Jacopo Serafini | Roma Tre University, Rome, Italy (original) (raw)
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Papers by Jacopo Serafini
12th AIAA/CEAS Aeroacoustics Conference (27th AIAA Aeroacoustics Conference), 2006
The acoustic field generated by a helicopter main rotor experiencing blade-vortex interaction (BV... more The acoustic field generated by a helicopter main rotor experiencing blade-vortex interaction (BVI) during a descent flight path is examined. The prediction procedure starts from the determination of the aeroelastic steady periodic solution. Then, a boundary integral formulation for the velocity potential suited for configurations where stong wake/blade impingement occurs is applied. It is fully three-dimensional, can be applied to blades with arbitrary shape and motion and performs the calculation of both wake shape and blade pressure field. Finally, the noise field generated by the helicopter rotor is evaluated through an aeroacoustic tool based on the Ffowcs Williams and Hawkings equation. The numerical investigation discusses the sensitivity of BVI noise prediction on the aeroelastic models applied for the calculation of blade steady periodic deformations. The effects of the different blade deformations given by the aeroelastic solvers considered are examined both in terms of local acoustic signatures and in terms of noise radiation characteristics.
International Journal of Aeroacoustics, 2007
E-MAIL: mscience@globalnet.co.uk WEBSITE: www.multi-science.co.uk aeroacoustics volume 6 · number... more E-MAIL: mscience@globalnet.co.uk WEBSITE: www.multi-science.co.uk aeroacoustics volume 6 · number 3 · 2007 -pages 199 -222 ABSTRACT This paper deals with the computational analysis of acoustic fields generated by helicopter rotors when Blade-Vortex Interactions (BVI) occur. The prediction procedure starts from the determination of the steady periodic blade deformations. Then, the BVI-affected, unsteady aerodynamics solution is obtained by a potential-flow boundary integral formulation suited for aeronautical configurations experiencing blade-wake impingements. It is applicable to blades with arbitrary shape and motion and evaluates both wake distortion and blade pressure field. Finally, the noise field radiated by the rotor is computed through an aeroacoustic tool based on the Ffowcs Williams and Hawkings equation. The numerical investigation examines the sensitivity of BVI noise prediction on the aeroelastic model applied for the calculation of blade deformations, and assesses the accuracy of the results through correlation with experimental data concerning a helicopter main rotor in descent flight. Noise predicted is examined in terms of both acoustic pressure signatures and noise radiation characteristics.
CEAS Aeronaut J, 2014
Your article is protected by copyright and all rights are held exclusively by Deutsches Zentrum f... more Your article is protected by copyright and all rights are held exclusively by Deutsches Zentrum für Luft-und Raumfahrt e.V.. This eoffprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
CEAS Aeronaut J, 2014
Your article is protected by copyright and all rights are held exclusively by Deutsches Zentrum f... more Your article is protected by copyright and all rights are held exclusively by Deutsches Zentrum für Luft-und Raumfahrt e.V.. This eoffprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
Progress in Aerospace Sciences, 2013
Fixed and rotary wing pilots alike are familiar with potential instabilities or with annoying lim... more Fixed and rotary wing pilots alike are familiar with potential instabilities or with annoying limit cycle oscillations that arise from the effort of controlling aircraft with high response actuation systems. Understanding, predicting and suppressing these inadvertent and sustained aircraft oscillations, known as aircraft (rotorcraft)-pilot couplings (A/RPCs) is a challenging problem for the designers. The goal of the present paper is to give an overview on the state-of-the-art in RPC problem, underlining the future challenges in this field. It is shown that, exactly as in the case of fixed wing APCs, RPCs existed from the beginning of rotorcraft development and that the problem of eliminating them is not yet solved: the current rotorcraft modelling for RPC analysis is rather limited to the particular case analysed and there is a lack of quantitative pilot behavioural models to analyse RPCs. The paper underlines the importance of involuntary pilot control actions, generally attributed to biodynamic couplings in predicting RPCs in rotorcraft. It is also shown that recent experiences demonstrate that modern rotorcraft seem to embed tendencies predisposing the flight control system FCS system towards dangerous RPCs. As the level of automation is likely to increase in future designs, extending to smaller aircraft and to different kinds of operation, the consequences of the pilot 'fighting' the FCS system and inducing A/RPCs needs to be eradicated. In Europe, the ARISTOTEL project (2010-2013) has been launched with the aim of understanding and predicting modern aircraft's susceptibility to A/RPC. The present paper gives an overview of future challenges to be solved for RPC-free design and some new solutions herein.
