Stepped Spillway (Stair Spillway) CFD Simulation, ANSYS Fluent Training

Description

Stepped Spillway Introduction

Stepped spillway is commonly used in reservoir dams in order to release flood safely.  The stairs of spillway increase energy dissipation greatly. Stair spillways are among the hydraulic structures which attracted great interest to the designers due to their high water capacity energy dissipation. The flow mechanism is complicated in such structures, and more research is being done about it. For this reason, more research and simulation are needed to understand the fluid flow pattern correctly.

Stair Spillway Project description

In this analysis, two-dimensional simulation of a stepped spillway by ANSYS Fluent software is presented. VOF model is activated for two phases of air and water and standard k-e model with the use of standard wall function is exploited for fluid flow analysis.

Stepped Spillway Geometry & Mesh

The modeled geometry is designed and meshed inside Gambit®. The mesh type used for this geometry is unstructured and the element number is 139067.

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 -9.8 m/s² in Y direction.

The applied settings are summarized in the following table.

(stepped spillway)	Models
Viscous model		k-epsilon
	k-epsilon model	standard
	near wall treatment	standard wall function
Multi phase		VOF
	Phase 1	Air
	Phase 2	Water
(stepped spillway)	Boundary conditions
Inlets		velocity inlet
Water inlet	velocity	1 m/s
	Turbulent kinetic energy	1 m2/s2
	Turbulent dissipation rate	1 m2/s3
Outlets		Pressure outlet
Walls
	wall motion	stationary wall
(stepped spillway)	Solution Methods
Pressure-velocity coupling		Simple
Spatial discretization	pressure	PRESTO!
	Volume fraction	first order upwind
	momentum	first order upwind
	turbulent kinetic energy	first order upwind
	turbulent dissipation rate	first order upwind
(stepped spillway)	Initialization
Initialization method		Standard
	gauge pressure	0 Pa
	velocity (x,y,z)	(1,0,0) m/s
	Turbulent kinetic energy	0 m2/s2
	Turbulent dissipation rate	1 m2/s3
	Water volume fraction	0

Results

The contours of pressure, velocity, volume fraction, streamlines and velocity vectors are presented.

You can obtain Geometry & Mesh file and a comprehensive Training Movie that presents how to solve the problem and extract all desired results.