scholarly journals Experimental Analysis of Scour Features at Chevrons in Straight Channel

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 971
Author(s):  
Deep Roy ◽  
Simone Pagliara ◽  
Michele Palermo
Keyword(s):  
River Restoration ◽  
Disposal Site ◽  
Scour Depth ◽  
Straight Channel ◽  
Wake Region ◽  
Densimetric Froude Number ◽  
Hydraulic Conditions ◽  
In Series ◽  
Dune Height ◽  
Scour Morphology

Eco-friendly river restoration structures are used to create localized scour pools which serve as fish nurseries and promote biodiversity. In this category, chevrons are relatively new structures designed to maintain navigability in rivers. The scour hole formed in the wake region of chevrons can either act as a disposal site for dredged material or as a resting spot for different fish species. However, only few studies are present in the literature dealing with the scour mechanism due to chevrons. Therefore, this work aims to analyze the scour features at equilibrium, under different hydraulic conditions and transversal locations in a straight channel. Tests were conducted with both isolated and multiple chevrons in series arrangement. Scour morphology types were classified and their fields of existence were established as well. A detailed dimensional analysis was conducted, allowing us to identify the main parameters governing the scour phenomenon and derive a novel equivalent densimetric Froude number. Finally, empirical equations were developed to predict the maximum scour depth and length as well as the maximum dune height.

scholarly journals Scour Features at Wood Bundles

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2118
Author(s):  
Simone Pagliara ◽  
Deep Roy ◽  
Michele Palermo
Keyword(s):  
Froude Number ◽  
Storage Site ◽  
Curved Channels ◽  
Wide Range ◽  
Hydraulic Conditions ◽  
Wood Debris ◽  
Channel Curvature ◽  
Fluvial Habitat ◽  
Dune Height ◽  
Scour Morphology

Structures like blunt-nosed chevrons, log deflectors and double-winged log frames help in modifying the flow regime in the channel by concentrating the flow and increasing navigability. Moreover, they create scour pools in the downstream stilling basin, which can be used either as fish refuge or as an in-stream storage site for previously dredged material. In this respect, the use of wood debris in the channel in the form of wood bundles has gained attention for the ability of these structures to integrate into the surrounding fluvial habitat and to divert the flow partially towards the central part of the channel when placed in curves. Considering the absence of studies dealing with wood bundles as a restoration structure, the aim of this paper is to analyse the scour mechanism and equilibrium scour morphology of wood bundles in straight and curved channels. In doing so, a wide range of hydraulic conditions, structure positions and configurations were tested. Thereafter, dimensional analysis was carried out to derive useful empirical relationships to predict the maximum scour depth and length as well as the maximum dune height based on a novel, equivalent Froude number, which accounts for the effects of channel curvature and structure position. Moreover, the various resulting scour morphology types were classified, and conditions of their existence were determined depending on the abovementioned Froude number and other key hydraulic parameters.

scholarly journals A STUDY OF PERMEABLE GROINS IN SERIES INSTALLED IN A STRAIGHT CHANNEL

2000 ◽  
Vol 44 ◽  
pp. 1047-1052 ◽  
Author(s):  
Shoji FUKUOKA ◽  
Akihide WATANABE ◽  
Hiroshi KAWAGUCHI ◽  
Yu YASUTAKE
Keyword(s):  
Straight Channel ◽  
In Series

scholarly journals Velocity and concentration profiles of saline and turbidity currents flowing in a straight channel under quasi-uniform conditions

2014 ◽  
Vol 2 (1) ◽  
pp. 167-180 ◽  
Author(s):  
M. Stagnaro ◽  
M. Bolla Pittaluga
Keyword(s):  
Cross Sections ◽  
Longitudinal Velocity ◽  
Fixed Bed ◽  
Velocity Profiles ◽  
Doppler Velocity ◽  
Turbidity Currents ◽  
Straight Channel ◽  
Densimetric Froude Number ◽  
Vertical Coordinate ◽  
Dimensionless Velocity

Abstract. We present a series of detailed experimental observations of saline and turbidity currents flowing in a straight channel. Experiments are performed by continuously feeding the channel with a dense mixture until a quasi-steady configuration is obtained. The flume, 12 m long, is characterized by a concrete fixed bed with a uniform slope of 0.005. Longitudinal velocity profiles are measured in ten cross sections, 1 m apart, employing an ultrasound Doppler velocity profiler. We also measure the density of the mixture using a rake of siphons sampling at different heights from the bottom in order to obtain the vertical density distributions in a cross section where the flow already attained a quasi-uniform configuration. We performed 27 experiments changing the flow discharge, the fractional excess density, the character of the current (saline or turbidity) and the roughness of the bed in order to observe the consequences of these variations on the vertical velocity profiles and on the overall characteristics of the flow. Dimensionless velocity profiles under quasi-uniform flow conditions were obtained by scaling longitudinal velocity with its depth averaged value and the vertical coordinate with the flow thickness. They turned out to be influenced by the Reynolds number of the flow, by the relative bed roughness, and by the presence of sediment in suspension. Unexpectedly, the densimetric Froude number of the current turned out to have no influence on the dimensionless velocity profiles.

