The paper shows preliminary results of aeroelastic analyses of two half-wing models, having curved and swept planform, carried out at the Aerospace Unit of the Department of Civil and Industrial Engineering of Pisa University. For a wing with a curved planform, as demonstrated in previous papers regarding rigid models of wings, the wave drag effects are strongly reduced in the transonic flight conditions. In the paper some results obtained by using Star-CCM+® 6.04.14 and Abaqus® 6.11 in "cosimulation" are summarized: for this reason the present numerical comparison, between a curved wing and a swept wing, includes the effects of structure's deformability (the wings have the same aspect ratio). The beneficial effects of the planform shape on drag polar curves are confirmed.
Authors: Giovanni Lombardi (Cubit), Mario Rosario Chiarelli (Università di Pisa)
Control surfaces, such as airplane elevators or rudders may use symmetric airfoil shapes which are mostly based on single airfoil geometry. For the 2013 America's Cup sailboat competition rigid sails were specified, based on tandem symmetrical airfoils of equal chord. Because of the unique geometry of this combination and because none of the traditional two-element airfoils were designed for this application, a more suitable airfoil shape was sought. Furthermore, control surfaces such as the rudder are not designed for high lift, while the rigid sail studied here is expected to operate near a lift coefficient of one. A parametric study, using numerical methods, on the effect of different geometrical variables led to the development of an improved sail geometry, compared with the initial baseline shape. Therefore, the first objective of the present study is to validate those predictions for this particular application. Because of the large dimensions of the actual sail, its operating Reynolds numbers are high compared with the available wind tunnel facility. The conservative approach in this study is based on the assumption that the smaller Reynolds number tests provide a satisfactory validation for the higher Reynolds number sailing conditions.
Authors: Giovanni Lombardi (Cubit), Joseph Katz (San Diego State University), Maurizio Foresta (Università di Pisa)
Most sailboats use flexible sails to generate the aerodynamic propulsive force. However, for the 2013 America's Cup sailboat competition, rigid sails were specified. These sails resemble an airplane's wing and traditional wing-design tools (computational and experimental) were used to study the performance of the multi-element sail system. The shape of the proposed sail is based on two, tandem, symmetric airfoils, resulting in a geometry, unlike any traditional two-element airfoil. Because racing regulations limit the sail shape, only the two-dimensional airfoil geometry was open for a redesign. Therefore, the first objective of this study was to identify the possible variables affecting the aerodynamic performance of such sails (within the framework of racing regulations). At the same time, a secondary objective was to evaluate the effectiveness of simple computational and experimental tools for such a design exercise.
Authors: Giovanni Lombardi (Cubit), Joseph Katz (San Diego State University), Maurizio Foresta (Università di Pisa)
Keywords: rigid sail, America's Cup, aerodynamics, multi-element airfoil, sailboat racing
Transactions of the Royal Institution of Naval Architects part B, 155(part B1), B13-B24, International Journal of Small Craft Technology, 138
Le applicazioni della Computational Fluid Dynamics (CFD) in ambito nautico hanno raggiunto un elevato livello di maturità, consentendo l'analisi integrata delle prestazioni, della stabilità e del comportamento dinamico di imbarcazioni ad alte prestazioni in condizioni di mare reale.
L'impiego di modelli non stazionari con superficie libera e moto rigido a sei gradi di libertà permette di simulare in modo realistico l'interazione tra aerodinamica delle parti emerse, idrodinamica dello scafo e risposta dinamica del sistema. Le procedure CFD risultano particolarmente efficaci sia nelle attività di ottimizzazione di componenti specifici, come derive e bulbi, sia nella valutazione delle prestazioni globali di configurazioni complete, inclusi yacht da competizione e catamarani veloci.
Le simulazioni forniscono informazioni quantitative su velocità, assetto, accelerazioni, carichi e frequenze dominanti del moto, difficilmente ottenibili con sole prove sperimentali. Nonostante gli elevati costi computazionali, l'uso di infrastrutture HPC rende la CFD uno strumento chiave nel processo di progettazione e validazione in ambito navale.
Conference/Journal: La Simulazione Fluidodinamica: Stato dell'Arte nelle Applicazioni Marine, UNIGE, 2013
Authors: G. Lombardi
Keywords: CFD nautico, idrodinamica, yacht, catamarano, ottimizzazione, superficie libera, HPC
La Simulazione Fluidodinamica: Stato dell’Arte nelle Applicazioni Marine, UNIGE
The evolution of computational resources has been a key enabler for the progressive integration of Computational Fluid Dynamics (CFD) into aerodynamics analysis and design. From early potential-flow solvers running on mainframe systems to modern high-performance computing (HPC) clusters, increasing computational power has allowed the transition toward large-scale RANS simulations, unsteady flow analysis, thermo-aerodynamics, optimization procedures, and fluid-structure interaction.
The availability of parallel architectures and fast networks has significantly reduced turnaround times while enabling the use of finer grids and more realistic geometries. This evolution has strengthened the synergy between CFD and experimental testing, positioning numerical simulation as a central tool in industrial design processes, particularly in automotive, naval, and aerospace applications.
Current trends toward massively parallel systems, GPU acceleration, and reduced memory per core highlight the need for new software paradigms and methodologies to further improve efficiency, accuracy, and predictive capability in future CFD-driven design workflows.
Conference/Journal: 2nd Future Automotive AeroDynamics Conference, Berlin (DE), 2013
