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Raffel M.,German Aerospace Center | De Gregorio F.,Centro Italiano Ricerche Aerospaziali CIRA | De Groot K.,German Aerospace Center | Schneider O.,German Aerospace Center | And 3 more authors.
Aeronautical Journal | Year: 2011

The GOAHEAD (Generation of an Advanced Helicopter Experimental Aerodynamic Database for CFD code validation) consortium was created in the frame of an EU-project in order to create an experimental database for the validation of 3 D-CFD and comprehensive aeromechanics methods for the prediction of unsteady viscous flows. This included the rotor dynamics for complete helicopter configurations, i.e. main rotor - fuselage - tail rotor configurations with emphasis on viscous phenomena like flow separation and transition from laminar to turbulent flow. The wind tunnel experiments have been performed during two weeks in the DNW-LLF on a Mach-scaled model of a modern transport helicopter consisting of the main rotor, the fuselage, control surfaces and the tail rotor. For the sake of controlled boundary conditions for later CFD validation, a closed test section has been used. The measurement comprised global forces of the main rotor and the fuselage, steady and unsteady pressures, transition positions, stream lines, position of flow separation, velocity profiles at the test section inlet, velocity fields in the model wake, vortex trajectories and elastic deformations of the main and tail rotor blades.

Capuano F.,University of Naples Federico II | Capuano F.,Centro Italiano Ricerche Aerospaziali CIRA | Coppola G.,University of Naples Federico II | de Luca L.,University of Naples Federico II
Journal of Computational Physics | Year: 2015

Energy-conserving numerical methods are widely employed within the broad area of convection-dominated systems. Semi-discrete conservation of energy is usually obtained by adopting the so-called skew-symmetric splitting of the non-linear convective term, defined as a suitable average of the divergence and advective forms. Although generally allowing global conservation of kinetic energy, it has the drawback of being roughly twice as expensive as standard divergence or advective forms alone. In this paper, a general theoretical framework has been developed to derive an efficient time-advancement strategy in the context of explicit Runge-Kutta schemes. The novel technique retains the conservation properties of skew-symmetric-based discretizations at a reduced computational cost. It is found that optimal energy conservation can be achieved by properly constructed Runge-Kutta methods in which only divergence and advective forms for the convective term are used. As a consequence, a considerable improvement in computational efficiency over existing practices is achieved. The overall procedure has proved to be able to produce new schemes with a specified order of accuracy on both solution and energy. The effectiveness of the method as well as the asymptotic behavior of the schemes is demonstrated by numerical simulation of Burgers' equation. © 2015 Elsevier Inc.

Capuano F.,University of Naples Federico II | Capuano F.,Centro Italiano Ricerche Aerospaziali CIRA | Coppola G.,University of Naples Federico II | Balarac G.,Grenoble Institute of Technology | de Luca L.,University of Naples Federico II
Journal of Computational Physics | Year: 2015

Energy-conserving discretizations are widely regarded as a fundamental requirement for high-fidelity simulations of turbulent flows. The skew-symmetric splitting of the nonlinear term is a well-known approach to obtain semi-discrete conservation of energy in the inviscid limit. However, its computation is roughly twice as expensive as that of the divergence or advective forms alone. A novel time-advancement strategy that retains the conservation properties of skew-symmetric-based schemes at a reduced computational cost has been developed. This method is based on properly constructed Runge-Kutta schemes in which a different form (advective or divergence) for the convective term is adopted at each stage. A general framework is presented to derive schemes with prescribed accuracy on both solution and energy conservation. Simulations of homogeneous isotropic turbulence show that the new procedure is effective and can be considerably faster than skew-symmetric-based techniques. © 2015 Elsevier Inc.

Montesarchio M.,Centro Euro Mediterraneo sui Cambiamenti Climatici CMCC | Montesarchio M.,Centro Italiano Ricerche Aerospaziali CIRA | Zollo A.L.,Centro Euro Mediterraneo sui Cambiamenti Climatici CMCC | Bucchignani E.,Centro Euro Mediterraneo sui Cambiamenti Climatici CMCC | And 5 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2014

This study aimed to assess the capabilities of high-resolution simulations in reproducing the main features of the climate in the complex topography region of the Alps for the period 1971-2000. This is to provide a reliable tool for impact studies on local scale. Two simulations, driven by ERA-40 Reanalysis, have been carried out, respectively, at spatial resolutions of 0.125° and 0.0715° with the regional climate model COSMO-CLM. The model response has been analyzed in terms of 2 m temperature and precipitation, and comparisons with available observations have been carried out. A number of climate indices have also been analyzed, widely adopted to monitor changes in extreme climate events. Finally, the effects of increasing spatial resolution have also been investigated. The model at high spatial resolution (0.0715°) provides a satisfactory representation of temperature. The simulated precipitation patterns are also improved due to the high model resolution that allows reproducing localized precipitation phenomena with a medium-high error, especially where summer thunderstorms over the complex topography of the Alpine region occurs. ©2014. American Geophysical Union. All Rights Reserved.

