Velocity profiles and turbulence intensities around side-by-side bridge piers under ice-covered flow condition

Abstract

Recent studies have shown that the presence of ice cover leads to an intensified local scour pattern in the vicinity of bridge piers. To investigate the local scour pattern in the vicinity of bridge pier under ice-covered flow condition comparing to that under open channel flow condition, it is essential to examine flow field around bridge piers under different flow conditions. In order to do so, after creation of smooth and rough ice covers, three-dimensional timeaveraged velocity components around four pairs of bridge piers were measured using an Acoustic Doppler velocimetry (ADV). The ADV measured velocity profiles describe the difference between the velocity distributions in the vicinity of bridge piers under different covered conditions. Experimental results show that the vertical velocity distribution which represents the strength of downfall velocity is the greatest under rough covered condition which leads to a greater scour depth. Besides, results show that the turbulent intensity increases with pier size regardless of flow cover, which implies that larger scour depth occurs around piers with larger diameter.

Velocity Field and Turbulence Structure around Spur Dikes with Different Angles of Orientation under Ice Covered Flow Conditions

“…The wake vortex develops behind the spur dike, which results in the extension of the scour hol stream of the dike. As pointed out by other researchers, wake vortexes are sma weaker than horseshoe vortexes; and they cannot carry sediment load that erod the scour hole [20,37]. This fact explains the development of the deposition ridg stream of the dike (Figure 6).…”

“…Regarding previous research, to obtain the most accurate data at each measuring location, the data sampling rate of ADV was set with the highest frequency (25 Hz) with a duration of 120 to 150 s [11,30,31]. Following the proper setting of ADV and filtering data spikes, the velocity measurements were reliable within the range of 0.25 cm/s, with an error of ±1.5% of the measurement scale [20,32].…”

“…Other researchers claimed that 80% of the maximum scour depth occurred at the first two hours of the experiment [35]. Namaee and Sui [20] conducted experimental research on local scour around side-by-side piers. They indicate that the equilibrium depth of a scour hole could be achieved within the first 6 h, although all their experimental runs lasted 24 h. In the present study, no change in scour depth was observed after about 12 h, and the scour hole reached its equilibrium condition.…”

“…Under an ice-covered flow condition, the location of the maximum flow velocity gets closer to the channel bed, which increases the bed shear stress [18][19][20]. In conclusion, the presence of ice on the water surface makes the flow condition much more complicated than an open flow condition.…”

Analytical Models of Velocity, Reynolds Stress and Turbulence Intensity in Ice-Covered Channels

“…The ice sheet in some Canadian rivers is at least 0.6 m thick and lasts for at least 4 months [1]. The wetted perimeter of the cross section and flow resistance in ice-covered flows increases with the presence of the ice sheet, which significantly affects the hydraulic characteristics of river and topographical features and greatly change the flow velocity distribution, flow transport capacity and sediment transport rate [2][3][4][5][6][7][8][9][10][11]. Therefore, it is necessary to study the ice-covered flows.…”