Checking date: 21/06/2021


Course: 2021/2022

Aeroelasticity
(15355)
Study: Bachelor in Aerospace Engineering (251)


Coordinating teacher: FAJARDO PEÑA, PABLO

Department assigned to the subject: Department of Bioengineering and Aerospace Engineering

Type: Electives
ECTS Credits: 3.0 ECTS

Course:
Semester:




Requirements (Subjects that are assumed to be known)
Before taking this course, the student should have completed the courses of aerodynamics, structures, and mechanics.
Objectives
Adequate and applied knowledge of Aerospace Engineering of Aerodynamics. Knowledge of the simplified laws of motion of fluids around bodies in different flight regimes. Understand the origin of aerodynamic forces and learn to quantify them by analytical and numerical methods. Adequate knowledge of Aeroelasticity. Adequate knowledge of the use of aerodynamic experimentation and of the most significant parameters in the theoretical application; the handling of the experimental techniques, equipment and measuring instruments typical of the discipline; simulation, design, analysis and interpretation of in-flight experimentation and operations.
Skills and learning outcomes
Description of contents: programme
Aeroelasticity & Dynamic Loads. Getting Started. - Aeroelasticity as a multidisciplinary task - Normal modes at a glance - Stability problems vs. Response problems - Basic flutter mechanisms. CS25.629 2D Aeroelasticity: fixing concepts with some analytical 2D solutions - The ¾ span aerofoil. Pitch and plunge modes. - Revisiting steady aerodynamics. The standard atmosphere. - Introduction to 2D unsteady aerodynamics. Wagner, Küssner, Theodorsen. - Solution of the 2D aeroelastic equation. - Sensitivity to Xcg. 2D & 3D Static aeroelasticity: divergence and control reversal - Static aeroelasticity of a 2D rigid aerofoil. - Static aeroelasticity of a fixed wing - Divergence. Effect of sweep angle on divergence speed. - Control effectiveness. Effect of wing flexibility on control effectiveness. 3D Aeroelasticity: The structural model & the normal modes - Revisiting 1 d.o.f system. - Multiple d.o.f. systems - The Finite Element Method (FEM) for structural analysis. - From stick models to full FEM models. The stiffness matrix. - Mass models. The mass matrix. - Condensation. - Structural Normal modes. Frequencies and mode shapes. The experimental modal analysis and the GVT. Dynamic model validation. - Ground Vibration Test (GVT) description. - Introduction to Digital Signal Processing (DSP). The Fast Fourier Transform (FFT). - Experimental Modal Analysis. - Comparison between test and simulations. MAC. - Updating FEM model to match GVT results. 3D Aeroelasticity: unsteady aerodynamics, origins (Wagner, Küssner, Theodorsen). Rodden and the Doublet Lattice Method (DLM) - Continuing with 2D unsteady aerodynamics. - The Finite Element Method (FEM) for aerodynamic analysis. - Rodden and the Doublet lattice Method - Aerodynamic corrections to match wind tunnel or flight tests. The flutter equation and its solution (natural aircraft) - Derivation of flutter equation from Lagrange equations. - Complex matrix eigenvalues & eigenvector solution. - Evolution of modal frequency and modal damping with flight speed. - The V-g plot unveiled - Physical description of classical lifting surface flutter mechanisms - Airworthiness regulations CS25.629 (and the evolution from FAR 25.629 and JAR 25.629) Flutter speed sensitivities. Control surface massbalance. Aeroservoelasticity (coupling with Flight Control System laws) - Sensitivity analyses: mass configuration, Mach number, control surface aerodynamic hinge moment, etc. - Physical description of classical control surface flutter mechanisms. - Sensitivity to control surface mass balance. - Covering uncertainties & addressing failure cases (structural single failures, damage tolerance, water ingress, composite delaminations...) - Revisiting aircraft controls. Introduction to aircraft flight control system laws. - Aeroservoelasticity. - Physical description of most common aeroservoelastic couplings. Flight Flutter Test. Aeroelastic model validation. Wrap up of aeroelastic stability problems. - Flight Flutter Test (FVT) description. - Aircraft response to control surface sweeps and pulses. - Revisiting Digital Signal Processing (DSP). Noise treatment. Averaging. Windowing. Aliasing. Leakage,... - Experimental Modal Analysis applied to Flight Test. - Comparison between flight test and simulations. Scatter. - Wrap up of aeroelastic stability problems. The concept of loads. Monitoring stations. Checkstress loads and fatigue loads. Dynamic loads and why they are different form static loads. Structural response to transient excitation. - What is fast and what is slow - Direct response vs. Modal response - Frequency domain response - Time domain response Ground dynamic loads: dynamic landing & Taxi - Relevance Dynamic Flight Loads. DTG, Continuous Turbulence and Buffet
Learning activities and methodology
One session per week.
Assessment System
  • % end-of-term-examination 60
  • % of continuous assessment (assigments, laboratory, practicals...) 40
Calendar of Continuous assessment
Basic Bibliography
  • Wright, J.R. and Cooper, J.E.. Introduction to Aircraft Aeroelasticity and Loads. John Wiley & Sons. 2007
Additional Bibliography
  • Bisplinghoff, R. L., Ashley, H., and Halfman, R.L.. Aeroelasticity. Addison-Wesley. 1955
  • Bisplinghoff, R., and Ashley, H. . Principles of Aeroelasticity. Dover. 1962
  • Dowell, E.H., Crawley, E.F., Curtiss, H.C., Peters, D.A., Scanlan, R.H. and Sisto, F. . A Modern Course in Aeroelasticity (3rd ed). Kluwer. 1995
  • Fung, Y.C. . An Introduction to the Theory of Aeroelasticity. John Wiley and Sons. 1955
  • Rodden, W.P. and Johnson, E.H. . MSC/NASTRAN Aeroelastic Analysis User¿s guide.. The MacNeal-Schwendler Corporation. 1994

The course syllabus and the academic weekly planning may change due academic events or other reasons.