TY - GEN

T1 - Intense focal and reynolds stress structures of a self-similar adverse pressure gradient turbulent boundary layer

AU - Sekimoto, Atsushi

AU - Kitsios, Vassili

AU - Atkinson, Callum

AU - Jimenez, Javier

AU - Soria, Julio

N1 - Funding Information:
The authors acknowledge the research funding from the Australian Research Council and European Research Council, and the computational resources provided by NCI and the Pawsey Supercomputer Centre both supported by the Australian government and PRACE supported by the EU. ————————————————————— ————————————–

PY - 2017

Y1 - 2017

N2 - 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.

AB - 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.

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M3 - Conference contribution

AN - SCOPUS:85033218709

T3 - 10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017

BT - 10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017

PB - International Symposium on Turbulence and Shear Flow Phenomena, TSFP10

T2 - 10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017

Y2 - 6 July 2017 through 9 July 2017

ER -