Coherent structures and flow topology of transitional separated-reattached flow over two and three dimensional geometrical shapes

Date

2017

Advisors

Journal Title

Journal ISSN

ISSN

Volume Title

Publisher

American Institute of Physics

Type

Conference

Peer reviewed

Yes

Abstract

Large-scale organized motions (commonly referred to coherent structures) and flow topology of a transitional separated-reattached flow have been visualised and investigated using flow visualisation techniques. Two geometrical shapes including two-dimensional flat plate with rectangular leading edge and three-dimensional square cylinder are chosen to shed a light on the flow topology and present coherent structures of the flow over these shapes. For both geometries and in the early stage of the transition, two-dimensional Kelvin-Helmholtz rolls are formed downstream of the leading edge. They are observed to be twisting around the square cylinder while they stay flat in the case of the two-dimensional flat plate. For both geometrical shapes, the two-dimensional Kelvin-Helmholtz rolls move downstream of the leading edge and they are subjected to distortion to form three-dimensional hairpin structures. The flow topology in the flat plate is different from that in the square cylinder. For the flat plate, there is a merging process by a pairing of the Kelvin-Helmholtz rolls to form a large structure that breaks down directly into many hairpin structures. For the squire cylinder case, the Kelvin-Helmholtz roll evolves topologically to form a hairpin structure. In the squire cylinder case, the reattachment length is much shorter and a forming of the three-dimensional structures is closer to the leading edge than that in the flat plate case.

Description

Keywords

Citation

Diabil, H.A., Li, X.K. & Abdalla, I.E., (2017). Coherent structures and flow topology of transitional separated-reattached flow over two and three dimensional geometrical shapes, in AIP Conference Proceedings 1872.

Rights

Research Institute