Positive displacement pumps operate based on which principle?

Positive displacement pumps operate based on the principle of physically moving a fixed volume of fluid with each cycle of the pump. In this context, the correct choice reflects how these pumps function—they displace a specific volume of liquid from the inlet to the outlet with each rotation or stroke. This results in a consistent and controllable flow of fluid, regardless of the pressure conditions downstream.

Additionally, positive displacement pumps are characterized by their ability to maintain flow regardless of variations in pressure within the system, distinguishing them from other pump types that may rely more on pressure changes to move fluid. The mechanism generally involves trapping a volume of liquid and then forcing it out of the pump upon the discharge stroke, showcasing how volume reduction in the pump chamber directly leads to liquid movement. This functioning is advantageous in various applications requiring precise flow rates and the ability to handle highly viscous fluids effectively.

The other concepts, such as pressure increase, flow regulation, and gravity assistance, relate to different aspects of fluid mechanics and are not fundamental principles driving the operation of positive displacement pumps specifically.