scholarly journals Estimation of maximum scour depth downstream of an apron under submerged wall jets

2019 ◽  
Vol 21 (4) ◽  
pp. 523-540 ◽  
Author(s):  
Mohammad Aamir ◽  
Zulfequar Ahmad
Keyword(s):  
Scour Depth ◽  
Regression Equations ◽  
Wall Jets ◽  
Statistical Parameters ◽  
Densimetric Froude Number ◽  
Sediment Size ◽  
Fuzzy Interference System ◽  
Interference System ◽  
Neuro Fuzzy ◽  
Artificial Neural Network Ann

Abstract An analysis of laboratory experimental data pertaining to local scour downstream of a rigid apron developed under wall jets is presented. The existing equations for the prediction of the maximum scour depth under wall jets are applied to the available data to evaluate their performance and bring forth their limitations. A comparison of measured scour depth with that computed by the existing equations shows that most of the existing empirical equations perform poorly. Artificial neural network (ANN)- and adaptive neuro-fuzzy interference system (ANFIS)-based models are developed using the available data, which provide simple and accurate tools for the estimation of the maximum scour depth. The key parameters that affect the maximum scour depth are densimetric Froude number, apron length, tailwater level, and median sediment size. Results obtained from ANN and ANFIS models are compared with those of empirical and regression equations by means of statistical parameters. The performance of ANN (RMSE = 0.052) and ANFIS (RMSE = 0.066) models is more satisfactory than that of empirical and regression equations.

Analysis of radionuclide migration with consideration of spatial and temporal change of migration parameters due to uplift and denudation

2015 ◽  
Vol 1744 ◽  
pp. 229-234
Author(s):  
Taro Shimada ◽  
Seiji Takeda ◽  
Masayuki Mukai ◽  
Masahiro Munakata ◽  
Tadao Tanaka
Keyword(s):  
Ground Water ◽  
Flow Velocity ◽  
Safety Assessment ◽  
Ground Surface ◽  
Disposal Site ◽  
Radionuclide Migration ◽  
Water Flow Velocity ◽  
Term Change ◽  
Hydraulic Conditions

ABSTRACTIntegrated safety assessment methodology that analyzes radionuclide migration reflecting the spatial and temporal changes of disposal systems was developed for a geological disposal site with uplift and denudation, and then some case analyses for an assumed site were carried out. The combination of uniform uplift and denudation has the largest effect on the radionuclide migration because the ground water flow velocity increases with decreasing depth from the ground surface. In the case without denudation, tilted uplift has more effect than uniform uplift because flow velocity in tilted uplift increases with increasing hydraulic gradient. The long-term change of the geological structures including the uplift and denudation, the hydraulic conditions, and the recharge and outlet of the ground water around a candidate site should be carefully investigated to determine the appropriate the place, depth and layout of the repository.

scholarly journals Investigating the Performance of Enhanced Permeable Groins in Series

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3531
Author(s):  
Manoochehr Shokrian Hajibehzad ◽  
Mahmood Shafai Bejestan ◽  
Vito Ferro
Keyword(s):  
Cost Effective ◽  
Effective Length ◽  
Scour Depth ◽  
Design Guideline ◽  
Scour Holes ◽  
Cost Effective Technique ◽  
In Series ◽  
Proper Design ◽  
Meander Bends ◽  
Deposition Height

The enhanced permeable groin is a novel eco-friendly and cost-effective technique for bank protection and restoration of meander bends. The behavior of bed deformations due to the distance between the structures has to be studied to design enhanced permeable groins in series properly. In this study, scour morphologies around enhanced permeable groins in series, characterized by four different distances and located in a 180° mild flume bend, for clear water conditions were investigated. The analysis indicated that scour geometrical patterns such as the maximum scour depth nearby the structures and the maximum deposition height between them are strongly affected by the distance between the groins. The results revealed that the maximum scour depth around the structures increases with the distance between structures, the scour holes develop towards the outer bank and create a series of pools that can lead to the bank collapse. All experiments, carried out with different structure distances, demonstrated that the location of thalweg effectively shifted towards the middle of the channel and near the inner bank for high and low particle Froude numbers, respectively. As a general result, a distance between enhanced permeable groins equal to four times the effective length of the structure is recommended for a 180° mild flume bend for the investigated particle Froude numbers. Finally, a general design guideline is presented to a proper design of enhanced permeable groins in series.

