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This blog explains how to use Ansys Fluent to simulate and set up a Computational Fluid Dynamics (CFD) model for analyzing flow in an open channel. The use of CFD modelling in open channel flow analysis can result in an improved understanding of flow behaviour, greater design accuracy, and saving time.

CFD Modelling of Open Channel Flow  

Open channel flow involves fluid movement in channels with a free surface, like rivers, canals, and tunnels. It could be challenging due to the free surface and turbulence. Understanding these challenges is crucial for flood risk assessment, irrigation improvement, and wastewater treatment analysis. CFD modelling can help overcome these challenges by simulating flow behaviour and predicting parameters such as velocity and turbulence intensity in different operating conditions. Furthermore, CFD modelling enables engineers to visualize and analyze complex flow patterns, such as recirculation zones, vortices, and flow separation. This information can help identify potential flow problems, optimize hydraulic structures, and improve the overall efficiency of open-channel flow systems. This allows engineers to evaluate the performance of design alternatives to optimize the designs and make informed decisions for open channel flow systems. This saves time and resources in the design and optimization process.


CFD Modelling of Open Channel Flow Using the VOF Method in Ansys Fluent

The VOF method can successfully model complex flow behaviour in open channel flow. It provides precise tracking of the interface between phases (liquids and gases), such as the free surface in the open channel between water and air. However, engineers need to use a fine grid resolution and assumptions about fluid incompressibility and immiscibility.

This post contains a case study on the CFD simulation of open channel flow. We have included a video that provides a step-by-step guide on how to set up VOF modelling for open channel flow using Ansys Fluent. The video demonstrates the setup process, which involves creating geometry and mesh, defining solver settings, running the simulation, and conducting post-processing. This tutorial is an invaluable resource that offers insights into configuring open channel flow simulations and creating captivating animations using iso-surfaces and contours.


VOF model setup and flow analysis of open channel flow


The animation below illustrates the surface waves propagating over the free surface between water and air and gives the wave velocity travelling over the free surface.



Flow velocity at the free surface of an open channel



CFD modelling accurately simulates and analyzes open channel systems, optimizing designs and ensuring efficient flow management. By leveraging CFD modelling, engineers can make informed decisions and improve performance. In the next section, we showcase a case where CFD analysis has been used to analyze flow in open channels with greater water depth.


Post by Mohsen Seraj
February 13, 2024