Journal of Guidance, Control, and Dynamics, 2013
This paper discusses the aeroelastic interaction between the helicopter and the pilot called coll... more This paper discusses the aeroelastic interaction between the helicopter and the pilot called collective bounce. The problem is mostly studied in the time domain, using the multibody system dynamics approach to model the dynamics of the vehicle and the aeroelasticity of the main rotor and a linear or quasilinear transfer function approach for the voluntary and involuntary dynamics of the pilot. Different models are considered for the aerodynamic forces acting on the rotor, ranging from blade-element/momentum theory to a boundary-element method used independently and in cosimulation with the multibody model. The problem is analyzed in hover and forward flight, highlighting modeling requirements and the sensitivity of the stability results to a variety of parameters of the problem. Nomenclature as = vertical acceleration of seat e = vertical position error G c = gearing ratio between collective inceptor and pitch rotation H abs s = transfer function between seat and hand absolute vertical accelerations H aircraft s = heave transfer function H ff s = active pilot feedforward transfer function H L s = loop transfer function H pilot s = active pilot transfer function H rel s = transfer function between seat absolute vertical and hand relative accelerations H zθ = heave transfer function L = length of collective control inceptor M = total mass of helicopter p 1 , p 2 = pseudointegrator poles R = main rotor radius s = Laplace's variable t = time u = generic transfer function input y = generic transfer function output Z = vertical force (thrust minus weight) z = vertical position z d = desired vertical position ζ = generic transfer function damping coefficient η = rotation of collective control inceptor θ 0 = collective pitch τ = generic dynamic system time constant τ e = active pilot equivalent time delay ω = frequency ω b = active pilot low-pass filter cutoff frequency ω c = active pilot crossover frequency ω 0 = generic transfer function characteristic frequency · : = derivative with respect to time
12th AIAA/CEAS Aeroacoustics Conference (27th AIAA Aeroacoustics Conference), 2006
The acoustic field generated by a helicopter main rotor experiencing blade-vortex interaction (BV... more The acoustic field generated by a helicopter main rotor experiencing blade-vortex interaction (BVI) during a descent flight path is examined. The prediction procedure starts from the determination of the aeroelastic steady periodic solution. Then, a boundary integral formulation for the velocity potential suited for configurations where stong wake/blade impingement occurs is applied. It is fully three-dimensional, can be applied to blades with arbitrary shape and motion and performs the calculation of both wake shape and blade pressure field. Finally, the noise field generated by the helicopter rotor is evaluated through an aeroacoustic tool based on the Ffowcs Williams and Hawkings equation. The numerical investigation discusses the sensitivity of BVI noise prediction on the aeroelastic models applied for the calculation of blade steady periodic deformations. The effects of the different blade deformations given by the aeroelastic solvers considered are examined both in terms of local acoustic signatures and in terms of noise radiation characteristics.
International Journal of Aeroacoustics, 2007
E-MAIL: mscience@globalnet.co.uk WEBSITE: www.multi-science.co.uk aeroacoustics volume 6 · number... more E-MAIL: mscience@globalnet.co.uk WEBSITE: www.multi-science.co.uk aeroacoustics volume 6 · number 3 · 2007 -pages 199 -222 ABSTRACT This paper deals with the computational analysis of acoustic fields generated by helicopter rotors when Blade-Vortex Interactions (BVI) occur. The prediction procedure starts from the determination of the steady periodic blade deformations. Then, the BVI-affected, unsteady aerodynamics solution is obtained by a potential-flow boundary integral formulation suited for aeronautical configurations experiencing blade-wake impingements. It is applicable to blades with arbitrary shape and motion and evaluates both wake distortion and blade pressure field. Finally, the noise field radiated by the rotor is computed through an aeroacoustic tool based on the Ffowcs Williams and Hawkings equation. The numerical investigation examines the sensitivity of BVI noise prediction on the aeroelastic model applied for the calculation of blade deformations, and assesses the accuracy of the results through correlation with experimental data concerning a helicopter main rotor in descent flight. Noise predicted is examined in terms of both acoustic pressure signatures and noise radiation characteristics.
