# Characterisation of the Pump-Suction Flow Field of Antarctic Krill and Key Influencing Factors
## 3 Results  
Relevant studies have shown that the possible factors affecting the damage rate of krill include the rotation speed of the impeller and the mixing ratio of krill-water. This study aims to simulate and analyse these two parameters to determine the synergistic effect of the two key variables, the mixing ratio of krill-water, and the rotation speed of the centrifugal pump on the performance of the pump. The simulation employs the VOF two-phase flow and DPM models to establish the ratio of krill-water, with the particle size set to replicate the dimensions of krill (20 mm). The ensuing simulation results are as follows. Its lateral velocity in pump variation contour is shown in Figures 5-7:  
Figure 4: Pressure contour in pump cross section for krill–water mixing ratio of 3/7. Figure 5: Velocity contour in pump cross section for krill–water mixing ratio of 3/7. The horizontal velocity contours for the three krill-water mixing ratios of 3/7, 4/6, and 5/5 are displayed in the figure above. It is evident from the figure that the velocity within the pump body is distributed in a clearly uneven manner. The velocity is higher in the centre of the impeller and at the outlet of the centrifuge. Notwithstanding the varying krill-water mixing ratios, the velocity within the impeller's proximity to the wall exhibits a consistent and gradual increase, indicating a notable enhancement in velocity. Prior to the centrifuge attaining 500 rev/min, a substantial change in the impeller velocity is evident, indicating a rapid growth phase. However, when the rotation speed exceeds 550 rev/min, the velocity change in the impeller centre becomes negligible and enters a slow change stage. The centrifuge outlet area exhibits a less significant change in velocity when compared to the impeller area, irrespective of the krill-water mixing ratio. However, it is evident that at rotation speeds below 550 rev/min, the outlet velocity distribution exhibits greater uniformity, resulting in a diminished squeezing force exerted on the krill by the wall surface. Conversely, at rotation speeds exceeding 550 rev/min, the flow at the  
Figure 6: Velocity contour in pump cross section for krill–water mixing ratio of 4/6. Figure 7: Velocity contour in pump cross section for krill–water mixing ratio of 5/5. outlet exhibits a pronounced tendency to deviate towards one side of the wall surface. This has the potential to result in a higher collision rate of krill with the wall surface in the outlet area, leading to an increased damage rate. At a constant rotation speed, the velocity changes at the centre of the impeller and at the outlet of the centrifuge when the krill-water mixing ratio of 4/6 and 5/5 are compared. Although the impact is minimal, the velocity changes are considerably more moderate than the krill-water mixing ratio of 3/7, particularly the velocity changes at the impeller wall. This will reduce the collision between the krill and the wall and minimise the damage to the krill caused by extrusion. Nevertheless, it is challenging to ascertain the most appropriate krill-water mixing ratio solely based on velocity changes in the cross section. The degree of contact between the krill and the wall surface can be further elucidated by examining  
As is evident from the longitudinal section, the centrifugal effect influence is more pronounced in the inlet area, resulting in a more uniform velocity distribution. The experimental results demonstrate a positive correlation between the duration of krill body exposure within the centrifugal region and the resultant velocity increase in the outlet pipe section. This enhancement in velocity was observed to be consistent across all tested krill-water mixing ratios, with the velocity measurements in the outlet pipe section of the centrifuge system consistently exceeding the initial velocities recorded in the inlet pipe region. However, the velocity distribution becomes more chaotic. The increase in rotation speed renders the chaotic degree more significant.