Abstract:

We examine the dynamics of the energy cascade of turbulence in scale, time, and physical space, using numerical simulations of homogeneous turbulence that have run for many turnover times. Using the spontaneous oscillations of the forcing amplitude, it is first shown that the energy moves as a ‘wave’ in scale space. The time that it takes to cross a range of scales is the sum of the time it takes to cross individual octaves, which is in turn proportional to the turnover time of the eddies in the octave [1]. It is then shown that this energy transfer is local in physical space, with eddies receiving energy from larger eddies in their neighbourhood, and passing it to smaller ones. This interaction takes place among scales differing by about a factor of two. Wider scale gaps only interact indirectly through intermediate octaves [2].

[1] Cardesa et al. (2015) Phys. Fluids 27, 111702
[2] Cardesa et al. (2017) Science 357, 782-784

Brief Biograph:

Javier Jimenez is a Distinguished Res. Professor of Fluid Mechanics at Universidad Politécnica de Madrid, and a member of Spanish Academy of Science (2008) and Spanish Academy of Engineering (2005).  He received a master’s degree from Caltech in 1970 and a Ph.D degree of applied Mathematics from Caltech in 1973, and worked at several prestigious institutes, e.g. Caltech, Centre Turbulence Research at Stanford University, and Ecole Polytechnique. Prof. Jimenez is considered to be one of the leading turbulence researchers and was selected as APS Fellow in 1993 and Euromech Fellow in 2014.

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