In the last years, thanks to the development of computational capabilities, the CAE methodology has become an essential tool in the design especially in the preliminary phase and configuration analysis. This happens also and above all in the fluid dynamic design by using CFD codes, which have reached high levels of reliability. In recent years the simulation times have significantly reduced and this means that the preprocessing phase has become the real bottleneck within the project. The engineering consulting companies can face trouble to define standard methodologies for the analysis, because of the wide range of application fields, and need to reduce operational costs and response times to be competitive. This kind of problems induce us to find a strategy to automate the entire design process as much as possible. This work aims at showing the use of ANSA tools for our cases, and the development of preprocessing automation methods easily adaptable to most of them.
Authors: Dr. Marco Maganzi (University of Pisa, CubitLab), Giovanni Lombardi (University of Pisa), Antonio Ercoli (University of Pisa)
Antonio Ercoli, Giacomo De Angeli, Giovanni Lombardi, Marco Maganzi
2019
Cubit, Maserati, Università di Pisa
Abstract
In automotive design, the study of the water thin layer over a car due to rain is becoming increasingly important: the challenge is to obtain a way to describe the behavior of the water over a vehicle in rainy conditions and its interactions with wipers and drainage systems, to determine potential failures of the vehicle design.
In this paper two similar numeric procedures have been realized with the software STAR CCM+ to analyze the dynamic of water thin layer starting from the impingement of the rain on the car surface and taking into account even the motion of the wipers over the windshield. Moreover, the water that flows through the drainage systems is monitored to figure out if the water could produce a malfunction of components near them.
In order to describe each status of the water, many multiphase models are used. These methodologies have been applied on a commercial vehicle model and the results have been examined and compared to each other. The analysis shows a better description of the reality for one of them, leading to the possibility of using it as a design tool in the automotive industry.
Conference/Journal: International Journal of Automotive Technology, Vol. 20, pp. 1123-1129 (2019)
Karim Abu Salem, Marco Maganzi, Vincenzo Binante, Vittorio Cipolla
2018
Cubit, Università di Pisa
Abstract
PARSIFAL is a Horizon 2020 project, started on May 2017, with the aim to design an innovative aircraft, based on the "PrandtlPlane" (PrP) configuration, for the civil aviation of the future. The PrP configuration allows us to reduce the fuel consumption and the external noise, especially during low speed flight.
The high aerodynamic performances are used to limit the span to 36m, compliant with ICAO Aerodrome Reference Code C standard, and to extend the payload capacity to 250-350 passengers without significant penalties of aerodynamic efficiency.
The paper presents the overall characteristics of this innovative aircraft and how the PrP configuration could allow to improve the civil air transport of the future, as far as aircraft manufacturers, airports, airlines and passengers are concerned; in particular, some aspects of the architectural solutions and the aerodynamic design and optimization are underlined in subsonic and transonic regimes.
The work concerns plane flows around wing sections at high free stream Mach numbers, limited by the validity of the assumptions that specific heats and Prandtl number are constant. The results of the evaluation by means of a commercial CFD code of simple predictive methods for skin friction, recovery temperature and heat flux at the wall with compressible boundary layer are presented for two wing section shapes, typical for supersonic flows: a rhomboidal shape with all laminar and all turbulent boundary layer flow conditions, with four thermal boundary conditions at free stream Mach number 1.5 and 2; a lenticular shape with laminar boundary layer flow and adiabatic wall conditions, at free stream Mach number 2. The results of this evaluation seem to contain interesting indications to evaluate CFD capability and to develop new investigations concerning predictive methods.
Authors: M. Maganzi, L. Polito
Conference/Journal: AIDAA XXIV International Conference, 18-22 September 2017, Palermo – Enna (Italy)
Diffuser rotating stall (in both cases of a vaneless or a vaned configuration) is still one of the open questions which has never been fully understood because of the complexity of the phenomenon and the experimental difficulties to get reliable measurements in such a complex environment.
Under this perspective, Computational Fluid Dynamics (CFD) is an interesting tool to "see" the flow and provide a basic understanding of the associated physics. Several published works have shown that a simplified model of the diffuser without the upstream impeller and the downstream return channel, with realistic boundary conditions entering the diffuser, can provide a qualitative analysis of the stall onset.
This research applies CFD methods to understand the onset mechanisms of rotating stall in centrifugal compressor diffusers, comparing vaneless and vaned configurations to identify design factors that influence stability and operating range.
The flow around a wing is usually well represented by a RANS simulation in cruise conditions, because the zones with flow separations are absent or very small. But, as the angle of attack increases, because of the request of higher lift values, the separated flow zones become important, and the flow is more complex. In these conditions, a RANS approach, also with an unsteady solution, could be not satisfactory. Therefore, we decided to investigate this aspect, by comparing the results of an unsteady RANS solution with a DES solution. In the paper, the setting of both cases are described, as well as the comparison in terms of global coefficients, local distributions and field vorticity distributions. The results show that, at low angle of attack, not significant differences between the RANS and DES solutions occur. On the contrary, at higher angles of attack, the flow highlights a different behaviour, with the DES approach that seems to give a more realistic representation of the flow itself. It is important to note that the difference between RANS and DES results is so considerable that also the lift, drag and pitching moment are significantly changed. Finally, it is possible conclude that the use of a DES approach appears an improvement to evaluate the aerodynamics characteristics of a wing close to the stall conditions, a relevant problem for the aerodynamics design of an airplane.
