Which type of pump accelerates water to a high velocity within the pump casing?

The correct answer is the velocity pump, which is specifically designed to impart a high velocity to the water as it passes through the pump casing. This type of pump works by converting kinetic energy into hydraulic energy, enabling a significant increase in flow speed. The functioning mechanism is characterized by the rapid movement of water due to the impeller's design, which rotates and throws the water outwards, often resulting in high discharge speeds.

Other types of pumps, such as radial flow pumps and axial flow pumps, operate primarily by increasing the pressure of the fluid rather than focusing solely on elevating the velocity. Radial flow pumps move fluid radially outward from the impeller, which can create a pressure head but is generally not optimized for attaining high velocities. Axial flow pumps, on the other hand, direct the flow along the axis of the pump and are used for moving large volumes of water at lower pressure heads instead of maximizing the velocity.

Mixed flow pumps combine elements of both axial and radial flow pumps but also do not emphasize generating high flow velocities to the same extent as velocity pumps. Therefore, the velocity pump stands out due to its unique capacity to accelerate water to a much higher speed within the pump casing, aligning with the question's focus.