M.Sc Thesis


M.Sc StudentAviv Romm
SubjectDynamic Aeroelastic Simulation of the Deployment Process of
a Wing with Variable Sweep Angle
DepartmentDepartment of Aerospace Engineering
Supervisor Professor Emeritus Karpel Mordechay


Abstract

A wing deployment process is investigated by a time marching simulation which solves the dynamic aeroelastic equation of motion in modal coordinates. The simulation is based on combined frequency- and time-domain formulations that take into account the changing external excitation, structural and aerodynamic effects during the deployment process. Each time step involves varying structural modal coupling, unsteady aerodynamic force coefficients and loads using a previously acquired database.


The analyzed configuration is a cylindrical body with a pair of planar wings and four tail fins in a cruciform orientation. The wings are able to change their sweep angle by rotation around an axis located in the root of each wing. The wings are connected to the body model by a modal coupling technique that uses fictitious masses in the interface degrees of freedom. Modal coupling with one set of separate wing and body modes yields very accurate combined wing-body low frequency modes at any wing sweep angle. Unsteady aerodynamic force coefficients are generated for various sweep angles in the frequency domain using the commercially available Zaero software.


The simulation is based on the recently developed Increased Order Modeling approach. A gust response simulation is calculated in four steps. First, the linear equations are formulated and solved in the frequency domain with a constant sweep angle for best computing efficiency and accuracy. These equations provide the baseline response of the system. In the second stage the solution is transformed to time domain by inverse fast Fourier transform. Input-output frequency response functions are also transformed at this stage to yield unit impulse responses .The third stage of the simulation is the addition of feedback loops. These effects are added in a time-marching process that modifies the linear solution using convolution integrals performed with the modal coupling effects. The final stage is updating the linear solution in the frequency domain to include the morphing effects. The simulation is executed by the Dynresp code which serves as a framework for industrial applications and research in nonlinear structural dynamics. Wing loads during the deployment process are obtained using the Mode Displacement Method in a way that accounts for the varying modal coupling effects.