• Fig FP TET
  • Fig FP ROMQGa
  • Fig FP DO1
  • Fig FP Jointa
  • Fig FP IP1
  • Long-term probabilistic quantification and short-term prediction of extreme waves
  • Targeted energy transfer in nonlinear oscillators with applications in energy harvesting and passive protection of structures
  • Statistical closure and reduced-order modeling of turbulent flows (ROMQG closure)
  • Stochastic attractors in low-dimensional, chaotic flows (DO method)
  • Probabilistic description of systems subjected to colored noise (Joint response-excitation method)
  • Mixing, clustering, and transport of finite size particles (bubbles and aerosols) in fluid flows

Welcome to the research group of Themis Sapsis!

In the Stochastic Analysis and Nonlinear Dynamics (SAND) lab our goal is to understand, predict, and/or optimize complex engineering and environmental systems where uncertainty or stochasticity is equally important with the dynamics. We specialize on the development of analytical and computational methods for modeling high dimensional nonlinear systems characterized by nonlinear energy transfers between dynamical components, broad energy spectra with complex statistics, and persistent or intermittent instabilities. We are particularly interested on the development of inexpensive predictive capacity for such systems as well as the development of design criteria for engineering applications.

Recent papers

Modes describing finite-time instabilities

JICF H. Babaee, T. Sapsis, A minimization principle for the description of modes associated with finite-time instabilities, Proceedings of the Royal Society A, 472 (2016) 20150779[pdf]

Precursors of rare events in water waves

15 JFM W. Cousins, T. Sapsis, Reduced order precursors of rare events in unidirectional nonlinear water waves, Journal of Fluid Mechanics, 790 (2016) 368-388. [pdf]

Analytical description of rare events

SIAM 14 M. Mohamad, T. Sapsis, Probabilistic description of extreme events in intermittently unstable systems excited by correlated stochastic processes, SIAM/ASA J. of Uncertainty Quantification, 3 (2015) 709-736. [pdf]

Localized instabilities in unidirectional water waves

Wave attractor W. Cousins, T. Sapsis, The unsteady evolution of localized unidirectional deep water wave groups, Physical Review E, 91 (2015) 063204[pdf]

Extreme events in the 1D MMT model

extreme waves W. Cousins, T. Sapsis, Quantification and prediction of extreme events in a one-dimensional nonlinear dispersive wave model, Physica D., 280-281 (2014) 48-58[pdf]

Stochastic closure for turbulent flows

PNAS 2013 T. Sapsis, A. Majda, Statistically Accurate Low Order Models for Uncertinaty Quantification in Turbulent Dynamical Systems, PNAS, 110 13705-13710 (2013). [pdf]