Abstract. Fluid-structure interactions are crucial for the design of rotor blades of wind power systems. Up to now, the mutual interactions between rotor blades and turbulent wind flows have been treated by complex simulations or were observed at individual discrete points. In this paper, a measurement concept is presented where spatial information of the motion/deformation of a rotating wind turbine as well as the wind flow are recorded in wind tunnel experiments. Wind flow and motion behaviour are recorded simultaneously and contactless. Techniques from the field of photogrammetry and flow measurement techniques are combined, resulting in high demands on the measurement concept. Furthermore, solutions for the realisation of a common coordinate system as well as for the synchronisation of both measuring systems are presented. In addition, the validation of the entire measurement concept is carried out based on of some wind tunnel tests in which a single rotor blade is used for the moment. This showed that the measurement concept and the proposed solutions for the simultaneous recording of wind flows and rotor blade movements are suitable in principle and that movements can be recorded and reconstructed with high accuracy.
Experimental studies of fluid-structure interaction on a single blade of the model wind turbine MoWiTO 1.8, which has been designed as an aerodynamically downscaled wind tunnel model of the NREL 5 MW turbine, were performed. Tailored inflow generated by means of a 2D active grid is used to induce dynamic stall through periodic angle of inflow changes. The interactions at the model wind turbine blade are investigated using two high-speed and non intrusive optical measurement techniques. The aerodynamics around the turbine blade is measured using temporal highly resolved particle image velocimetry (PIV) measurements at the suction side of the blade. Synchronized measurements with a high-speed photogrammetric system are linking the aerodynamic events to high accuracy measurements of the blade deflections.
The design of rotor blades is based on information about aerodynamic phenomena. An important one is fluid-structure interaction (FSI) which describes the interaction between a flexible object (rotor blade) and the surrounding fluid (wind). However, the acquisition of FSI is complex, and only a few practical concepts are known. This paper presents a measurement setup to acquire real information about the FSI of rotating wind turbines in wind tunnel experiments. The setup consists of two optical measurement systems to simultaneously record fluid (PIV system) and deformation (photogrammetry system) information in one global coordinate system. Techniques to combine both systems temporally and spatially are discussed in this paper. Furthermore, the successful application is shown by several experiments. Here, different wind conditions are applied. The experiments show that the new setup can acquire high-quality area-based information about fluid and deformation.
Abstract. In the last few years, photogrammetric methods for 3D surface reconstruction at close range have increased significantly in importance. On the one hand, this is due to the increased performance of the systems and on the other hand to the improved quality (accuracy, completeness) of the created point clouds. In order to verify the accuracy of various area probing methods, the German VDI guideline 2634 part 2 and 3 is applied. However, the high-precision test reference objects existing so far consist of diffuse textureless surfaces, so that passive methods, like image matching, cannot be compared with active methods (e.g. structured light systems). In order to make this possible, a certified textured dumbbell with an accuracy of better than 10 μm is presented in this paper, with the aim to examine the suitability of the textured dumbbell artefact for close-range photogrammetric 3D surface reconstruction. Furthermore, the accuracy level of a structured light system, Structure from Motion (SfM) and Multi-View Stereo Method (MVS) is verified and compared with each other.
Wind tunnel experiments with wind turbine models are a promising method for investigating fluid structure interaction (FSI) phenomena. However, the lack of suitable models that feature properly scaled blades and the complexity of aeroelastic and fluid dynamic measurements during turbine operation is challenging. In this paper, the design methodology for aeroelastically scaled blades which are intended for Model Wind Turbine Oldenburg (MoWiTO) 1.8 is presented. The scaling relations are formulated, initiating from the existing turbines’ design. Next, the manufactured blades are equipped on MoWiTO and are subsequently evaluated, during operation under gusty wind fields produced by an active grid. The tip deflection is recorded using an innovative photogrammetry setup. Simulations of an OpenFAST model, which has properties extracted from the scaling formulation, are used as reference. The recorded loads and blade deformations show similar dynamics, compared to the reference. These results prove the design successful, and the capability of measuring FSI phenomena in wind tunnel environment is showcased.
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