Viviani A.,The Second University of Naples | Pezzella G.,Centro Italiano Ricerche Aerospaziali CIRA | Golia C.,The Second University of Naples
Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering | Year: 2011

A numerical study has been conducted to assess the effects of thermo chemical modeling and surface catalyticity on the design of a crew return vehicle re-entering from low Earth orbit. The effects of: complexity of chemical models, kinetics of reactions, vibrational relaxation, and wall reaction mechanism on vehicle aerothermodynamics and aerodynamics performances, and on some flow field features, are highlighted. To this end, several numerical results derived for perfect and non-equilibrium reacting gas approximations are provided and compared. In this framework, a possible Earth-entry scenario for the proposed capsule-type vehicle is reported and extensively analysed by means of Navier-Stokes computations, performed both in trajectory based and in space-based design approaches. Numerical results highlight that the accuracy of aerodynamic coefficients depends on the complexity of reaction mechanism considered in flowfield computations. For example, if the Zeldovich model is considered, the results produced are within 1 per cent of that of a solution with complete reaction mechanism, while the simulation speed up efficiency reaches about 40 per cent. This work underlines the fact that the CPU speed up depends, in particular, on the accuracy expected in vehicle pitching moment assessment, thus confirming that this parameter is one of the most critical vehicle aerodynamic performances to address in the case of a real gas-dominated flow. On the contrary, vehicle aerothermodynamic results show that, for a reliable heat flux evaluation, flow field computations require a full reaction mechanism, as wall catalyticity plays a significant role when assessing vehicle aeroheating.

Pezzella G.,Centro Italiano Ricerche Aerospaziali CIRA | Viviani A.,The Second University of Naples
Acta Astronautica | Year: 2011

The paper deals with the aerodynamic analysis of a manned braking system entering the Mars atmosphere, with the aim to support planetary entry system design studies. The capsule configuration is an axisymmetric blunt body close to the Apollo capsule. Several fully three-dimensional Computational Fluid Dynamics analyses have been performed to assess the flowfield environment around the vehicle to address the aerodynamic performance of the entry capsule within mission exploration to Mars. To this end, a wide range of flow conditions including reacting and non-reacting flow, different angles of attack, and Mach numbers have been investigated and compared. Moreover, non-equilibrium effects on the flowfield around the capsule have been also investigated. Results show that real-gas effects, for all the angles of attach considered, increase both the aerodynamic drag and pitching moment, whereas the lift is only slighted affected. Finally, comparison of the results highlights that experimental and CFD aerodynamic findings available for the Apollo capsule in air adequately represent the static coefficients of the capsule in the Mars atmosphere. © 2011 Elsevier Ltd. All rights reserved.

Paladino E.,University of Catania | Paladino E.,CNR Institute of Neuroscience | Mastellone A.,University of Catania | Mastellone A.,CNR Institute of Neuroscience | And 5 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We present a general route to reduce inhomogeneous broadening in nanodevices due to 1/f noise. We apply this method to a universal two-qubit gate and demonstrate that for selected optimal couplings, a high-efficient gate can be implemented even in the presence of 1/f noise. Entanglement degradation due to interplay of 1/f and quantum noise is quantified via the concurrence. A charge-phase √ i-SWAP gate for spectra extrapolated from single-qubit experiments is analyzed. © 2010 The American Physical Society.

Cutrone L.,Centro Italiano Ricerche Aerospaziali CIRA | Cutrone L.,Polytechnic of Bari | De Palma P.,Polytechnic of Bari | Pascazio G.,Polytechnic of Bari | Napolitano M.,Polytechnic of Bari
Computers and Fluids | Year: 2010

This paper provides an efficient numerical method for solving reacting flows of industrial interest in the presence of significant real-gas effects. The method combines a state-of-the-art solver of the Reynolds-averaged Navier-Stokes equations - equipped with the low-Reynolds number k - ω turbulence closure - with a combustion flamelet-progress-variable approach. A real-gas model as well as a detailed kinetic scheme are used to generate the flamelet library. The method is tested versus several applications chosen to demonstrate the importance of the real-gas effects and of the kinetic scheme for computing high-pressure combustion. The major contribution of the paper is to provide a single-phase approach which solves turbulent reacting real-gas flows at a computational cost comparable with that of the simulation of a non-reacting flow thanks to the use of the flamelet library. © 2009 Elsevier Ltd. All rights reserved.

Ferraiuolo M.,Centro Italiano Ricerche Aerospaziali CIRA | Martucci A.,Centro Italiano Ricerche Aerospaziali CIRA
ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) | Year: 2013

In the frame of the HYPROB/Bread project, whose main goal is to design build and test a 30 kN regeneratively cooled thrust chamber, a breadboard has been conceived in order to evaluate the thermal properties of methane in supercritical conditions. The breadboard is called MTP (Methane Thermal Properties) and it is made of Glidcop Al 15. The heating process of the breadboard is obtained by means of Nickel-Chrome wire wrapped cartridges. The methane flows through a rectangular cross section with a mass flow rate of 20 g/s. The aim of the present paper is to illustrate the thermo-structural design conducted on the breadboard by means of a Finite Element Method code taking into account the viscoplastic behaviour of Glidcop Al 15. An optimization process has been carried out in order to keep the structural integrity of the breadboard maximizing the life cycles of the component. Copyright © 2013 by ASME.

Ameduri S.,Centro Italiano Ricerche Aerospaziali CIRA
Advanced Materials Research | Year: 2014

This paper analyses a morphing leading edge device, activated by a Shape Memory Alloy (SMA) actuator. The objective is to achieve the Droop Nose effect for particular phases of the flight (e.g. take-off, landing), both obtaining an increased lift and preserving the laminar flow. The device is constituted of: a kinematic chain at the level of the wing section, transmitting motion to the skin, this way fitting the Droop Nose target shape; a span-wise architecture integrated with a SMA actuator, ensuring both a reduction of the actuation forces and the balancing of the aerodynamic external load. A dedicated logical framework was adopted for the design, taking into account the SMA material features and the device intrinsic non-linearity. The framework was integrated within an optimization genetic algorithm, to fit the target shape with an appropriate architecture topology. The optimized system proved to produce the desired morphing, also under the most severe aerodynamic loads. © (2014) Trans Tech Publications, Switzerland.

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