AE Seminar
Toshiyuki Gotoh
Emeritus Professor at Nagoya Institute of Technology
Visiting Professor at Keio University Fellow of APS and JSFM (Japan Society of Fluid Mechanics)
JAPAN gotoh.toshiyuki@nitech.ac.jp
Friday, November 22
11:00 a.m.
Montgomery Knight Building, Room 317
In turbulent flow the velocity fluctuations become stronger and stronger with decrease of scale, recognized as intermittency which is one of the central issues in the turbulence research. The probability density functions (PDFs) of the kinetic energy dissipation rate and the enstrophy (squared vorticity) have been extensively studied for long times and are found to have long tails. Curiously, the PDF tail of the enstrophy is always longer than that of the dissipation PDF, and also the PDF tail of the one dimensional dissipation surrogate which is usually measured in experiments due to difficulties to access the full dissipation is longer than the PDF tail of the full dissipation. From these observations there have been arguments that the one dimensional surrogates are more intermittent and obey the statistical laws different from those in terms of the full definitions.
In this seminar, I would like to briefly review these problems and to present a mathematical theory to answer some of these questions. Starting from the Gaussian random velocity field we study the PDFs of the full dissipation (enstrophy) and one dimensional surrogates, and then proceed to the turbulence. The theory describes a transform that connects the PDF of the one-dimensional dissipation (enstrophy) surrogate to the PDF of the full dissipation (enstrophy) under the assumption of the isotropy. The transform is independent of the Reynolds number. Theoretical prediction is examined by using the DNS data and found to be very satisfactory. The physical implication of the present results will be discussed.
About the speaker:
Professor Toshiyuki Gotoh obtained his B.Eng., M.E Eng. and D. Eng. degrees in Applied Physics and Nagoya University in Japan. He has been on the faculty at the Nagoya Institute of Technology since 1987 and was Vice President at NITech in 2006-2007. Professor Gotoh was a visitor at Los Alamos National Laboratory, National Center for Atmospheric Research, and the center for Turbulence Research at Stanford University. He served on the Editorial Advisory Board of Physics of Fluids in 2014-2015 and likewise of Physical Review Fluids in 2016-2021. His research interests include the statistical theory of turbulence, computational physics, and cloud turbulence.
Contact: Prof. P.K Yeung, School of AE (pk.yeung@ae.gatech.edu)