Tuesday 01 Sep 2015GAFD Seminar

Prof Tsutomu Kambe - Former Professor, University of Tokyo, Japan.

Laver LT6 10:30-12:00

"A new scenario of turbulence theory and application to wall-bounded streaky flows".

In my talk, I will not consider `hard turbulence', or the traditional statistical theory of turbulence, because it is regarded as describing small scale turbulence controlled by viscosity, and its existence is verified by theory and experiment. However, the point is that it is not the whole story.

My talk is mainly concerned with large-scale coherent structures of turbulence, which are characterized by a wavy nature with strong damping. Traditional theory regards large-scale structures to be boundary-dependent. However, in pipe turbulence, large-scale structures are detected experimentally even though no scale larger than the pipe diameter D exists: the largest scale of streaks in pipe flow detected experimentally could be more than 15 D. I am going to explain this with a new scenario, which I consider to be promising.

I will talk about such streaky flows in wall turbulence and regard these as evidence of the existence of a new transverse wave field, or ``S-H field''. I will concentrate on the physical ideas and theoretical concepts from dynamics point of
view in the first half, and in the second part present experimental observations, predictions of my theory, and comparison of both.

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