Diaphragm Pump

Diaphragm Pump CFD Simulation, ANSYS Fluent Training

Description

This project simulates a diaphragm pump using ANSYS Fluent. A pump is a mechanical device that transfers liquid from one location to another, drawing mechanical energy from an external source such as a motor and transferring it to the fluid passing through, thereby increasing the fluid's energy as it exits the pump.

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 diaphragm pump falls into this reciprocating category, using a flexible composite membrane that moves up and down over the working fluid: as the membrane rises, fluid is drawn in through the intake valve, and as it descends, fluid is pushed out through the outlet valve.

This project models the water flow inside a diaphragm pump, focusing on capturing the membrane's reciprocating motion and its effect on the surrounding flow. Since this motion continuously alters the fluid domain, the computational mesh must deform correspondingly over time.

The geometry was designed in Design Modeler, representing the pump's internal space along with the moving membrane, and meshed in ANSYS Meshing using an unstructured grid totaling 222,986 cells.

Methodology

Since a moving boundary or deforming zone is present, the dynamic mesh model was applied throughout the simulation. Here, the moving wall — the membrane — generates a wave-like motion that deforms the mesh over time, defined through a UDF implementing the Grid Motion approach to prescribe this wavy wall behavior.

Given the membrane's reciprocating motion as a rigid body, the mesh region adjacent to it was assigned the Deforming option to accommodate this continuous change. Since the resulting fluid behavior is inherently time-dependent, the simulation was run using an unsteady (transient) solver.

Conclusion

Results include pressure and velocity contours, along with corresponding animations capturing how these fields evolve as the membrane moves through its cycle. The results confirm that pressure and velocity fluctuate continuously in direct response to the membrane's reciprocating motion — this motion drives fluid suction through the intake valve during the upstroke and compression toward the outlet valve during the downstroke, reproducing the diaphragm pump's core operating cycle.