Giovanni Paolo Reina

Abstract: Computational fluid dynamics is employed to evaluate the mean wind loads on sun-tracking ground-mounted solar photovoltaic panel arrays. Reynolds-averaged Navier-Stokes simulations are performed using a finite volume-based numerical method. The mean turbulent flow around the panel is simulated by following two different approaches, by considering either the full three-dimensional model or the reduced model with periodic boundary conditions in the spanwise homogeneous direction. The periodic model is demonstrated to well reproduce the aerodynamics of the panel with a considerable reduction of the computational cost. The wind loading history due to the continuous rotation of the system is directly simulated by means of the dynamic meshing technique, which allows for a further savings of computational resources with respect to static calculations.

Abstract: The objective of this paper is to propose a novel approach to the study of the steady and unsteady aeroelastic behavior of a wing during the flight, as for example in cases where there is a release of underwing bodies in military aircrafts. This new methodology is based on a structural modal superposition approach and a mesh morpher fully integrated in the fluid dynamic (CFD) solver, that allows to greatly reduce the analysis time of the classic approach to a FSI problem, typically characterized by an exchange of data between the structural and the fluid dynamic solver. The following describes the whole procedure developed and the main obtained results.

Abstract: Computational fluid dynamics is employed to evaluate the mean aerodynamic loading on the retractable landing-gears of a regional transport commercial aircraft. The mean turbulent flow around simplified landing-gear systems including doors is simulated by using the Reynolds-averaged Navier–Stokes approach, where the governing equations are solved with a finite volume-based numerical method. Using a dynamic meshing method, the computational grid is automatically and continuously adapted to the time-changing geometry, while following the extension/retraction of the landing-gear systems. The temporal evolution of the aerodynamic forces on both the nose and the main landing-gears, along with the hinge moments of the doors, is numerically predicted. The proposed computational modeling approach is verified to have good practical potential when compared with reference experimental data provided by the Leonardo Aircraft structural loads group.

Abstract: Computational fluid dynamics is used to study the wind loads on a high aspect ratio ground-mounted solar panel. Reynolds-averaged Navier-Stokes simulations are performed using a commercial finite volume-based code with two different numerical approaches. First, the entire panel is directly simulated in a three-dimensional domain. Then, a small portion of the panel is considered, by imposing periodic boundary conditions in the spanwise homogeneous direction. The comparison shows a good match between the results obtained with the two different models, in terms of pressure coefficient and aerodynamic loads. The main consequence is a considerable reduction of the computational costs when using the reduced model.

Abstract: CFD analysis is carried out to evaluate the mean aerodynamic loads on the retractable main landing-gear of a regional transport commercial aircraft. The mean flow around the landing-gear system including doors is simulated by using the Reynolds-averaged Navier-Stokes modelling approach, the governing equations being solved with a finite volume-based numerical technique. The computational grid is automatically adapted to the time-changing geometry by means of a dynamic meshing technique, while following the deployment of the landing-gear system. The present computational modelling approach is verified to have good practical potential by making a comparison with reference experimental data provided by the Leonardo Aircraft Company aerodynamicists.

Abstract: This paper aims to present a fast and effective approach to tackle complex fluid structure interaction problems that are relevant for the aeronautical design.,High fidelity computer-aided engineering models (computational fluid dynamics [CFD] and computational structural mechanics) are coupled by embedding modal shapes into the CFD solver using RBF mesh morphing.,The theoretical framework is first explained and its use is then demonstrated with a review of applications including both steady and unsteady cases. Different flow and structural solvers are considered to showcase the portability of the concept.,The method is flexible and can be used for the simulation of complex scenarios, including components vibrations induced by external devices, as in the case of flapping wings.,The computation mesh of the CFD model becomes parametric with respect to the modal shape and, so, capable to self-adapt to the loads exerted by the surrounding fluid both for steady and transient numerical studies.

