scholarly journals Scour Induced by Single and Twin Propeller Jets

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 1097 ◽  
Author(s):  
Yonggang Cui ◽  
Wei Haur Lam ◽  
Tianming Zhang ◽  
Chong Sun ◽  
Gerard Hamill
Keyword(s):  
Normal Distribution ◽  
Maximum Depth ◽  
Scour Depth ◽  
Scour Hole ◽  
Scour Holes ◽  
Ship Propeller ◽  
Gaussian Normal Distribution

Single and twin ship propeller jets produce scour holes with deposition dune. The scour hole has a maximum depth at a particular length downstream within the propeller jet. Existing equations are available to predict maximum scour depth and the corresponding scour length downstream. Experiments conducted with various physical propeller models, rotational speeds, propeller-to-propeller distances and bed clearances are presented. The measurements allowed a better understanding of the mechanism of temporal scour and deposition formation for scour caused by single-propeller and twin-propeller. Results show that the propeller jet scour profiles can be divided into three zones, which are the small scour hole, primary scour hole and deposition dune. An empirical 2D scour model is proposed to predict the scour profile for both a single-propeller and twin-propeller using a Gaussian normal distribution.

scholarly journals Experimental Scours by Impinging Twin-Propeller Jets at Quay Wall

2020 ◽  
Vol 8 (11) ◽  
pp. 872
Author(s):  
Yonggang Cui ◽  
Wei Haur Lam ◽  
Zhi Chao Ong ◽  
Lloyd Ling ◽  
Chee Loon Siow ◽  
...  
Keyword(s):  
Scour Depth ◽  
Water Tank ◽  
Quay Wall ◽  
Depth Position ◽  
Scour Hole ◽  
Scour Holes ◽  
Horseshoe Vortices ◽  
Three Stages ◽  
Deposition Height ◽  
The Relationship

Experiments were conducted to investigate the seabed scour holes due to the interaction between the twin-propeller jet and quay wall. Vertical quay wall was modelled by using a polyvinyl chloride (PVC) plastic plate in a water tank. The relationship between the positions of the propeller and the vertical quay wall was designed according to the actual working conditions of a ship entering and leaving a port. Propeller-to-wall distance and rotational speed were changed to observe the various scour conditions. The scour depth was measured by using an Acoustic Doppler Velocimeter (ADV). Primary scour hole was found within the jet downstream and secondary scour hole occurred beneath of the propeller. Third scour hole was found close to the quay wall due to horseshoe vortices. The maximum scour position of this third scour hole was found at the jet centre near the quay wall. Temporal formation of scour holes can be divided into three stages: axial scour formation, obstructed scour expansion and equilibrium stages. The quantitative relationships for six characteristic parameters of the scour pit were established including the maximum scour depth (εmax,q), maximum scour depth position (Xm,q), maximum scour width (Wm,q), length of main scour pit (XS,q), maximum deposition height (ZD,q), and location of maximum deposition height (XD,q).

scholarly journals Improving the 2D Numerical Simulations on Local Scour Hole around Spur Dikes

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1462
Author(s):  
Chung-Ta Liao ◽  
Keh-Chia Yeh ◽  
Yin-Chi Lan ◽  
Ren-Kai Jhong ◽  
Yafei Jia
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Local Scour ◽  
Bridge Piers ◽  
Scour Depth ◽  
Foundation Design ◽  
Mobile Bed ◽  
Scour Hole ◽  
Scour Holes ◽  
Spur Dikes

Local scour is a common threat to structures such as bridge piers, abutments, and dikes that are constructed on natural rivers. To reduce the risk of foundation failure, the understanding of local scour phenomenon around hydraulic structures is important. The well-predicted scour depth can be used as a reference for structural foundation design and river management. Numerical simulation is relatively efficient at studying these issues. Currently, two-dimensional (2D) mobile-bed models are widely used for river engineering. However, a common 2D model is inadequate for solving the three-dimensional (3D) flow field and local scour phenomenon because of the depth-averaged hypothesis. This causes the predicted scour depth to often be underestimated. In this study, a repose angle formula and bed geometry adjustment mechanism are integrated into a 2D mobile-bed model to improve the numerical simulation of local scour holes around structures. Comparison of the calculated and measured bed variation data reveals that a numerical model involving the improvement technique can predict the geometry of a local scour hole around spur dikes with reasonable accuracy and reliability.

