Atuactor Disc Model in a Horizontal Wind

Turbine with CFD

Comparison of methods applied in CFD and linear models

PRESENTATION TOPICS

• Company Overview (2-3 minutes);

• Problem Description;

• Methodology;

• Goals;

• Conclusion and next steps.

Company Overview

• STE – is a technology-based company that helps

other organizations to obtain better results through

innovation and optimization of industrial process,

employing numerical simulation and developing

mathematical models

• In almost 9 years of existence, more than 40 R&D

and consulting projects for over 15 clients

Company Overview – STE actuation areas

METALLURGY MINING

ENERGY ENVIRONMENTAL

Company Overview – STE expertise

• STE acts in different

industry sectors,

employing numerical

simulation tools and

developing custom

mathematical models

for transport and

thermodynamic

phenomenon

Opera3d/Elektra Ansys/CFX

WRF Model FactSage

C++, Visual Basic, Fortran, Java

Problem Description

• In wind power projects want to get the most energy efficient and that the

distribution of wind turbines on the ground should be done optimally;

• For a proper distribution, is crucial to understanding the behavior of winds

downstream of the rotor wind (wind wake);

Problem Description

• Model the wind farm wakes trough cfd.

Problem Description

• The complete modeling of the wind rotor, to calculate in computational

environment, needs large number of finite elements to capture the effects of

small-scale, and thus the simulation over a turbine, a park, has prohibitive

computational cost;

• The actuators are alternative methods to modeling full rotor and intended to

represent the same with low computational cost;

• There are analytical methods, with low computational costs, which can be

employed and was used to comparison with another methods;

Methodology

• NREL wind turbine of Phase VI campaign.

Methodology

• NREL wind turbine of Phase VI campaign.

Methodology

• Modeling the wind turbine in computational environment. Geometry of wind

turbine.

Methodology

• Discratization of the calculation domain through finite volume method.

Methodology

• Applying the boundary conditions.

Methodology

• Flow calculation through wind turbine by the iterative solution of RANS (Reynolds

Average Navier-Stokes), flow governing equations.

• Mass Conservation:

• Momentum:

0i

i

u

x

1i i

i j

j i j j

u upu u

t x x x x

Methodology

• Validation of mesh elements through comparative analysis of the results and the

experimental data provided by NREL;

• With the work mesh, the actuator discs are modeled.

Passo Nome Nº volumes TC Diferença

0° malha 1 1.360.000 0,3508 -17,1%

0° malha 2 1.787.246 0,4005 -5,33%

0° malha 3 2.292.235 0,4173 -1,35%

0° malha 4 2.875.594 0,4181 -1,13%

Methodology

• Applying actuator disc methods using the values of thrust obtained with the

simulation of the complete rotor;

Methodology

• Mesh of uniform actuator disc method (UADM);

Methodology

• Applying the same boundary conditions of complete rotor case and solution of

velocity field;

Methodology

• Applying blade element method with the values obtained with the 2-D simulation

of different blade sections;

Methodology

• Application of the method of the blade element (BEM method) require values of

lift obtained with 2-D simulation in different sections of the rotor blade wind;

Methodology

• Mesh of Blade Element Moment Method (BEM) with annular subdomains;

Methodology

• Applying the same boundary conditions of complete rotor case and solving

velocity field;

• Comparison between models applied.

Methodology

• Linear methods may also represent in a simplified manner the effects of treadmill,

thus, this study also makes a comparison between the results obtained using

numerical methods and results obtained by Wenzel (2009) with linear model

Park.

Goals

• Using experimental results of wind tunnel tests with a wind turbine in scale to

compare the effectiveness of the suggested models applicable in cfd;

• Applying the complete rotor model and two actuator methods to predict the wake

of a horizontal axis wind turbine through computational fluid dynamics tool;

• Compare actuator methods with linear methods.

Goals

• Comparison between anemometers values obtained with complete rotor model,

actuator models and experimental data:

Goals

• Comparison between anemometers values obtained with complete rotor model,

actuator models and experimental data [m/s]:

Anemômetro Larwood CR UADM BEM

1 7,38±0,91 7,2382 7,6436 7,2571

2 5,41±0,68 5,7134 5,6598 5,6713

Goals

• 1 - Comparison between velocity results (u/Uinf) of complete rotor and actuator

data;

Goals

• 1 - Comparison between velocity results (u/Uinf) of complete rotor and actuator

data;

Goals

• 1 - Comparison between velocity results (u/Uinf) of complete rotor and actuator

data;

Goals

• 1 - Comparison between velocity results (u/Uinf) of complete rotor and actuator

data;

Goals

• 2 - Comparison between complete rotor and actuator methods with Park linear

model;

Goals

• 2 - Comparison between complete rotor and actuator methods with Park linear

model;

Goals

• 2 - Comparison between complete rotor and actuator methods with Park linear

model;

Conclusion and next steps

• The proximity of the numerical and experimental results show a computational

methodology suitable employment in both the mathematical model and the

turbulence model as the spatial discretization of the domain;

• The actuators models are employable, with low computational cost (getting

results around 1 hour with a computer / i7, 8gb ram), and percentage differences

of less than 5% at speeds along the track relative to simulations with the model of

the complete rotor (duration 2 days with same computer);

• The PARK linear method presented results of lower quality and accuracy, but that

can be an alternative analysis of wakes, especially at low computational cost.

According to the study by Wenzel (2009) model also showed good recovery

speed on the treadmill;

Conclusion and next steps

• Verify the efficiency of the models to predict the wake in a configuration with more

than one wind turbine;

• Check the effectiveness of the models in wake predictions of wind turbines

installed in complex terrain subject to adverse pressure gradients.

• Thanks:

- STE;

- UFRGS;

- CNPQ;

- ANSYS;

- ESSS.

Thank you!