Physical model study of bedrock scour downstream of dams due to spillway plunging jets

The erosive power of a free-falling high-velocity water jet, flowing from a dam spillway, could create a scour hole downstream of the dam, endangering the foundation of the dam. Despite extensive research since the 1950s, there is presently no universally agreed method to predict accurately the equilibrium scour depth caused by plunging jets at dams. These formulae yield a large range of equilibrium scour dimensions. The hydrodynamics of plunging jets and the subsequent scour of a rectangular, horizontal and vertical fissured rock bed were investigated in this study by means of a physical model. Equilibrium scour hole geometries for different fissured dimensions (simulated with rectangular concrete blocks tightly prepacked in a regular rectangular matrix), for a range of flow rates, plunge pool depths, and dam height scenarios were experimentally established with 31 model tests. From the results, non-dimensional formulae for the scour hole geometry were developed using multi-linear regression analysis. The scour depth results from this study were compared to various analytical methods found in literature. The equilibrium scour hole depth established in this study best agrees with that predicted by the Critical Pressure method.

Download Full-text

PREDICTION OF EQUILIBRIUM SCOUR HOLES USING OPTIMIZATION PROCEDURES

Coastal Engineering Proceedings ◽

10.9753/icce.v36v.papers.12 ◽

2020 ◽

pp. 12

Author(s):

Xerxes Mandviwalla ◽

Jesper Roland Kjaergaard Qwist ◽

Erik Damgaard Christensen

Keyword(s):

Equilibrium Shape ◽

Optimization Procedure ◽

Bed Load ◽

Scour Depth ◽

Transient Solution ◽

Marine Structures ◽

Scour Hole ◽

Scour Holes ◽

Speed Up ◽

Equilibrium Scour Depth

This paper presents an optimization procedure that finds the equilibrium scour depth under a pipeline. Even though much knowledge on scour is available for the most typical marine structures such as a vertical circular monopile of a horizontal pipelines the calculation of the scour depth complex and time-consuming as the transient solution is often modelled as well. In this paper we present a optimization procedure that combined with a computational fluid dynamics, and a model of the bed load finds the equilibrium shape of a scour hole. This can potentially speed up the calculation of the shape of the equilibrium scour hole with a factor of 100. However, it comes with a coast as we will not model the transition and the time scale of the scour hole development.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/LpKq9Twj7zo

Download Full-text

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

Journal of Marine Science and Engineering ◽

10.3390/jmse9121373 ◽

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.

Download Full-text

Hydrodynamic Structure with Scour Hole Downstream of Bed Sills

Water ◽

10.3390/w12010186 ◽

2020 ◽

Vol 12 (1) ◽

pp. 186 ◽

Cited By ~ 5

Author(s):

Mouldi Ben Meftah ◽

Francesca De Serio ◽

Diana De Padova ◽

Michele Mossa

Keyword(s):

Flow Velocity ◽

Phenomenological Theory ◽

Scour Depth ◽

Shear Stresses ◽

Alluvial Channels ◽

Spectral Exponent ◽

Turbulence Measurements ◽

Scour Hole ◽

Hydrodynamic Structure ◽

Equilibrium Scour Depth

Experimental turbulence measurements of scour hole downstream of bed sills in alluvial channels with non-cohesive sediments are investigated. Using an Acoustic Doppler Velocimeter (ADV), the flow velocity-field within the equilibrium scour hole was comprehensively measured. In this study, we especially focus on the flow hydrodynamic structure in the scour hole at equilibrium. In addition to the flow velocity distribution in the equilibrium scour hole, the turbulence intensities, the Reynolds shear stresses, the turbulent kinetic energy, and the turbulent length scales are analyzed. Since the prediction of equilibrium scour features is always very uncertain, in this study and based on laboratory turbulence measurements, we apply the phenomenological theory of turbulence to predict the maximum equilibrium scour depth. With this approach, we obtain a new scaling of the maximum scour depth at equilibrium, which is validated using experimental data, satisfying the validity of a spectral exponent equal to −5/3. The proposed scaling shows a quite reasonable accuracy in predicting the equilibrium scour depth in different hydraulic structures.

Download Full-text

The Equilibrium Scour Depth around a Pier under the Action of Collinear Waves and Current

Journal of Marine Science and Engineering ◽

10.3390/jmse8010036 ◽

2020 ◽

Vol 8 (1) ◽

pp. 36 ◽

Cited By ~ 1

Author(s):

Ainal Hoque Gazi ◽

Subhrangshu Purkayastha ◽

Mohammad Saud Afzal

Keyword(s):

Velocity Profile ◽

Arbitrary Shape ◽

Scour Depth ◽

Mathematical Equation ◽

Flowing Fluid ◽

Scour Hole ◽

Sediment Particles ◽

Equilibrium Scour Depth ◽

Work Done ◽

Good Agreement

In this paper, a mathematical equation is developed for the equilibrium scour depth considering an arbitrary shape of the scour hole around a pier under the action of collinear waves and current. A power-law current velocity profile is assumed for the purpose of the analysis. The equilibrium scour depth is obtained by equating the work done by the flowing fluid while interacting with the pier under the action of the collinear waves and the current and the work done by the total volume of the sediment particles removed from the scour hole, respectively. The equilibrium scour depths predicted by the model show good agreement with the experimental and numerical results available in the literature.

