Spillway: 2-Phase Flow, Transient (2-D)

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

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; an ogee profile is shaped specifically 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 of the problem and a classic application of free-surface CFD in civil and hydraulic engineering. Within the Free Surface Flow: Beginner CFD Training Package, this project builds on the ogee spillway case by solving it as a fully transient two-phase problem, watching the free surface develop over the crest in time.

Methodology

The physics is handled with the Volume of Fluid (VOF) multiphase model, which tracks the sharp air–water interface as it deforms over the spillway, with the standard k-ε model closing the turbulence. Because the whole point is to watch the water move, accelerate, and form its surface profile over the crest, the case is 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 air phase. The geometry is built in ANSYS Design Modeler and meshed in ANSYS Meshing with a structured mesh of 12,846 elements — structured here because the spillway's smooth, well-defined geometry suits a clean, aligned grid along the flow path.

Analysis

Contours of pressure, velocity, and phase volume fraction are extracted across the domain, revealing the water surface profile over the crest, the acceleration of the flow down the spillway face, and the pressure distribution along the structure — exactly the quantities a hydraulic engineer uses to assess discharge capacity and surface pressures. The project includes the geometry and mesh file plus a comprehensive training movie walking through the full setup, solution, and extraction of all results. By the end of this project, you'll be able to set up a transient VOF air–water free-surface case, define mass-flow inflow over a curved spillway, apply standard k-ε turbulence, and read the free-surface profile and pressure field from volume-fraction and pressure contours.