Simpack Wind 2010 Swe Loadsimulations

7/22/2019 Simpack Wind 2010 Swe Loadsimulations

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Aeroelastic Load Simulations

and Aerodynamic and StructuralModeling Effects

Stefan Hauptmann

Denis Matha

Thomas Hecquet

Hamburg, 17 June 2010

SIMPACK Conference: Wind and Drivetrain


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SIMPACK Conference: Wind and Drivetrain, 17 June 2010 2

Contents

Dynamic Simulations in the WT Design Process

Wind Turbine Modeling in SIMPACK

Wind Turbine Aerodynamics in SIMPACK

Blade element Momentum Theory (BEM)

Non-linear Lifting Line Vortex Wake Model

Computational Fluid Dynamics (CFD)

Simulation Results

Offshore Code Comparison Collaboration (OC3)

Evaluation of Lifting Line Vortex Wake Model

Validation of CFD Approach for Aeroelastic Simulations

Offshore Applications

Conclusions


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WindEner

gySpecific

s

tandardsand

Guidelines

Standards, Guidelines

Guideline

Environmental

ConditionsLoads

States of

Operation

Wind

Field

Dynamic Simulation of the System Wind Turbine

Hydro-

dynamics

Aero-

dynamics

Structural

Dynamics

Electr.

System

Control,

Operation

Structural Loads(time series or spectra, extreme values,

load collectives)

Site WT-Type

(Static) Mechan. Component model(FEM, analytical oder empirical)

Ultimate Strength Analysis(fracture, buckling, fatigue)

Natural

Frequencies and

Damping

Displacements

Serviceability Analysis(geometry, resonance, dynamic stability)

CommonS

tandards

andGuidel

ines

Validation

via

Measure-

ments

[Fig.: R. Gasch, Windkraftanlagen]

Dynamic simulations in the WT design process


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Major modules of a wind turbine simulation tool

1. wind field

2. rotor aerodynamics

3. structural dynamics including electro-mechanical system

4. control unit and actuators5. Hydrodynamics (Offshore turbines)

Wind field

Wave field,

currents, ice

Soil

Aero-dynamics

Hydro-dynamics

Soil-

dynamics

Rotor

Support

structure

(Tower &

Foundation)

Grid

Environment Loads Support structure Consumption

Electro-

mech.System

Control

Offshore Wind Turbine

Dynamic

interactions:

major

minor

[Fig.: M. Khn]

Integrated system model


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Model with 28 modal

degrees of freedom (dof)

Foundation:6 dofs

3 translational (1, 2, 4)

3 rotational (3, 5, 6)

Rotor blade (each):

4 dofs2 flapwise (e.g. 16, 17)

2 edgewise (e.g. 18, 19)

Tower:

5 dofs

2 fore-aft (7, 8)

2 lateral (9, 10)

1 torsional (11)

Addit ionals dofs:

nacelle tilt (12)

rotor rotation (13)

main shaft bending (14, 15)drive train torsion (28)

Traditional dynamic model for aeroelastic simulation

RN

K

F, T

16, 17 18, 19

20-23

24-27

28

1

2

3

45

6

7, 8

9, 10

11

12

13

1415

x

yz

flexural beam

Wind

[Fig.: Vestas]


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Motivation - Improvements needed

Limitations of the traditional dynamic model

Structure: Fixed number of only few modal degrees of Freedom

Aerodynamics: Simplified representation of rotor aerodynamics by BEM theory

Problem: Coupling effects are NOT considered

Improvements for Structural dynamics

Flexible levels of detail for the wind turbine models

More accurate models for rotor blades, drive train etc.

