Energy budget analysis of aeroelastic limit-cycle oscillations

Abstract

In this work limit-cycle oscillations (LCOs) caused by aerodynamic non-linearities were analysed using fluid-structure interaction (FSI) simulations of a two-degree-of-freedom airfoil system. A comparison with sinusoidal forced motion oscillation simulations at the fundamental frequency was performed. The results show that using the first harmonic component for the forced motion oscillations is a good approach to describe the limit-cycle oscillations considered in this work. Following the work of G. Dietz, G. Schewe and H. Mai (2004), Journal of Fluids and Structures, Vol. 19, an energy budget analysis of the limit-cycle oscillations was performed. Power analysis of the LCO reveals that the power of the lift and moment show non-linear behaviour with increasing amplitude. The linearised equivalent power components that would occur in case of flutter were computed. These show that the defect in the power of the lift in the non-linear case is caused by the increase of the phase of the lift with oscillation amplitude, which is the result of the unsteady shock wave motions on both upper and lower surface of the airfoil. The power of the moment also shows a defect, which is much smaller than in case of the lift. This defect is caused by variations in both the magnitude and the phase of the moment with oscillation amplitude.

Prediction of Aeroelastic Limit-Cycle Oscillations Based on Harmonic Forced-Motion Oscillations

“…In ADePK, only the complex-valued first harmonic of the motion and the aerodynamic response are taken into account. Although there are significant higher harmonics in the aerodynamic response (as observed from coupled FSI simulations), the work they perform on the airfoil is negligible, since the higher harmonics in the motion of the structure were observed to be very small compared to the first harmonic component (see [22]). Furthermore, every harmonic only performs work on itself.…”

“…where the aerodynamic forces are applied. The equations of motion of the system (as shown in [22]) are given by:…”

“…They are given in For reference, limit-cycle oscillations are also computed in the time domain. As described in [22] the coupling is partitioned. To achieve so-called "strong" coupling of the CFD and the structural solver, the forces and displacements are exchanged between these solvers multiple times during each physical time step.…”

Modeling, Validation, and Performance of Two Tandem Cylinder Piezoelectric Energy Harvesters in Water Flow

“…Especially, piezoelectric energy harvesters (PEHs) have been widely used for energy harvesting from ambient vibration [ 12 , 13 , 14 , 15 , 16 ]. Hence, the piezoelectric conversion mechanism can be used to capture energy from fluid kinetic energy, which has attracted much attention among scholars [ 17 , 18 , 19 , 20 , 21 , 22 ].…”

Subcritical Limit Cycle in Airfoil Aeroelastic System with Freeplay: Prediction and Mechanism

“…Several types of concentrated structural nonlinearities such as cubic stiffness, freeplay, and hysteresis have received significant attention from the aeroelastics community [1]. Of them, freeplay as a typical nonsmooth nonlinearity is usually modeled as representative of worn or loosened rotation springs, or control surface hinges [6][7][8][9][10].…”