Nonlinear Aeroelasticity

 

Title: Nonlinear Aeroelasticity - CFD Based Harmonic Balance Methods

Investigators: Richard Hayes

Sponsor: DEL

 

Project Background

In the aeronautical industry vast amounts of work is carried out in the pursuit of engineering efficient aircraft with the ability to withstand all possible loading situations that may occur during all flight scenarios. At certain points in the flight envelope the interaction between the aircraft structure and air may create peculiar loading conditions. These are known as aeroelastic phenomena and are detrimental to aircraft performance and more importantly safety. The source of these phenomena is often aerodynamic non-linearity caused by the occurrence of shock waves or flow separation. This underlines the need for CFD in aeroelastic problems but this requires expensive and time consuming computations when modelling practical applications. A promising approach is to use a Harmonic Balance technique to model the aerodynamics rather than typical time domain solvers. Harmonic Balance can exploit the periodicity associated with aeroelasticity by computing in the frequency domain. Significant time savings can be obtained and thus aeroelastic problems can be investigated more efficiently. The goal of this project is to create an effective and efficient method of simulating complex aeroelastic problems. The approach taken consists of the development a multidisciplinary solver which can accurately model the interaction between the structure and the aerodynamics based around the Harmonic Balance.

There are a few key milestones to be reached to accomplish the project goal:

  1. Investigate Harmonic Balance (HB) methods to model unsteady non-linear aerodynamic forces in transonic conditions.
  2. Couple a structural solver with the Harmonic Balance CFD solver.
  3. Extend Harmonic Balance CFD solver for RANS simulations.
  4. Test and validate the code for a wide range of test cases including implementation on a large scale, ie. a full wing/aircraft configuration.
  5. Investigate the effects of aleatory uncertainty on the response of aeroelastic systems, focusing on limit cycle oscillation behaviour.

Duffing Oscillator: Effects of number of harmonics retained in HDHB analysis


Transonic Pitch/Plunging Aerofoil: Simulation performed using an Harmonic Balace CFD method.

References

Hayes, R. & Marques, S., UNCERTAINTY QUANTIFICATION FOR LCO USING AN HARMONIC BALANCE METHOD, IFASD, Bristol, U.K., 2013, IFASD_2013_H.pdf

Hayes, R. & Marques, S.,Aeroelastic predictions using a CFD based harmonic balance solver, MultiPhysics 2012, Lisbon, Portugal, 2012