A visual study of vortex-induced subcritical instability on a flat plate laminar boundary layer

Flow past a circular cylinder in the vicinity of a plane wall

“…The proximity of the cylinder to the wall significantly alters the dynamics of the near-and far-wake of the cylinder. The flow separation phenomenon from the plane wall is directly determined by the induced adverse pressure gradient, both in the up-and downstream direction of the cylinder, as explained in Sengupta et al (2003a) and Lim et al (2004) in terms of a vortex-induced instability. Upstream of the cylinder, on the plane wall, the plotted contours clearly indicate streamline divergence, and exactly below this one notices unsteady flow separation.…”

“…This has been clearly identified in Price et al (2002) and Lei et al (1999) for this particular flow field. While such mutual interactions can occur at large distance due to Biot-Savart law, they can have a more subtle effect in terms of triggering an instability that was explained theoretically and experimentally in Sengupta et al (2003a) and Lim et al (2004). Such an instabilitys, arising out of interactions between a convecting finite-core vortex and an underlying shear layer, is important as it typifies qualitatively with experimental results.…”

Numerical investigation of flow past single and tandem cylindrical bodies in the vicinity of a plane wall

“…The flow separation phenomenon from the plane wall is due to the induced adverse pressure gradient, both in the upstream and downstream direction of the cylinder. Sengupta et al (2003) and Lim et al (2004) have explained that the phenomenon of flow separation on the plane wall is predominantly observed downstream of the cylinder where the shed vortices induce a strong adverse pressure gradient which leads to the unsteady separation of the plane wall shear layer. A similar observation was reported by Dipankar and Sengupta (2005) at relatively higher Reynolds number (Re ¼1200).…”

Flow control with rotating cylinders

“…Strykowski & Sreenivasan (1990) demonstrate a displacement effect of a static control cylinder on the wake of a larger upstream cylinder. Lim et al (2004) report experimental visualizations of the influence of a displacement and also of a circulation effect of a rotating cylinder Figure 16. The pressure recovery from separation to reattachment of the dividing streamline (top) and from separation to the base of the cylinder at θ = π (bottom), plotted with respect to the inviscid momentum flux scaling, ξd * (left) and the viscous momentum flux scaling, ξ 3/2 d * 1/2 (right).…”