Adding aerodynamic damping: the wing design for the Third Bosphorus Bridge

This paper is about the design of wing profiles adequate for giving to the Third Bosphorus Brige an additional aerodynamic damping on both vertical bending as well as torsional modes. The additional damping estimate procedure is made through a simplified quasi steady approach. A CFD approach has been used for a preliminary design and optimization of the wing profile and its position over the wind screen at the upwind and downwind location

Full scale monitoring of the twin chimneys of the rovinari power plant

The presented paper deals with the structural identification and monitoring of two twin chimneys in very close arrangement. Due to twin arrangement, important interference effects are expected to modify the chimney response to wind action, causing vortex shedding and state-dependent excitation associated to the oscillatory motion of the leeward chimney, in and out of the windward chimney wake. The complexity of the physics of this problem is increased by the dependency of the aerodynamics of circular cylinders on Reynolds number; however, there is a weakness of literature about cylinders behaviour at critical and super-critical range of Reynolds number, due to experimental limitations. Also the International Committee on Industrial Chimneys (CICIND) does not provide, at present, any specific technical guideline about twin chimneys whose interaxis distance is less or equal two times the diameter, as in this case. For this reason a Tuned Mass Damper (TMD) has been installed in order to increase the damping of the chimney, as merely suggested. This work aims at assessing the effectiveness of the installed TMD and characterizing the tower dynamic behaviour itself due to the wind excitation, as well as providing full scale measurements for twin cylinders configuration at high Reynolds numbers

On the functional design of the DTU10 MW wind turbine scale model of LIFES50+ project

This paper illustrates the mechatronic design of the wind tunnel scale model of the DTU 10MW reference wind turbine, for the LIFES50+ H2020 European project. This model was designed with the final goal of controlling the angle of attack of each blade by means of miniaturized servomotors, for implementing advanced individual pitch control (IPC) laws on a Floating Offshore Wind Turbine (FOWT) 1/75 scale model. Many design constraints were to be respected: among others, the rotor-nacelle overall mass due to aero-elastic scaling, the limited space of the nacelle, where to put three miniaturized servomotors and the main shaft one, with their own inverters/controllers, the slip rings for electrical rotary contacts, the highest stiffness as possible for the nacelle support and the blade-rotor connections, for ensuring the proper kinematic constraint, considering the first flapwise blade natural frequency, the performance of the servomotors to guarantee the wide frequency band due to frequency scale factors, etc. The design and technical solutions are herein presented and discussed, along with an overview of the building and verification process. Also a discussion about the goals achieved and constraints respected for the rigid wind turbine scale model (LIFES50+ deliverable D.3.1) and the further possible improvements for the IPC-aero-elastic scale model, which is being finalized at the time of this paper

UNAFLOW project: UNsteady Aerodynamics of FLOating Wind turbines

UNAFLOW (UNsteady Aerodynamics for Floating Wind) is a joint EU-IRPWIND founded experiment on wind turbine rotor unsteady aerodynamics. It brings together four different academic contributors: Energy research Centre of the Netherlands (ECN), DTU Wind Energy, University of Stuttgart (USTUTT) and Politecnico di Milano (PoliMi) sharing knowledge both in numerical modelling and in experimental tests design, allowing direct numerical and experimental comparison. The experimental tests carried out for UNAFLOW are of the same type of the ones carried out during the ongoing EU H2020 project LIFES50+ [1], regarding both the unsteady behaviour of the 2d blade section and the entire turbine rotor, although with improved setup and wider test matrix. The project partners are already currently jointly collaborating in the AVATAR project [2], developing and validating numerical models of different accuracy level. The numerical models used in the UNALFOW project range from engineering tool (eg. BEM) to high fidelity CFD methods. Numerical simulations are used both in the design of experiment phase and in the results analysis allowing for an in depth understanding of the experimental findings through advanced modelling approach. The UNAFLOW project, together with a new understanding of the unsteady behaviour of the turbine rotor aerodynamics, will provide also an open database to be shared among the scientific community for future analysis and new models validation

Demonstration of synchronised scanning Lidar measurements of 2D velocity fields in a boundary-layer wind tunnel

This paper combines the currently relevant research methodologies of scaled wind turbine model experiments in wind tunnels with remote-sensing short-range WindScanner Lidar measurement technology. The wind tunnel of the Politecnico di Milano was equipped with three wind turbine models and two short-range WindScanner Lidars to demonstrate the benefits of synchronised scanning Lidars in such experimental surroundings for the first time. The dual- Lidar system can provide fully synchronised trajectory scans with sampling time scales ranging from seconds to minutes. First, staring mode measurements were compared to hot wire probe measurements commonly used in wind tunnels. This yielded goodness of fit coefficients of 0.969 and 0.902 for the 1 Hz averaged u- and v-components of the wind speed, respectively, validating the 2D measurement capability of the Lidar scanners. Subsequently, the measurement of wake profiles on a line as well as wake area scans were executed to illustrate the applicability of Lidar scanning to measuring small scale wind flow effects. The downsides of Lidar with respect to the hot wire probes are the larger measurement probe volume and the loss of some measurements due to moving blades. In contrast, the benefits are the high flexibility in conducting both point measurements and area scanning, and the fact that remote sensing techniques do not disturb the flow while measuring. The research campaign revealed a high potential for using short-range WindScanner Lidar for accurately measuring small scale flow structures in a wind tunnel

Testing the Capabilities of Wind Tunnel Fans as large-scale velocity fluctuation generators

Wind tunnel testing requires an accurate representation of natural flows. In particular, large vorticose structures represent a challenge for the wind engineer. Classical passive turbulence generation techniques, such as grids and spire elements, show limitations in scale dimensions and turbulence quality. Conversely, active methods like moving grids, struggle to target very low frequencies of the spectrum and may incur high installation costs. A cost-effective and promising solution for injecting energy into the low-frequency spectrum is the active control of fans. In this paper, the authors propose a straightforward methodology for the characterization of the facility’s generators, highlighting possibilities and limitations of this solution

Multi-fidelity actuator-line modelling of FOWT wakes

Large Eddy Simulations (LES) are considered the proper tool for predicting the physics of a wind turbine wake, thereby establishing a solid foundation for investigating the interaction among floating turbines within wind farms. In this work the Actuator Line Model, implemented in the OpenFoam environment, is combined with both U-RANS and LES simulations to underline the differences in accuracy when reproducing the near and far wake of a single turbine. Both a fixed-bottom and a surge motion case are tested to highlight the wake phenomena strictly generated by the platform motion. The use of LES simulation becomes fundamental by virtue of its ability to accurately simulate turbulence and mixing with free-stream flow, hence, this research aims at advancing the knowledge of wake dynamics from multiple perspectives while ensuring reliability thanks to the use of the experimental wake data from the UNAFLOW test campaign on the scaled laboratory model of the DTU 10 MW. In the near wake, limited flow unsteadiness and similar mean velocity are predicted by the two models. In the far wake, instead, the LES approach estimates a strong rise of flow unsteadiness which, in case of surge motion, affects the mean velocity value making evident the difference between LES and RANS estimation