Spillway: Transient, 2-D

Spillway (2-D & Transient) CFD Simulation, Two-Phase Flow, ANSYS Fluent Training

Description

This project simulates the two-phase flow of water and air over an ogee spillway — the curved overflow structure used in dams to pass excess water safely downstream. When flow meets an obstruction, the water level rises behind it and accelerates over the crest; the ogee profile is specifically shaped to match the natural nappe of falling water, minimizing pressure problems and maximizing discharge efficiency. Capturing the free water surface as it spills over the crest is the core focus of this simulation — a classic application of free-surface CFD in civil and hydraulic engineering.

The geometry was built in Design Modeler and meshed in ANSYS Meshing using a structured mesh totaling 12,846 elements. A structured mesh was chosen here because the spillway's smooth, well-defined geometry suits a clean, flow-aligned grid.

Methodology

The physics is handled using the Volume of Fluid (VOF) multiphase model, tracking the sharp air-water interface as it deforms over the spillway crest, with the standard k-ε model closing the turbulence equations. Since the primary objective is to observe the water accelerating and forming its surface profile as it moves over the crest, the simulation was solved as transient.

Water enters the computational domain at a mass flow rate of 0.05 kg/s and flows over the spillway against the surrounding air phase.

Conclusion

Results include contours of pressure, velocity, and phase volume fraction extracted across the domain, revealing the water surface profile as it passes over the crest, the flow's acceleration down the spillway face, and the pressure distribution along the structure — precisely the quantities a hydraulic engineer relies on to assess discharge capacity and surface pressure loading.