טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentEvgeny Basov
SubjectStatic Aeroelastic Investigation of a Forward Swept Wing
at Transonic Speeds
DepartmentDepartment of Aerospace Engineering
Supervisors Professor Emeritus Karpel Mordechay
Professor Arieli Rimon
Full Thesis textFull thesis text - English Version


Abstract

The influence of static aeroelasticity can be a significant part in aerodynamic design. Static aeroelastic effects are especially important in forward swept wings because they increase the design loads, and may have dramatic effects on aerodynamic derivatives. Often the most complicated aeroelastic effects are at transonic speeds.

The purpose of this research is to develop efficient, yet fairly accurate models for the multidisciplinary design of flight vehicles with swept forward wings. It is assumed that the important aerodynamics can be described in terms of section lift and moment coefficients along the span. The solution is based on a process that corrects local lift and moment coefficients according to lookup tables generated in CFD runs with a rigid vehicle at several angles of attack (AOA). The solution process starts with including CFD-based aerodynamic pressure distribution at zero AOA in the static aeroelastic equilibrium equations, and corrections of the panel aero coefficients to agree with the CFD ones at low AOAs.  An iterative process is then employed where aeroelastic equilibrium is obtained and external loads are added to close the gaps between linearly predicted aeroelastic section loads and the nonlinear ones according to the lookup tables. 

Calculations were made for a 260 forward-swept supercritical-airfoil wing with AR=6 at Mach numbers 0.5 to 0.95.  The ZAERO linear code and the EZNSS Navier-Stokes with k-w turbulence model code were used in the study. The two codes used exactly the same structural model. All CFD solutions used an O-O topology with wing tip collapsed and periodic camber mesh around the wing. The CFD convergence requirement was that the residual drops at least 6 orders of magnitude. Significant nonlinear effects are shown at AOAs above 6 degrees, due to the existence of sizeable separated flow regions. The sensitivity of the results to CFD grid density and location of boundary conditions, were carefully checked.

Results obtained by the proposed procedure were compared with a full CFD-based aeroelastic solution performed with the aeroelastic module of EZNSS. The results for forces and moments on one hand as well as wing deflections and twist on the other, are in good agreement, which shows that a high quality design process can be carried out with the suggested efficient procedure, while full aeroelastic CFD runs performed for a few design versions only for verification purposes.