LAISA
In the municipality of Krummendeich (Stade district), DLR is establishes the Research Wind Farm WiValDi (https://windenergy-researchfarm.com) to address what the IEA (International Energy Agency) calls the three biggest challenges in wind energy research.
Specifically, these are
- an improved understanding of the physics of atmospheric flow in the critical zone of wind turbine operation,
- the materials, structural and system dynamics of individual wind turbines, and
- the optimization and control of wind turbines and farms. In the medium term, a virtual wind farm is to be added to this real research park.
In the DLR-internal project LAISA, numerical tools from different disciplines, which were created and already partially validated in previous projects, will be further developed and linked with each other. The concrete goals of the project are:
- the establishment of a consistent simulation chain, starting from the flow simulation around the wind turbine in the atmospheric boundary layer at the site, via the sound generation up to the sound propagation to an immission site.
- the development of a methodology (simulation chain, interfaces, load scenarios, etc.) that allows the design of a load-adaptive rotor blade with flap.
To achieve these goals, work is taking place in three thematic blocks:
Low-noise wind farm
In this work package, on the one hand, the simulation capability of the processes in the meteorological boundary layer is developed in order to be able to numerically represent the interaction with the turbine, the characteristics of the wake and the interaction with the wake flow accurately (i.e., capturing all essential processes), taking into account the real location of the turbine. For this purpose, turbulence-resolving meteorological simulations of the atmospheric boundary layer at the site are coupled with Hi-Fi CFD simulations of the wind turbine in a multi-scale approach. Thus, the interaction of the perturbed inflow on the downwind turbine can be investigated in the next step.
On the other hand, the methods for the simulation of the sound generation are extended by the "off-design" sound sources detachment noise and leading edge interaction noise, which are currently still missing, but which occur repeatedly in the application case. In combination with the simulation of sound propagation through the atmosphere to the point of immission, site-specific sound reduction measures can thus be developed for a given parking situation in the medium to long term.
Load-adaptive rotor
The focus of this work package is to upgrade existing design and simulation tools to allow the design of a flexible trailing edge flap and the evaluation of its effectiveness. Throughout the design cycle, the flap must be integrated into the models as a separate component of the rotor blade and considered in interaction and coupling with the blade and the entire turbine. For this purpose, the interfaces between the fast turbine simulation and the design process of the flap have to be adapted and the turbine simulation itself has to be extended to consider a flap.
Furthermore, an existing Hi-Fi flow-structure coupling will be further developed to simulate and thus quantify the influence of realistic turbulence in the atmospheric boundary layer on the dynamics of the plant simulation and the load fluctuations that arise.
Assessment
The (further) development of assessment methods serves the goal of achieving long-term capability for technology, plant and wind farm assessment. The above-mentioned topics result in concrete requirements for the assessment. For the certification of load-adaptive rotors, for example, additional flap-specific scenarios not yet covered by the IEC standard must be developed and taken into account. In order to be able to evaluate the load reduction targeted with a flap and the possible increase in service life, corresponding fatigue models are being further developed. In addition, initial design guidelines are to be developed, with the aid of which the design process for new blades can be significantly shortened using digital methods. The guidelines will be used, for example, for the predetermination of effective noise reduction measures, the effectiveness of which must be analyzed both in relation to the plant and in the parking context, i.e. on a site-specific basis.