Multi-fidelity aeroelastic analysis of high aspect ratio aircraft wings

• Κύριος συγγραφέας: Φωτοπούλου, Μαρία
• Άλλοι συγγραφείς: Fotopoulou, Maria
• Γλώσσα: English
• Έκδοση: 2022
• Θέματα: Computational fluid dynamics (CFD); Fluid-structure interaction; ONERA M6 wing; NASA common research model; Static aeroelasticity; Υπολογιστική ρευστομηχανική; Σύζευξη δομής-ροής; Στατική αεροελαστικότητα

In the foreseeable future, the rapid rise in aircraft travel demand will induce several environmental threats. On that front, the European Union envisages a 75% decrease in CO2 and NOΧ emissions in the atmosphere for future commercial transport aircrafts. Key enabler for this effort is the introduction of novel, more efficient airframe designs with improved aerodynamic as well as structural efficiency. Regarding the aerodynamics, increasing the aspect-ratio of a wing is a well-established practice for increasing the aerodynamic efficiency by reducing the induced drag, which in turn improves fuel efficiency. As far as the structure is concerned, the introduction of composite materials in the design process results in lighter yet stiffer configurations. Nevertheless, such configurations are prone to certain phenomena, the most prominent being the elevated flexibility of the wing that on one hand induces a material and/or geometric nonlinear behavior and on the other hand a closer coupling between the structure and the surrounding fluid, aggravating static and dynamic aeroelastic phenomena. Furthermore, accounting for this type of phenomena requires sophisticated analyses, which in turn are bound by the associated, often prohibitive, computational time, hence they are preferred only for the later design stages of an aircraft structure. Aiming to alleviate the aforementioned issues, low-to-medium fidelity tools are often utilized early on the design stages, albeit suffering from reduced accuracy and inability to capture higher-order phenomena that might be present. This thesis aims to identify in detailed fashion the differences between the various fidelities of the numerical tools present and investigate the static aeroelastic behavior of a contemporary transport aircraft wing, namely uCRM13.5, a modified high aspect ratio version of the original Common Research Model (CRM) developed for very flexible wing design studies. As a preliminary study, the accuracy of two numerical CFD solvers of low and high-fidelity, are investigated via the transonic ONERA M6 wing case study. A convergence study with various computational grids of increasing size is conducted along with an influence analysis regarding the selection of the turbulence model as well as the first cell wall distance (Y+), necessary feature for capturing the boundary layer using RANS turbulence models. The resulting pressure coefficients at various spanwise sections of the wing are compared to their corresponding experimental ones as well as the lift, drag and moment coefficients are compared to those from NASA’s wind simulation. Having examined the results of the case study and having comprehend the methodology used, grid convergence studies are also conducted with the low and high-fidelity aerodynamic solvers for the uCRM wing with 13.5 aspect ratio in order to find the optimum CFD grid and to carry out the aeroelastic analysis. So, as a final step, the CFD obtained pressure field is applied to the structural FEM mesh of the wing, with the resulting displacements and stress field constituting the quantities of interest for the structural analysis.