HIGH PERFORMANCE NUMERICAL METHODS FOR FLUID-STRUCTURE INTERACTION PROBLEMS IN AERONAUTICS

mustardarchaeologistMechanics

Feb 22, 2014 (3 years and 3 months ago)

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HIGH PERFORMANCE NUMERICAL METHODS FOR
FLUID-STRUCTURE INTERACTION PROBLEMS
IN AERONAUTICS


1- INTRODUCTION
The proposed research program aims to develop novel numerical methods in order to solve some
fluid-structure interaction problems encountered in aeronautics. It is a continuation of our
previous NSERC research project where we address further developments on generic numerical
methods as well as tackle challenging applications. The applications are aeroelasticity studies for
aircraft wings and helicopter blades and simulations of noise radiation generated by air flow and
structural vibrations. This field of studies blends solution methods from computational fluid
dynamics (CFD), computational structural dynamics (CSD) and computational acoustics and
aeroacoustics (CAA). Therefore, to obtain accurate results with high computational performance,
state of the art numerical methods must be developed, or employed, which make efficiently use
of the formidable enabling parallel computing resources.

2- GENERAL OBJECTIVES
In the present research program, we are proposing that we pursue our research activities on fluid-
structure interaction problems. We propose using more sophisticated fluid, structure and acoustic
physical models in order to attain higher fidelity simulations and to expand our computational
software capabilities. The numerical methods will be rigorously studied and the computational
models will be validated. We will continue our work on computational acoustics by
progressively increasing the complexity of the acoustic models so that we can address the
simulation of propagation and noise generation from aero-structures. Finally, we intend to
consider applications, related to engineering aeronautics, with increasing complexity.
Specific objectives for Aeroelasticity:
A first goal is to propose enhanced CFD methods for the simulation of unsteady viscous
compressible flows around flexible structures (wings, wing-bodies, full aircraft configurations).
We propose to use the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations for fluid
computations. Indeed, using URANS models will significantly increase the computational
complexity, but it will also greatly enhance the predictive capabilities of the overall analysis for
aero-structures. A second goal is to extend these applications to rotating blades. The focus is on
developing a CFD methodology for rotorcraft that includes aeroelastic deformations. On the
other hand, the study of the interactions between the rotor and the fuselage flow fields is
important for helicopter studies, yet very challenging.
Specific objectives for Aeroacoustics:
A first goal is to continue the study of some fundamental issues for resolving wave equations,
such as higher space discretizations, absorbing boundary conditions, solutions methods for
discrete systems, and so on. These studies will make use of the Helmholtz equation as the model
problem. A second goal is to develop more sophisticated wave equations, using different
assumptions, for studying wave propagation on general flow fields. For sound generation
problems, the objective is to develop or use a method to predict rotorcraft noise.

3- MOTIVATING APPLICATIONS
3.1 Aeroelasticity for aircraft structures
The aerodynamic forces induced by the flow on a flexible aero-structure depend on its geometric
configuration. However, the elastic deformations and displacements of the structure are caused by
the aerodynamic forces. Accurate prediction of aeroelastic phenomena, such as static divergence
and flutter, is essential to the design and control of safe and high performance aircraft. With the
advanced subsonic and transonic civil aircraft, it is becoming increasingly important to perform
static and dynamic aeroelastic analysis using highly accurate fluid and structural computational
models.
In general, aeroelasticity analysis treats static and dynamic aspects. A static analysis is usually
associated with performance [6]. In a dynamic analysis, concern focuses on safety through
stability, and dynamic response studies. Instability problems occur when the structure sustains
energy from the fluid, which exceeds the capacity of elastic potential energy. Thus, there exists a
critical flight speed beyond which instabilities take place, which are characterized by high
amplitude oscillations. Wing flutter is an example of such instabilities. The occurrence of flutter
within the flight envelope of an aircraft usually leads to structural failure and loss of the vehicle.
Computational aeroelasticity analyses of 3D flexible aero-structures are within reach due to the
recent highly developed computing technology and numerical methods [7,8]. However, there are
still difficulties in predicting aeroelastic phenomena in the transonic regime and for separated
flows. The transonic regime is critical since the flutter speed is minimal in this regime. Thus,
computational aeroelasticity methods should be able to at least simulate the nonlinear effects due
to shocks; however, accurate turbulence models are necessary to deal with separation.
3.2 Aeroelasticity and aeroacoustics for helicopter rotors
Helicopters are capable of much more complex manoeuvrings compared to aircraft. However,
their rotors are susceptible to several structural instabilities. Therefore, designing a new
generation of rotors for reduced noise and vibrations will require a better understanding of the
physical phenomena causing such instabilities. Rotorcraft flow simulations are among the most
challenging applications in CFD. We need to take into account the interactions of blade dynamics
and flow field in order to enhance the predictive capabilities of the overall analysis for all
helicopter flight scenarios [9]. Elastic blades deformations have to be integrated into the
aerodynamic analysis; otherwise wrong local effective angles of attack may be produced. A
reliable analysis of the aerodynamic and acoustic behaviour of helicopter rotors requires accurate
and comprehensive CFD, aeroelasticity and aeroacoustics tools.