1. Abstract
This Co-op with Voith Hydro took place between the months of August and December
under the supervision of Mr. Michael Graf. My primary project was to create a baseline
of Francis turbines in order to study how making changes to blade geometry will effect
the stress levels in the blades. This multi-disciplinary study consisted of Computational
Fluid Dynamics (CFD) using ANSYS CFX and Finite Element Analysis (FEA) using
ANSYS Mechanical. The following tasks were performed…
Flow and Structural Analysis
Acquired Knowledge and Experience
Useful Information to Know
At Voith Hydro the hydraulic engineers incorporate structural analysis early in the
design process of creating the hydraulic design for the turbine. This process provides
an early detection system for possible structural problems prior to more enhanced FEA
analysis as their runner design moves towards release. My project was to compile a
baseline of Francis turbines for various Specific Speeds (Nq). The CFD analysis and
post processing provided the pressures on the runner wetted surfaces to be used as
input for the FEA calculation. Once this was completed, I could start a sensitivity
analysis by making minor changes in the blade geometry to see how it effects the
stresses on the runner. To accomplish this I...
Made use of Microsoft Excel
 to create a database of results
Used Unigraphics NX6 and in-house software
 to model the geometry of the runner
Utilized ANSYS CFX and in-house software
 to create a mesh of the machinery
 to solve the simulation
 to post process the simulation data
Utilized ANSYS Mechanical and in-house software
 to create a mesh of the runner
 to preprocess the data from CFD results
 to solve the simulation
 to post process the results
I found the following helped me perform the tasks asked of me while I
was on Co-op.
 A knowledge of Excel
 A knowledge of MATLAB, C, and Perl
 A familiarity with Linux
 An understanding of Unigraphics, ANSYS CFX and ANSYS
Mechanical
Challenges
 Determining the correct mathematics to calculate the desired results
 Creating easy to use macros
 Generalizing the macros to work in almost any case
Successes
 Macros met all requirements in the test suite
 The macros require limited input from the user
Relevance to Voith Hydro
Engineers depend on CFD to get a general idea of performance. The
faster they can obtain good results, the more time they have to make
improvements on their designs. These macros will help them be more
productive.
Challenges
Successes
Relevance to Voith Hydro
Name: Chris Schleicher
Date: August – December 2010 (Fall)
Period: Co-op III
Supervisor: Mr. Michael Graf
Advisor: Dr. Celik
 Seeing Fluid Mechanics in Action
This past year, I have taken my first class dealing with fluid
mechanics. It was interesting to witness first hand how the concepts
learned in the class room were applied to real world situations.
 Ability to Use ANSYS CFX
ANSYS CFX was an important tool during this co-op, and the
majority of my time was spent using this package. I learned to create
different types of meshes and learned what constitutes a good mesh.
Also, I learned how to setup up appropriate boundary conditions to a
mesh so that a desired solution can be obtained. Building from my
last co-op experience I also gained a better understanding of post
processing results.
 Understanding Concepts of an Iterative Solver
Because computers can not evaluate the Navier-Stokes equations
directly, simplifications and an iterative solving process is used. The
true solution is not be obtainable, so turbulence models and
convergence criteria are used. I learned what to look for in these
solutions to see if the solution has converged appropriately.
 To learn the software
 To understand and apply CFD and FEA best practices
 To critically analyze the results
There are many checks and balances at Voith Hydro to make sure that their products
perform as expected in the field. There are, however, times when unexpected results
occur. This project is designed to look into how Voith can detect possible structural
faults earlier in the design phase for the turbine runner.
Different Types of Hydraulic Turbines
 Fixed Blade
This turbine looks like a propeller of a ship. The blades are fixed in a
single position which limits the operating range of this turbine.
 Kaplan
Similar to the fixed blade turbine, but the advantage of this design is that
the blades are adjustable in pitch; allowing a wider operating range than
that of the fixed blade turbine.
 Francis
This is one of the most common turbines. The image to the left is an
example of one blade passage for a Francis runner.
 Pump Turbine
A pump turbine has a similar geometry to a Francis turbine. What makes
this turbine special is that it can also pump water back to its upper
reservoir during times when energy is cheaper and let it flow back down
when energy costs more; a very large rechargeable battery!
I was able to obtain the necessary computer simulation results and post process the
results in a structured database for further analysis.
The CFD Process
 Build the Geometry
I used Unigraphics NX6, but it is possible to use other CAD packages.
ANSYS supports a variety of geometry types.
 Create a Mesh
A mesh is a 3D grid of nodes, points in space defining the surface and
volume, that the solver will solve the Navier-Stokes equations. The mesh
should be refined in places such as near walls or corners in order to
resolve the boundary layer between the fluid and the surface. A more
refined mesh will typically provide better results but it will also take longer
to calculate.
 Apply Boundary Conditions
Boundary conditions for the inlet, outlet, walls, and free surfaces need to
be defined. In addition, the fluid properties, turbulence model and many
additional solver settings need to be defined to setup a CFD calculation.
 Solve the Simulation
High performance clusters (HPC) are employed that have many
processing cores to reduce the solving time. Monitoring points of interest
and residuals for different properties help to determine if the results are
converged.
 Process the Results
With the results from your simulation you can add streamlines, contour
and vector plots, and manipulate your results in order to study how the
fluid interacts with your geometry and how it moves.
CFD Post Processing Macros
Macros are used to speed up the post processing of CFD results. These
macros are used in ANSYS CFX Post to quickly generate plots that the
hydraulic engineers can use to help visualize and analyze their simulation
results. To write these macros I needed to...
Learn Perl and the ANSYS CFX Macro language to write the logic to
generate the plots.
Make use of trigonometric functions to convert frames of reference.
Make use of research skills to find references as needed.