EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

A CFD Investigation of the Near-Blade 3D Flow for a Complete Wind Turbine

Sugoi Gomez-Iradi & Xabier Munduate (CENER)George N. Barakos (Liverpool University)

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

OUTLINE

Introduction: Background and CFD method

NREL blade

Validation cases (isolated rotor)

Cp

Integrated loads

Local Flow Angles

Isolated rotor

Yawed flow

Full wind turbine

Summary & Future steps

01 & 02

03

08

17

04

05 to 06

07

09 to 10

11

12 to 16

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

INTRODUCTION: BACKGROUND01/17

+ The design of large-diameter wind turbines is outsidethe knowledge envelope of wind turbine manufacturers (Larger diameters wind turbines)

» Flow compressibility

» Stalled flow

» Blade deflection

+ CFD base WT design

+ The objectives are to take into account compressibility effects, aeroelastic influence and to analyze the computation of HAWT

http://ec.europa.eu/research/energy/pdf/renews5.pdfFrom EWEA

http://www.supergen-wind.org.uk/images/blade_transport_reducedsize.jpg

From SUPERGEN WIND

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

INTRODUCTION: CFD METHOD02/17

+ PDE solver (WMB)

+ Implicit time marching

+ Osher's scheme for convective fluxes

+ MUSCL scheme for formally 3rd order accuracy

+ Central differences for viscous fluxes

+ Multi-block capability

+ Paralleled using the SPMD paradigm (just requires MPI)

+ Flow Physics: Euler, RANS, URANS, DES

+ Aeroelastic analysis based on modal representation of structures

+ Moving, deforming and sliding grids

+ Documentation (validated for wind turbine flows)

+ Developed and used by academics and engineers

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

NREL UAE Phase VI Experiments03/17

M.M. Hand, D.A. Simms, L.J. Fingersh, D.W. Jager, J.R. Cotrell, S. Schreck and S.M. Larwood, Unsteady Aerodynamics Experiment Phase VI: Wind Tunnel Test Configurations and Available Data Campaigns, Technical Report TP-500-29955, NREL, December 2001.

Twist

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

NREL UAE Phase VI Experiments04/17

S. Gómez-Iradi and G. Barakos, Computational Fluid Dynamics Investigation of Some Wind Turbine Rotor Design Parameters, Proceedings of the Institution of Mechanical Engineers,Part A: Journal of Power and Energy, 222(5):455–470, 2008. DOI:10.1243/09576509JPE526.

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

Isolated Rotor - 30%R, 46.6%R & 63.3%R05/17

5m/s 7m/s 10m/s 13m/s 20m/s

30%R

46.6%R

63.3%R

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

Isolated Rotor - 80%R & 95%R06/17

5m/s 7m/s 10m/s 13m/s 20m/s

80%R

95%R

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

INTEGRATED LOADS07/17

Averaged Thrust Averaged Torque

Averaged: Azimuth angles between 120o and 240o excluded (tower influence)

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

2D / 3D COMPARISON08/17

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

ISOLATED ROTOR – LOCAL FLOW ANGLE09/17

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

2D / 3D COMPARISON10/17

+ Compute 3D flow

+ Extract LFA and CN (3D)

+ Compute 2D at same Relocal and

match Cn to CN varying AoA

+ Extract 2D LFA

+ Down-wash:

the influence of the induction

Down-wash = LFA3D

-LFA2D

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

YAWED FLOW11/17

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

FULL WIND TURBINE12/17

Sliding Grid Location

Tower

Approximate Nacelle geometry

HubCFD ≉K experimental

S. Gómez-Iradi, R. Steijl and G.N. Barakos, Development and Validation of a CFD Technique for the Aerodynamic Analysis of HAWT, Journal of Solar Energy Engineering-Transactions of the ASME, 131(3):031009, 2009. DOI: 10.1115/1.3139144.

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

FULL WIND TURBINE - CP13/17

Rotor/Tower Grid7 million cells198 chord-wise95 span-wiseWilcox k-ω3 Revolutions0.25o time step

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

FULL WIND TURBINE - INTEGRATED LOADS14/17

1.6% Reduction due to the tower

Nacelle Tower Rotor Total

Thrust (N) 31.6 127.5 1,233.7 1,392.8

(2.3%) (9.2%) (88.5%)

Thrust (N) 1,280.0 / 1,233.7

Torque (Nm) 823.2 / 810.2

ROTOR: Isolated / Tower

Full surface integration22 P.T. integration

Torque (Nm) 0.5 -41.8 810.2 768.9

(0.1%) (-5.4%) (105.3%)

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

FULL WIND TURBINE - LFA15/17

ΔLFA

-1⋍ o ΔLFA

-3⋍ o

ΔLFA

-1⋍ o

ΔLFA

0⋍ o ΔLFA

0.5⋍ o

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

FULL WIND TURBINE - λ216/17

Wake expansion

Tip vortex

Root vortex

Vortices shed from tower

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

CONCLUSIONS & FUTURE WORK17/17

+ CFD solver was validated for working conditions.Stalled flow needs further investigation.

+ LFA comparisons show good agreement in the outer half span of the blade.+ The relation between 2D & 3D LFA has been studied.

This could be useful for more engineering methods.+ LFA associated to Yawed flow were studied.

Further research is needed (varying the grid).+ Tower / blade interaction was correctly predicted.

Important for design purposes since the blade tower pass interaction is one of the relevant issues on the blade and tower fatigue.

LFA prediction comparison agrees well with the experiments regarding the shape and the deviation in angle for the outer stations is minimal.

+ Work more with structural model coupling (CFD/modal).To take into account blade deflections and torsion during the computations.

EWEC 2010, Warsaw, Poland, 20/04-23/04 2010

THANKS FOR YOUR TIME !!!Info@cener.comwww.cener.comT: + 34 948 252 800