Minimum pressure zone in a pump
Centrifugal, helical-centrifugal and axial-flow pumps: cavitation

Consider the evolution of mean pressure in a pump (figure 2 a ). The lowest mean pressure, p ₁ , obviously prevails at the impeller inlet, when no energy has yet been transmitted to the fluid. The pressure p ₁ is not, however, the minimum local pressure in the pump. In fact, we know that, due to the transmission of energy by the impeller blades, pressures evolve differently on the two faces of these blades and that, in particular, there is a zone of strong depression on the face seen in the vicinity of the inlet edge. This is where the minimum pressure is, and where cavitation is likely to occur.

Consider figure