Computational Fluid Dynamics

Analysis of a Wind Turbine

Jon Leary

Academic Supervisor – Rob Howell

Industrial Supervisor – Stuart Walker (AECOM)

What is Computational Fluid

Dynamics (CFD)?

• Computational tool for modelling fluids

• Uses computers to perform mind numbing

calculations

• Lewis Fry Richardson (1881-1953) performed 1st

CFD calculation for weather prediction

• Took 6 weeks and ended in failure!

• Proposed ‘forecast factory’

• Stadium of 64,000 people, each with a mechanical calculator

• Leader in centre with coloured lights and telegraph

communication

What Can You Use CFD For?

• Predicting real world behaviour of fluids

• Design optimisation

• Flow visualisation tool

How Does CFD Work?

• Real world continuous fluids split into

manageable ‘chunks’

• Properties of each chunk dependant on those

of the surrounding ‘chunks’

• Governing equations solved for each ‘chunk’

simultaneously until an overall solution can be

found

How Does CFD Work?

What Are The Limitations of

CFD?• Accuracy dependant on:

• ‘Chunk’ size

• ‘Chunk’ distribution

• How well the chosen equations match the type of flow

• Interpretation of the results

• Accuracy of boundary conditions

• Solution convergence

• Skill of the user!

Why Use CFD to Model a Wind

Turbine?

• Design optimisation

• Prediction of power output without having to

make any real parts

• Flow visualisation

• Further understanding of flow physics

Why Use CFD to Model a Wind

Turbine

• Design optimisation

• Prediction of power output without having to

make any real parts

• Flow visualisation

The Modelling Process

Input Geometry

Create Mesh

Define Boundary Conditions

Run the Simulation

Interpret the Results

Refine the Mesh

My Strategy

• Begin with a 2D model

• Airfoil - cross section of a blade

• Model flow around airfoil

• Predict forces on

blade from airflow

• Predict power

output

The Modelling Domain

Edge of

modelled

domain

Airfoil

Airflow

Step 1 – Input Geometry

Step 2 – Create a Mesh

Airflow

Airfoil

Step 3 – Define Boundary

Conditions

Airflow

Airfoil

Step 4 – Run the Simulation

Step 5 – Interpret the Results

Step 6 – Refine Mesh

Step 2 – Create a Mesh

• Gambit

Step 2 – Create a Mesh

• Gambit

Step 2 – Create a Mesh

• Gambit

Step 6 – Refine Mesh

My Results

My Results

What Will the Model be Used

For?

• Comparison of a hand made

blade with a conventional factory

manufactured blade

• Hugh Piggott design

• Increase performance without

increasing manufacturing time or

effort

Future Work

• Next 2 months:

• Fix 2D model

• Factory vs. hand made

• Create and run a 3D model

• Factory vs. hand made

• Wind tunnel testing

• Factory vs. hand made

Questions?