Waterfall: 2-Phase Flow

Waterfall Using Two-Phase Flow — ANSYS Fluent CFD Simulation

Description

Welcome to the Waterfall using Two-Phase Flow CFD Simulation module. This project introduces civil and hydraulic engineers to the world of waterfall hydraulics using ANSYS Fluent. A waterfall is one of the most intuitive free-surface flows: water falls freely through air, entraining bubbles and dissipating energy as it lands. Beyond their natural appeal, waterfalls play a real engineering role in landscape design, stormwater management, and energy dissipation in structures such as dam spillways. Modeling one well means capturing free-fall conditions and air entrainment at the dynamic interface between water and air. As the opening project of the Hydraulic & Civil: Beginner CFD Training Package, it introduces the core tool used throughout the package — the two-phase Volume of Fluid (VOF) method for tracking the water–air interface — through the simplest and most approachable free-surface case.

Methodology

The workflow begins with creating a basic geometry representing a waterfall configuration and applying an appropriate meshing strategy for accurate flow analysis. The two-phase flow is then set up by defining the properties of water and air within ANSYS Fluent. The boundary conditions are central to a realistic result: inlet flow rates and outlet conditions are specified to represent the waterfall scenario, while free-surface and wall boundary conditions capture the water surface, the air interface, and the solid boundaries. The solver parameters — including time-stepping and convergence criteria — are configured to suit a free-surface hydraulic simulation, and the solution is monitored for stability and convergence throughout.

Analysis

Post-processing focuses on extracting meaningful insight from the flow. Velocity fields and streamlines are visualized to understand the flow behavior through the waterfall, while velocity profiles and air-entrainment patterns are examined to assess performance and downstream impact. Free-surface visualization reveals the dynamic water–air interface at the heart of the problem. By the end of this project, you'll be able to set up and run a basic two-phase waterfall simulation in ANSYS Fluent, capture flow patterns and air entrainment in free-fall conditions, interpret the free surface and velocity results, and apply those insights to waterfall design and the broader hydraulic structures that rely on free-surface flow.