Pressure field in skimming flow over a stepped spillway

Juny, Martí Sánchez; Pomares, Juan José Pomares; Dolz, Josep

doi:10.1201/9781003078609-22

Cited by 8 publications

(7 citation statements)

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“…Therein, the S-shape far downstream of the slope reduction was less pronounced, likely due to a lower density of measurement points. The above findings are consistent with those of others (e.g., [2][3][4][5][6][7][8][9][11][12][13]22,24]). They demonstrate that (1) the pressure near the step edge is influenced by flow impact, i.e., the interaction of the lower edge of the shear layer formed downstream of each step singularity with the horizontal face of the step, as characterized in [25], (2) the step corner pressure is influenced by the flow recirculation, and (3) the highest absolute pressures occur at the impact region, near the flow separation in between these two regions.…”

Section: Bottom-pressure Profilessupporting

confidence: 93%

“…The results show that the vertical position has a small influence on the pressure, for 0.3 ≤ z/h ≤ 0.7. Similar results were found by others, within this range of positions along the vertical step face (e.g., [2][3][4][6][7][8]11,13,22,24]). However, smaller values would be expected to occur near the step edge due to the flow separation [2][3][4][6][7][8]11,13,22,24,29,30].…”

Section: Bottom-pressure Profilessupporting

confidence: 90%

“…The knowledge of the fluctuating bottom-pressure distribution is important to ensure the structural integrity of smooth and stepped chutes, especially under negative pressures. For stepped chutes with a constant bottom slope, the mean or fluctuating pressures acting on the steps were assessed by several laboratory studies (e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13]). On the horizontal face of the step, a typical S-shape pressure distribution was observed, with maximum pressures occurring at the so-called impact flow region, near the outer edge of the step, whereas minimum pressures were noticed on the upstream half of the step face, due to the boundary separation of the recirculating flow (e.g., [3,4,7,8,[11][12][13]).…”

Section: Introductionmentioning

confidence: 99%

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Bottom-Pressure Development Due to an Abrupt Slope Reduction at Stepped Spillways

Tehrani

Matos

Pfister

et al. 2021

Water

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Fluctuating bottom-pressures on stepped chutes are relevant for the spillway design. An abrupt slope reduction causes a local alteration of the bottom-pressure development. Little information is available regarding the air–water flow properties near an abrupt slope reduction on stepped chutes, particularly on the local pressure evolution. Nevertheless, the option of providing a chute slope reduction may be of interest in spillway layout. The experiments presented herein include pressure distributions on both vertical and horizontal step faces, subsequent to an abrupt slope reduction on stepped chutes. A relatively large-scale physical model including abrupt slope reductions from 50° to 18.6° and from 50° to 30° was used, operated with skimming flow. The data indicate a substantial influence of the tested slope reductions on the bottom-pressure development. In the vicinity of the slope reduction, the mean pressure head near the edge of the horizontal step face reached 0.4 to 0.6 times the velocity head upstream of the slope reduction, for critical flow depths normalized by the step height ranging between 2.6 and 4.6.

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Section: Bottom-pressure Profilessupporting

confidence: 93%

Section: Bottom-pressure Profilessupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

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Bottom-Pressure Development Due to an Abrupt Slope Reduction at Stepped Spillways

Tehrani

Matos

Pfister

et al. 2021

Water

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“…Juny et al (2000) [17]conduct research on stepped spillway with a slope of 1V:0.8H and relative critical depth over the crest to demonstrate the unit discharge ranging between yc/h = 0.891 -2.246. The authors studied the pressure distribution along the stepped chute, by using a piezo-resistive pressure transducer and flow visualizing technique.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…Regarding the location of maximum and minimum pressure impact on the tread and rise respectively, the previous studies related to this topic (e.g., Ojaimi, 2013; Juny et al, 2000; Matos et al 1999;and Frizell, 2006) [11,17,27,28] concluded that the maximum pressure on a tread must be measured near the outer edge of the step, and to get an indication to a minimum pressure on the rise it must be measured as close as possible to the top edge of the step. Accordingly, the pressure taps for tread and rise have been installed in a position along the centerline of the spillway nearly the external edges.…”

Section: Experimental Workmentioning

confidence: 99%

Distribution of Pressures on Modified Stepped Spillway by Using Toothed-Steps

Maatooq¹,

Jasim²

2021

ETJ

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 A new stepped spillway shape was used in experimental work under the skimming flow regime by adding block (tooth) on the step.  The tooth-stepped spillway reduces the positive and negative pressure on steps close to the crest by a large amount and especially at high discharge.  When the spacing between tooth increase the pressure along the chute will have bad distribution compare to the traditional model.In the present study a new steeped spillway shape at which "toothed steps" have been adopted instead of traditional steps to enhance the amount and distribution of water pressure along the chute of the stepped spillway. Experiments were conducted under a skimming flow regime, on five physical models of spillway one of which consisted of traditional steps used as a base model. For all investigated models, the chute angle was 45° with fourteen steeps each of 3cm height. Generally, the results show that the new shape models enhance the pressure distribution and reducing the potential for negative pressures along the chute, as well as, reducing the values of positive pressures that usually impact the tread. Specifically, close to the crest, the differences in pressure values being clearly large between the toothed steps modelsand the traditional steps. The new configurations of steps reduce the positive pressures between 116.66% to 1.28 % and the negative pressures were generally close to zero.

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