Aeroelastic stability of a two-degrees of freedom system with combined narrow band random and harmonic excitation

0487126 - ÚTAM 2018 eng C - Conference Paper (international conference)
Náprstek, Jiří - Pospíšil, Stanislav
Aeroelastic stability of a two-degrees of freedom system with combined narrow band random and harmonic excitation.
2017.
[European-African Conference on Wind Engineering 2017 /7./. Liège (BE), 04.07.2017-07.07.2017]
R&D Projects: GA ČR(CZ) GA15-01035S; GA MŠMT(CZ) LO1219
Institutional support: RVO:68378297
Keywords : Fokker-Planck equation * aero-elastic stability * two degrees of freedom system
OECD category: Civil engineering

The Linear deterministic approach of aero-elastic stability of a slender prismatic beam in a cross flow has been widely investigated in the past. Due to character of the system and regulations in practice (civil engineering, aircraft design, etc.) they can be used to determine of the lowest flow velocity of various types of instability onset. Two degrees of freedom (TDOF) theoretical models have been worked out and experimentally validated. However, a part of the differences between the model and the experiments may me attributed to the the random components appearing in an external excitation can influence significantly the effective aeroelastic stability of this system. Combination of deterministic and random types of external excitation are taken into account regarding simultaneous vortex shedding and turbulence in the shear layer around the profile. Thus, combination of deterministic and random types of external excitation should be taken into account when modeling the simultaneous action of vortex shedding and turbulence in the free shear layer. To investigate the random response and stability of the system, the employment of the Fokker-Planck equation (FPE) is necessary. However, the dynamic system investigated should include Gaussian white noises only. To overcome this limitation an extended definition of correlation coefficients (in integral meaning) is used when constructing Ito system using stochastic averaging. Then original narrow band processes emerge in the relevant Ito system only as a couple of input process spectral density values in significant points of the system resonance curves. Finally, stability limits of amplitudes and phase shifts can be deduced in the meaning of the probability density with respect to all main parameters of the system. Theoretical results are compared with experiments and the illustrative examples are discussed. Possible extensions in the future are outlined.
Permanent Link: http://hdl.handle.net/11104/0282122