## Abstract

In this paper, direct numerical simulations are carried out to study single-square grid-generated turbulence at a Reynolds number Re_{L0} = 20 000 (based on the inlet velocity U_{in} and the length of grid bar L_{0}). Different from the regular grid and the multiscale/fractal grid, here only single large square grid is placed at the center near the inlet. First, we investigate the evolutions of turbulence characteristics (e.g., mean streamwise velocity, turbulence intensity, Taylor microscale, etc.) along the centerline. The common characteristics possessed by turbulent flows generated by the single square grid and by the fractal square grid are presented. We confirm the hypothesis proposed by Mazellier and Vassilicos ["Turbulence without Richardson-Kolmogorov cascade," Phys. Fluids 22, 075101 (2010)] that for the fractal square grid, the location of turbulence intensity peak along the centerline is mainly determined by large-scale wake interactions. Current numerical results show that in turbulence generated by the single square grid,wake interactions occur close to the grid and cause extreme/intense events. Then, the spatial development of invariants of the velocity gradient tensor is studied. For example, the (Q_{W}, -Q_{S}) maps are analyzed to show how turbulence generated by a single square grid obtains large scale vortices along the centerline.

Original language | English |
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Article number | 045102 |

Journal | Physics of Fluids |

Volume | 26 |

Issue number | 4 |

DOIs | |

Publication status | Published - Apr 4 2014 |

Externally published | Yes |

## ASJC Scopus subject areas

- Computational Mechanics
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering
- Fluid Flow and Transfer Processes