Experiments on an airfoil with adjustable pitch and heave under transonic buffet leading to lock-in coupling
Abstract
This paper presents aeroelastic experiments conducted in the ONERA S3Ch transonic wind tunnel using a supercritical OAT15A airfoil mounted on a rig allowing independent control of pitch and heave degrees of freedom (DOF). The study investigates fluid-structure interaction (FSI) mechanisms and lock-in phenomena between transonic buffet and structural modes. Aerodynamic and structural responses were monitored using steady and unsteady pressure sensors, high-speed stereoscopic Particle Image Velocimetry (PIV), accelerometers, and optical sensors. Four configurations were tested: rigid (0 DOF), pitch-only (1 DOF pitch), heave-only (1 DOF heave), and combined pitch-heave (2 DOF). The test campaign spanned selected Mach numbers, angles of attack, and structural natural frequencies for each configuration. Results show that buffet-induced lock-in occurs abruptly when the Mach number increases, but only when the pitch DOF is enabled, in both the 1-DOF pitch or 2-DOF configuration. These findings establish that pitch-buffet frequency proximity is a necessary condition for lock-in. In the 2-DOF configuration, continuous Mach number excursions revealed a three-way coupling involving the buffet, pitch, and bending modes, with the bending mode modulating the coupled dynamics. This coupling generates large-amplitude limit-cycle oscillations (LCO) within seconds, persisting over a narrow Mach range before buffet cessation.
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BibTeX
@misc{themiot2026experiments,
title = {{Experiments on an airfoil with adjustable pitch and heave under transonic buffet leading to lock-in coupling}},
author = {Cédric Themiot and Vincent Brion and Arnaud Lepage},
howpublished = {HAL},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.16366},
eprint = {2610.16366},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05773401v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Experiments on an airfoil with adjustable pitch and heave under transonic buffet leading to lock-in coupling
AU - Cédric Themiot
AU - Vincent Brion
AU - Arnaud Lepage
PY - 2026
DA - 2026/10/09
PB - HAL
DO - 10.48550/arxiv.2610.16366
UR - https://hal.science/hal-05773401v1
AB - This paper presents aeroelastic experiments conducted in the ONERA S3Ch transonic wind tunnel using a supercritical OAT15A airfoil mounted on a rig allowing independent control of pitch and heave degrees of freedom (DOF). The study investigates fluid-structure interaction (FSI) mechanisms and lock-in phenomena between transonic buffet and structural modes. Aerodynamic and structural responses were monitored using steady and unsteady pressure sensors, high-speed stereoscopic Particle Image Velocimetry (PIV), accelerometers, and optical sensors. Four configurations were tested: rigid (0 DOF), pitch-only (1 DOF pitch), heave-only (1 DOF heave), and combined pitch-heave (2 DOF). The test campaign spanned selected Mach numbers, angles of attack, and structural natural frequencies for each configuration. Results show that buffet-induced lock-in occurs abruptly when the Mach number increases, but only when the pitch DOF is enabled, in both the 1-DOF pitch or 2-DOF configuration. These findings establish that pitch-buffet frequency proximity is a necessary condition for lock-in. In the 2-DOF configuration, continuous Mach number excursions revealed a three-way coupling involving the buffet, pitch, and bending modes, with the bending mode modulating the coupled dynamics. This coupling generates large-amplitude limit-cycle oscillations (LCO) within seconds, persisting over a narrow Mach range before buffet cessation.
ER -