Emerging Obstacles in Supercritical Open-Channel Flows: Detached Hydraulic Jump versus Wall-Jet-Like Bow Wave

Rivière, Nicolas; Vouaillat, Guillaume; Launay, Gaby; Mignot, Emmanuel

doi:10.1061/(asce)hy.1943-7900.0001291

Cited by 21 publications

(17 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Based on the preceding analysis, the present experiments overall suggest that local bed morphological characteristics around boulders are controlled by two parameters indicative of the flow hydraulics, namely, the boulder relative submergence and the Froude number. Some of the effects that these parameters have on obstacle controls to flow and sediment have been reported in previous studies (Boyer & Roy, ; Papanicolaou & Tsakiris, ; Riviere et al, ). From the directly comparable tests herein, however, three distinct cases of local depositional morphology around boulders are uniquely discerned and linked to < H >/ d c and Fr : Material deposits in the wake (downstream) region of a boulder controlled by the near‐wake recirculation and reduction in local bed shear stress

\begin{matrix} lefttrue \\ < H > / d_{c} = 3.5 (HRS) \\ Fr < 1 . \end{matrix}

…”

Section: Resultsmentioning

confidence: 60%

See 1 more Smart Citation

Boulder Array Effects on Bedload Pulses and Depositional Patches

et al. 2018

View full text Add to dashboard Cite

The influence of boulders in high gradient gravel‐bed rivers can be significant. Yet few studies have isolated their role in regulating bedload. It is hypothesized that boulder relative submergence and the corresponding eddies developing around boulders affect the frequency of bedload pulsations and the location of sediment deposits. Results show the occurrence of two distinct timescales in bedload exiting a boulder array, which were identified via time series analysis. These are the small‐scale periodicity, PS, and the large‐scale periodicity, PL. PS was identified in the range of 4–6 min and is believed to result from congested bedload movement due to reduced conveyance area within the array. PL was identified in the range of 8–46 min. It is suggested that PL corresponds to large bedload releases around boulders, which the authors consider to be caused by feedbacks between boulder eddies and bedload deposits. It is also found that boulder submergence and Froude number, Fr, influence the location of predominant deposition. At High Relative Submergence, deposition occurs in the boulder wake regions. At Low Relative Submergence, deposition instead occurs upstream of boulders in locations that depend on Fr. For Fr < 1, material deposits in the stoss of boulders due to the necklace structure of the horseshoe vortex. However, for Fr > 1, material deposits at the flanks of boulders due to the influence of local wave crests around boulders. The trapping efficiency of boulders reduces the dimensionless mean bedload transport rate by three orders of magnitude compared to conditions without boulders.

show abstract

\begin{matrix} lefttrue \\ < H > / d_{c} = 3.5 (HRS) \\ Fr < 1 . \end{matrix}

…”

Section: Resultsmentioning

confidence: 60%

“…Journal of Geophysical Research: Earth Surface Papanicolaou & Tsakiris, 2017;Riviere et al, 2017). From the directly comparable tests herein, however, three distinct cases of local depositional morphology around boulders are uniquely discerned and linked to <H>/ d c and Fr:…”

Section: 1029/2018jf004753mentioning

confidence: 72%

Boulder Array Effects on Bedload Pulses and Depositional Patches

et al. 2018

View full text Add to dashboard Cite

show abstract

“…The study in [20] recently showed that the flow pattern around an obstacle in a supercritical flow varies as a function of the obstacle width (D) to flow depth (h) ratio, distinguishing the following patterns:…”

Section: Supercritical Flowsmentioning

confidence: 99%

“…The wall jet pattern: at small ratios of foundation width to flow depth (i.e., D/h < 0.5-2.0) a so-called wall-jet-like bow wave develops (Figure 2b; [20]). The flow remains in the supercritical regime (unaffected by the presence of the obstacle) until reaching the foot of the obstacle.…”

Section: Supercritical Flowsmentioning

confidence: 99%

See 1 more Smart Citation

Scour at Bridge Foundations in Supercritical Flows: An Analysis of Knowledge Gaps

Link

Mignot

Roux³

et al. 2019

Water

View full text Add to dashboard Cite

The scour at bridge foundations caused by supercritical flows is reviewed and knowledge gaps are analyzed focusing on the flow and scour patterns, available measuring techniques for the laboratory and field, and physical and advanced numerical modeling techniques. Evidence suggests that the scour depth caused by supercritical flows is much smaller than expected, by an order of magnitude compared to that found in subcritical flows, although the reasons for this behavior remain still unclear. Important questions on the interaction of the horseshoe vortex with the detached hydraulic-jump and the wall-jet flow observed in supercritical flows arise, e.g., does the interaction between the flow structures enhance or debilitate the bed shear stresses caused by the horseshoe vortex? What is the effect of the Froude number of the incoming flow on the flow structures around the foundation and on the scour process? Recommendations are provided to develop and adapt research methods used in the subcritical flow regime for the study of more challenging supercritical flow cases.Large-scale supercritical free-surface flows can occur in different environments. Some examples can be found in cases of flooded urban streets, fish-ways, tsunami inland flows, coastal channels, and mountain rivers. This paper focuses on the flow and scouring patterns at bridge foundations in rivers with supercritical conditions. The occurrence of supercritical flows in rivers is defined by high longitudinal slopes (>1%) and/or rapid flood waves. Commonly, steep rivers present gravel beds or mixtures of fine and coarse sediments, containing all possible sizes, from clay and silt up to boulders tens of centimeters in size. In dentritic networks, streams with a low Strahler's order (i.e., <3) are steep and produce flash floods but normally possess a small cross-sectional width. Therefore, deck bridges without foundations in these riverbeds are usually selected. At piedmont, however, rivers widen and it is common to observe cross sections with widths over 50 m, where bridge foundations may have to be included. Salient examples of such configurations are often encountered in steep watersheds subjected to heavy rains, such as on the Panamericana Route along Perú and Chile, La Réunion Island (Indian Ocean) in Taiwan or Japan, and also in a few European Alpine piedmont rivers (Figure 1). The examples in Figure 1 clearly highlight that supercritical flows are associated with a significant amount of energy for scouring and dynamic loading of the superstructure. Wood debris can also enhance the risk of pier stability. Such flows thus produce among the worst hydraulic conditions for bridge design. A recent bridge collapse due to scour in a supercritical flow occurred at the Rivière Saint Etienne in the La Réunion island due to cyclone Gamède. This bridge, which connected a road with traffic of 65,000 vehicles per day, collapsed and modified the terrestrial transport route for a long time (Figure 1f,g), thereby producing large economic losses. This event motivated, i...

show abstract