Kaplan turbine CFD Simulation by ANSYS Fluent Training

Turbine Introduction

Turbomachines, also known as fluid machines, are widely used in the industry. Therefore, it is very important to study their behavior in the fluid environment around them. Turbomachines are divided into two general categories. The first group works by taking energy and transferring it to the fluid and the second group, by doing work and taking energy from the fluid transferring it to the system in various forms. The first group’s examples are fans and compressors, and wind and water turbines can be mentioned as the second category. Kaplan turbines fall into the second category.

Inward Flow Reactive Turbines are one of the most popular turbines used in the industry, using the concepts of Axial and Radial flows. The inlet is a tube that rotates around the guide valves. The water enters the runner tangentially through the guide valves and becomes spiral by the runner propeller blades, which eventually causes the runner to rotate.

Kaplan Turbine Project description

In this project, the water flow passing over the Kaplan turbine is investigated. The Kaplan turbine rotates at 3300 rpm and sucks the water in. RNG k-epsilon model is exploited to solve turbulent flow equations. It should be noted that the MRF option has been activated to model the rotation of the turbine.

Geometry and mesh

We design the geometry of this project in ANSYS design modeler and mesh in ANSYS meshing. The mesh type used for this geometry is unstructured and the element number is 919824.

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 steady and do not change as a function time.
• The effect of gravity has not been taken into account.

The applied settings are summarized in the following table.

	Models
Viscous model		k-epsilon
	k-epsilon model	RNG
	near wall treatment	standard wall function
	Cell zone conditions
Frame motion		on
Fluid	Rotational velocity	3300 rpm
	Boundary conditions
Inlet		pressure inlet
	Gauge pressure	0 Pa
Outlet		Pressure outlet
	Gauge pressure	0 Pa
Walls		Stationary wall
	Solution Methods
Pressure-velocity coupling		SIMPLE
Spatial discretization	Pressure	Second order
	Momentum	second order upwind
	turbulent kinetic energy	first order upwind
	turbulent dissipation rate	first order upwind
	Initialization
Initialization method		Standard
	gauge pressure	0 Pa
	Velocity (x,y,z)	(0,0,0) m/s
	Turbulent kinetic energy	0 m2/s2
	Turbulent dissipation rate	0 m2/s3

Results & discussion

As can be seen in the pressure contour for the turbine’s surface, there are sections on the turbine blades which are exposed to decreased pressure. Now, these parts have the potential to be the places where the cavitation can occur and should be studied and examined more carefully.

There is a mesh file in this product. By the way, the Training File presents how to solve the problem and extract all desired results.