scholarly journals A new formula based on computational fluid dynamics for estimating maximum depth of scour by jets from overflow dams

2014 ◽  
Vol 16 (5) ◽  
pp. 1210-1226 ◽  
Author(s):  
Sherong Zhang ◽  
Bohui Pang ◽  
Gaohui Wang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Maximum Velocity ◽  
Maximum Depth ◽  
Scour Depth ◽  
Absolute Deviation ◽  
Scour Hole ◽  
Computational Fluid Dynamics Cfd ◽  
New Formula ◽  
Lm Algorithm

The prediction of the maximum depth of the scour hole formed downstream of overflow dams is critical in determining the safety of hydraulic structures. Most of the conventional formulae are not able to consider complex hydraulic and morphologic conditions. A new formula for estimating the maximum depth of the scour hole based on computational fluid dynamics (CFD), which can be used to simulate the complicated phenomenon, is proposed. The relationship between the maximum velocity in numerical simulations and the maximum scour depth is reflected in this formula, which is established using the Levenberg–Marquardt (LM) algorithm. The validity of this proposed formula is discussed by comparing this formula with three other conventional formulae. The prediction formula based on CFD is applied to the Wuqiangxi Dam, and the absolute deviation of the predicted maximum scour depth (35.44 m) from the measured depth (36.00 m) is 0.56 m.

scholarly journals PREDICTION OF EQUILIBRIUM SCOUR HOLES USING OPTIMIZATION PROCEDURES

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

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

2020 ◽  
Vol 62 (3) ◽  
Author(s):  
A Bosman ◽  
G R Basson
Keyword(s):  
Physical Model ◽  
Linear Regression Analysis ◽  
Scour Depth ◽  
Model Study ◽  
Fissured Rock ◽  
Scour Hole ◽  
Plunging Jets ◽  
Concrete Blocks ◽  
Rock Bed ◽  
Equilibrium Scour Depth

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.

scholarly journals Effects of weir geometry on scour development in the downstream of Piano Key Weirs

2020 ◽  
Author(s):  
Alireza Mosalman Yazdi ◽  
S. Abbas Hoseini ◽  
Sohrab Nazari ◽  
Nosratollah Amanian
Keyword(s):  
Discharge Rate ◽  
Scour Depth ◽  
Scour Hole ◽  
Weir Height ◽  
The One ◽  
Rectangular Model

Abstract Scouring in the downstream of all weirs, including Piano Key Weirs (PKWs), can have major safety implications. Since the research on downstream scouring of PKWs is very limited, and the weir geometry is also known to have an impact on downstream scouring, this study investigated scouring in the downstream of PKWs with rectangular and trapezoidal geometries and two different heights. The scour hole measurements showed that in both rectangular and trapezoidal models, scour hole parameters increased both with the increase in discharge rate and the increase in weir height. Under similar discharge conditions, the scour depth downstream from the rectangular model was greater than that downstream from the trapezoidal model. The dimensionless maximum scour depth, the distance of maximum scour depth from the weir toe, and the scour hole length for the trapezoidal PKW were, on average, 6, 13, and 11% lower than the corresponding ones for the rectangular PKW, respectively. However, these differences decreased with the increase in falling height. For both weir geometries, the maximum scour depth was aligned with the outlet keys. In addition, the maximum scour depth under the outlet keys was 13% greater than the one under the inlet keys.

scholarly journals Scale effect on mean pressures: study of two reduced models of a ski jump spillway

RBRH ◽  
2019 ◽  
Vol 24 ◽  
Author(s):  
João Gerdau de Borja ◽  
Daniela Guzzon Sanagiotto ◽  
Marcelo Giulian Marques ◽  
Alba Valéria Brandão Canellas ◽  
Cassius Palauro
Keyword(s):  
Scale Effect ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
Jet Flow ◽  
Reduced Models ◽  
Physical Experiments ◽  
Scour Hole ◽  
Scour Holes ◽  
Energy Dissipation System ◽  
The Impact

