The Work Plan consists of 2 technical Work Packages. WP1 and WP2 are focused on experiments and calculations respectively where WP3 ensures a good cooperation with other IEA Tasks.
In WP1 and WP2 several calculations are performed. It is then important to know that the present consortium covers the entire spectrum of design models ranging from efficient low fidelity models as used in industry to high fidelity computational extensive models used by research institutes with a variety of intermediate models in between. In this way a very good insight is obtained on how different models cope with the design of large wind turbines under real inflow.
The main goal of WP1 to share experiences on the specialistic field of detailed aerodynamic measurements . Several new aerodynamic experiments are currently being initiated. This is true in Denmark, France, Germany, Italy, Netherlands, Switzerland and the USA.
In the WP the experimental parties learn from each other about methods and techniques which work successfully and what should be prevented so that they all improve the quality of the experiments. Moreover the measurement results will be shared into the consortium so that the theoretical partners get first hand information from these unique new data. For example unsteady pressure distribution at special events (standstill, heavy gusts) will provide much insight on the aerodynamics at such events and forms inspiration for theory development. Measurements from at least the DanAero experiment will be simulated under turbulent conditions.
Thereto it should be known that the first three phases of IEA Task 29 considered measurements at non-turbulent wind tunnel conditions . In the final phase DanAero measurements in the field were simulated but mostly under steady time averaged conditions. Obviously in cases of turbulent inflow a statistical evaluation e.g. an evaluation based on mean values as carried out in Task 29 is useful but it is equally important to analyse the development of forces over time. It was found that modelling the aerodynamic response at turbulent conditions leads to several additional complications which have large impact on the loads and which are not or poorly understood yet. Moreover a major research effort is needed to ensure a consistent comparison procedure between low and high fidelity models which is explained below and which forms part of WP2. a
An even larger challenge, which forms subject of WP1.2 lies in a consistent comparison between calculations and measurements. The wind speed in the DanAero experiment is measured at a mast some distance away from the turbine which may not form sufficient input for a comparison between calculations and measurements on a time series basis.
It is anticipated that 2 rounds of calculations are carried out where every round will consist of several iterations. Within IEA Task 29 much experience has been gained with modelling the Danaero turbine already so that a fully tested model description is available.
The first round is planned to start in August 2021 and lasts until October 2022
WP2 is defined around turbulent calculations on a large scale 15 MW wind turbine. Thereto a large variety of aerodynamic and aero-elastic models are available in the consortium. In this way a very good insight is obtained on how different models cope with the design of 15MW wind turbines under real inflow and what the most important uncertainties are. These insights can be used in WP1 to define experiments which can answer these questions, even if the experiment is done on a smaller scale.
As an example calculations at parked storm conditions on a 15 MW RWT might lead to loads which depend heavily on the dynamic stall model used: one model may predict a stable solution, and another may predict an unstable solution leading to failure of the blades. If this becomes true, special attention is paid to the design of an experiment which measures dynamic stall effects in standstill. Another example is that torsional flexibility of large blades might lead to unsteady aerodynamic effects. If this becomes true special attention need to be paid to measure such effects.
It is noted that the set-up and character of the calculations on the 15 MW RWT is very similar to the calculations in WP1. However the present calculations are performed on the 15 MW RWT without measurements where WP1 carries out calculations on the DanAero turbine which are not only compared mutually but also with measurements. As explained in the description of WP1.2 for turbulent calculations attention needs to be paid to a consistent comparison procedure between low and high fidelity models under turbulent conditions.
In 2021 preparatory calculations are carried out which aim to establish the aerodynamic reference, i.e. a correct aerodynamic input so that each model will simulate the 15MW RWT in the follow up tasks without trivial input errors. Thereto aerodynamic simulations will be carried out under relatively simple conditions, e.g. uniform steady flow, prescribed shear, prescribed gusts etc.
Results from thrust, power (also on sectional level) will be compared until confidence is obtained on the correct input. Moreover an aero-elastic Benchmark will be carried out which aims to gain confidence on the aero-elastic input. Thereto several aero-elastic properties (e.g. eigen frequencies modes etc.) are compared. It is then expected that the turbulent calculations on the 15 MW RWT will start in 2022.
It is anticipated that 2 rounds of calculations are carried out.
In WP3 the main achievements from Task 47 are communicated to other IEA Wind Tasks which have connections to aerodynamics and vice versa. It is anticipated that in the present IEA Task many participants will be active in other IEA Tasks and the most effective way of communication is seen to be the appointment of these participants as contact persons to other Tasks.