Counterflow in a Canal

Counterflow within a Canal — ANSYS Fluent CFD Simulation

Description

This project uses ANSYS Fluent to simulate counterflow in a canal and analyze the resulting fluid behavior. The setup features a main water stream moving along the canal while a second stream is injected in the opposite direction from a floor-mounted pipe. The opposing jet disturbs the flow and the free surface, creating a localized interaction between the two streams that is characteristic of many practical canal and hydraulic-mixing situations. Within the Free Surface Flow: Beginner CFD Training Package, this project builds on the basic open-channel case by introducing two interacting streams, adding complexity to the free-surface behavior captured with the VOF method.

Methodology

The 3D geometry, built in DesignModeler, represents a straight channel 8 m long with a 3 m × 1 m rectangular cross-section, with a 4 m long pipe of 0.05 m diameter lying along the canal floor. Meshing in ANSYS Meshing yields 256,899 elements, and a transient solver is used. The main channel inflow velocity is 0.3 m/s, while the pipe issues flow at 2 m/s in the opposite direction. The region above the water surface is open to air, represented by a pressure-inlet boundary at 0 Pa gauge for ambient conditions. Because both water and air are present, a VOF multiphase model is employed, with the standard k–ε model for turbulence.

Analysis

Post-processing provides 2D and 3D fields of pressure, velocity, and phase volume fraction for water and air. The opposing jet perturbs the free surface and entrains air, producing zones with a locally reduced water volume fraction where the counterflow interacts with the main stream. From these results you can evaluate how the opposing jet disturbs the main flow, how air is entrained at the free surface, and where the strongest mixing and interaction between the two streams occurs.