Watering Lawns

Description

This project simulates the operation of a lawn sprinkler using ANSYS Fluent, investigated through CFD analysis. Efficient irrigation is a central concern of agricultural engineering, and understanding how water is thrown from a sprinkler and distributed over the ground surface is key to designing systems that water lawns and crops evenly.

The system involves two fluids: air as the primary phase and water as the secondary phase, modeled with the Eulerian multiphase approach. The water jet enters the domain at a velocity of 0.5 m/s, with gravity included at −9.81 m/s² along the y-axis.

Geometry & Mesh

The 2D geometry was created in Design Modeler. Meshing was performed in ANSYS Meshing using an unstructured grid with no element quality below 0.54, giving a total cell count of 19,203,911.

Methodology

Several assumptions underpin the simulation: the solver is pressure-based and transient; only the fluid behavior is examined, so heat transfer is not modeled; and gravity acts at 9.81 m/s² along the y-axis.

Viscous model — k-omega SST with the shear-flow correction option

Multiphase model — Eulerian, with air as the primary phase and water as the secondary phase, using the explicit formulation

Boundary conditions — Inlet: velocity inlet with an initial mixture gauge pressure of 0, a water velocity magnitude of 0.5 m/s, and a water volume fraction of 1; Outlet: pressure outlet with backflow volume fractions of 1 for air and 0 for water; Walls: stationary

Methods — phase-coupled pressure-velocity coupling; PRESTO! for pressure; first-order upwind for momentum, specific dissipation rate, and volume fraction

Initialization — standard method, with a water velocity of 0.5 m/s in the y-direction, zero air velocity, and a secondary-phase (water) volume fraction of 1

Conclusion

On completion of the solution, two- and three-dimensional results for velocity and for the air and water volume fractions were obtained, along with an animation of the process. The simulation shows the water leaving the sprinkler nozzle, reaching the spreader fin, and — as time progresses — falling to the ground and spreading across the surface. This captures how the sprinkler distributes water over the lawn, providing insight useful for designing and optimizing irrigation systems in agricultural applications.