External Gear Pump: UDF

External Gear Pump CFD Simulation, Dynamic Mesh, ANSYS Fluent

Description

This project simulates an external gear pump using ANSYS Fluent. A pump draws mechanical energy from an external source and transfers it to the fluid passing through, increasing the fluid's pressure and energy as it exits — a process achieved through either dynamic (non-positive displacement) or positive displacement methods. External gear pumps fall into the positive displacement category, moving liquid through the meshing action of two separate, externally-toothed gears.

The geometry was designed in Design Modeler, representing the pump's internal computational domain around the two intermeshing external gears, and meshed in ANSYS Meshing.

Methodology

Since gear 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. Each gear was defined as a Rigid Body to represent its rotational motion, with a custom UDF governing this motion, while the mesh region surrounding the gears was assigned the Deforming option to accommodate the continuous change as the gears rotate. Given the inherently time-dependent nature of the resulting fluid behavior, the simulation was run using an unsteady (transient) solver, with solver settings tuned to maintain accuracy and stability throughout the rotating, deforming-mesh solution process.

Conclusion

Results include pressure and velocity contours, along with animations capturing gear rotation and the resulting flow behavior throughout the pump. These results confirm the gear pump mechanism operates correctly — fluid becomes trapped in the space between the meshing gear teeth as they come together, then is carried and pushed toward the outlet at elevated pressure, reproducing the external gear pump's core operating principle and demonstrating effective fluid transfer and pressure increase throughout the cycle.