טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentMichael Iovnovich
SubjectA Study of the Shock-Buffet Phenomenon and Related
Unsteady Aerodynamics on 2D and 3D Wings
DepartmentDepartment of Aerospace Engineering
Supervisor Professor Raveh Daniella
Full Thesis textFull thesis text - English Version


Abstract

The study employs Unsteady Reynolds-averaged Navier-Stokes (URANS) Computational Fluid Dynamics (CFD) simulations to study the transonic shock-buffet instability phenomenon and related unsteady aerodynamic responses on 2D and 3D wings. Shock-buffet is a transonic, non-linear, flow instability phenomenon, in which a shock-wave generated on a lifting surface interacts with a partially, or fully separated boundary layer, resulting in oscillating flow over the surface. Shock-buffet degrades the performance of airfoils and wings, and it may also compromise flight vehicle safety. Moreover, the interaction of shock-buffet with the elastic structural motion of the airfoil or wing may induce aeroelastic responses that are highly undesirable from the point of view of structural integrity, aerodynamics, and flight handling qualities. The motivation for this research is to understand non-linear transonic aerodynamic phenomena, to enable better prediction methods, and to improve design techniques for future transonic air vehicles. Accordingly, the thesis is divided into three chapters. The first chapter deals with the fundamental physical mechanism of shock-buffet flows on 2D airfoils. The second chapter deals with the unsteady aerodynamic response of a 2D airfoil to prescribed structural excitation in pitch and flap motion in the vicinity of shock-buffet flow conditions. The third chapter deals with the fundamental physical mechanism of shock-buffet flows on 3D finite wings. The study sheds new light on shock-buffet characteristics and suggests novel ideas such as: instability mechanism of buffet on 2D airfoils; identification of essential conditions for instability onset; classification of buffet-related aeroelastic instabilities; and the discovery of a new instability mechanism on 3D swept wings. Special emphasis is put on numerical validation of the computational tools used in this study by means of comparison with experimental data for several cases of 2D airfoils and 3D swept wings.