Water in the impeller is in composite movement, that is, on the one hand it should follow the leaf working surface outward swimming, on the other hand it should adjust the rotation with the impeller. The former is called the relative movement, its speed is called the circular motion, its speed is called the peripheral speed, uses u to indicate. The synthesis of two kinds of movement, that is, the absolute movement of water within the pump, the speed of that V said.
When the impeller is working, the movement of any point on the radius of the liquid state can be expressed by the size and direction of the three speed, composed of these three speed graphics called speed triangle. When studying pumps, it is important to understand the fluid flow at the inlet and outlet of the impeller, so generally only draw the inlet velocity triangle and the exit velocity triangle.