Download Full-text

Secondary Currents with Scour Hole at Grade Control Structures

Water ◽

10.3390/w13030319 ◽

2021 ◽

Vol 13 (3) ◽

pp. 319

Author(s):

Mouldi Ben Meftah ◽

Diana De Padova ◽

Francesca De Serio ◽

Michele Mossa

Keyword(s):

Secondary Flow ◽

Control Structure ◽

Scour Depth ◽

Control Structures ◽

Secondary Currents ◽

Scour Hole ◽

Grade Control ◽

Flow Motion ◽

The Cross ◽

Equilibrium Scour Depth

Most studies on local scouring at grade control structures have principally focused on the analysis of the primary flow field, predicting the equilibrium scour depth. Despite the numerous studies on scouring processes, secondary currents were not often considered. Based on comprehensive measurements of flow velocities in clear water scours downstream of a grade control structure in a channel with non-cohesive sediments, in this study, we attempted to investigate the generation and turbulence properties of secondary currents across a scour hole at equilibrium condition. The flow velocity distributions through the cross-sectional planes at the downstream location of the maximum equilibrium scour depth clearly show the development of secondary current cells. The secondary currents form a sort of helical-like motion, occurring in both halves of the cross-section in an axisymmetric fashion. A detailed analysis of the turbulence intensities and Reynolds shear stresses was carried out and compared with previous studies. The results highlight considerable spatial heterogeneities of flow turbulence. The anisotropy term of normal stresses dominates the secondary shear stress, giving the impression of its crucial role in generating secondary flow motion across the scour hole. The anisotropy term shows maximum values near both the scour mouth and the scour bed, caused, respectively, by the grade control structure and the sediment ridge formation, which play fundamental roles in maintaining and enhancing the secondary flow motion.

Download Full-text

Physical Model Study of Flowerpot Discharge Outlet, Western Closure Complex, New Orleans, Louisiana

10.21236/ada583046 ◽

2013 ◽

Author(s):

Stephen T. Maynord

Keyword(s):

New Orleans ◽

Physical Model ◽

Model Study

Download Full-text

Two-Dimensional Numerical Modeling of Flow in Physical Models of Rock Vane and Bendway Weir Configurations

Water ◽

10.3390/w13040458 ◽

2021 ◽

Vol 13 (4) ◽

pp. 458

Author(s):

Drew C. Baird ◽

Benjamin Abban ◽

S. Michael Scurlock ◽

Steven B. Abt ◽

Christopher I. Thornton

Keyword(s):

Numerical Modeling ◽

Physical Model ◽

Numerical Models ◽

Hydraulic Performance ◽

Physical Models ◽

Protection Measures ◽

Design Engineers ◽

Model Study ◽

Study Results ◽

Wide Range

While there are a wide range of design recommendations for using rock vanes and bendway weirs as streambank protection measures, no comprehensive, standard approach is currently available for design engineers to evaluate their hydraulic performance before construction. This study investigates using 2D numerical modeling as an option for predicting the hydraulic performance of rock vane and bendway weir structure designs for streambank protection. We used the Sedimentation and River Hydraulics (SRH)-2D depth-averaged numerical model to simulate flows around rock vane and bendway weir installations that were previously examined as part of a physical model study and that had water surface elevation and velocity observations. Overall, SRH-2D predicted the same general flow patterns as the physical model, but over- and underpredicted the flow velocity in some areas. These over- and underpredictions could be primarily attributed to the assumption of negligible vertical velocities. Nonetheless, the point differences between the predicted and observed velocities generally ranged from 15 to 25%, with some exceptions. The results showed that 2D numerical models could provide adequate insight into the hydraulic performance of rock vanes and bendway weirs. Accordingly, design guidance and implications of the study results are presented for design engineers.

Download Full-text

Estimating Equilibrium Scour Depth at Cylindrical Piers in Experimental Studies

Journal of Hydraulic Engineering ◽

10.1061/(asce)hy.1943-7900.0000410 ◽

2011 ◽

Vol 137 (9) ◽

pp. 1089-1093 ◽

Cited By ~ 27

Author(s):

Gonzalo Simarro ◽

Cristina M. S. Fael ◽

António H. Cardoso

Keyword(s):

Experimental Studies ◽

Scour Depth ◽

Equilibrium Scour Depth

Download Full-text

Canal Wave Oscillations from Expansion of I-84 Bridge in Boise, Idaho

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/2309-19 ◽

2012 ◽

Vol 2309 (1) ◽

pp. 200-205

Author(s):

William Rahmeyer ◽

J. M. Clegg ◽

S. L. Barfuss

Keyword(s):

New York ◽

Physical Model ◽

Unique Solution ◽

Wave Phenomenon ◽

Bridge Columns ◽

Bridge Abutments ◽

Wave Problem ◽

Model Study ◽

Bridge Crossing

Recent improvements and the widening of the I-84 Bridge crossing of the New York Canal in Boise, Idaho, have increased the number of bridge columns from 28 to 60. The resulting structure has two parallel rows of columns that extend across the width of the bridge longitudinally within the canal. After the widening of the bridge and addition of the bridge columns, the canal began experiencing an oscillating wave phenomenon that originated from the bridge columns and caused erosion of upstream and downstream canal banks and bridge abutments. A physical model study was conducted to investigate the wave phenomenon and determine what modifications to the columns or canal would be necessary to prevent the wave oscillations. The physical model was successful in simulating the wave phenomenon, and four different modifications for resolving the wave problem were tested in the model. A unique solution was found that used precast nose cones attached to selected columns. The nose cones have been installed in the prototype bridge crossing, and no wave oscillations have occurred since installation. This paper discusses the study to simulate the wave phenomenon and the four modifications that were evaluated to reduce or prevent wave oscillations.

Download Full-text