Methods of continuation and their implementation in the COCO software platform with application to delay differential equations

Z Ahsan, H Dankowicz, M Li, J Sieber - Nonlinear Dynamics, 2022 - Springer
This paper treats comprehensively the construction of problems from nonlinear dynamics
and constrained optimization amenable to parameter continuation techniques and with …

Real-time thermoacoustic data assimilation

A Nóvoa, L Magri - Journal of Fluid Mechanics, 2022 - cambridge.org
Low-order thermoacoustic models are qualitatively correct, but typically, they are
quantitatively inaccurate. We propose a time-domain bias-aware method to make …

Learning ergodic averages in chaotic systems

F Huhn, L Magri - International Conference on Computational Science, 2020 - Springer
We propose a physics-informed machine learning method to predict the time average of a
chaotic attractor. The method is based on the hybrid echo state network (hESN). We assume …

Variational optimization and data assimilation in chaotic time-delayed systems with automatic-differentiated shadowing sensitivity

N Chandramoorthy, L Magri, Q Wang - arXiv preprint arXiv:2011.08794, 2020 - arxiv.org
In this computational paper, we perform sensitivity analysis of long-time (or ensemble)
averages in the chaotic regime using the shadowing algorithm. We introduce automatic …

A real-time digital twin of azimuthal thermoacoustic instabilities

A Nóvoa, N Noiray, JR Dawson, L Magri - arXiv preprint arXiv:2404.18793, 2024 - arxiv.org
When they occur, azimuthal thermoacoustic oscillations can detrimentally affect the safe
operation of gas turbines and aeroengines. We develop a real-time digital twin of azimuthal …

[PDF][PDF] An efficient algorithm for sensitivity analysis of chaotic systems

N Chandramoorthy - 2021 - mit.edu
How does long-term chaotic behavior respond to small parameter perturbations? Using
detailed models, chaotic systems are frequently simulated across disciplines–from climate …

Sensitivity analysis for periodic orbits and quasiperiodic invariant tori using the adjoint method

H Dankowicz, J Sieber - arXiv preprint arXiv:2111.02122, 2021 - arxiv.org
This paper presents a rigorous framework for the continuation of solutions to nonlinear
constraints and the simultaneous analysis of the sensitivities of test functions to constraint …

Optimizing Thermoacoustic Characterization Experiments for Identifiability Improves Both Parameter Estimation Accuracy and Closed-Loop Controller Robustness …

X Chen, J O'Connor, H Fathy - Combustion Science and …, 2022 - Taylor & Francis
This article examines the degree to which optimizing a Rijke tube experiment can improve
the accuracy of thermoacoustic model parameter estimation, thereby facilitating robust …

Bias-aware thermoacoustic data assimilation

A Novoa, A Racca, L Magri - INTER-NOISE and NOISE-CON …, 2023 - ingentaconnect.com
Ensemble data assimilation algorithms combine experimental data and numerical models to
estimate the state and parameters of a system. If the model is unbiased, the estimation …

An adjoint-based formalism for optimal design of time-delay systems and uncertainty quantification in stochastic systems

Z Ahsan - 2022 - ideals.illinois.edu
The objectives of this dissertation are to develop computational techniques for i) tracking
solutions to multi-segment, delay-coupled boundary-value problems, with particular …