Alessio Tosini, Enrico Cardile, Giovanni Lombardi, Marco Maganzi
2014
Cubit, Ferrari, Università di Pisa
Abstract
The experimental data corrections on automotive wind tunnel tests usually benefit of pre-test corrections methodology, which can break down working time. This methodology is based on the use of CFD simulations and yields a global correction term, sum of different contributions. It is interesting to analyze such contributions and their possible dependencies by the involved parameters, in order to have a better comprehension of the phenomenon.
In the present paper, the main purpose is to describe, with the support of a CFD analysis, the influence of the wind tunnel walls, supports and Reynolds number effects, to the global correction factor. A high performances car was taken as reference and RANS equations were used as fluid dynamic model. The CFD methodology and its validation, through a comparison with experimental data, are preliminarily presented. Afterward, the contributions to the correction term are shown and discussed. Finally, is evaluated their effect on different elements of the car. The car was split in body, wheels, underbody, radiators, rear wing and internal volumes.
Conference/Journal: ATA, Vol.67, N. 3-4, 2014
Authors: G. Lombardi, A. Tosini, E. Cardile, D. Zinelli
Federico Cartoni, Giovanni Lombardi, Marco Maganzi
2014
Cubit, Università di Pisa
Abstract
The wing-sail is an interesting idea for sailboats, and the last America’s Cup shown that its use is possible and very effective. At the University of Pisa it was decided to use this type of sail on the small boat realised for the inter-university race “1001 vele”. A first wing sail has been used in 2013 with satisfactory results, but it was evident that high improvement in the performances can be obtained. The performances of this system are impressive, but the flow is complex and the number of geometrical parameters very high. In order to tackle this problem resort was made to a direct numerical optimization technique; this approach was attractive, as it made it possible to address the problem systematically, and offered flexibility in the choice of the design variables. The approach is capable of meeting multi-disciplinary requirements, but it requires, given the complexity of the flow, the use of sophisticated CFD solver; STAR CCM+ was then chosen for the aerodynamics evaluation in the optimisation loop. The optimization procedure is completely described in the paper, within the results and a critical analysis of the flow around the wing-sail, in order to have indication on the aerodynamics behaviour. This for a better understanding of the physical aspects and also to give to the sailors the indications for the more efficient set-up.
Authors: G. Lombardi, M. Maganzi
Conference/Journal: Star Global Conference 2014, Wien (AT)
Keywords: wing-sail, CFD, optimization, sailing, STAR CCM+
Enrico Cardile, Federico Cartoni, Giovanni Lombardi, Marco Maganzi
2014
Cubit, Ferrari, Università di Pisa
Abstract
The use of Computational Fluid Dynamics (CFD) provides an effective approach for the qualitative analysis of exhaust gas trajectories in high-performance vehicles under transient driving conditions. Complex flow interactions occurring during acceleration and braking phases require advanced numerical models capable of capturing unsteady effects on realistic geometries.
A CFD workflow based on automated mesh generation, unsteady simulations, and particle tracking techniques enables the investigation of exhaust plume behavior and its interaction with the vehicle underbody. The adoption of an Eulerian-Discrete Phase Model allows a reliable representation of exhaust dispersion while maintaining a balance between accuracy and computational cost, in line with industrial time constraints.
Large-scale simulations performed on HPC architectures support detailed time-dependent analyses using experimentally derived boundary conditions. The results provide valuable qualitative insight into critical flow regions potentially affecting cockpit comfort, supporting targeted experimental testing and local design modifications.
Conference/Journal: ANSYS User Group Meeting, Milano (IT)
When designing passenger cars, HVAC (Heating, Ventilation, Air Conditioning) plays an important role to the overall vehicle design process in order to satisfy thermal comfort criteria for occupants while reducing energy consumption required. In this context, a Ferrari car is analyzed with Computational Fluid Dynamics (CFD) methods to improve the internal flow inside the cockpit.
In the work detailed here the toolbox for HVAC applications available in the open source CFD software HELYX was employed. The HVAC module exploits an improved internal radiation model, a solar radiation module, support for humidity modelling, functionality to assess human comfort by parameters like PMV, PPD, DR, etc.
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
In modern automotive design, aerodynamics plays a central role and is strongly coupled with styling, structural constraints, cooling requirements, and vehicle dynamics. This paper discusses the role, potential, and critical issues of numerical optimization techniques applied to car aerodynamics, with particular emphasis on CFD-based approaches.
The continuous growth of computational power has enabled the integration of automated optimization procedures into the aerodynamic development process, allowing the systematic exploration of large design spaces and the evaluation of thousands of geometrical configurations.
The basic principles of aerodynamic optimization are outlined, from the definition of cost functions and constraints to mesh generation and solver coupling. Examples of industrial-oriented applications are presented, showing how optimization can support the designer in improving performance, reducing drag, and enhancing flow control solutions. At the same time, the paper highlights the main limitations of current methodologies, including computational cost, robustness, and the difficulty of managing complex real-world constraints.
Conference/Journal: Future Automotive AeroDynamics Conference, Berlin (DE), 2012
Authors: G. Lombardi
Keywords: numerical optimization, car aerodynamics, CFD-based design, drag reduction, automotive development
Future Automotive AeroDynamics Conference, Berlin (DE)
