Galloping instability of a two-degree-of-freedom cube pendulum in an air flow
Abstract
The stability of a two-degree-of-freedom cube pendulum in an air flow is experimentally investigated at reduced velocities U*> 20 and large Reynolds numbers Re~10^5 . Depending on the initial conditions of the cube pendulum at equilibrium (free-stream velocity, yaw and pitch angles), a galloping instability can result in two distinct types of swinging motions: unidirectional cross-flow motions or elliptical motions. An energy-based quasi-steady linear model is developed to analyse the stability of the system and the type of motion resulting from an instability. A good agreement is found between the experimental stability map and the model predictions in situations where the instability develops from rest. The main aerodynamic parameters influencing the stability of the system are identified and linked to the dynamics of flow separation/reattachment on the sides of the cube at the equilibrium state. In addition to the aerodynamic parameters classically highlighted in the Den Hartog criterion regarding cross-flow galloping of bluff bodies, the derivative of the lateral aerodynamic coefficient of the body with respect to its pitch angle is shown to drive the onset of elliptical galloping. Unsteady mechanisms, consisting in delayed dynamics of the flow reattachment line on the sides of the cube, are shown to be involved in the onset of elliptical galloping and highlight the limitations of the quasi-steady approach.
Related
- Galloping instability of a cross-flow pendulum
- A New Degree of Freedom in Stellarator Coil Design
- Rotational elastography: six degree-of-freedom seismology in soft tissues measures local elasticity with diffuse fields
- Observational constraints on a non-minimally coupled scalar field in non-metricity gravity with an extra degree of freedom
- Six-Degree-of-Freedom Rotor-Load Cross-Spectral Density from Rotor-Plane Turbulence Cross-Spectra
BibTeX
@article{myskiw2026galloping,
title = {{Galloping instability of a two-degree-of-freedom cube pendulum in an air flow}},
author = {Antoine Myskiw and Christophe Sicot and Yann Haffner and Jacques Borée},
journal = {Journal of Fluid Mechanics},
year = {2026},
month = sep,
doi = {10.1017/jfm.2026.11964},
url = {https://hal.science/hal-05771489v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Galloping instability of a two-degree-of-freedom cube pendulum in an air flow
AU - Antoine Myskiw
AU - Christophe Sicot
AU - Yann Haffner
AU - Jacques Borée
PY - 2026
DA - 2026/09/01
JO - Journal of Fluid Mechanics
DO - 10.1017/jfm.2026.11964
UR - https://hal.science/hal-05771489v1
AB - The stability of a two-degree-of-freedom cube pendulum in an air flow is experimentally investigated at reduced velocities U*> 20 and large Reynolds numbers Re~10^5 . Depending on the initial conditions of the cube pendulum at equilibrium (free-stream velocity, yaw and pitch angles), a galloping instability can result in two distinct types of swinging motions: unidirectional cross-flow motions or elliptical motions. An energy-based quasi-steady linear model is developed to analyse the stability of the system and the type of motion resulting from an instability. A good agreement is found between the experimental stability map and the model predictions in situations where the instability develops from rest. The main aerodynamic parameters influencing the stability of the system are identified and linked to the dynamics of flow separation/reattachment on the sides of the cube at the equilibrium state. In addition to the aerodynamic parameters classically highlighted in the Den Hartog criterion regarding cross-flow galloping of bluff bodies, the derivative of the lateral aerodynamic coefficient of the body with respect to its pitch angle is shown to drive the onset of elliptical galloping. Unsteady mechanisms, consisting in delayed dynamics of the flow reattachment line on the sides of the cube, are shown to be involved in the onset of elliptical galloping and highlight the limitations of the quasi-steady approach.
SN - 0022-1120
SN - 1469-7645
ER -