EXTENDING A VAN DER POL BASED REDUCED-ORDER MODEL FOR FLUID-STRUCTURE INTERACTION APPLIED TO NON-SYNCHRONOUS VIBRATIONS IN TURBOMACHINERY
- 13 September 2021
- journal article
- research article
- Published by ASME International in Journal of Turbomachinery
- Vol. 144 (3), 1-14
- https://doi.org/10.1115/1.4052405
Abstract
This paper expands upon a multi-degree-of-freedom, Van der Pol oscillator used to model buffet and Nonsynchronous Vibrations (NSV) in turbines. Two degrees-of-freedom are used, a fluid tracking variable incorporating a Van der Pol oscillator and a classic spring, mass, damper mounted cylinder variable; thus, this model is one of fluid-structure interaction. This model has been previously shown to exhibit the two main aspects of NSV. The first is the lock-in or entrainment phenomenon of the fluid shedding frequency jumping onto the natural frequency of the oscillator, while the second is a stable limit cycle oscillation (LCO) once the transient solution disappears. Improvements are made to the previous model to better understand this aeroelastic phenomenon. First, an error minimizing technique through a system identification method is used to tune the coefficients in the Reduced Order Model (ROM) to improve the accuracy in comparison to experimental data. Secondly, a cubic stiffness term is added to the fluid equation; this term is often seen in the Duffing Oscillator equation, which allows this ROM to capture the experimental behavior more accurately, seen in previous literature. The finalized model captures the experimental cylinder data found in literature much better than the previous model. These improvements also open the door for future models, such as that of a pitching airfoil or a turbomachinery blade, to create a preliminary design tool for studying NSV in turbomachinery.Keywords
This publication has 8 references indexed in Scilit:
- Non-synchronous vibration in axial compressors: Lock-in mechanism and semi-analytical modelJournal of Sound and Vibration, 2020
- Frequency lock-in during nonlinear vibration of an airfoil coupled with van der Pol OscillatorJournal of Fluids and Structures, 2019
- Frequency lock-in during vortex induced vibration of a rotating bladeJournal of Fluids and Structures, 2018
- Vortex-Induced Vibration and Frequency Lock-In of an Airfoil at High Angles of AttackJournal of Fluids Engineering, 2015
- Modelling vortex-induced fluid–structure interactionPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2007
- Predicting the onset of flow unsteadiness based on global instabilityJournal of Computational Physics, 2007
- Nonsynchronous Vibration (NSV) due to a Flow-Induced Aerodynamic Instability in a Composite Fan StatorJournal of Turbomachinery, 2005
- VORTEX-INDUCED VIBRATIONSAnnual Review of Fluid Mechanics, 2004