Experimental study of a vertical vortex propagating above a smooth wall

Yann Devaux (1) , G. Pineau (2) , D. Calluaud (2) , Lionel Thomas (2)

1 PPrime [Poitiers] - Institut Pprime [UPR 3346]
2 HydEE - Hydrodynamique et écoulements environnementaux [Institut Pprime]

This paper proposes an investigation of a vortex propagation over a smooth wall. An isolated vortex is generated experimentally by a pitching plate (chord of 5cm), and propagates along a water channel at a Reynolds of 13000. We focus our study on the near wall region, performing measurements of the flow characteristics with a stereo-PIV technique over five horizontal planes at different heights, and with a PIV technique over one vertical plane. A main vortex can be observed, rotating clockwise, followed by a small secondary vortex with opposite rotation. Those measurements highlight a strong three-dimensional effect, influenced by the characteristics of the pitching plate (maximum angle α_max and velocity K_c): a specific pattern with two patches of opposite spanwise velocity is observed, with fluctuations reaching the main flow velocity. The main vortex is columnar at first time steps, and curved itself as it moves forward, convected by the flow: the convection velocity seems to be constant along the streamwise axis, and the main axis of the vortex core does not visibly follow the boundary layer profile.

Mots clés: vertical vortex; Particle Image Velocimetry; stereoscopic Particle Image Velocimetry; instantaneous flow; isolated vortex

Domaines: Mécanique des fluides [physics.class-ph]

Yann Devaux, G. Pineau, D. Calluaud, Lionel Thomas. Experimental study of a vertical vortex propagating above a smooth wall. 18 th International Symposium on Flow Visualization, Jun 2018, Zurich, Switzerland. ⟨hal-02140181⟩