Abstract: The recent development of the adaptive-anisotropic wavelet-collocation method, which incorporates the use of coordinate transforms, opens new horizons for wavelet-based simulations of wall-bounded turbulent flows. The new wavelet-based adaptive unsteady Reynolds-averaged Navier–Stokes approach for computational modelling of turbulent flows is presented. The proposed methodology that is integrated with anisotropic wavelet-based mesh refinement is demonstrated for a two-equation eddy-viscosity turbulence model. The performance of the method is assessed by conducting numerical simulations of the turbulent flow past a circular cylinder at subcritical Reynolds number. The present study demonstrates both the feasibility and the effectiveness of the new wavelet-based adaptive unsteady Reynolds-averaged turbulence modelling procedure for external flows.

Abstract: Purpose The present paper aims to address the description of a numerical optimization procedure, based on mesh morphing, and its application for the improvement of the aerodynamic performance of an industrial glider which suffers of a large separation occurring in the wing–fuselage junction region at high incidence angles. Design/methodology/approach Shape variations were applied to the baseline configuration through a mesh morphing technique founded on the mathematical framework of radial basis functions (RBF). The aerodynamic solutions were obtained coupling an RANS code with the mesh morphing tool RBF Morph™. Two shape modifiers were set up to generate a parametric numerical model. An optimization procedure, based on a design of experiment sampling, was set up implementing the fully automated workflow within a high performance computing (HPC) environment. The optimal candidates maximizing the aerodynamic efficiency were identified by means of a cubic RBF response surface approach. Findings The separation was significantly reduced, modifying the local geometry of fuselage and fairing and maintaining the wing aerofoil unchanged. A relevant aerodynamic efficiency improvement was finally gained. Practical implications The developed procedure proved to be a very powerful and efficient tool in facing aerodynamic design problems. However, it might be computationally very expensive if a large number of design variables are adopted and, in those cases, the method can be suitably used only within the HPC environment. Originality/value Such an optimization study is part of an explorative set of analyses that focused on better addressing the numerical strategies to be used in the development of the EU FP7 Project RBF4AERO.

Abstract: An aerodynamic numerical optimisation procedure for an AC72 rigid wing sail was developed. The core of the method is the geometric parameterisation strategy based on a mesh morphing technique. The morphing action, which uses radial basis functions, is integrated within the Reynolds-averaged Navier-Stokes solver and provides an efficient parametric sail aerodynamic analysis method which is integrated in an optimisation environment based on a velocity prediction program. A hydrodynamic model is coupled to the parametric numerical solver in an iterative procedure. The shape modifiers operate on angle of attack and twist of the fore and aft wing element. For each true wind condition, the velocity of the boat is maximised by iterating between the solution of the velocity prediction program and the solution of the fluid dynamic solver. The effectiveness of the proposed method is demonstrated testing a range of wind speeds.

Abstract: In a solar tower plant, temperatures up to 700°C are reached by moving mirror systems called "heliostats" tracking the sun and concentrating its radiation to the top of a tower for large scale electricity production and industrial process heating. To enable a breakthrough of this solar energy technology the heliostat costs have to be further reduced. With precise knowledge of the wind loads they can be built lighter and cheaper. The objective of the presented thesis is to close knowledge gaps and to reduce uncertainties regarding the wind loading of heliostats. Some of the main open questions were the following: - How can the wind loads on heliostats be reduced in an economic way? - Which is the optimum aspect ratio of the mirror panel? - At which heliostat feld position do maximum wind loads occur? - Do the wind load coefcients of heliostats depend on the wind speed? - Which turbulence properties have to be matched by wind tunnel tests? - Can the peak wind loads be reduced by shock absorbers? By wind tunnel tests and full scale measurements these questions were addressed. The results are also valid for double axis photovoltaic trackers. With the gained knowledge, new heliostat designs were developed with cost reductions of up to 25%. The theory of extreme value statistics for the determination of the wind load peak values and the correlation between eddy diameters and turbulent energy spectra are explained in the appendix.