Which method describes a common pump type known for its positive displacement mechanism?

Positive displacement pumps are characterized by their ability to move fluid by trapping a fixed volume and then forcing it into the discharge pipe. This mechanism allows them to maintain a constant flow rate regardless of the pressure conditions in the system, making them particularly effective for applications that require precise volume delivery or when handling viscous fluids.

In contrast, centrifugal pumps utilize a different operating principle that relies on rotational energy imparted by an impeller, which generates a flow by creating a pressure difference. Airlift pumps, while effective for certain applications in moving water, function using entrained air to lift the fluid rather than employing a positive displacement mechanism. Vacuum pumps are designed to remove gas molecules from a sealed volume to create a vacuum, and they operate on principles that differ significantly from positive displacement technology.

Therefore, the choice of positive displacement pumps clearly reflects the method described in the question, as their operational characteristics make them distinct within the range of pump mechanisms.