Project Description

The present problem simulates two-phase flow (water and air) inside an open channel with a 180-degree arc using ANSYS Fluent software. To simulate the mentioned two-phase flow, the multiphase VOF model (Volume of Fluid) have been used; Because this two-phase flow is considered free surface currents. Therefore, the VOF model is used to define different phases of the flow. In this multiphase model, airflow is defined as the primary phase and water flow as the secondary phase. Also, because the free surface of water flow inside the canal, the open channel flow model has been used; So that the level of water flow is equivalent to 0.2 m. A stream of water with a height of 0.2 m and a mass flow of 94.83 kg.s-1 enters the channel and, after passing through an arc path of 180 degrees, exits the channel's outlet at a pressure equal to atmospheric pressure. Also, for the upper level of the duct, which is for the passage of airflow, the relative pressure limit condition equal to 0 pascals has been used.

Geometry & Mesh

The present model is designed in three dimensions using Design Modeler software. The present model is a channel with a rectangular cross-section that has an arc path of 180 degrees. The rectangular cross-section of the canal has a width of 1 m and a height of 0.7 m.

We carry out the model's meshing using ANSYS Meshing software. The mesh type is structured. The element number is 2316480. The following figure shows the mesh.

CFD Simulation

We consider several assumptions to simulate the present model:

• We perform a pressure-based solver.
• The simulation is steady.
• The gravity effect on the fluid is equal to -9.81 m.s-2 along the vertical axis.

The following table represents a summary of the defining steps of the problem and its solution:

Results

At the end of the solution process, three-dimensional contours related to pressure, velocity, kinetic turbulence energy, the volume fraction of water, and the volume fraction of air inside the 180-degree arc channel are obtained.