IEC TR 61400-12-4:2020

IEC TR 61400-12-4 ®
Edition 1.0 2020-09
TECHNICAL
REPORT
Wind energy generation systems –
Part 12-4: Numerical site calibration for power performance testing of wind
turbines
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IEC TR 61400-12-4 ®
Edition 1.0 2020-09
TECHNICAL
REPORT
Wind energy generation systems –

Part 12-4: Numerical site calibration for power performance testing of wind

turbines
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.180 ISBN 978-2-8322-8781-1

– 2 – IEC TR 61400-12-4:2020 © IEC 2020
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions, abbreviations and symbols . 7
3.1 Abbreviations . 7
3.2 Symbols and units. 8
4 Overview of Numerical Flow Simulation Approaches . 10
4.1 Linear Flow Models . 10
4.2 Reynolds-averaged Navier-Stokes (RANS) Models . 11
4.3 Large Eddy Simulation (LES) and Hybrid RANS/LES Models . 12
5 Existing Guidelines for Numerical Flow Modelling Applications . 13
5.1 General . 13
5.2 AIAA (1998) Guide for the Verification and Validation of Computational Fluid
Dynamics Simulations . 14
5.3 Standard for Verification and Validation in Computational Fluid Dynamics
and Heat Transfer – ASME V&V 20-2009 . 14
5.4 COST Action 732 “Quality Assurance of Microscale Meteorological Models” . 15
5.5 Architectural Institute of Japan Guidelines . 16
5.5.1 General . 16
5.5.2 The guidebook for practical applications of CFD to pedestrian wind
environment around buildings [18] . 16
5.5.3 Guidebook of recommendations for loads on buildings 2 [19] . 16
5.6 VDI 3783 Part 9 “Environmental meteorology – prognostic microscale wind
field mode- evaluation of flow around buildings and obstacles” . 16
5.7 International Energy Agency Task 31 Wakebench – Model Evaluation
Protocol for Wind Farm Flow Models . 17
5.8 MEASNET – Evaluation of Site-Specific Wind Conditions . 17
6 Summary of Benchmarking Validation Tests . 17
6.1 General . 17
6.2 DEWI Round Robin on Numerical Flow Simulation in Wind Energy . 17
6.3 Bolund Experiment . 18
6.4 European Wind Energy Association Comparative Resource and Energy Yield
Assessment Procedures I and II (2011, 2013) . 18
6.5 IEA Task 31 Wakebench Experiments . 19
6.6 New European Wind Atlas Experiments [32] . 19
6.6.1 Perdigão (double ridge) . 19
6.6.2 Alaiz (complex terrain with a strong mesoscale component) . 19
6.6.3 Østerild (flow over heterogeneous roughness) . 19
6.6.4 Kassel (flow over forested hill) . 20
6.7 Wind Forecast Improvement Project 2 [34] . 20
6.8 Wind Tunnel Test Validation Data . 20
6.8.1 Compilation of Experimental Data for Validation of Microscale
Dispersion Models [23] . 20
6.8.2 AIJ wind tunnel . 20
6.8.3 Wind tunnel test for flow over hill . 20

7 Important Technical Aspects for Performing Flow Simulations over Terrain for
Wind Energy Applications . 21
7.1 General . 21
7.2 Quality of Topographical Input Data . 21
7.3 Computational Domain . 21
7.4 Boundary Conditions for Computational Domain . 21
7.5 Mesh Parameters . 21
7.6 Convergence Criteria . 21
7.7 Atmospheric Stability . 21
7.8 Coriolis Effects . 22
7.9 Obstacles effects . 22
7.10 Suggestion on Model Range Applicability for NSC . 22
8 Open Issues . 22
8.1 General . 22
8.2 Determination of Flow Correction Factors from Numerical Simulation Results
for Power Curve Testing . 23
8.2.1 General . 23
8.2.2 Correlation check for linear regression . 23
8.2.3 Change in correction between adjacent wind direction bins . 23
8.2.4 Site calibration and power performance measurements in different
seasons . 23
8.3 Uncertainty quantification . 23
8.4 Proposal for Validation Campaign for NSC Procedures . 24
8.4.1 General . 24
8.4.2 Assessment of terrain at the test site . 24
8.4.3 Experimental layout . 24
Bibliography . 26

Table 1 – symbols used in this Technical Report . 8

– 4 – IEC TR 61400-12-4:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND ENERGY GENERATION SYSTEMS –

Part 12-4: Numerical site calibration for power
performance testing of wind turbines

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