Purpose - The present paper aims to address the description of a numerical optimization procedure, based on mesh morphing, and its application for the improvement of the aerodynamic performance of an industrial glider which suffers of a large separation occurring in the wing-fuselage junction region at high incidence angles. Design/methodology/approach - Shape variations were applied to the baseline configuration through a mesh morphing technique founded on the mathematical framework of radial basis functions (RBF). The aerodynamic solutions were obtained coupling an RANS code with the mesh morphing tool RBF Morph™. Two shape modifiers were set up to generate a parametric numerical model. An optimization procedure, based on a design of experiment sampling, was set up implementing the fully automated workflow within a high performance computing (HPC) environment. The optimal candidates maximizing the aerodynamic efficiency were identified by means of a cubic RBF response surface approach. Findings - The separation was significantly reduced, modifying the local geometry of fuselage and fairing and maintaining the wing aerofoil unchanged. A relevant aerodynamic efficiency improvement was finally gained. Practical implications - The developed procedure proved to be a very powerful and efficient tool in facing aerodynamic design problems. However, it might be computationally very expensive if a large number of design variables are adopted and, in those cases, the method can be suitably used only within the HPC environment. Originality/value - Such an optimization study is part of an explorative set of analyses that focused on better addressing the numerical strategies to be used in the development of the EU FP7 Project RBF4AERO
In this paper a fast and efficient mesh morphing based technique to perform FSI analyses for aeroelastic design and optimization applications is presented. The procedure is based on the finite volume CFD solver (OpenFOAM® and SU2) coupled with the RBF Morph™ tool capable of deforming the surface and volume mesh of the computational domain according to the mode superposition method. Structural vibration modes of the geometry of interest are calculated in a pre-processing stage by means of a FEM solver and later imported into the RBF Morph™ tool to create a set of individual basic deformations. Aerodynamic loads calculated with a CFD solver are then projected onto the accounted structural modes to get modal loads and modal coordinates which are applied to the computational model in order to obtain the deformed configuration. An FSI cycle incorporating a CFD simulation and morphing of its mesh can be iteratively repeated upon convergence to the final deformed shape. Since the modal parameterization and the mesh calculation have to be prepared only once per FSI analysis, its computation time is drastically reduced compared to a standard two-way coupling method in which a structural analysis has to be done at each cycle. Present procedure was applied to two geometries, HIRENASD fuselage-wing geometry for the purpose of testing the procedure and a Pipistrel's electric aircraft propeller for the purpose of optimization of its shape. By utilizing a DoE and a response surface method an increase of four percent of propeller efficiency was obtained by converging to a most favourable propeller pitch and twist configuration incorporating also FSI deformation. The abovementioned procedure was developed in the framework of the EU-funded RBF4AERO project (Grant Agreement No: 605396) and is available through the RBF4AERO platform.
Abstract. In this paper, the continuous adjoint method, developed by NTUA in the Open-FOAM R environment, is coupled with an RBF-based morpher developed by UTV to tackle optimization problems in low-speed aeronautics. The adjoint method provides a fast and accurate way for computing the sensitivity derivatives of the objective functions (here, drag, lift and losses) with respect to the design variables. The latter are defined as a set of variables controlling a group of RBF control points used to deform both the surface and volume mesh of the computational domain. The use of the RBF-based morpher provides a fast and robust way of handling mesh and geometry deformations, facing two challenging tasks related to shape optimization with the same tool. The coupling of the above-mentioned tools is used to tackle (a) the minimization of the cooling losses for an electric motor installed on a lightweight aircraft, by controlling the cooling air intake shape and (b) the shape optimization of a glider geometry targeting maximum lift-to-drag ratio by mainly optimizing the wing-fuselage junction. Regarding problem (a), a porous media is utilized to simulate the pressure drop caused by the radiator; the adjoint to this porosity model is developed and presented. This work was carried out in the framework of the EU-funded RBF4AERO project and the presented methods are available through the RBF4AERO platform (www.rbf4aero.eu).
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