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CREATe Colloquium Series: Tim Colonius

  • September 21, 2020
  • 4:00 p.m.
  • For Zoom credentials, please sign up here.
  • Tim Colonius, California Institute of Technology

Turbulence structure and modeling: some adventures in the frequency domain

Abstract: Amongst many available data-driven modal decompositions of utility in fluid mechanics, the frequency-domain (spectral) version of the proper orthogonal decomposition (SPOD) plays a special role in the analysis of stationary turbulence. SPOD modes are optimal in expressing structures that evolve coherently in both space and time, and they can be regarded as
optimally-averaged DMD modes. Importantly, the SPOD spectrum is also related to the resolvent spectrum of the
linearized dynamics and examination of the relationships between the SPOD and resolvent modes yields information about how coherent structures are forced by nonlinear interactions amongst coherent and incoherent turbulence. We discuss the application of these tools to analyze and model turbulence in high-speed jets and boundary layers. We highlight recent developments including (a) utilizing eddy-viscosity models in resolvent analysis to enable RANS-based prediction of coherent structures, and (b) nonlinear extensions of resolvent analysis to discover worst-case disturbances for laminar-turbulent transition, and (c) the development fast spatial marching methods for large-scale resolvent problems.

Bio: Tim Colonius is the Frank and Ora Lee Marble Professor of Mechanical Engineering at the California Institute of Technology. He received his B.S. from the University of Michigan in 1987 and M.S and Ph.D. in Mechanical Engineering from Stanford University in 1988 and 1994, respectively. He and his research team use numerical simulations to study a range of problems in fluid dynamics, including aeroacoustics, flow control, instabilities, shock waves, and bubble dynamics. Prof. Colonius also investigates medical applications of ultrasound, and is a member of the Medical Engineering faculty at Caltech. He is a Fellow of the American Physical Society and the Acoustical Society of America, and he is Editor-in-Chief of the journal Theoretical and Computational Fluid Dynamics. He was the recipient of the 2018 AIAA Aeroacoustics Award.