Flow resistance due to a single spur dike in an open channel

Azinfar, Hossein; Kells, James A.

doi:10.3826/jhr.2009.3327

Cited by 28 publications

(11 citation statements)

References 16 publications

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“…This paper focuses on the force experienced by a rigid obstacle, which in this case is taken to be a square cylinder, a shape that is representative of a building. Most studies have focused on the subcritical regime (Azinfar & Kells 2009), which is a typical situation in civil engineering because the hydraulic jump in the choked regime promotes scour, for example near the foundations of a bridge. Earlier work by Raju et al (1983) analysed the drag force on circular cylindrical structures in the subcritical regime; the forces were determined by integrating the pressure distribution over the whole surface of the cylinder.…”

Section: Introductionmentioning

confidence: 99%

Force acting on a square cylinder fixed in a free-surface channel flow

Eames

Johnson

2014

J. Fluid Mech.

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We describe an experimental study of the forces acting on a square cylinder (of width b) which occupies 10-40 % of a channel (of width w), fixed in a free-surface channel flow. The force experienced by the obstacle depends critically on the Froude number upstream of the obstacle, Fr 1 (depth h 1 ), which sets the downstream Froude number, Fr 2 (depth h 2 ). When Fr 1 < Fr 1c , where Fr 1c is a critical Froude number, the flow is subcritical upstream and downstream of the obstacle. The drag effect tends to decrease or increase the water depth downstream or upstream of the obstacle, respectively. The force is form drag caused by an attached wake and scales as 2 )/2, where experimentally we find C K 1. The r.m.s. lift force is significantly smaller than the mean drag force. A consistent model is developed to explain the transitional behaviour by using a semi-empirical form of the drag force that combines form and hydrostatic components. The mean drag force scales as F D λρbg

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Section: Introductionmentioning

confidence: 99%

Force acting on a square cylinder fixed in a free-surface channel flow

Eames

Johnson

2014

J. Fluid Mech.

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“…Previous studies have examined the two-dimensional (2D) flow fields around a single groin, the simplest layout, to interpret the mechanism of groin-induced turbulent flow. Most scholars focus on the flow separation from the groin tip [6], back water upstream of the groin [7], dead-water zones in the mixing layer [8], water surface oscillation [9] and the recirculation zone downstream [10,11], as shown in Figure 1. Among issues above, the large-scale recirculation zone of the groin downstream is the hottest topic large-scale recirculation zone of the groin downstream is the hottest topic discussed du to its key role on the local scour near the structure.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Backflow Patterns Induced by a Bilateral Groin Pair with Different Spacing

Kuang

Zheng

et al. 2021

Applied Sciences

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Groins are one of the popular manmade structures to modify the hydraulic flow and sediment response in river training. The spacing between groins is a critical consideration to balance the channel-depth and the cost of construction, which is generally determined by the backflow formed downstream from groins. A series of experiments were conducted using Particle Image Velocimetry (PIV) to observe the influence of groin spacing on the backflow pattern of two bilateral groins. The spacing between groins has significant effect on the behavior of the large-scale recirculation cell behind groins. The magnitude of the wake flow induced by a groin was similar to that induced by another groin on the other side, but the flow direction is opposite. The spanwise velocity near the groin tip dictates the recirculation zone width behind the groins due to the strong links between the spanwise velocity and the contraction ratio of channel cross-sections between groins. Based on previous studies and present experimental results, quantitative empirical relationships are proposed to calculate the recirculation zone length behind groins alternately placed at different spacing along riverbanks. This study provides better understanding and a robust formula to assess the backflow extent of alternate groins and identify the optimum groins array configuration.

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“…The spur dike group in large-scale consists of sole spur dikes or small-scale spur dike groups, which are independent of each other without interaction; while spur dike group in small-scale consists of sole spur dikes, which interact with each other noticeably and present the role as a whole. To date, previous researches on spur dike hydraulics are mainly focusing on two aspects: (a) sole spur dike, including flow field around the spur dike [18][19][20][21], local scour mechanism [9,10], backwater effects [16,22], flow resistance and local head loss [16,23] and (b) spur dike group in small-scale, specifically including determination of reasonable spacing [24,25], estimations of water surface oscillation and water surface curves under different spacing [7]. These studies on spur dikes mainly concern the local response of river system.…”

Section: Introductionmentioning

confidence: 99%

Exploring Proper Spacing Threshold of Non-Submerged Spur Dikes with Ipsilateral Layout

Cao²,

et al. 2020

Water

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Concerning the clustering of spur dikes on river systems, the spacing thresholds of twin spur dikes are important parameters to influence the estimations on the impact scales of spur dike groups and the overall responses of river systems. In this study, both numerical investigations and experimental measurements are proceeded to quantify the influence of the spacing threshold of non-submerged twin spur dikes with ipsilateral and orthogonal layout in a straight rectangular channel. Through dimensional analysis, three normalized indices, i.e., Froude number Fr, ratios of channel width to dike length B/b, and ratios of channel width to water depth B/h are identified as the main influencing factors of the relative spacing threshold Sc/b, i.e., dike spacing threshold to dike length. The simulation results indicate that the similarity of mean velocity along the water depth nearby the tips of twin spur dikes is determined by the criterion of the spacing threshold of non-submerged twin spur dikes with ipsilateral and orthogonal layout in straight rectangular channel. The results also show that: Fr plays the least impact among the three influencing factors; with the fixed values of Fr and B/h, the relative threshold Sc/b sharply increases first and then decreases slightly as B/b factor increases, with which the relationship presents approximately convex quadratic function; while both Fr and B/b are fixing, the Sc/b changes oppositely, i.e., slightly increasing first and then sharply decreasing as B/h increases, which, again presents a convex quadratic function. Hence, the normalized empirical formula of spacing threshold can be deduced by multivariate regressions and verified by the corresponding measurements in good agreements. Such empirical formula further suggests that the reasonable spacing threshold ranges from 24b to 130b, which is wider than the recovery area scales found in literature. The outputs of this study provide foundation for the characterization of impact scales of spur dike groups.

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Flow resistance due to a single spur dike in an open channel

Cited by 28 publications

References 16 publications

Force acting on a square cylinder fixed in a free-surface channel flow

Force acting on a square cylinder fixed in a free-surface channel flow

Experimental Study on Backflow Patterns Induced by a Bilateral Groin Pair with Different Spacing

Exploring Proper Spacing Threshold of Non-Submerged Spur Dikes with Ipsilateral Layout

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