טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentTihomirov Dimitry
SubjectNon-Linear Aerodynamic Effects on Static Aeroelasticity
of Flexible Missiles
DepartmentDepartment of Aerospace Engineering
Supervisor Professor Daniella Raveh


Abstract

The effect of static aeroelasticity on the aerodynamic characteristics of interceptors is investigated in this study. The change in the aeroelastic effect due to nonlinear aerodynamics is also demonstrated. Both of the effects decrease the static stability of the missile. The study presents a novel computationally efficient methodology for assessment of these effects on flexible missiles. The Nonlinear Strip Method (NSM) is based on the coupling of a structural modal model with a database of nonlinear aerodynamic force coefficients provided at strips over the missile's length. An iterative process computes the local elastic angle of attack (AoA) at each segment from the missile's deformed shape. A segment's aerodynamic force is computed from the segment's AoA and the rigid force coefficient from the database. Generalized aerodynamic forces are computed from the segments' aerodynamic forces and used to compute the deformed shape. The process is repeated to convergence. The advantage of the NSM is that it is based on a database of rigid aerodynamic force coefficients, which is typically available either from CFD analyses or wind-tunnel experiment. It accounts for nonlinear aerodynamics, such as flow separation, without relying on computationally elaborate aeroelastic CFD-based analyses. The NSM can be used to compute the elastically deformed shape of a flexible missile and asses its effect on the missile's stability early on  in the design process. The methodology is demonstrated on a generic, flexible interceptor configuration at Mach numbers of $1.2$ and $2.0$ and a range of AoAs. A full nonlinear aeroelastic simulation in a CFD code is used to assess the accuracy of the NSM. A reference linear aeroelastic analysis, based on a panel code, is used to demonstrate the significance of accounting for nonlinear aerodynamics in computing missile stability at these flight conditions.