scholarly journals Evaluation of governing parameters on pier scour geometry

2017 ◽  
Vol 44 (1) ◽  
pp. 48-58 ◽  
Author(s):  
Priscilla Williams ◽  
Tirupati Bolisetti ◽  
Ram Balachandar
Keyword(s):  
Scale Effects ◽  
Estimation Method ◽  
Estimation Methods ◽  
Scour Depth ◽  
Pier Scour ◽  
Densimetric Froude Number ◽  
Scouring Process ◽  
Equilibrium Scour Depth ◽  
Definition Of ◽  
Limiting Value

Current scour estimation methods typically over-predict scour, resulting in uneconomical design. This tendency is partly due to the complexity of the scouring process, which indicates that some of its aspects are still not well understood, and can also be attributed to scale effects. Here, experiments are conducted to isolate the influence of relative coarseness (D/d50) and flow shallowness (h/D) on scour depth. For the range of D/d50 in the present study, equilibrium scour depth (dse/D) decreases with increasing D/d50 until a limiting value of D/d50 = 175, after which dse/D ≈ 0.75. Furthermore, dse/D is found to depend on h/D when all other scour influencing parameters are held constant. A revised definition of the densimetric Froude number using the velocity along the separating streamline is shown to have an influential role in scour. An improved scour estimation method employing these parameters is presented and compared with current methods.

scholarly journals Impact of armour layer on the depth of scour hole around side-by-side bridge piers under ice-covered flow condition

2019 ◽  
Vol 67 (3) ◽  
pp. 240-251
Author(s):  
Mohammad Reza Namaee ◽  
Jueyi Sui
Keyword(s):  
Grain Size ◽  
Froude Number ◽  
Large Scale ◽  
Bridge Piers ◽  
Scour Depth ◽  
Flow Conditions ◽  
Densimetric Froude Number ◽  
Open Flow ◽  
Scour Holes ◽  
The Impact

Abstract In the present study, experiments were conducted in a large-scale flume to investigate the issue of local scour around side-by-side bridge piers under both ice-covered and open flow conditions. Three non-uniform sediments were used in this experimental study. Analysis of armour layer in the scour holes around bridge piers was performed to inspect the grain size distribution curves and to study the impact of armour layer on scour depth. Assessments of grain size of deposition ridges at the downstream side of bridge piers have been conducted. Based on data collected in 108 experiments, the independent variables associated with maximum scour depth were assessed. Results indicate that the densi-metric Froude number was the most influential parameter on the maximum scour depth. With the increase in grain size of the armour layer, ice cover roughness and the densimetric Froude number, the maximum scour depth around bridge piers increases correspondingly. Equations have been developed to determine the maximum scour depth around bridge piers under both open flow and ice covered conditions.

scholarly journals Experimental Study of Local Scour around Tripod Foundation in Combined Collinear Waves-Current Conditions

2021 ◽  
Vol 9 (12) ◽  
pp. 1373
Author(s):  
Ruigeng Hu ◽  
Xiuhai Wang ◽  
Hongjun Liu ◽  
Yao Lu
Keyword(s):  
Laboratory Experiments ◽  
Euler Number ◽  
General Trend ◽  
Scour Depth ◽  
Dimensionless Time ◽  
Structural Elements ◽  
Scour Hole ◽  
Main Column ◽  
Equilibrium Scour Depth ◽  
Scour Morphology

A series of laboratory experiments were conducted in a wave-current flume to investigate the scour evolution and scour morphology around tripod in combined waves and current. The tripod model was made using the 3D printing technology, and it was installed in seabed with three installation angles α = 0°, 90°and 180° respectively. In the present study, the scour evolution and scour characteristic were first analyzed. Then, the equilibrium scour depth Seq was investigated. Furthermore, a parametric study was carried out to study the effects of Froude number Fr and Euler number Eu on equilibrium scour depth Seq respectively. Finally, the effects of tripod’s structural elements on Seq were discussed. The results indicate that the maximum scour hole appeared underneath the main column for installation angle α = 0°, 90° and 180°. The Seq for α = 90° was greater than the case of α = 0° and α = 180°, implying the tripod suffered from more severe scour for α = 90°. When KC was fixed, the dimensionless time scale T* for α = 90° was slightly larger than the case of α = 0° and α = 180° and the T* was linearly correlated with Ucw in the range of 0.347 < Ucw < 0.739. The higher Fr and Eu both resulted in the greater scour depth for tripod in combined waves and current. The logarithmic formula can depict the general trend of Seq and Fr (Eu) for tripod in combined waves and current.

Sign in / Sign up

Export Citation Format

Share Document