Velocity Field Characteristics at the Inlet to a Pipe Culvert

Rigid flow deflectors are usually used on water flow beds to protect engineering structures such as breakwater in coasts and to regulate flow routes in open channels. To reduce its side-effects, i.e., local scour at the toe of deflectors, a flexible flow deflector is proposed, and the corresponding local scour was investigated in this study. A flume experiment was conducted to investigate local scour. To show the advantage of flexible deflectors, a control experimental test was also conducted using a traditional rigid deflector under the same blockage area configuration and the same flow conditions. The flow field near the flexible deflector was also measured to reveal the local flow field. The results show that the bed-scour develops near the toe edges of both flexible and rigid deflectors, but the maximum and averaged scour depths for the flexible deflector are smaller. This advantage of flexible deflector in scour depth is mainly caused by its prone posture, which induces the upward stretching and enlarging horizontally rotating vortex and the upward shifted vertically rotating vortex. The former dissipates more turbulent energy and the latter results in smaller bed shear stress, which lead to smaller scour depth directly. In addition, the up- and down-swaying movement of the flexible deflector can also assistant to dissipate more turbulent energy, thereby damping the intense of the horseshoe vortices and thus weakening scour depth as well. The results of this study provide an elementary understanding on the mechanisms of a flexible flow structure and an alternative deflector-device to reduce scour depth.

Section: Turbulence Intensity Near a Flexible Flow Deflectormentioning

confidence: 98%

Local Scour Near Flexible Flow Deflectors

Xie

Zhu

Huang

et al. 2020

“…Perpendicular crossings between transport infrastructure and natural streams are favored when installing new culverts, but this is not always possible as natural creeks meander through the landscape. Maintaining a perpendicular intersection and not aligning the culvert with the main flow direction leads to reduced flows, higher blockage risks [1][2][3], and sedimentation and erosion [4][5][6]. Today, three different methods are used to approach this problem; skewed barrels, upstream realignments, or misaligned structures.…”

Section: Introductionmentioning

confidence: 99%

Improving Flows in Misaligned Culverts

Jaeger

Jacobs

Tondera

et al. 2019

This study investigated different approaches to optimize flows in misaligned culverts. Structures aligned with the natural stream are always preferred, as misalignments cause a change of direction at the culvert inlet associated with lower performance and sedimentation and erosion problems. This optimal positioning can cause high financial costs and a flow optimization minimizing the associated problems could be a viable alternative. In this study, we used computational fluid dynamics analysis to evaluate the flow in 44 different scenarios with misalignment angles ranging from 0 • to 90 • . It was found that smooth transitions towards the narrowest point in the stream (culvert) were possible for any degree of misalignment resulting in improved, uniform velocity distributions and less turbulence. An experimental setup was able to confirm the possible flow improvements. The proposed approach of flow redirection can lower construction costs and gives planners and designers more flexibility as tailored reinforcement and redesign of the stream embankment can be used as an alternative to costly creek alignments.

“…Several factors influence the discharge capacity of a culvert, but the cross-sectional area and the inlet configuration are the two that can be controlled the easiest with the biggest impact on water flow. The importance and benefits of well-designed inlets were recognized in early research [16], yet modern design guidelines have failed to adopt these benefits [17][18][19][20][21]. A review of the geometric influence on hydraulic performances in rectangular culverts was completed in 2004 by Jones et al [19]; but only a few sizes of the inlet design were investigated, and most subsequent alterations were limited to the top bevel and/or wingwall setups rather than to the shape of the complete opening.…”

Section: Introductionmentioning

confidence: 99%

“…A review of the geometric influence on hydraulic performances in rectangular culverts was completed in 2004 by Jones et al [19]; but only a few sizes of the inlet design were investigated, and most subsequent alterations were limited to the top bevel and/or wingwall setups rather than to the shape of the complete opening. Since then, few publications have discussed culvert inlets [20][21][22][23][24], and none have focused on discharge improvements.…”

Section: Introductionmentioning

confidence: 99%

Numerical and Physical Modeling to Improve Discharge Rates in Open Channel Infrastructures

Jaeger

Tondera

Jacobs

et al. 2019

This paper presents the findings of a study into how different inlet designs for stormwater culverts increase the discharge rate. The objective of the study was to develop improved inlet designs that could be retro-fitted to existing stormwater culvert structures in order to increase discharge capacity and allow for changing rainfall patterns and severe weather events that are expected as a consequence of climate change. Three different chamfer angles and a rounded corner were simulated with the software ANSYS Fluent, each of the shapes tested in five different sizes. Rounded and 45 ∘ chamfers at the inlet edge performed best, significantly increasing the flow rate, though the size of the configurations was a critical factor. Inlet angles of 30 ∘ and 60 ∘ caused greater turbulence in the simulations than did 45 ∘ and the rounded corner. The best performing shape of the inlet, the rounded corner, was tested in an experimental flume. The flume flow experiment showed that the optimal inlet configuration, a rounded inlet (radius = 1/5 culvert width) improved the flow rate by up to 20% under submerged inlet control conditions.