CEAS Aeronaut J, 2014
Your article is protected by copyright and all rights are held exclusively by Deutsches Zentrum f... more Your article is protected by copyright and all rights are held exclusively by Deutsches Zentrum für Luft-und Raumfahrt e.V.. This eoffprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
CEAS Aeronaut J, 2014
Your article is protected by copyright and all rights are held exclusively by Deutsches Zentrum f... more Your article is protected by copyright and all rights are held exclusively by Deutsches Zentrum für Luft-und Raumfahrt e.V.. This eoffprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
Progress in Aerospace Sciences, 2013
Fixed and rotary wing pilots alike are familiar with potential instabilities or with annoying lim... more Fixed and rotary wing pilots alike are familiar with potential instabilities or with annoying limit cycle oscillations that arise from the effort of controlling aircraft with high response actuation systems. Understanding, predicting and suppressing these inadvertent and sustained aircraft oscillations, known as aircraft (rotorcraft)-pilot couplings (A/RPCs) is a challenging problem for the designers. The goal of the present paper is to give an overview on the state-of-the-art in RPC problem, underlining the future challenges in this field. It is shown that, exactly as in the case of fixed wing APCs, RPCs existed from the beginning of rotorcraft development and that the problem of eliminating them is not yet solved: the current rotorcraft modelling for RPC analysis is rather limited to the particular case analysed and there is a lack of quantitative pilot behavioural models to analyse RPCs. The paper underlines the importance of involuntary pilot control actions, generally attributed to biodynamic couplings in predicting RPCs in rotorcraft. It is also shown that recent experiences demonstrate that modern rotorcraft seem to embed tendencies predisposing the flight control system FCS system towards dangerous RPCs. As the level of automation is likely to increase in future designs, extending to smaller aircraft and to different kinds of operation, the consequences of the pilot 'fighting' the FCS system and inducing A/RPCs needs to be eradicated. In Europe, the ARISTOTEL project (2010-2013) has been launched with the aim of understanding and predicting modern aircraft's susceptibility to A/RPC. The present paper gives an overview of future challenges to be solved for RPC-free design and some new solutions herein.
Journal of Guidance, Control, and Dynamics, 2013
This paper discusses the aeroelastic interaction between the helicopter and the pilot called coll... more This paper discusses the aeroelastic interaction between the helicopter and the pilot called collective bounce. The problem is mostly studied in the time domain, using the multibody system dynamics approach to model the dynamics of the vehicle and the aeroelasticity of the main rotor and a linear or quasilinear transfer function approach for the voluntary and involuntary dynamics of the pilot. Different models are considered for the aerodynamic forces acting on the rotor, ranging from blade-element/momentum theory to a boundary-element method used independently and in cosimulation with the multibody model. The problem is analyzed in hover and forward flight, highlighting modeling requirements and the sensitivity of the stability results to a variety of parameters of the problem. Nomenclature as = vertical acceleration of seat e = vertical position error G c = gearing ratio between collective inceptor and pitch rotation H abs s = transfer function between seat and hand absolute vertical accelerations H aircraft s = heave transfer function H ff s = active pilot feedforward transfer function H L s = loop transfer function H pilot s = active pilot transfer function H rel s = transfer function between seat absolute vertical and hand relative accelerations H zθ = heave transfer function L = length of collective control inceptor M = total mass of helicopter p 1 , p 2 = pseudointegrator poles R = main rotor radius s = Laplace's variable t = time u = generic transfer function input y = generic transfer function output Z = vertical force (thrust minus weight) z = vertical position z d = desired vertical position ζ = generic transfer function damping coefficient η = rotation of collective control inceptor θ 0 = collective pitch τ = generic dynamic system time constant τ e = active pilot equivalent time delay ω = frequency ω b = active pilot low-pass filter cutoff frequency ω c = active pilot crossover frequency ω 0 = generic transfer function characteristic frequency · : = derivative with respect to time