Numerical Study on Large-Amplitude Limit Cycle Oscillation of Delta Wing

2008 ◽  
Author(s):  
Atsushi Hashimoto ◽  
Takashi Aoyama ◽  
Yoshiaki Nakamura
Keyword(s):  
Limit Cycle ◽  
Large Amplitude ◽  
Delta Wing ◽  
Numerical Study ◽  
Limit Cycle Oscillation ◽  
Cycle Oscillation

Delta Wing with Store Limit-Cycle-Oscillation Modeling Using a High-Fidelity Structural Model

2008 ◽  
Vol 45 (3) ◽  
pp. 1054-1061 ◽  
Author(s):  
Peter J. Attar ◽  
Earl H. Dowell ◽  
Deman Tang
Keyword(s):  
Limit Cycle ◽  
Structural Model ◽  
Delta Wing ◽  
Limit Cycle Oscillation ◽  
High Fidelity ◽  
Cycle Oscillation

Onset of convection induced by centrifugal buoyancy in a rotating cavity

2017 ◽  
Vol 826 ◽  
pp. 484-502 ◽  
Author(s):  
Diogo B. Pitz ◽  
Olaf Marxen ◽  
John W. Chew
Keyword(s):  
Rayleigh Number ◽  
Limit Cycle ◽  
Numerical Study ◽  
Limit Cycle Oscillation ◽  
Turbulent Regime ◽  
Final State ◽  
Onset Of Convection ◽  
Rotating Systems ◽  
Cycle Oscillation ◽  
Energy Saturation

Flows induced by centrifugal buoyancy occur in rotating systems in which the centrifugal force is large when compared to other body forces and are of interest for geophysicists and also in engineering problems involving rapid rotation and unstable temperature gradients. In this numerical study we analyse the onset of centrifugal buoyancy in a rotating cylindrical cavity bounded by two plane, insulated disks, adopting a geometrical configuration relevant to fundamental studies of buoyancy-induced flows occurring in gas turbine’s internal air systems. Using linear stability analysis, we obtain critical values of the centrifugal Rayleigh number $Ra$ and corresponding critical azimuthal wavenumbers for the onset of convection for different radius ratios. Using direct numerical simulation, we integrate the solutions starting from a motionless state to which small sinusoidal perturbations are added, and show that nonlinear triadic interactions occur before energy saturation takes place. At the lowest Rayleigh number considered, the final state is a limit-cycle oscillation affected by the presence of the disks, having a spectrum dominated by a certain mode and its harmonics. We show that, for this case, the limit-cycle oscillations only develop when no-slip end walls are present. For the largest $Ra$ considered chaotic motion occurs, but the critical wavenumber obtained from the linear analysis eventually becomes the most energetic even in the turbulent regime.

scholarly journals Reducing parametric uncertainty in limit-cycle oscillation computational models

2017 ◽  
Vol 121 (1241) ◽  
pp. 940-969 ◽  
Author(s):  
R. Hayes ◽  
R. Dwight ◽  
S. Marques
Keyword(s):  
Limit Cycle ◽  
Computational Models ◽  
Structural Parameters ◽  
Parametric Uncertainty ◽  
Limit Cycle Oscillation ◽  
Posterior Distributions ◽  
Input Parameters ◽  
Data Points ◽  
Cycle Oscillation ◽  
True Values

ABSTRACTThe assimilation of discrete data points with model predictions can be used to achieve a reduction in the uncertainty of the model input parameters, which generate accurate predictions. The problem investigated here involves the prediction of limit-cycle oscillations using a High-Dimensional Harmonic Balance (HDHB) method. The efficiency of the HDHB method is exploited to enable calibration of structural input parameters using a Bayesian inference technique. Markov-chain Monte Carlo is employed to sample the posterior distributions. Parameter estimation is carried out on a pitch/plunge aerofoil and two Goland wing configurations. In all cases, significant refinement was achieved in the distribution of possible structural parameters allowing better predictions of their true deterministic values. Additionally, a comparison of two approaches to extract the true values from the posterior distributions is presented.

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