A 2D vortex panel model with a viscous boundary layer formulation has been developed for the numerical simulation of a vertical axis wind turbine (VAWT), including the operation in dynamic stall. The model uses the ‘double wake’ concept to reproduce the main features of the unsteady separated flow, including the formation and shedding of strong vortical structures and the wake–blade interaction. The potential flow equations are solved together with the integral boundary layer equations by using a semi-inverse iterative algorithm. A new criterion for the reattachment of the boundary layer during the downstroke of a dynamically stalled aerofoil is implemented. The model has been validated against experimental data of steady aerofoils and pitching aerofoils in dynamic stall at high and low Reynolds numbers (Re = 1.5 × 10^6 and Re = 5 × 10^4). For the low Reynolds number case, time-resolved 2D particle image velocimetry (PIV) measurements have been performed on a pitching NACA 0012 aerofoil in dynamic stall. The PIV vorticity fields past the oscillating aerofoil are used to test the model capability of capturing the formation, growth and release of the strong leading edge vortex that characterizes the dynamic stall. Furthermore, the forces extracted from the PIV velocity fields are compared with the predicted ones for a quantitative validation of the model. Finally, the model is applied to the computation of the wake flow past a VAWT in dynamic stall; the predicted vorticity fields and forces are in good agreement with phase-locked PIV data and CFD-DES available in the literature

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An increasing demand of environmental radioactivity monitoring comes both from the scientific community and from the society. This requires accurate, reliable and fast response preferably from portable radiation detectors. Thanks to recent improvements in the technology, γ spectroscopy with sodium iodide scintillators has been proved to be an excellent tool for in-situ measurements for the identification and quantitative determination of γ ray emitting radioisotopes, reducing time and costs. Both for geological and civil purposes not only (40)K, (238)U, and (232)Th have to be measured, but there is also a growing interest to determine the abundances of anthropic elements, like (137)Cs and (131)I, which are used to monitor the effect of nuclear accidents or other human activities. The Full Spectrum Analysis (FSA) approach has been chosen to analyze the γ spectra. The Non Negative Least Square (NNLS) and the energy calibration adjustment have been implemented in this method for the first time in order to correct the intrinsic problem related with the χ(2) minimization which could lead to artifacts and non physical results in the analysis. A new calibration procedure has been developed for the FSA method by using in situ γ spectra instead of calibration pad spectra. Finally, the new method has been validated by acquiring γ spectra with a 10.16 cm × 10.16 cm sodium iodide detector in 80 different sites in the Ombrone basin, in Tuscany. The results from the FSA method have been compared with the laboratory measurements by using HPGe detectors on soil samples collected particular, the (137)Cs isotopes has been implemented in the analysis since it has been found not negligible during the in-situ measurements.

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The present work focuses on the fast prediction of the interaction noise (IN) components of a Contra Rotating Open Rotor (CROR) engine at take-off. The flow field past the CROR is computed using a steady RANS approach coupled with the concept of mixing plane between the rotors to remove the flow unsteadiness due to the propeller interaction. The effects of such interaction are then recovered applying the analytical model of Jaron et al. (2014), balanced with data extracted from the RANS solution, to extrapolate the information about the wake of the front rotor and the potential flow fields through the mixing plane. This RANS-informed approximation allows recovering the unsteadiness of the flow-blades interaction in terms of unsteady blade response. The tonal noise at the blade passing frequency and the interaction noise are then estimated using the analytical frequency domain model proposed by Hanson (1985). The present method for the fast prediction of CROR noise has been validated by comparison with the results of URANS simulations and noise measurements. CROR geometry UDF F7/A7 with both 8 × 8 and 11 × 9 blade counts has been considered. The flow velocity profiles extrapolated through the mixing plane agree well with the URANS results, except in the vicinity of the blade tip, where the analytical extrapolation method is not able to deal properly with the strongly 3D tip vortex flow. The comparison of the predicted interaction noise with acoustic measurements shows that the present fast RANS-informed approach is capable of estimating the directivity of the CROR noise with reasonable accuracy.

Multi-megawatt Vertical Axis Wind Turbines (VAWTs) have inherent design and operational advantages that make them relevant for floating offshore applications. Many offshore VAWT concepts use stall for power regulation. Stall regulation imposes several constrains in the aerodynamic, structural and generator design. Due to the azimuthally varying and unsteady aerodynamics experienced by a VAWT, designing an airfoil for stall regulation is still a significant challenge. In this work, a family of airfoils for stall regulated VAWT is defined through numerical airfoil optimization, based on the original work of Simão Ferreira and Geurts [20]; the optimization is multi-objective, optimizing structural and aerodynamic performance. The control performance is not yet implemented in the function. The optimization is performed at Reynolds numbers representative of multi-megawatt VAWT. The performance of the VAWT, including operation in dynamic stall, is evaluated with an unsteady double-wake viscous-inviscid panel method and CFD simulations. The performance of the optimized airfoils is compared against a conventional airfoil, namely the NACA 0018 airfoil. The stall regulatory performance is assessed to provide insight for future optimizations. The aerodynamic performance is evaluated using three different numerical models: a single wake panel model coupled to airfoil polar data; a viscous-inviscid double wake panel model, capable of simulating dynamic stall; and an eulerian RANS CFD model. The airfoils are also design for a robust performance in the case of surface roughness. The preliminary results show that the design for surface roughness conflicts with the design for dynamic stall control. An extensive study of multi-objective optimisations with different weights of the different elements of aerodynamic performance is presented

22In this paper we present maps of K, eU, and eTh abundances of Elba Island (Italy) 23 obtained with a multivariate spatial interpolation of airborne γ-ray data using the 24 45