Evolution of Turbulent Horseshoe Vortex System in Front of a Vertical Circular Cylinder in Open Channel

Abstract

A turbulent horseshoe vortex (HV) system around a wall-mounted cylinder in open channel is characterized by random variations in vortex features and an abundance of vortex interactions. The turbulent HV system is responsible for initiating the local scour process in front of the cylinder. The evolution of the turbulent HV system is investigated statistically and quantitatively with time-resolved particle image velocimetry. The cylinder Reynolds numbers of the flow are 8600, 10,200, and 13,600, respectively. A novel vortex tracking method was proposed to obtain the variations in position, size, and strength of the primary HV (PHV) which dominates the system most of the time. Relationships between the various features of the PHV during its evolutionary process were obtained through correlation analyses. Results show that the dimensionless mean lifespan of the PHV is about 5.0. Statistically, the downstream movement of the PHV toward the cylinder is accompanied with its bed-approaching movement and decreasing in size, and the opposite is true. The circulation strength of the PHV decreases and increases dramatically in the region downstream of its time-averaged position when the PHV approaches and departs from the cylinder, respectively. Meanwhile, mechanisms responsible for the generation, movement, variation, and disappearance of the PHV are re-investigated and enriched based on its interactions with vortices in the separation region and structures in the incoming flow. The obtained change trends of the features of the PHV and the underlying mechanisms for its evolution are valuable for predicting and controlling the initial stage of the local scour in front of cylinders.

Influence of Scour Development on Turbulent Flow Field in Front of a Bridge Pier

“…Recently, Li et al (2018) [24] used the high-resolution PIV system to study the flow characteristics induced by the horseshoe vortex in front of the pier. Similar experimental studies can be found by Chen et al (2019) [25] who systematically analyzed the transient evolution process of horseshoe vortex. The previous relevant PIV studies are mainly confined on the flow of a pier mounted on a flatbed without scour hole, which can be regarded as the initial scour state.…”

Numerical Modeling of Sediment-flow around Obstacle Inspired by Marine Sponges: Considering Body Configurations

“…In Figure 10(c), CRVP and similar mushroom vortex 1 can be detected. A mushroom vortex is often realized behind concave walls or along streamlines with a curvature form [36]. By reducing the perforation area distribution and pores'vertical distance (M5 scenario), the GÖrtler instability changes into the large dual mushrooms.…”

Geometry of obstacle marks at instream boulders—integration of laboratory investigations and field observations

“…(c) Upstream cross-sectional profile of the frontal scour hole indicating internal differentiation and positions of primary horseshoe vortex (HV1) in back-flow mode, and secondary horseshoe vortex (HV2) (not to scale) [Colour figure can be viewed at wileyonlinelibrary.com] located close to the obstacle base. During incision, HV1 sinks into the frontal scour hole and extends down to S b , where it promotes sediment mobilization by saltation and rolling (Chen et al, 2019;Dargahi, 1990;Dey & Raikar, 2007). Upstream of HV1, a smaller and less coherent vortex (HV2) is located within the outer region of the frontal scour hole (Figures 1c and 2).…”

“…The largest and most stable vortex is denoted as the primary horseshoe vortex (HV1) and is located close to the obstacle base. During incision, HV1 sinks into the frontal scour hole and extends down to S b , where it promotes sediment mobilization by saltation and rolling (Chen et al, 2019; Dargahi, 1990; Dey & Raikar, 2007). Upstream of HV1, a smaller and less coherent vortex (HV2) is located within the outer region of the frontal scour hole (Figures 1c and 2).…”