Improvements for Aerodynamics

New engineering models for BEM ? Codes, based on more advanced theories than

BEM are needed to consider some aeroelastic effects

Multibody

simulation

approach

More

sophisticated

aerodynamic

approaches

Solution

Solution


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Modular Integrated Simulation: SIMPACK - Wind

7

SIMPACK

Wind Turbine MBS Model

Rotoraerodynamics

v1

v2v3

S

BEM

Wind Field

Lifting Line-Method

CFDGenerator, Converter

AS-Lufer

Filter~

=

DC

~

=

Trafo

PLufer

zum Netz///

PStnder,, fNetz

fLufer

Stnder

///

[Fig.SW

E,

ECN,

IAG,

SIMPACKAG]

Controller Interface


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Dynamic wind turbine model in SIMPACK

Traditional Dynamic Model

28 Degrees of Freedom

Used for a large number of

load simulations

Foundation_Ground

,

yaw), (tilt)2 DOF

UF22 Aerodyn

x, y , z , , ,6 DOF

0 DOF

Foundation

0 DOF

0 DOF

Bedplate_Connect

Drive train / base plate

LSS_Gearbox

1 DOF1 DOF

, ,

Shaft torsion, bending

3 DOF

LSS_Hub

0 DOF

HSSLSS_Hub

Blade_

Connect 1

0 DOF

(pitch)

0 DOF

(pitch)

0 DOF

Blade_

Connect 2

Blade_

Connect 3

generator

Drive Train

Tower (Flexible Body)

4DOF

brake

Blades (Flexible Body)

4DOF/blade

Foundation

Hub

C14-Gearbox

Gearratio (constraint)

Tower

Pitch_

Reference_1

(pitch)

Pitch_

Reference_2

Pitch_

Reference_3

0 DOF 0 DOF 0 DOF

FE-43 Bushing

FE-13 Spring Rot

FE-110 Proportional

Actuator Cmp

FE-165 Kinematic

Measurement

FE-143 Connector and

Fct generators

FE-43 Bushing


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Rotor Blade Models

Automatic generation of 2 different kinds of rotor blade models

Euler-Bernoulli or Timoshenko beam elements

Modal Reduction

Geometric stiffening

Simple rotor blade Only bending modes are considered

Sophisticated rotor blade

Bending and Torsional Modes are considered

Coupling effects are included


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The Control System Interface

DLL interface

Bladed compatible

Baseline controller

Variable speed below rated

Collective pitch control aboverated power

Advanced control algorithms

Individual pitch control

(Tower-) Feedback controller

Etc.

El.po

wer

Prated

Pitchangle[o]

Wind speed

Vin VratedVcut out

Rot.speed

90o


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Generator Models (Variable Speed Generator)

Static look-up table

Simulation of generator/converter system dynamics

Detailed electrical model of the coupled generator, converter and grid

FiFo PT2Control

systemPT1PT1

Losses

Msetx

+

MgenoWgenWgen

Pel

Electric

system

dead time

Low pass

Drivetrain

filter

Converter

delays

Electro-

technical

inertia

Electrical &

mechanical

Losses(look-up table)

Wgen Look-up tableMgeno

AS-Lufer

Filter~

=

DC

~

=

Trafo

PLufer

zum Netz///

PStnder,, fNetz

fLufer

Stnder

///

MatSIM

Modeled in Matlab/SIMULINK

Exported to SIMPACK

Using MatSIM


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Blade Element Momentum TheoryBasic approach: Load equil ibrium in axial and radial direction

=> Iterative derivation of induced velocities

Important assumptions:

1. Stream Tube theory andsplitting in isolated annuli

(no radial interdependency)

2. No radial flow along the blades

(problematic in combination with flow seperation

and at the blade tip)

3. No tangential variation within the annuli

(but empirical correction for finite number of blades)

Loads derived from the

global momentum balance(depending on the induced

velocities)

Loads at the

local blade element(depending on the induced

velocities)

=


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AeroDyn - Blade Element Momentum Theory

Developed at the National Renewable Energy Laboratory, USA

Empirical correction models: Tip-Loss Model: Prandtl

Hub-Loss Model: Prandtl

Turbulent wake state: Glauert Correction

Dynamic stall model: Beddoes-Leishman

Skewed Wake Correction: Pitt and Peters


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OC3 Participants & Codes 3Dfloat

ADAMS-AeroDyn-HydroDyn

ADAMS-AeroDyn-WaveLoads

ADCoS-Offshore

ADCoS-Offshore-ASAS

ANSYS-WaveLoads

BHawC

Bladed

Bladed Multibody

DeepC

FAST-AeroDyn-HydroDyn

FAST-AeroDyn-NASTRAN

FLEX5

FLEX5-Poseidon

HAWC

HAWC2

SESAM

SIMPACK-AeroDyn

Simo


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Exemplary SIMPACK/AeroDyn Result in OC3

