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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. Source

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. Source

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. Source

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. Source

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. Source

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