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• NUMECA International • • av Franklin Roosevelt 5 • B - 1050 Brussels • 22-Jan-12 Page 1

Wind Turbine


1 2

4

Content

Configuration...

CAD Import & Mesh…

Results…

5 Conclusions

3 Computation…

0 Introduction


Introduction


0 Introduction

This document presents the result of a Wind Turbine flow simulation using FINE™/Turbo, the Numeca FLOW

INTEGRATED ENVIRONMENT dedicated to rotating-machinery flow analysis including wind turbines.

The 3 bladed NREL S809 wind turbine is presented in 3D, 2.5D and 2D configurations

The geometry is generated from XYZ coordinates data points. The data is then imported directly into the mesh

generator IGG™ and AutoGrid™.

The mesh is generated using IGG™, interactive and automated grid generator and AutoGrid V5, the automated mesh

generator for rotating machinery.

The RANS solver EURANUS of FINE™/Turbo is used for 3D, 2.5D and 2D flow computations

CFView™, the NUMECA flow analysis and visualization tool provides all type of qualitative and quantitative data for

detailed 2D/3D post-processing.

This benchmarking report aims to present the whole CFD chain process in FINE/Turbo applied to wind turbine flow.

Upon request more detailed simulation and flow analysis can be presented.


0 Introduction

Flow analysis

Initial Geometry

IGG™, AutoGrid™ Mesh Generators

Euranus Multi-stage flow solver

FINE™/Turbo

Boundary Conditions

CFView™ Post-processor

FINE™/Turbo


Configuration


Blade Tip

Configuration

3D NREL S809 Geometry 1

3 blades turbine

External boundary

Hub Area


Configuration

2D Geometry

NREL S809 1

2 D geometry is expressed in cartesian frame.

No rotation effect is taken into account.

The flow conditions respect the flow at 47% span of the 3D blade.


Configuration

2.5D Geometry 1 3 blades Turbine

Only one periodic passage is shown here

2.5D geometry represents a 2-D case in cylindrical frame with an arbitrary periodic boundary at a given spanwise position (47%

span in this study).


CAD Preparation

&

Mesh


2 CAD Preparation and Mesh

Summary

Characteristics :

• The geometry definition in a set of points of the NREL S809 airfoil (2D)

• The 3D blade is defined by two surfaces defining the pressure and the suction sides. The pressure side and the suction side are defined by a set of airfoils of the blade at several spanwise location. Each airfoil is defined by a set of points.

• The geometry can also directly be imported in AutoGrid™ V5 from CAD definition in IGES or Parasolid or CATIA V5 format

• The meshes have been automatically generated using the mesh generator IGG™ (2D) and AutoGrid™ V5 (2.5D and 3D);

• The 3D mesh include the external boundary located at 1 blade radius from the blade tip.

• In order to obtain y+ ~ 1, the first cell thickness next to the wall is: 2 X 10-5 m.

Mesh Meshing Process Number of cells

2D 10 seconds 36 920

2.5D 30 seconds 191 035

3D 11 minutes 16 seconds 2 065 404


2 CAD Preparation

ASCII data point, IGES, Parasolid or CATIA Direct Import


2 CAD Preparation and MESHING 3D Configuration

• Linking the geometry to the mesh generator AutoGrid V5

• Starting the mesh generation


3D Meshing Process

2


5 Block Mesh in main channel and 7 blocks in the external area.

Blocks in the main channel:

4 H blocks around the skin topology block

1 Skin Topology block (C-block) around the blade with blunt TE

Blocks in the external area

5 blocks as the extension of the main channel blocks

2 blocks as the extension of the wind turbine blade: 1 H block in the center and C-block around the H-block

2 3D Mesh

Topology

Fully matching connection between all blocks

Non-matching or matching connection at the periodic faces


2 3D MESH

The blade surface mesh

Blade Tip

Hub Area


MESHING

2D Geometry

NREL S809

Automatic mesh generation and geometry creation tasks on similar geometries using scripts.

Meshing time 10 seconds

2


2D Meshing Process

2


CAD Preparation and MESHING

2.5D Geometry 2

• Identical meshing process to the 3D case

7 blocks mesh: 191 035 cells.

Time of meshing 30 seconds.

Only small thickness is kept in spanwise direction.

5 layers from hub to shroud required to respect multigrid convergence acceleration technique of FINE/Turbo.

