Final report

Dates and location

8 June — 10 June 2017, Sweden

Chairperson

Dan Henningson

Co-chairperson

Henrik Alfredsson

Conference fees

Early Registration Fee: 280.00 €
Late Registration Fee: 350.00 €

What other funding was obtained?

Line FLOW Centre, Swedish Research Council and STandUP for Wind

What were the participants offered?

Conference Dinner, lunches, coffee breaks and book of abstracts,

Applicants (members)

Hauke Beck
Dennice Gayme
Richard Stevens
Xiaohua Wu

Applicants (non members)

Ali Al Sam
Johan Arnqvist
Jacob Berg
James Bleeg
Karl Bolin
Erik Boström
Mattias Brynjell-Rahkola
Francesco Castellani
Jan-Åke Dahlberg
Ralf Deiterding
Ebba Dellwik
Kurt Schaldemose Hansen
Yngve Heggelund
Ann Hyvärinen
Giacomo Valerio Iungo
Stefan Ivanell
Mahmood Jabareen
Hans-Jakob Kaltenbach
Michael Kholmyansky
Yusik Kim
Elektra Kleusberg
Hannes Kröger
Jose Laginha Palma
Stefano Leonardi
Paolo Luzzatto-Fegiz
Davide Medici
Matthias Mohr
Nhung Nguyen
Hugo Olivares Espinosa
Carlos Peralta
Andreas Rettenmeier
Philipp Schlatter
Yasemin Sengul Tezel
Inanc Senocak
Michael Stoellinger
Frederik Thönnißen
Timothy Van Renterghem
Björn Witha

Scientific report

The increasing need of renewable energy in Europe has lead to the growth of wind farms both off-shore and over complex terrains. For the latter, hills, forestry and in general surface inhomogeneities make the wind-resource assessment more challenging than in off-shore sites. There are several open issues that are now investigated by the wind-energy community to improve the current evaluation methodologies and, simultaneously, to increase the physical understanding of such complex flow scenarios.
The EUROMECH Colloquium 576 was motivated by the need to gather researchers actively working in the wind-energy field, to compare the available experimental/numerical/analytical techniques and propose new ideas to improve the current know-how as the wind energy field is a relatively new field that combines both fundamental and applied fluid dynamics.
Various fundamental and applied aspects of the site-assessment process have been discussed, with particular focus on the effect of complex terrains (forests, hills, inhomogeneous surface roughness, etc.) on the available wind resource and its prediction with the current evaluation methods. Recurring issues during the talks were:
• Wind turbine wakes: several methods to simulate for wind-turbine wakes and their dynamics have been discussed. There is still a visible gap between what industry is currently using and the new research methods, but the increased understanding of the wake dynamics is leading to faster and more reliable methods, so there is a clear interest from the industrial world in meetings like this.
• Forestry and topography: since the meeting was based on the terrain complexity, many talks reported experimental and numerical results on forestry and/or terrain complexity. It is anyhow clear that more high-quality data are required to develop a better comprehension of the flow features near the ground and how that influences the wind-turbine wake behavior.
• Atmospheric stability: the continuous growth of the wind-turbine hub height implied an increasing importance of stability effects, which have significant effects on the wake dynamics and the energy production from wind farms. At least 20% of the talks discussed stratification effects, something different from just 5 years ago where stratification effects were seldom discussed.
• Wind farms control: several methods are now adopted to control wind farms in order to alleviate fatigue loads or to produce more power. Several control approaches were discussed and compared mostly with numerical simulations, while experimental data were reported about steady curtailment of existing farms.
• Synthetic turbulence: with the growth of computational resources, large-eddy simulations have become the most reliable tool to simulate the wind flow over complex terrains with turbines. However, an initial velocity field must be prescribed, ensuring that some characteristic features of the wind field are kept. Several methods have been compared independently by many researchers but it still appears as an open issue.
• Atmospheric measurements: measurements in the atmosphere have for a long time been made mostly with cup and sonic anemometers. Nowadays, LIDAR measurements have become the main players since they allow for remote measurements of the mean flow with some information about the turbulence characteristics. They allow for measurements in many points and heights, providing a spatial coverage that overcomes traditional masts. However, it is unclear their precision and a comparison with mast data is still required to identify the reliability of the measurements.

The conference organisers were:
• Dan Henningson, Linné FLOW Centre, KTH Mechanics
• Henrik Alfredsson, Linné FLOW Centre, KTH Mechanics
• Jens Sørensen, DTU Wind Energy
• Antonio Segalini, Linné FLOW Centre, KTH Mechanics

7 invited speakers were present:
• Hans Bergström, Uppsala University
• James Brasseur, University of Colorado
• Jakob Mann, DTU Wind Energy
• Charles Meneveau, Johns Hopkins University
• Johan Meyers, Leuven University
• Joachim Peinke, ForWind, University of Oldenburg
• Bharathram Ganapathisubramani, University of Southampton

In total, 50 participants were present (16 from Sweden, 9 from USA, 8 from Germany, 5 from Denmark, 3 from UK, 2 from Italy and Belgium, 1 from Canada, Israel, Netherlands, Norway and Portugal). A book of abstract of 100 pages has been distributed amongst the participants. Many of them appreciated the meeting for its coverage over many interesting topics related to wind energy.

We also acknowledge the financial support of the Linné FLOW Centre, the Swedish Research Council (VR) and STandUP for Wind.

Number of participants from each country

Country	Participants
Sweden	12
Germany	8
United States	7
Denmark	3
United Kingdom	3
Italy	2
Israel	2
Norway	1
Portugal	1
Netherlands	1
Belgium	1
Canada	1
Total	42