Wind tunnel validation of AeroDyn within LIFES50+ project: Imposed Surge and Pitch tests

This paper presents the first set of results of the steady and unsteady wind tunnel tests, performed at Politecnico di Milano wind tunnel, on a 1/75 rigid scale model of the DTU 10 MW wind turbine, within the LIFES50+ project. The aim of these tests is the validation of the open source code AeroDyn developed at NREL. Numerical and experimental steady results are compared in terms of thrust and torque coefficients, showing good agreement, as well as for unsteady measurements gathered with a 2 degree-of-freedom test rig, capable of imposing the displacements at the base of the model, and providing the surge and pitch motion of the floating offshore wind turbine (FOWT) scale model. The measurements of the unsteady test configuration are compared with AeroDyn/Dynin module results, implementing the generalized dynamic wake (GDW) model. Numerical and experimental comparison showed similar behaviours in terms of non linear hysteresis, however some discrepancies are herein reported and need further data analysis and interpretations about the aerodynamic integral quantities, with a special attention to the physics of the unsteady phenomenon

Aerodynamic design methodology for wind tunnel tests of wind turbine rotors

This paper illustrates the methodology and the experimental verification of the design of a 1/75 aero-elastic scaled rotor of the DTU 10 MW reference wind turbine for wind tunnel tests. The aerodynamic design was focused on the minimization of the difference, in terms of thrust coefficient, with respect to the full scale reference. From the Selig low-Reynolds airfoils database, the SD7032 one was chosen for this purpose and a corresponding constant section wing was tested at DTU red wind tunnel, providing force and distributed pressure coefficients for the design, in the Reynolds range 30−250×103 and for different angles of attack. The aero-elastic design algorithm was set to define the optimal spanwise thickness over chord ratio (t/c), the chord length and the twist, in order to match at least the first flapwise scaled natural frequency. An aluminium mould for the carbon fibre autoclave process was CNC manufactured based on B-Splines CAD definition of the external geometry given as an output of the design procedure. Wind tunnel tests at were carried out Politecnico di Milano on the whole 1/75 wind turbine scale model, confirming the successful aerodynamic design and manufacturing approaches. The experimental modal analysis carried out to verify the structural consistency of the scaled blade is also reported

Modal parameters identification and monitoring of two arches

The paper presents the results of the modal parameters identification and of the continuous monitoring of two arches built in the new area of Expo 2015 in Milan. The activities on the arches were performed during the erection stage and they were planned as a consequence of preliminary studies performed at Politecnico di Milano wind tunnel, that highlighted dynamic instability due to the wind. In particular, the first two bending modes of the structures showed a critical behaviour and for this reason a TMD (Tuned Mass Damping) system was designed in order to control these modes. At first, frequencies, damping and modal deflected shapes were evaluated in order to check the numerical FEM model, to tune the TMD system and to check its correct functioning. The two arches were then monitored for several months to observe their dynamic behaviour under different wind conditions. A good database about the strongest and the most frequent winds in the site was obtained. The accelerations registered under strong wind conditions did not reach dangerous levels for the structures, moreover these results showed a good agreement with the wind tunnel ones