of the pump device. According to the energy analysis results of the wavelet packet decomposition of the flow pulsation measuring points in the straight outlet conduit without a division pier, the energy proportion of the sub-band 0-31.25 Hz was the largest, and thus the power spectrum of the time domain signal of the sub-band was analyzed after reconstruction; the comparison of the power spectrum of the reconstructed time domain signal of the two monitoring points in the straight outlet conduit with and without a division pier is shown in Table 3.  
Figure 19: Energy comparison of two monitoring points with and without division pier. Figure 18: The physical picture of the test section of the straight outlet conduit with division pier. The division pier has a certain effect on the change of the flow field in the straight outlet conduit, and the change of the flow field must result in a change of pressure; there were differences in the power spectrum of the main frequency and the corresponding main frequency of the two monitoring points P1 and P3 in the straight outlet conduit after setting the division pier, and the power spectrum values corresponding to the main frequency of the two monitoring points at the straight outlet conduit level were different with or without the division pier. After the division pier was set, the power spectrum values corresponding to the main frequency of the two monitoring points were reduced, but the degree of reduction had a direct impact on the operating conditions of the pump device.