Open Channel Flow (Two-Phase) CFD Simulation, ANSYS Fluent Training

Introduction

Open channel is waterway channel, or artificial waterways, for water conveyance, or to service water transport vehicles. They may also help with irrigation. It can be thought of as an artificial version of a river. Nowadays, the use of canals in the industry has received a lot of attention in applications including air ducts and water transmissions. The shape and dimensions of the channels also largely depend on their uses.

Open Channel Flow Project description

In this analysis, the two-phase flow of water and air inside an open channel is investigated by ANSYS Fluent software. The standard k-omega model is used for solving turbulent flow equations. Also, multi phase VOF model with the use of an open channel setting is activated to simulate two phases of water and air inside the channel. The water enters the channel with a mass flow rate of approximately 60Kg/s and its interaction with the air phase inside the channel is simulated.

Open Channel Geometry and mesh

The geometry of this project is designed in ANSYS design modeler® and meshed inside ANSYS meshing®. The meshes type used for this geometry is structured and the total number of elements is 214560.

Open Channel Flow CFD Simulation Settings

The key assumptions considered in this project are:

• Simulation is done using pressure-based solver.
• The present simulation and its results are considered to be steady and do not change as a function time.
• The effect of gravity has been taken into account and is equal to -9.81 in Y direction.

The applied settings are recapitulated in the following table.

	Models
Viscous model		k-omega
	k-omega model	standard
	k-omega option	Shear flow correction
Multiphase		VOF
	VOF sub-model	Open channel
	Primary phase	Air
	Secondary phase	water
	Boundary conditions
Inlet		Mass flow inlet
	Water Mass flow rate	60.071524 Kg/s
		Open channel
	Free surface level	0.24 m
	Bottom level	0 m
	Density interpolation method	From neighboring cell
Outlet		Pressure outlet
Walls
	wall motion	stationary wall
	Solution Methods
Pressure-velocity coupling		SIMPLE
Spatial discretization	pressure	PRESTO!
	momentum	second order upwind
	Volume fraction	compressive
	turbulent kinetic energy	first order upwind
	turbulent dissipation rate	first order upwind
(open channel)	Initialization
Initialization method		Standard
	gauge pressure	0 Pa
	velocity (x,y,z)	0 m/s-1
	Turbulent kinetic energy	1 m2/s2
	specific dissipation rate	1 m2/s3
	Water volume fraction	0

Results

Different contours of velocity, pressure and water volume fraction are presented in 3D and 2D.