Aeroelastic response of an elastically mounted 2-DOF airfoil and its gust-induced oscillations
Publication date
2023-01
Document type
Research article
Organisational unit
Project
DFG-Projekt: BR 1847/17-1 Wind Gusts and their Dynamic Effects on Flexible Structures: Modeling and High-Resolution Simulations
Series or journal
Journal of Fluids and Structures
Periodical volume
117
Periodical issue
103828
Peer-reviewed
✅
Part of the university bibliography
✅
Keyword
Wind gust
Split velocity method
Fluid–structure interaction (FSI)
2-DOF aeroelastic oscillations
Limit-cycle oscillation (LCO)
Airfoil flutter
Large-eddy simulation (LES)
Energy analysis
Abstract
The paper is concerned with numerical investigations on the effect of vertical wind gusts on airfoils in a parameter range relevant for Micro-Air Vehicles. Using a simplifiedsubstitute model instead of an elastic wing, a rigid but elastically mounted airfoil with two degrees of freedom (heave and pitch) is considered. The coupled problem is tackled by a partitioned fluid–structure interaction coupling scheme based on the large-eddy simulation (LES) technique and a rigid-body solver. In order to describe the effect of deterministic 1-cosine gusts of different gust lengths and gust strengths, the split velocity method (SVM) is incorporated into the simulation framework relying on the Arbitrary Lagrangian–Eulerian (ALE) formulation on temporally varying control volumes. First the flow fields and the corresponding aerodynamic forces during the direct airfoil–gust interaction are compared for a fixed and an elastically mounted airfoil. The intrinsic study on the elastic case includes nine different gust scenarios in the transitional Reynolds number regime in order to investigate the resulting flow fields and motion patterns and to answer the question whether limit-cycle oscillations (LCO) or even flutter can be induced. The results show that in seven of the studied cases, the airfoil–gust interaction leads to sustained heave and pitch oscillations of bounded amplitudes (i.e., LCO). Further investigations clarify that this can be physically attributed to the laminar separation taking place on the upper and lower surfaces of the airfoil. The two strongest gust cases, however, excite the airfoil to levels above its critical angle of attack and triggered a pitch-induced diverging flutter. An energy analysis of both characteristic scenarios (i.e., LCO and flutter) further elucidates the differences between both cases. The former case is driven by the heave motion, whereas the pitch DOF acts as an energy sink. Contrarily, in the case of flutter the pitching motion is powering the coupled system, whereas the heave motion dissipates energy.
Cite as
Journal of Fluids and Structures 117 (2023) 103828
Version
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