Merging and auto-generation of vortices in wall bounded flow
Gerrit Elsinga (TU Delft - Mechanical Engineering)
Manu Goudar Vishwanathappa (TU Delft - Mechanical Engineering)
Wim-Paul Breugem (TU Delft - Mechanical Engineering)
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Abstract
For channel flow, we explore how a hairpin
eddy may reach a threshold strength required to produce additional
hairpins by means of auto-generation. This is done by studying the
evolution of two eddies with different initial strengths (but both below
the threshold strength), initial sizes and initial stream-wise spacing
between them. The numerical procedure followed is similar to Zhou et al
[1]. The two eddies were found to merge into a single stronger eddy in
case of a larger upstream and a smaller downstream eddy placed within a
certain initial stream-wise separation distance. Subsequently, the
resulting stronger eddy was observed to auto-generate new eddies.
Merging of eddies thus is a viable explanation for the creation of the
threshold strength eddies.
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[1] J. Zhou, R.J. Adrian, S. Balachandar, and T.M. Kendall, Journal of
Fluid Mechanics, 387:353-396, 1999.