EFFICIENT APPLICATION OF CFD AEROELASTIC METHODS USING COMMERCIAL SOFTWARE Luca Cavagna, Giuseppe Quaranta, Gian Luca Ghiringhelli and Paolo Mantegazza Dipartimento di Ingegneria Aerospaziale, Politecnico di Milano, via La Masa 34, 20156 Milano, Italy email: {cavagna,quaranta,ghiringhelli,mantegazza}@aero.polimi.it Key words: Computational Fluid Dynamics, Transonic Aeroelasticity, Flutter Analysis. Abstract. Aeroelastic analyses in transonic regime require the adoption of accurate aerodynamics physical models, such as Euler or Navier-Stokes equations. To move the application of these type of analyses from a pure academical environment to an industrial one, it is necessary to show that the technology is mature enough to be implemented without using specialized pieces of software. This paper presents a numerical procedure defined to solve Fluid-Structure Interactions (FSI) for aeroelastic problems using par- titioned procedures based on the adoption of “black-box” commercial software for the solution of each field. A special attention is given to the efficiency of the procedure, keep- ing in mind the high number of analyses that have to be run during the development of a new aircraft. 1 INTRODUCTION Aeroelastic phenomena in transonic speed range may become extremely complex, because under these conditions shock waves appear and move in the flow field as consequence of air- craft unsteady flexible motions. Usually, the appearance of shock waves may cause a drop of the flutter velocity, the well known “transonic dip” effect, which is under-predicted by classical potential methods used for unsteady aerodynamic loads description. Im- provements in the flutter boundary evaluation can be obtained by using more complex descriptions of the aerodynamic domain, capable of predicting shock waves in the flow, such as those based on the Euler or Navier-Stokes equations. Starting from the pioneering works of Lee-Raush and Batina 1;2 , given the fast increase in the computer performances of the last few years, the application of unsteady CFD solutions for aeroelastic problems has grown into a large and successful research field, with applications to complete aircraft con- figurations 3 . However, up to now the complexity of the procedures and the high amount of specialized computational resources required for the application of these methodologies precludes them from being extensively used in industrial aeroelastic analysis 4;5 . The purpose of this paper is to show that times are mature for trying to define pro- cedures to solve transonic aeroelastic problems effectively in an industrial environment. To do so, we tested the possibility to create specific procedures for aeroelastic analyses using “off-the-shelf” software products, such as the commercially available Computational Fluid Dynamics (CFD) software FLUENT. Figure 1 shows a block diagram with all the elements needed for conducting an aeroelastic assessment with CFD. Three main elements of this block diagram have a key role in generating an efficient and robust solution pro- cedure: the first is the grid interpolation between the structural and the aerodynamic discretization; the second is the grid deformation which must be used in order to adapt it to the motion of the aircraft under investigation, and third is the definition of a “smart” 1