Merging and auto-generation of vortices in wall bounded flows
M. Goudar Vishwanathappa (TU Delft - Fluid Mechanics)
WP Breugem (TU Delft - Fluid Mechanics)
Gerrit Elsinga (TU Delft - Fluid Mechanics)
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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 interaction of two eddies with different initial strengths (but both below the threshold strength), initial sizes and initial streamwise spacing between them. The numerical procedure followed is similar to Zhou et al. (1999). 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 streamwise 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.