Models and software tools actually used for aircraft simulation and design are typically based on a separate modeling of flight dynamics and aeroelasticity. While this approach was justified for past relatively stiff configurations, it may not adequately capture the inherently coupled behavior of modern increasingly flexible vehicles. As aircraft flexibility increase, assuming a rigid-body model when studying flight dynamics may give incorrect results on performance, stability, handling qualities, and control effectiveness. In the same way, neglecting the aircraft motion as a whole when investigating aeroelastic behavior may lead to inaccurate prediction of flutter margins and response to atmospheric disturbances. Unique models and analysis tools should be thus used to effectively describe modern and future aeronautical configurations. The scope of this project is to develop a computational environment for aircraft simulation and design based on an integrated formulation of flight dynamics and aeroelasticity. The underlying physical model fully captures couplings between rigid-body dynamics, structural dynamics, and aerodynamics. In addition, it is oriented to the integration of state-of-the-art high-order solvers and software tools for the single disciplines in a unique reduced-order multidisciplinary framework. Due to these features, the model allows to analyze drawbacks and potential benefits arising from mutual interactions, which is not possible using standard single-discipline solvers, and to describe complex configurations with high fidelity but at the same time computational burden feasible for design. In the past years, the model has been implemented to study fully coupled linear stability and response of flexible aircraft around steady maneuvers. The present project aims to improve and extend the existing computational environment to make it an advanced tool for simulation and design of modern flexible vehicles.
NOTE: Citations by numbers refer to the numbering considered in Section "Pubblicazioni del responsabile della ricerca". Citations by capital letters are listed at the end of the section.
The modeling and computational environment developed in this project give innovative contributions with respect to the state-of-the-art in the field of aircraft simulation and design:
1) integrated study of flight dynamic and aeroelasticity, which is cannot be addressed by means of standard software tools used at industrial level [B];
2) use of advanced solvers and tools available for the involved disciplines in unique multidisciplinary computational environment, which is not typically done in the low-order models and codes recently developed for integrated analysis of flexible vehicles [D, E]; 3) reduced-order modeling approach for the integration of disciplines, which allows to achieve a compromise between simulation fidelity and computational burden that is acceptable for design. These innovative contributions are better underlined in the following.
Well-established software tools nowadays allow for high-fidelity modeling of flight dynamics, structural dynamics, and aerodynamics as separate disciplines, but are not capable of capturing mutual interactions playing a key role for modern configurations. The use of these solvers is frequently related to sequential simulation and design approaches, according to which each discipline is considered individually and at different steps of the design cycle. This approach may lead to inaccurate results for configurations showing relevant couplings, which should be analyzed in a multidisciplinary framework. Moreover, focusing on each discipline alone does not enable to describe drawbacks and potential benefits of arising from mutual interactions since the early design, which is a clear limitation when significant technology and performance improvements must be accomplished. The modeling approach proposed in this project is fully integrated, so it is tailored to the analysis of modern configurations that cannot be effectively studied by focusing each discipline as stand-alone [1, 7].
Low-order integrated simulation tools have been recently developed for coupled flight dynamics and aeroelastic simulation of flexible vehicles and their preliminary design [D, E]. The common limitation of these tools is that the structure is typically described in terms of a set of beam-type members, while steady and unsteady aerodynamics is frequently based on two-dimensional analytical solutions or surrogate models. A low-order modeling approach for structures and aerodynamics does not allow to describe complex configurations with high detail since the early design cycle. Moreover, the use of surrogate models prevents extensive expansion and exploration of the space of the design variables, so limiting design to well-established concepts that cannot lead to the achievement of significant technology improvements. The modeling methodology which is proposed in the present project is tailored to the integration of existing solvers for separate disciplines in a unique reduced-order multidisciplinary framework. This allows to apply the developed computational environment to generically complex vehicles, so allowing detailed analyses and study of unconventional configurations [1, 7].
Despite the high-fidelity modeling of the single disciplines, the integrated physical model and the related implementation are based on a reduced-order modeling approach, which allows to keep computational times and costs acceptable for simulation and design. Therefore, the computational environment developed within this project will on one side provide increased fidelity in the modeling and simulation of modern aircraft compared to state-of-the-art software and on the other hand will still be low-cost to be used for aircraft design.
The natural application of this project is in the framework of multidisciplinary design and multi-objective optimization [11, 14]. These require integrated models and computational tools that should be first-principle based and high-fidelity in order to adequately describe aircraft behavior of modern conventional and non-conventional configurations but also computationally-efficient in order to allow investigation of several possible configurations in relatively short times.
D. Patil, M.J., and Hodges, D.H., "Flight Dynamics of Highly Flexible Flying Wings", Journal of Aircraft, Vol. 43, No. 6, 2006, pp. 1790¿1799.
E. Su,W., and Cesnik, C.E.S., "Nonlinear Aeroelasticity of a Very Flexible Blended-Wing-Body Aircraft", Journal of Aircraft, Vol. 47, No. 5, 2010, pp. 1539-1553.