The constant spanwise boundary conditions are set to MIRROR

Periodic boundary conditions (120 degrees for 3 bladed turbine)


2.5D Mesh 2


2.5D Meshing Process

2


Computation


Computation Flow Physics et Models (1) 3

Flow setting, computation running and monitoring are realized using the NUMECA Flow Integrated Environment GUI FINE™



Three bladed NREL Wind Turbine (Duque, et al., 2000):

• Rectangular blade planform, untwisted and untapered;

• Rotor diameter: 10 meters;

• Blade span (from flange to tip): 4.521 meters

• Blade profile: NREL S809 with maximum chord of 0.46 meter.

• The blade is pitched down by 12º.

Flow Physics

2D configuration = plane at 47% span.

The angle of attack: Case 1 = 9.64° Case 3 = 24.58°



Fluide : air (assumed as perfect gas)

Flow Models:

• Steady turbulent flow simulation

• Turbulence Model: One equation model Spalart-Allmaras

Boundary condition:

• External BC and Inlet and Outlet BC:

• Vz : 7 m/s and 13 m/s

• Standard atmospheric conditions;

• Flow angle: Parallel to rotational axis;

• Wall: the hub and the blade are rotating at 71.68 and 71.19 RPM.

• For 2D cases Vx and Vy are given for identical relative conditions as the cases 1 and 3

Initial Conditions:

• Constant initial conditions are applied for 2D cases.

• For 2.5D and 3D cases, FINE™/Turbo allows to specify initial conditions dedicated for rotating machinery assuming constant rothalpy on the stream surfaces.


Results


Flow analysis and visualization with the NUMECA post-processor CFView™ :

Results 4


Results Relative Velocity Streamlines

at Hub and 3D Tip Vortex 4

Hub area: SUCTION SIDE, LE at left side, TE at right side

3D Tip Vortex

Case 1

Case 3

Case 1

Case 3


Results Relative Velocity Streamlines

at Hub Area 4

Hub Area: Pressure side TE at left side LE at right side

The wake from flow near the hub area

Flow direction Flow direction

Case 1

Case 3

Case 1

Case 3


Results Static Pressure

at Blade Surface 4

Case 1 Case 3

Pressure Side

Suction Side

Pressure Side

Suction Side


Results 2D streamlines

Case 1

3D

2.5D

2D

4


Results 2D streamlines

Case 3

2.5D

2D

3D

4


Results Cp distribution at 47% span (3D)

Case 1

Case 3

4


4 Results

CASE 3 - Static Pressure distribution at 47% span (3D)

2.5D

2D

3D


4 Results

CASE 3 – Velocity distribution at 47% span (3D)

2.5D

2D

3D


Conclusions


5 Conclusions

Conclusions

Highly complex flow around the blade is observed in 3D flow simulation.

In Case 3 the flow close to the hub creates 3D vortex flow that propagates in spanwise direction toward the

tip. While in Case 1 the vortex flow stays close to the hub.

The 2D streamlines show that Case 1 does not present separation while a strong separation is well generated

in the Case 3.

The Cp distribution along the blade for all cases is in good agreement with the experimental result.

Similar qualitative agreement are observed for the 2D, 2.5D and 3D (at 47% spanwise section) (pressure,

velocity distribution, streamlines).

Flow analysis in 2D, 2.5D and 3D configurations are treated by one single tool only, FINE/Turbo, ensuring

quick turn-around time in wind turbine design cycle.


Annex

ADDITIONAL INFORMATION


6 FLOW MODEL & TURBULENCE MODELS SELECTION

in FINE GUI


6 WALL FUNCTION SET-UP

in FINE GUI in case High-Reynolds k-e turbulence model


6 TRANSITION SET-UP

in FINE GUI


FINETM/Design3D: Introduction

Optimization Process

AutoBlade Parametric Blade Modeler

Design3D Blade Optimization

FINE/Turbo CFD system for turbomachinery

FINE/Design3D

- Geometrical / Mechanical Constraints

- Design / Optimization Targets

Optimized

3D Blade

Initial Geometry Initial

3D Blade

6


FINETM/Design3D: Introduction (cont’d)

Optimization Process 6

AutoBlade™

Parametric Blade Modeller

AutoBlade™

Fitting

Parameterisation of existing geometries

Design 3D

Optimisation Artificial Neural

Network + Genetic Algorithm and

Gradient App.

FINE™/Design 3D

Design 3D

Database generation

Skeleton for a Project *.Presentation - NUMECA RU mesh is generated using IGG™, interactive and automated grid generator and AutoGrid V5, the automated mesh ... Skeleton for a Project

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