ABSTRACT The ski jump type spillway is present in large Brazilian dams. After the operation of this type of spillway, a scour hole is originated downstream of the spillway toe, complementing the energy dissipation system, because the jet is cushioned by the waterbed. As the excavation of the scour hole evolves, its shape changes, with the induction of different behaviors of the jet flow within the waterbed. The importance of this scientific study is due to the fact that scour holes downstream of ski jump spillways are in constant transformation, which can cause changes in the patterns of dynamic pressures caused on the bottom. Unexpected erosions can cause instability in the submerged slopes of the pit, jeopardizing the foundation of the dam. In this work it was proceeded physical experiments, by sectional modeling (2D), in two reduced models of 1:50 and 1:100 scales, considering two stages of erosion depths in solid bottom (fixed). It was analyzed the impact site of the jet flow on the bottom, which has the major mean dynamic pressure. As result, it was possible to identify the scale effect in the pressure coefficient between the two models tested, which allowed the adjustment of trend lines that aid to estimate the pressures that occur in prototypes, increasing safety in operation of ski jump spillways.

scholarly journals Open Channel Sluice Gate Scouring Parameters Prediction: Different Scenarios of Dimensional and Non-Dimensional Input Parameters

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 353 ◽  
Author(s):  
Ali Yousif ◽  
Sadeq Sulaiman ◽  
Lamine Diop ◽  
Mohammad Ehteram ◽  
Shamsuddin Shahid ◽  
...  
Keyword(s):  
Scour Depth ◽  
Sluice Gate ◽  
Analysis Technique ◽  
Dimensionless Groups ◽  
Scour Hole ◽  
Adaptive Regression ◽  
Learning Machine ◽  
Bed Material ◽  
Statistical Metrics

The determination of scour characteristics in the downstream of sluice gate is highly important for designing and protection of hydraulic structure. The applicability of modern data-intelligence technique known as extreme learning machine (ELM) to simulate scour characteristics has been examined in this study. Three major characteristics of scour hole in the downstream of a sluice gate, namely the length of scour hole (Ls), the maximum scour depth (Ds), and the position of maximum scour depth (Lsm), are modeled using different properties of the flow and bed material. The obtained results using ELM were compared with multivariate adaptive regression spline (MARS). The dimensional analysis technique was used to reduce the number of input variable to a smaller number of dimensionless groups and both the dimensional and non-dimensional variables were used to model the scour characteristics. The prediction performances of the developed models were examined using several statistical metrics. The results revealed that ELM can predict scour properties with much higher accuracy compared to MARS. The errors in prediction can be reduced in the range of 79%–81% using ELM models compared to MARS models. Better performance of the models was observed when dimensional variables were used as input. The result indicates that the use of ELM with non-dimensional data can provide high accuracy in modeling complex hydrological problems.

scholarly journals Scour around Piers under Waves: Current Status of Research and Its Future Prospect

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2212 ◽  
Author(s):  
Ainal Hoque Gazi ◽  
Mohammad Saud Afzal ◽  
Subhasish Dey
Keyword(s):  
Process Development ◽  
Future Prospect ◽  
Review Article ◽  
Current Status ◽  
Scour Depth ◽  
Pier Scour ◽  
Scour Hole ◽  
The Future ◽  
Bridge Failure

In this review article, the current status of research on pier scour under waves is presented. This includes a summary of different bridge failure events due to scour, scour mechanism, scour depth predictors under waves, influence of pier shape on scour depth formation, shape of scour hole around piers, and many others. Further, this article describes the scour process, development of scour depth predictors, and the complexity involved in the scour related calculations. Finally, the future scope of research is delineated.

Formula Type of Local Scour Depth on Spur Dike Nose

2014 ◽  
Vol 641-642 ◽  
pp. 271-274
Author(s):  
Qiang Ying
Keyword(s):  
Formation Process ◽  
Local Scour ◽  
Scour Depth ◽  
Calculation Methods ◽  
Spur Dike ◽  
Scour Hole ◽  
Main Factors ◽  
Formula Type ◽  
Suggested Formula

This passage introduces the formation process of scour hole, analyzes the main factors contributed to the local scour hole’s depth and classifies today’s calculation methods of scour depth into three categories. Then, given the conditions where those methods can be applied and drawbacks of those methods, this article also recommends some suggested formula in calculation.

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