Lobe Pump

Lobe Pump CFD Simulation, ANSYS Fluent Training

Description

This project simulates a lobe pump using ANSYS Fluent. A pump is a mechanical device that transfers liquid from one location to another, increasing fluid pressure to raise it to a higher elevation (via head increase) or drive it into another destination such as a tank. The pump draws mechanical energy from an external source, such as an engine, and transfers it to the fluid passing through, increasing the fluid's energy as it exits.

Pumps transfer this energy through either dynamic or displacement methods, dividing them into dynamic (non-positive displacement) pumps and positive displacement pumps — the latter further split into rotary types (gear, lobe, vane) and reciprocating types (piston, diaphragm). A lobe pump is among the most common types used to increase a fluid's hydraulic power, moving liquid using rotating lobes. Lobe pumps resemble gear pumps in operating principle, with one key difference: the lobes are designed to nearly meet rather than physically touch and turn one another.

Lobe pumps consist of two lobes rotating in opposite directions. As the two lobes come together, fluid becomes trapped between them; as rotation separates the lobes again, this high-pressure fluid is carried through toward the outlet.

The geometry was designed in Design Modeler, representing the pump's internal space with two superimposed lobes. The domain was meshed in ANSYS Meshing using an unstructured grid totaling 128,072 cells.

Methodology

This project simulates water flow inside the lobe pump, focusing on capturing the rotation of both lobes and its effect on the surrounding flow. Since this rotation continuously alters the fluid domain, the computational mesh must deform correspondingly over time — requiring the dynamic mesh model, used whenever a moving boundary or deforming zone is present.

Since the two lobes rotate in opposite directions, causing the mesh to deform over time, a Rigid Body was defined for each lobe to represent its rotational motion, with a custom UDF governing this motion. The mesh region surrounding the lobes was assigned the Deforming option to accommodate this continuous change. Given the inherently time-dependent nature of the resulting fluid behavior, the simulation was run using an unsteady (transient) solver.

Conclusion

Results include pressure and velocity contours along with velocity vectors, with corresponding animations capturing how these fields evolve as the lobes rotate through their cycle. The results confirm that the lobe pump operates correctly, effectively transferring fluid while raising its pressure: fluid becomes trapped in the space between the contacting lobes, then is pushed toward the outlet at elevated pressure — reproducing the lobe pump's core operating principle as intended.