0,0

20000,0

40000,0

60000,0

80000,0

100000,0

120000,0

NREL FAST (kNm)

GH Bladed (kNm)

SWE FLEX5 (kNm)

NREL ADAMS (kNm)

Risoe HAWC2 (kNm)

SWE SIMPACK (kNm)

Model Results for Tower Base Bending Moment (OC3 Phase 1 DLC 3.2)


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AWSM Non-linear Lifting Line Vortex Wake Theory

Developed at ECN, NL

Blade representation: Lifting line

Near Wake representation:

Free surface of shed vortices

[Fig.:

ECN]


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Coupled Simulations: SIMPACK - AWSM

Simulation time: 12sec

Mean Wind speed: 5 m/s

Gust: 9m/s for 0.2 sec

Vorticity of rotor blade 1

Start-up procedure

Occurring wind gust

Aeroelastic effects

because of gust

t

t = 0st = 6s

t = 12s Rotor


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Demonstration Simulation

Turbine:

1,5 MW NREL generic wind turbine

8 m/s wind speed

Modeling approach

Only the rotor (hub and three rotor blades) is modeled

Flexible rotor blades Sophisticated model

Coupling effects are considered

Aerodynamics

AWSM

AeroDyn (with empirical correction models activated)


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Fast Individual Pitch Action

Change of pitch angle for blade 1

(+7.3 for 10 seconds)

Tip deflection blade 1

Tip deflection blade 3

Tip deflection blade 3 (detail view)


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FLOWer A RANS solver

Developed to solve the three-dimensional, compressible, unsteady Euler or

Reynolds averaged Navier-Stokes (RANS) equations

Analyses the flow field around rotors (primarily for helicopters, adapted to wind

turbines)

Different turbulence models are available(but the k- SST turbulence model is the

sole model used in this project)

FLOWer features the Chimera techniqueallowing for arbitrary relative motion of

aerodynamic bodies.


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Fluid

Structure

Qn+1

Qn+1 Qn+2Qn

Qn+2Qn

tn tn+1 tn+2

1

2

Blade surface SIMPACK beam model

SIMPACK blade modelwith deformation

SIMPACKFLOWer

Loads calculation Loads on element nodes(principle of virtual disp.)

load projection onbeam elements

Conversion ofdeformations

to quarter chord lineCalculation of deformationGrid deformation

SIMPACKWEA model

Time-Accurate Fluid-Structure Coupling of Wind Rotors


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AeroDyn + SIMPACK

FLOWer + SIMPACK

AeroDyn + SIMPACK

FLOWer + SIMPACK

Rotormoment[Nm]

Rotothrust[N]

Time-accurate aeroelastic simulation

of the start-up phase

(FLOWer + SIMPACK)

Validation of Fluid-Structure Coupling


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Offshore Application I

Adding capability of SIMPACK to model Offshore Wind Turbines

(Floating & Monopile)

Coupl ing of HydroDyn

and SIMPACK

Hydrodynamic Forces

calculated with HydroDyn

HydroDyn

developed

by NREL

Participation

in OC4

SIMPACK

HydroDyn

[Jon

kman,NREL/TP-500-41958]


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Offshore Application II

Mooring Lines are an important component for Floating WT Dynamics

Currently mainly quasi static and linear models

Introduction of a nonlinear mult i-body mooring systemmodel

Improvement of load predictions by considering linedynamics, hydrodynamics, line-seabed interaction,

nonlinear effects & anchor system

Goal: Detailed modeling of floating WT in SIMPACK


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Conclusions

The traditional approach for load simulations has limitations:

The number of degrees of freedom for dynamic models is fixed

The rotor aerodynamics is modeled using simplistic BEM theory

SIMPACK offers advantages for load simulations

MBS models with a variable level of detail can be generated

Different aerodynamic modules can be coupled to SIMPACK to consideraeroelastic effects with the needed accuracy

SIMPACK Interfaces to several aerodynamic codes have been developed

AeroDyn (Blade Element Momentum Theory)

AWSM (Non-linear Lifting Line Vortex Wake Theory)

FLOWer (RANS solver)

Simpack Wind 2010 Swe Loadsimulations

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