## Abstract

The turbulence statistics and structures of a self-similar adverse pressure gradient turbulent boundary layer (APGTBL) are investigated using direct numerical simulation (DNS) of the flow at the verge of separation. The desired self-similar APG-TBL is achieved by a modification of the far-field velocity boundary condition. The required wallnormal velocity in the far-field to produce the necessary adverse pressure gradient was estimated based on the analytical free-stream streamwise velocity distribution for a flow at the point of separation, and the assumption that the streamlines of the outer flow follow the growth of the boundary layer thickness. The APG-TBL develops over a momentum thickness based Reynolds number upto 12000, and achieves a self-similar region of constant friction coefficient, pressure velocity and shape factor. Turbulence statistics in this region show self-similar collapse by using the scaling of the external velocity and the displacement thickness. In this study, the structure of the APG-TBL is investigated using topological methodology and visualisation techniques for a zero pressure gradient turbulent boundary layer (ZPG-TBL) and for the self-similar APG-TBL. The second invariants of the velocity gradient tensor (VGT), which are representative of coherent structures dominated by vortical motions, show a stark difference in the structure and location of coherent vortical structures that exists between the self-similar APGTBL and a ZPG-TBL. Further details based on the structure and distributions of the invariants of VGT and intense Reynolds stress structures of the self-similar APG-TBL are presented.

Original language | English |
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Title of host publication | Tenth International Symposium on Turbulence and Shear Flow Phenomena 2017 |

Editors | Lex Smits |

Place of Publication | Chicago IL USA |

Publisher | International Symposium on Turbulence and Shear Flow Phenomena, TSFP10 |

Number of pages | 5 |

Volume | 1 |

Publication status | Published - 2017 |

Event | Turbulence and Shear Flow Phenomena 2017 - Swissotel, Chicago, United States of America Duration: 6 Jul 2017 → 9 Jul 2017 Conference number: 10th http://tsfp10.org/ |

### Conference

Conference | Turbulence and Shear Flow Phenomena 2017 |
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Abbreviated title | TSFP-10 |

Country/Territory | United States of America |

City | Chicago |

Period | 6/07/17 → 9/07/17 |

Internet address |