I am confused a bit about fact that there is a decrease in pressure as velocity is increased which is the principle behind cavitation. Now cavitation occurs when velocity of liquid increases so much that pressure decreases (as according to bernoullis equation) and reaches below it's vapour pressure and boiling starts. Now my confusion is that why would pressure fall down? To increase the velocity of liquid we have to increase the pressure on the other side or we have to force the liquid we can say which will increase fluid pressure at that position. Due to this a large pressure difference will be set up and fluid will flow with high speed but this pressure difference is due to increase in pressure on the other side and not due to decrease in pressure where cavitation would occur. Why would cavitation occur then? There should be no decrease in pressure , only difference between pressures would be more . so why cavitation occurs.