Conference/Journal: Star Global Conference, Prague (CZ)
Diffuser rotating stall (in both cases of a vaneless or a vaned configuration) is still one of the open questions which has never been fully understood because of the complexity of the phenomenon and the experimental difficulties to get reliable measurements in such a complex environment.
Under this perspective, Computational Fluid Dynamics (CFD) is an interesting tool to "see" the flow and provide a basic understanding of the associated physics. Several published works have shown that a simplified model of the diffuser without the upstream impeller and the downstream return channel, with realistic boundary conditions entering the diffuser, can provide a qualitative analysis of the stall onset.
This research applies CFD methods to understand the onset mechanisms of rotating stall in centrifugal compressor diffusers, comparing vaneless and vaned configurations to identify design factors that influence stability and operating range.
Nel corso degli ultimi anni si è assistito a continui miglioramenti nelle capacità predittive dei codici CFD, grazie alla combinazione dell'aumento della potenza di calcolo e di software sempre più efficaci ed efficienti.
Nel presente articolo sarà illustrata la storia delle potenze di calcolo disponibili, e cosa ciò ha comportato per il progetto aerodinamico, per poi discutere le prospettive per i prossimi anni e le loro implicazioni.
Questi impressionanti miglioramenti hanno ovviamente comportato che la CFD ha assunto un ruolo sempre più importante nell'ambito del progetto aerodinamico. Non solo: grazie alla maggiore accuratezza dei risultati, ormai notevole, e alla rapidità con la quale questi sono ottenuti, si è assistito anche a un rilevante incremento del ruolo dell'aerodinamica nel progetto generale.
Un aspetto da tenere in considerazione, per non rimanere "spiazzati" dai futuri sviluppi nel campo del calcolo, è la previsione delle future capacità di calcolo, in modo da non trovarsi impreparati e iniziare già a immaginare le modifiche all'approccio del progetto aerodinamico che saranno necessarie. Sono quindi descritte le prospettive di sviluppo delle capacità di calcolo, attraverso un'analisi dei futuri processori e delle possibili architetture che i software dovranno gestire nei prossimi anni.
L'uso di GPU (Graphic Processor Unit), possibile nel codice ANSYS-FLUENT, appare molto promettente, ed è stato testato in via preliminare su delle macchine di limitata potenza. I risultati sono promettenti, e questa sembra una strada che offre buone possibilità di forti incrementi nelle capacità computazionali.
Già ora è possibile risolvere flussi complessi con grande accuratezza nella rappresentazione dei dettagli. In un futuro prossimo modelli matematici come le LES e le DES diventeranno lo standard, e si potranno affrontati problemi sempre più complessi.
Giovanni Lombardi, Marco Maganzi, Sandra Baldini, Walter Rosellini
2015
Cubit, Piaggio, Università di Pisa
Abstract
The flow around a scooter is analysed by means of the CFD. In a first phase the results are compared with those obtained through a wind tunnel test campaign, showing a good data accordance. Therefore, the CFD approach can be considered a useful engineering tool in the scooter design, and, with respect to the experimental approach, it has the advantage of providing a complete description of the flow field. This aspect appears particularly important when a modification of the geometry must be verified from the aerodynamics point of view. Finally, as an example, the procedure is applied to the analysis of the effects of deflectors, introduced to increase the comfort. From the CFD a complete description of the flows, with and without the spoiler, are obtained and compared. The results show a significant increase in the comfort grade, coupled with a decrease in the drag of the scooter.
Authors: Giovanni Lombardi, Marco Maganzi, Sandra Baldini, Walter Rosellini
Numerical optimization procedures are today a key tool in engineering design, especially when integrated with parametric CAD, automatic mesh generation, CFD solvers, and advanced search algorithms. This approach enables a systematic exploration of large design spaces, making it possible to identify configurations that significantly improve aerodynamic performance. Applications range from aeronautics to automotive engineering, from sailing and yacht design to wind energy systems, including the development of airfoils, rear diffusers, transonic air intakes, wind turbines, and unconventional lifting surfaces. A central aspect is the comparative optimization of alternative solutions, which allows objective evaluations by bringing each configuration to the same level of design maturity. The integration of CFD-based optimization into development processes makes it possible to reduce industrial time and costs, limit the need for physical prototypes, and support more robust, efficient, and informed engineering decisions.
Authors: G. Lombardi
Conference/Journal: ModeFrontier International User Meeting, Trieste (IT), 2014
