Wind Tunnel Validation of AeroDyn within LIFES50+ project: imposed surge and pitch tests

Editor's Notes

• #2: I am …Post doc A first set of wind tunnel test results carried out which have the final aim of validating Fast/AeroDyn within the European LIFE50+ project framework
• #3: The physics of FOWTs is complex and when it comes to designing scale model tests as these, we come accross in some constraints related to the fact the the similutude of each adimensional parameter governing the dynamics cannot be ensured at the same time…therefore a few choices must be done for example Taking int account Which also helps to exploit
• #4: With this idea Lifes50+ project is developing advanced experimental techiniques with the combined employment of wind tunnel and ocean basin. As siad the testing approach is what is called hybrid appraoch or hardware in the loop, so that in the ocean basin… Whereas in the wind tunnel… The results communicate one each other in the sense that numerical model running in real time are validated complementarily
• #5: The wind turbine model for the tests was built with reference to the DTU 10MW prototype, with the goal of reproducing the same performance beyond the high discrepancy (about 150 times) in the Reynolds number As well as reproducing the scaled overall mass and natural frequency so that it was defined velocity and length scale as well as the tsr similutude, For this project, the goal for the blade was to have same thrust coefficients, this was possible thanks to the adoption of low reynolds profiles and chord, twist and t/c modification with respect to the full scale blade this was combined also with a structural optimization to match the 1° and overall mass. The nacelle was design to allow individual pitch control the the rotor, although very havy constrains were found in terms of overall mass with respect to the target, this was mainly due to the impossibility to get rid of the weight of commercial cmponents such as motors and slip rings who defined the majority of the mass. Also the limited space and the requiriments in terms of control bandwith forced to chase non trivial solutions. For both blade and nacelle design you are referred to a couple of posters
• #6: I briefly report here the blade sectional wind tunnel measurements on the chosen low reynolds airfoil to extract the aerodynamic coefficients, from pressure and wake measurements, afer having built a sectional model with the same manufacturing approach as the real one.
• #7: The final carbon fiber blade, which for the tests presented is a rigid version of the aerolastic one, is here reported along its peculiarty in terms of chord and twist with respect to the geometrical scale of the DTU reference
• #8: Accordingly, just an overview of the complexity and the miniaturized solution for the mechatronic design.
• #9: Steady wind tunnel tests demostrated an excellent maching of the thrust, which was the target, in the whole range of wind speed and a good matching also for the torque with a need of changing a bit the angle of attack above rated with respect to the nominal pitch angle. However the goal of the project was, in a floating offshore scenario, the thrust
• #10: On top of this a set of surge and pitch amplitude and frequency in the low and wave ranges were chosen for investigating the effect of single harmonic motion on the aerodynamics, and the same cases were simulated in Fast/Aerodyn with these simulation parameters. So by the first run no dynamic stall was implemented.
• #11: Only surge results are reported for the sake of simplicity and without loss of generality. Therefore, we can define an apparent wind speed wich is composed of the steady wind speed and the a dynamic component due to the motion of the platform. Moreover, with the willing of defining an adimensional parameter to capture the unsteady nature of the aerodynamic thrust, the proposal is to look at the reduced velocity which depends on wind speed and surge frequency and wind turbine’s diameter, so it has also the meaning of how many rotors diameters are travelled by the wind in on surge period. In other words it gives an idea if the thrust enters its own wake going back and forth. Higher quasi static Lower more unsteadiness might be occur
• #12: Imposing single harmonic motion, the aerodynamic force, say the thrust, can be splitted in the steady contribution and a single harmonic contribution which can be splitted in turn in In phase component and quadrature compnent. In this video you can see a simple example with different rapresentations of the same phenomenon, in time, as function of dynamic speed and in the gauss diagramm, for example on the left, we have…., which turns out to a change in the slope when plotted againts dynamic wind speed Whereas on the right, if the we go from pure in phase to pure quadrature component the effect is an enlargment of the ellypsis potentially up to a circle.
• #14: Very similar behaviour, although
• #16: Grouping separaterly experimental from numerical Decreasing the reduced frequency, with different Ap and Aq ratio, but both experiments and aerodyn predict the enlargement of ellipsis and then incresing in quadrature components
• #17: To be conclude