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research-article

Numerical Investigation of Vortex Ring Ground Plane Interactions

[+] Author and Article Information
Kate Bourne

506 Lorimer St Port Melbourne, VIC 3207 Australia
kate.bourne@dsto.defence.gov.au

Stefano Wahono

506 Lorimer St Port Melbourne Victoria, 3207 Australia
Stevano.Wahono@dsto.defence.gov.au

Andrew Ooi

1-100 Grattan Street Parkville Melbourne, Victoria 3010 Australia
a.ooi@unimelb.edu.au

1Corresponding author.

ASME doi:10.1115/1.4036159 History: Received August 16, 2016; Revised February 06, 2017

Abstract

The interaction between multiple laminar thin vortex rings and solid surfaces was studied numerically so as to investigate flow patterns associated with helicopter brownout. Brownout refers to operational conditions in dusty environments whereby ground-based particles are entrained through the rotor and cockpit visibility is compromised. Although a significant simplification to the helical downwash generated by a helicopter rotor, vortex ring interactional dynamics provide insight into the fundamental flow features and phenomena that underlie the unsteady and highly complex flow field. In this study the vortex-wall interaction was used to investigate the tendency of the flow towards recirculatory behaviour, and to assess the flow field for conditions conducive to brownout. The numerical model shows very good agreement with previous studies of single vortex rings for the case of orthogonal impact (angle of incidence, theta = 0º) and oblique impact (theta = 20º). The case of two vortex rings was also investigated, with particular focus on the interaction of vortex structures post-impact. Compared to the impact of a single ring with the wall, the interaction between two vortex rings and a solid surface resulted in a more highly energized boundary layer at the wall, and merging of vortex structures. The azimuthal variation in the vortical structures yielded flow conditions at the wall likely to promote agitation of ground based particles.

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