An in-depth examination of flow structures organization downstream of a delta-winglet pair vortex generator under laminar, transitional, and turbulent flow regimes

Abstract

In the present study, we experimentally investigate the time-averaged and time-evolving flow structures generated downstream of a delta-winglet pair vortex generator in an airflow channel. The Stereoscopic Particle Image Velocimetry technique is used to measure the velocity fields in the cross-sectional planes at various axial positions along the channel. The analysis of time-averaged flow topology shows that the flow is predominantly composed of two main counter-rotating longitudinal vortices under laminar, transitional, and turbulent regimes. While the time-averaged flow behavior might appear simple, the real-time organization of the instantaneous flow structures presents more complex features. The study of the flow's temporal evolution indicates that the transition from laminar to turbulent regime is controlled by a meandering mechanism referred to the motion of the main vortex centers around their axis and the emergence of secondary structures that evolve periodically over time.