Preface
This volume contains the 2020 Annual Research Briefs that summarize the research
activities at the Center for Turbulence Research (CTR) in its thirty-fourth year of operation. Foremost scientific objectives of CTR are the fundamental understanding of
turbulent flows and the development of physical models and computational tools for
multi-scale analysis and prediction of engineering systems. In addition, CTR has a longstanding tradition of facilitating collaboration and the exchange of scientific ideas by
bringing together key individuals in research fields related to turbulent flows. These synergistic collaborations have resulted in many technical advances over the years, including
the development of the Dynamic Subgrid-Scale Model for large-eddy simulations (LES)
of turbulent flows during the 1990 CTR Summer Program. On the occasion of the thirtieth anniversary of that development, this volume begins with a brief account of how
the Dynamic Subgrid-Scale Model came about during the 1990 CTR Summer Program.
The remaining thirty-three reports contained in this volume are arranged as follows.
The first report is focused on recent fundamental work and open research questions in
hypersonic turbulent flows at high enthalpies. New concepts and applications of wall
modeling for LES is taken up in the next group of reports. This area has received renewed attention at CTR since the 2018 Summer Program when it was demonstrated that
accurate prediction of forces in realistic aircraft geometries was possible at surprisingly
low computational cost. Jet noise and characteristic boundary conditions for compressible flows are the focus of the second group of reports. Fundamental studies of turbulent
and transitional flows, including closure modeling using machine learning and uncertainty
quantification, are collected in the next group. The second half of this volume is devoted
to studies of multi-physics turbulent flows including combustion and multi-phase flows.
These include combustion noise, supercritical flows, turbulent breaking waves, elastoplastic deformation of solids in high-speed flows, and interfacial instabilities.
The investigations reported in this volume have been supported by a number of different organizations. These include the Department of Energy’s National Nuclear Security
Administration (NNSA) through the Advanced Simulation and Computing (ASC) Program, along with the Air Force Office of Scientific Research (AFOSR), Office of Naval
Research (ONR), and National Aeronautics and Space Administration (NASA).
Last year CTR hosted sixteen resident Postdoctoral Fellows. The CTR roster for 2020
is provided in the Appendix. Also listed are the members of the CTR Steering Committee,
which has met quarterly to act on fellowship applications.
It is a great pleasure to thank Pamela Nelson Foster and Vi Nguyen for their help on
the day to day management of CTR.
This volume is available online, including color versions of the figures in the reports,
at the CTR website:
http://ctr.stanford.edu
Parviz Moin
Javier Urzay

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