Open Channel Flow: 2-Phase

Description

This project uses ANSYS Fluent to simulate two-phase open channel flow, modeling the interaction between water and air inside a channel — a core problem in hydraulic and open-channel flow engineering. Open channels, whether natural (rivers) or artificial (canals, irrigation channels, water transmission systems), are widely used for water conveyance, transport, and irrigation. Water enters the channel at a mass flow rate of approximately 60 kg/s, and its interface behavior with the air phase above it is resolved using Fluent's open channel flow modeling capability.

Methodology

The geometry is built in DesignModeler and meshed in ANSYS Meshing using a structured grid of 214,560 elements. The simulation uses a pressure-based, steady-state solver, with gravity applied at -9.81 m/s² in the Y direction. Turbulence is modeled using the standard k-omega model with shear flow correction, while the VOF multiphase model with the open channel sub-model captures the water-air interface, with air as the primary phase and water as the secondary phase.

Boundary conditions specify a mass flow inlet for water (60.071524 kg/s), with an open channel free surface level of 0.24 m and bottom level of 0 m, using density interpolation from neighboring cells. The outlet is set as a pressure outlet, and walls are treated as stationary. The solution uses the SIMPLE scheme for pressure-velocity coupling, PRESTO! for pressure discretization, second-order upwind for momentum, a compressive scheme for volume fraction, and first-order upwind for turbulent kinetic energy and dissipation rate. Standard initialization is applied with zero gauge pressure, zero velocity, and a water volume fraction of 0.

Conclusion

Results include 3D and 2D contours of velocity, pressure, and water volume fraction, characterizing the flow behavior and free-surface interaction within the open channel.