In this paper, the accuracy of an in-house Actuator Line (AL) model is tested on aeroelastic simulations of a Wind Turbine (WT) rotor and a helicopter Main Rotor (MR) under uniform free-stream flow. For the scope of aeroelastic analyses, the AL model is coupled with an in-house multibody dynamics code in which the blades are modeled as beams. The advantage from the introduction of CFD analysis in rotorcraft aeroelasticity is related to its capability to account in detail for the interaction of the rotor wake with the boundary layer developed on the surrounding bodies. This has proven to be of great importance in order to accurately estimate the aerodynamic forces and thus the corresponding structural loads and deflections of the blades. In wind turbine applications, a good example of the above is the rotor/ground interaction. In helicopter configurations, the interaction of MR with the ground or the fuselage and the interaction of tail rotor with the duct in fenestron configurations are typical examples. Furthermore, CFD aerodynamic analysis is an obvious modeling option in which the above mentioned asset can be combined with the consideration of the mutual interaction of the rotor with the ambient turbulence. A WT rotor operating inside the atmospheric boundary layer under turbulent free-stream flow is such a case. In the paper, AL results are compared against Blade Element Momentum (BEM) and Lifting Line (LL) model results in the case of the WT, whereas LL and measured data are considered in the helicopter cases. Blade loads and deflections are mainly compared as azimuthal variations. In the helicopter MR cases, where comparison is made against experimental data, harmonic analysis of structural loads is shown as well. Overall, AL proves to be as reliable as LL in the canonical cases addressed in this paper in terms of loads and deflections predictions. Therefore, it can be trusted in more complex flow conditions where viscous effects are pronounced.

In the present paper the methodology and the procedures for the implicit coupling of an Actuator Line (AL) aerodynamic code with a beam like structural code for the analysis of wind turbine rotors are detailed. Results from benchmark aeroelastic simulations of canonical inflow conditions, comparing the newly developed AL model against a standard Blade Element Momentum (BEM) model are presented in the paper. The two models provide very similar results in simple, uniform inflow, axisymmetric flow cases. The advantages of this newly developed tool emerge when more complex inflow conditions are addressed. In the present paper, besides axial flow conditions, operation under high yaw misalignment is also considered. BEM model accounts for the effect of the wake skewness through the application of an a posteriori engineering correction. Therefore, in this particular non symmetric flow case, deviations between AL and BEM are expected to be higher, especially as yaw misalignment angles increase. In the paper the above differences are assessed and interpreted.

This paper presents a hybrid CFD solver that couples a standard Eulerian approach that solves the compressible Navier-Stokes equations under a cell-centered finite volume discretization, with a Lagrangian one, based on particles representation which carry mass, pressure, dilatation and vorticity. The velocity field is calculated using the Helmholtz’s decomposition theorem. Computational performance is enhanced by employing the Particle Mesh (PM) technique in order to solve the Poisson equations for the scalar potential ϕ and the stream function ψ. Even though validated for 2D flows over airfoils, this specific solver is used for the first time in order reproduce the flow around a wind turbine rotor. The validation simulations concern axial flow over the wind turbine model rotor used in the New MEXICO experimental campaign. Results of the hybrid solver, presented as blade pressure distribution and axial flow velocities are compared against the ones produced by its pure Eulerian counterpart and experimental measurements. PM grids of up to 5 points per chord of the blade section at 75% radius have been used. Comparison with the standard Eulerian solver suggest that the produced blade loads are over-predicted by approximately 7% near the tip and 14% near the root. However, the calculated velocity field is much closer to the experimental measurements as compared to the one produced by the Eulerian approach, which is attributed to the reduced numerical diffusion of the Lagrangian-vorticity formulation.

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In this work we present the design of a compact, high-resolution echelle spectrograph for monitoring the Night Sky Background. This spectrograph is combined with a 25.4 cm telescope and uses an appropriate CCD camera as detector. It can operate in a wide spectral range from Ultraviolet to near Infrared (i.e. 300-780 nm) corresponding to the sensitivity spectral window of photocathodes used in the fluorescence telescopes. In the design we also made effort to compromise a sufficient sensitivity and a reasonable exposure time. This instrumentation could become a versatile tool for the operation and development of fluorescence telescopes used in Ultra High Energy Cosmic Ray Experiments.