When pressure decreases at the centrifugal pump inlet, cavitation occurs in the pump flow area (i.e., violation of the fluid flow continuity and formation of cavities filled with steam and gas released from the fluid). In pumps, cavitation initiates when the inlet pressure (Pin) substantially exceeds the evaporation pressure at a given fluid temperature. Hence, the minimum pressure regions are located inside the pump flow area. With blade streamlining, the lower pressure regions are formed. Qualitatively, the arrangement of lower pressure regions for pumps with the axial (screw) wheel is presented in Figure 8.1; for pumps with the centrifugal wheel, it is illustrated in Figure 8.2 [150]. These regions are located on the nonoperating side of the blade front side.