A parametric modeling approach for prediction of load distribution due to fluid structure interaction on aircraft structures

The Fluid Structure Interaction effect is one of the crucial issues to be examined in aerospace applications. The shape of a flexible structure changes due to the load caused by the air flow around the structure. The deformations directly affect the air flow around the structure. Considering the fluid-structure interaction for aircraft, this effect should be examined for the aircraft wing since the wing produces the majority of the necessity lift and it is flexible. Deformation on the aircraft wing consists of this effect. The incorporation of the fluid-structure interaction effect into the calculations requires a high computional cost. In this thesis, a parametric method is developed to recalculate the load distribution due to the deformation on an aircraft wing. As the basis of the study is to obtain a faster and effective results, the simplification of the part of fluid flow and structural analysis are done seperately. The high-fidelity structural model is reduced to a much simpler structure, i.e. to a stick model, while preserving its properties. Thus, the deformed state of the structure under a certain load can be estimated quickly. In the part of fluid flow analysis, instead of using Computational Fluid Dynamics (CFD), which has a high computational cost, a linear aerodynamic assumption, called the Aerodynamic Influence Coefficients (AIC) matri, is used to estimate the pressure distribution on the wing and the associated load. This matrix includes the information of the pressure change corresponding to the deformation. The AIC matrix is created with the help of the Bezier surface functions which is one of the parametric surface modeling methods. The outer surface of the aircraft wing is generated using the Bezier surface modeling method for this purpose. The control vertices (CVs) of the generated surface are used to estimate the load distribution of the deformed shape. The distribution of the load change corresponding to each control vertex per unit perturbance value is combined in the AIC matrix. The major advantage of this method is that it deforms a few control vertices rather than deforming all points on the surface, thus mitigating the computational cost. In addition, the deformation of the CVs results in a smooth deformed surface. Thus, the AIC matrix can be generated with the parametric modeling approach instead of the analysis with high computational cost and the load change information on the aircraft wing can be estimated quickly and effectively. The deformation information obtained from the reduced structural model is transferred to the CVs and the surface of the deformed aircraft wing is obtained by the Bezier curves. The distribution of the load change on the aircraft wing is obtained when the new position of the control points is associated with the AIC matrix. The methods used in this study can be used in the preliminary design stage of an aircraft or when iterative solutions are requested to achieve a faster and effective result for aeroelastic analysis. In addition, although the use of the proposed method is shown for an aircraft wing example in this thesis, it can also be used for other structures which involve the fluid-structure interaction effect. Keywords: Fluid-structure interaction, Bezier surface modeling, Aerodynamic influence coefficient matrix, Aeroelasticity, Multy-physics.