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This paper deals with the development of suitable surrogate models for the acoustic assessment of the shielding effects due to engine installation on top of unconventional aircraft configurations. The interest of the aeronautic community towards finding solutions to reduce the environmental impact has increased tremendously in the last decade, in particular to reduce acoustic emissions. The Advisory Council for Aviation Research and Innovation in Europe (ACARE) has in fact set ambitious noise reduction targets for 2050, which can only be reached through important technological advances such as the development of highly innovative configurations. Among solutions proposed in literature, one of the most promising and most investigated is the Blended Wing Body (BWB) aircraft configurations. Because of the peculiar center-body shape of this concept, the engines can be installed on top of the aircraft, making its noise shielding properties particular appealing. Therefore, the choice of the optimal position of the engines to maximize the masking effect represents a crucial aspect that must be taken into account from the early design stages. However, as experimental and historical data are not available in this context, there are no alternative to perform direct simulations for the acoustic assessment needed in conceptual design phase, which would lead to an unacceptable increase of computational resources for optimization purposes. A possible solution is to limit the number of performed simulation by using them to develop metamodels based on stochastic radial basic functions for the evaluation of the acoustic shielding factor, instead of calculating the actual value at each call of the objective functions. Specifically, starting from few high–fidelity simulations by means of a bidimensional integral solver based on the convective Helmholtz equation, an adaptive metamodel is developed for the evaluation of the shielding factor of airfoils, which takes into account the variation of crucial design variables.

Air trac growth and the expansion of urban areas around airports make the aviation community noise a key aspect of aircraft design. The analysis of innovative con gu- rations is becoming activity of primary interest within the scienti c community. The current e ort to attain the strict noise{abatement targets imposed by the authorities risks to be pro tless without a signi cant technological breakthrough. A promising innovative con guration in terms of noise reduction is the Blended{Wing{Body air- craft. Indeed, the installation of the propulsion system above the centre{body surface ensures a signi cant masking e ect of the engine noise components. The lack of ex- perimental data needed to validate the advantages introduced by these technologies, and therefore carry out parametric analysis, can only be overcome by formulating reliable and cost{e ective models to predict the noise shielding induced by engines installation on unconventional geometries. The present work introduces the develop- ment of tailored models for the correction of the existing semi-empirical prediction techniques. Such models are embedded within the modules of the existing conceptual design framework FRIDA. Without excluding other disciplines, the introduction of a noise prediction tool allows to cast a wide net in the research of optimal con guration in the future aviation context.

Air trac growth and the expansion of urban areas around airports make the aviation community noise a key aspect of aircraft design. The analysis of innovative con gu- rations is becoming activity of primary interest within the scienti c community. The current e ort to attain the strict noise{abatement targets imposed by the authorities risks to be pro tless without a signi cant technological breakthrough. A promising innovative con guration in terms of noise reduction is the Blended{Wing{Body air- craft. Indeed, the installation of the propulsion system above the centre{body surface ensures a signi cant masking e ect of the engine noise components. The lack of ex- perimental data needed to validate the advantages introduced by these technologies, and therefore carry out parametric analysis, can only be overcome by formulating reliable and cost{e ective models to predict the noise shielding induced by engines installation on unconventional geometries. The present work introduces the develop- ment of tailored models for the correction of the existing semi-empirical prediction techniques. Such models are embedded within the modules of the existing conceptual design framework FRIDA. Without excluding other disciplines, the introduction of a noise prediction tool allows to cast a wide net in the research of optimal con guration in the future aviation context.

The present work reports an investigation on the use of adaptive metamodels based on radial basis functions (RBFs) for aeroacoustic applications of highly innovative configurations. The relevance of the topic lies on the paramount importance of metamodelling techniques within the design optimisation process of disruptive aircraft layouts. Indeed, the air traffic growth, consequently the hard environmental constraints imposed by regulations, will make a technological breakthrough, an imperative need within few years. As a consequence, the engineering community is paying particular attention to the development of innovative techniques for the design of unconventional configurations. For this class of applications, the designer cannot successfully rely on historical data or low-fidelity models, and the expensive direct simulations remain the only valuable design strategy. In this regard, it can be demonstrated that the use of surrogate models, i.e., metamodels, significantly reduces the computing costs, especially in view of a robust approach to the optimised design. In order to further improve the efficiency of metamodel-based techniques, dynamic approaches based on hyperparameter optimisation and adaptive sampling procedures have been recently developed. The case study presented here pertains the exploiting of dynamic RBF-based metamodels for noise shielding applications. The analysis of the metamodel performances and its convergence properties shows how the final number of direct simulations is significantly reduced by the hyperparameter optimisation algorithm, still strongly depending on the choice of the RBF kernel function.

The present work deals with the development of an innovative approach to the weight estimation in the conceptual design of a Hybrid-Electric-Powered (HEP) Blended Wing Body (BWB) commercial aircraft. In the last few decades, the improvement of the environmental impact of civil aviation has been the major concern of the aeronautical engineering community, in order to guarantee the sustainable development of the system in presence of a constantly growing market demand. The sustained effort in the improvement of the overall efficiency of conventional aircraft has produced a new generation of vehicles with an extremely low level of emissions and noise, capable of covering the community requirements in the short term. Unfortunately, the remarkable improvements achieved represent the asymptotic limit reachable through the incremental enhancement of existing concepts. Any further improvement to conform to the strict future environmental target will be possible only through the introduction of breakthrough concepts. The aeronautical engineering community is thus concentrating the research on unconventional airframes, innovative low-noise technologies, and alternative propulsion systems. The BWB is one of the most promising layouts in terms of noise emissions and chemical pollution. The further reduction of fuel consumption that can be achieved with gas/electric hybridisation of the power-plant is herein addressed in the context of multidisciplinary analyses. In particular, the payload and range limits are assessed in relation to the technological development of the electric components of the propulsion system. The present work explores the potentialities of an energy-based approach for the initial sizing of a HEP unconventional aircraft in the early conceptual phase of the design. A detailed parametric analysis has been carried out to emphasise how payload, range, and degree of hybridisation are strictly connected in terms of feasible mission requirements and related to the reasonable expectations of development of electric components suitable for aeronautical applications.