The design and development of the next generation vertical lift vehicles, capable of meeting increasingly strict mission requirements, demand the use of advanced design tools and an integrated approach. While top level requirements and mission definition can still be managed by low to medium fidelity tools, critical issues typically neglected at an early design stage may completely compromise the success of the project, especially if they are safety-related. In this context, it is of paramount importance to be able to assess the impact of various parametric modifications on the generated concept by means of more refined modelling approaches. The product of this thesis work is a Python-based rotorcraft parametric model generator - RPM - intended as an actual preprocessor for MBDyn, a general purpose multibody code developed at Politecnico di Milano over the past 20+ years. The RPM generation approach is extensively validated against results obtained considering the ATTILA model (Advanced Testbed for TILtrotor Aeroelastics), in the framework of the Clean Sky 2 Joint Undertaking Program. For this purpose, a collection of postprocessing tools is also developed. In order to demonstrate the capabilities of RPM in terms of conceptual design, an interface with the rotorcraft conceptual design tool NDARC (NASA Design and Analysis of Rotorcraft) is set up and a test case scenario related to the NextGen tiltrotor concept is considered. A complete review of tiltrotor design is presented with the purpose of identifying critical parameters and the role of main vehicle components, especially in relation to the whirl flutter aeroelastic instability, which has often been one of the limiting factors in achieving high speed capabilities. Also, given the important role of robust design optimization in advanced conceptual design, and in view of future developments and expansion of the mentioned toolbox, a brief discussion is presented in relation to the most common methodologies which can be adopted for problems involving non-intrusive black-box approaches, such as those potentially compatible with an MBDyn simulation.
La definizione e lo sviluppo della prossima generazione di velivoli a decollo verticale, capaci di soddisfare stringenti requisiti di missione, richiede l’utilizzo di strumenti di progetto avanzati e di un approccio integrato. Benché sia possibile gestire i requisiti di alto livello e la definizione di missione tramite tool di progetto concettuale tradizionali, aspetti critici tipicamente trascurati nelle fasi iniziali possono completamente pregiudicare la buona riuscita del progetto, soprattutto se legati alla sicurezza della configurazione. In questo contesto, è estremamente importante essere in grado di valutare l’impatto di modifiche parametriche sul modello preliminare generato, utilizzando metodologie di modellazione più avanzate. Il prodotto di questo lavoro di tesi è un generatore di modelli parametrici per velivoli ad ala rotante - RPM - pensato come preprocessore per il solutore multicorpo MBDyn, sviluppato al Politecnico di Milano da oltre 20 anni. Il processo di generazione di RPM è stato validato rispetto ai risultati ottenuti considerando il modello utilizzato per il progetto ATTILA (Advanced Testbed for TILtrotor Aeroelastics), nell’ambito del programma Clean Sky 2 Joint Undertaking. Al fine di dimostrare le potenzialità di RPM in termini di progetto concettuale, è stata definita una interfaccia con il tool NDARC (NASA Design and Analysis of Rotorcraft), considerando il convertiplano NextGen come caso di esempio. Una revisione completa della teoria relativa al progetto di convertiplani è presentata al fine di identificare parametri critici ed il ruolo dei componenti principali del velivolo, in particolar modo in relazione all’instabilità di whirl flutter, da tempo fattore limitante rispetto al raggiungimento degli obiettivi di velocità massima in modalità aeroplano. Inoltre, dato il ruolo importante dell’applicazione di tecniche di ottimizzazione applicate al progetto strutturale, ed in vista di future espansioni del toolbox considerato, una breve discussione è presentata in merito alle metodologie più adatte per essere utilizzate con simulazioni di tipo black-box, quali quelle potenzialmente compatibili con una esecuzione di MBDyn.
Development of a parametric multibody generator for design and aeroelastic analyses of unconventional rotorcraft configurations
Buccio, Angela Elisabeth
2020/2021
Abstract
The design and development of the next generation vertical lift vehicles, capable of meeting increasingly strict mission requirements, demand the use of advanced design tools and an integrated approach. While top level requirements and mission definition can still be managed by low to medium fidelity tools, critical issues typically neglected at an early design stage may completely compromise the success of the project, especially if they are safety-related. In this context, it is of paramount importance to be able to assess the impact of various parametric modifications on the generated concept by means of more refined modelling approaches. The product of this thesis work is a Python-based rotorcraft parametric model generator - RPM - intended as an actual preprocessor for MBDyn, a general purpose multibody code developed at Politecnico di Milano over the past 20+ years. The RPM generation approach is extensively validated against results obtained considering the ATTILA model (Advanced Testbed for TILtrotor Aeroelastics), in the framework of the Clean Sky 2 Joint Undertaking Program. For this purpose, a collection of postprocessing tools is also developed. In order to demonstrate the capabilities of RPM in terms of conceptual design, an interface with the rotorcraft conceptual design tool NDARC (NASA Design and Analysis of Rotorcraft) is set up and a test case scenario related to the NextGen tiltrotor concept is considered. A complete review of tiltrotor design is presented with the purpose of identifying critical parameters and the role of main vehicle components, especially in relation to the whirl flutter aeroelastic instability, which has often been one of the limiting factors in achieving high speed capabilities. Also, given the important role of robust design optimization in advanced conceptual design, and in view of future developments and expansion of the mentioned toolbox, a brief discussion is presented in relation to the most common methodologies which can be adopted for problems involving non-intrusive black-box approaches, such as those potentially compatible with an MBDyn simulation.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/177959