Non-equilibrium turbulent phenomena in transitional channel flows

ABSTRACT

Non-equilibrium turbulent flows were considerably investigated in recent years, but most studies are restricted in grid-generated turbulence. In the present contribution we show by large-eddy simulation (LES), that there exists a weakly non-equilibrium turbulence region before the beginning of the full-developed turbulence. Both the dissipation coefficient and the skewness of longitudinal velocity gradient are used as characteristic non-equilibrium quantities, illustrating that the non-equilibrium turbulence region in channel flow is weakly similar to previous studies in grid-generated turbulence. The observation of non-equilibrium turbulence region in transitional channel flow is also expected to inspire future improvement of turbulence models.

KEYWORDS:

• Non-equilibrium turbulence
• fully-developed turbulence
• transitional channel flow
• turbulence model

Acknowledgments

We are grateful to Chong Pan, Jinjun Wang, Liang Shao, Wouter Bos and Robert Rubinstein for the inspiring discussions, and to the two anonymous referees for the many constructive suggestions as well as the guides on science.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work is supported by the National Science Foundation of China [Grant numbers 11772032, 51420105008, 11572025] and the National Basic Research Program of China [Grant number 2014CB046405].