A nacelle-mounted lidar system pointing downstream has been used to measure wind turbine wake dynamics. The new measurement and data analysis techniques allow estimation of quasi-instantaneous wind fi elds in planes perpendicular to the rotor axis. A newly developed wake tracking procedure delivers the instantaneous transversal wake position which is quantitatively compared with the prediction of the Dynamic Wake Meandering model. The results, shown for two 10-min time series, suggest that the conjecture of the wake behaving as a passive tracer is a fair approximation; this corroborates and expands the results of one-dimensional measurements already presented in the fi rst part of this paper. Consequently, it is now possible to separate the deterministic and turbulent parts of the wake wind fi eld, thus enabling capturing the wake in the meandering frame of reference. The results correspond, qualitatively and to some extent quantitatively, to the expectations from CFD simulations which are compared in the paper. LIDAR measurements of wake dynamics J.-J. Trujillo et al. 62with high resolution. In this regard, the light detection and ranging (lidar) technology presents great advantages due to its speed, robustness and fl exibility in measuring wind fi elds. For instance, infl ow measurements from the nacelle of a wind turbine have been successfully tested. 3,4 In that case the fast measurement at a fi xed point in front of the turbine assisted an advanced wind turbine control system. This paper describes the application of lidar to wind fi eld measurements in the wake of a 95 kW wind turbine. As in the previous example, the lidar system is installed at the nacelle but pointing downstream and implementing more complex scanning. The measurements were performed at a downstream distance of four diameters, which is considered to cover the far-wake regime. This investigation is conceived as a proof of concept of this type of measurement. New analysis techniques are developed to provide data useful for steady and dynamic wake model verifi cation. Part I of this paper 5 exposes the fi rst measurement campaign of this type along with the working principles of the instrument. Furthermore, the installation procedure on the wind turbine nacelle at the Risø test fi eld in Roskilde is also explained. Part II of the paper deals mainly with the analysis of the so-called two-dimensional wake measurements. These enable estimation of the wake wind fi eld in cross-sections perpendicular (here also named transversal) to the mean rotor axis and eventually large-scale dynamics of the wake. Here we explain fi rstly, the two-dimensional wake measurements in detail and the methods developed to capture wake dynamics; secondly, models for dynamic and deterministic wake are exposed and fi nally compared with two individual measurements.

Abstract.Presently there is a lack of data revealing the behaviour of the path followed by the near wake of full scale wind turbines and its dependence on yaw misalignment. Here we present an experimental analysis of the horizontal wake deviation of a 5 MW offshore wind turbine between 0.6 and 1.4 diameters downstream. The wake field has been scanned with a short-range lidar and the wake path has been reconstructed by means of two-dimensional Gaussian tracking. We analysed the measurements for rotor yaw misalignments arising in normal operation and during partial load, representing high thrust coefficient conditions. We classified distinctive wake paths with reference to yaw misalignment, based on the nacelle wind vane, in steps of 3 • in a range of ±10.5 • . All paths observed in the nacelle frame of reference showed a consistent convergence towards 0.9 rotor diameters downstream, suggesting a kind of wake deviation shift. This contrasts with published results from wind tunnels which in general report a convergence towards the rotor. The discrepancy is evidenced in particular in a comparison which we performed against published paths obtained by means of tip vortex tracking.

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This paper describes a pilot study assessing the psychosocial impact of political violence in the Peruvian Andes, utilizing a collaborative approach with local professionals and communities. The study team prioritized dialogue and information exchange with the local professional community and villagers participating in the assessment in order to raise awareness of psychosocial issues and provide education and support. Participation in the pilot study had positive therapeutic effects for villagers, and inspired ongoing discussion groups to address psychosocial problems in communities. This paper also describes a psychosocial assessment strategy utilizing qualitative methods and an adaptation of the Harvard Trauma Questionnaire in collaboration with Andean villagers. Usefulness and limitations of the data will be reviewed, in terms of cultural and context relevance, usefulness for informing interventions, and comparisons with ethnographic methodologies and other survey instruments.

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