Experimental study on the role of spanwise vorticity and vortex filaments in the outer region of open-channel flow

Chen, Qigang; Adrian, Ronald J.; Zhong, Qiang; Li, Danxun; Xingkui, Wang

doi:10.1080/00221686.2014.919965

Cited by 18 publications

(21 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The size of the camera viewing area is 32 × 20 mm such that the spatial resolution is 24.5 pixels/mm. Based on the flow velocity in our experiment, the interval time of 2 ms assured that the maximum particle displacement between two consecutive frames is 5 pixels, which satisfies the one-quarter rule for PIV correlation analysis [44]. For more specific details of the PIV setup, see the recent work of Qi et al [45].…”

Section: Methodssupporting

confidence: 53%

Influence of turbulent horseshoe vortex and associated bed shear stress on sediment transport in front of a cylinder

Fuhrman

et al. 2018

Experimental Thermal and Fluid Science

Self Cite

View full text Add to dashboard Cite

This study concerns the flow and associated sediment transport in front of a cylinder in steady currents. The study comprises (i) flow characteristics induced by the turbulent horseshoe vortex (THV), (ii) bed shear stress within the THV region, and (iii) predicted sediment transport rates. The velocity fields in front of a wall-mounted circular cylinder were measured using time-resolved particle image velocimetry (PIV). The flow characteristics show that two time-averaged THVs are formed, and the dynamics of instantaneous THVs exhibit a quasi-periodic process from generation to death. Both the mean and fluctuations of bed shear stress within the THV region are significantly amplified, and their values are comparable. The probability density function of the instantaneous bed shear stress exhibits a double-peaked distribution and cannot be represented by the normally-used log-normal distribution for uniform channel-open flows. The comparisons of sediment transport rates where turbulent fluctuations in the bed shear stress are, or are not, taken into account show that the sediment transport rates calculated by the mean bed shear stress are under-predicted. Furthermore, a new sediment transport model incorporating the influence of bed shear stress fluctuations is proposed and validated by comparing the initial scour rate in front of the cylinder.

show abstract

Section: Methodssupporting

confidence: 53%

Influence of turbulent horseshoe vortex and associated bed shear stress on sediment transport in front of a cylinder

Fuhrman

et al. 2018

Experimental Thermal and Fluid Science

Self Cite

View full text Add to dashboard Cite

show abstract

“…For the present application, the final interrogation window size was 32 × 32 pixels which have an overlap of 50%, that is the adjacent velocity vector interval is 16 pixels. Based on the flow velocity in our experiment, the interval time of 2 ms assured that the maximum particle displacement between two consecutive frames is 5 pixels, which satisfies the one-quarter rule for PIV correlation analysis [32,33]. The accuracy of the velocity vectors is approximately 0.1 pixels, which corresponds to approximately 0.7% of the full-scale velocity in the present measurement.…”

Section: Experimental Setup and Methodologysupporting

confidence: 53%

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

Yang

2020

Water

View full text Add to dashboard Cite

This study concerns the turbulent flow field influenced by the scour development around a bridge pier. The scour hole evolution as well as the temporal variation of scour depth around the pier were firstly analyzed. Subsequently, the flow fields in front of the pier at different instants during the scour process were measured using particle image velocimetry (PIV). It shows that the scour depth at the pier front exceeds that of the pier side at the later scouring stage. The temporal development of scour depth can be well predicted by a simple practical engineering model based on an exponential function with a change in the two adjustable coefficients. The flow field indicates that with the development of scour hole, the downward flow in front of the pier becomes more prominent, meanwhile the flow becomes more turbulent. The variation tendency for both velocities and turbulence intensities along the streamwise direction in front the pier shows similarity. The Reynolds shear stress generally increases with developing scour hole, and the region with large value enlarges and moves upstream of the scour hole.

show abstract

“…The experimental results of Apsilidis et al [12] also showed a similar mechanism. Meanwhile, previous research [28] has shown that the population of prograde vortices in the incoming turbulent open channel flow changes with the Reynolds number. Therefore, the evolution and dynamics of the turbulent HV system are anticipated to be influenced by the Reynolds number, as indicated by previous investigations [12,17].…”

Section: Strength Variation Of Phvmentioning

confidence: 98%

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

Chen

Yang

2019

Water

View full text Add to dashboard Cite

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.

show abstract

Experimental study on the role of spanwise vorticity and vortex filaments in the outer region of open-channel flow

Abstract: The dynamic importance of spanwise vorticity and vortex filaments has been assessed in steady, uniform open-channel flows by means of particle image velocimetry (PIV). By expressing the net force due to Reynolds' turbulent shear stress, ( )

Cited by 18 publications

References 57 publications

Influence of turbulent horseshoe vortex and associated bed shear stress on sediment transport in front of a cylinder

Influence of turbulent horseshoe vortex and associated bed shear stress on sediment transport in front of a cylinder

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

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

Contact Info

Product

Resources

About