scholarly journals Modeling Local Scour around a Cylindrical Pier with Circular Collar with Tilt Angles (Counterclockwise around the Direction of the Channel Cross-Section) in Clear-Water

Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3281
Author(s):  
Hongliang Qi ◽  
Weiping Tian ◽  
Haochi Zhang
Keyword(s):  
Cross Section ◽  
Tilt Angle ◽  
Early Stage ◽  
Flow Direction ◽  
Local Scour ◽  
Channel Cross Section ◽  
Scour Depth ◽  
Clear Water ◽  
Eddy Simulation ◽  
Scouring Depth

This research explores how a circular collar with a tilt angle (counterclockwise around the direction of the channel cross-section) could affect the local scour depth around a single cylindrical pier in clear-water based on Large Eddy Simulation (LES) in six cases. The results show that a horizontal circular collar is the best for reducing the local scour depth. With the increases of the tilt angle, the effect on reducing the local scour depth decreases gradually and is even counterproductive at the scour equilibrium. At the early stage of scouring, cases with circular collars show obvious scouring depth reductions. The smaller the tilt angle is, the better and longer-lasting the protection that the circular collar can provide. When the tilt angle is smaller than 5°, the location of the maximum local scouring is around 90–115° (the angle is measured clockwise from the flow direction) on both sides of the pier. When the tilt angle is greater than 5°, the depth of local scouring in the range around −115° to 115° is close to the maximum local scouring depth. Significantly larger areas reach the maximum scouring depth when the tilt angle increases. Compared to Case 1 (the pier without a circular collar), in the cases with a circular collar, the topographies downwards the pier in 1.0D (D is the diameter of the bridge pier) are changed to siltation from scouring. The topography downwards the pier changes from scouring to siltation with the increase of the tilt angle, and the shape of siltation changes from a long-narrow rectangle to an equilateral triangle. This study may provide valuable insights into the protection of the local scour of the pier.

Reduction of scouring depth by using inclined piers

2010 ◽  
Vol 37 (12) ◽  
pp. 1621-1630 ◽  
Author(s):  
Zafer Bozkus ◽  
Murat Çeşme
Keyword(s):  
Experimental Study ◽  
Dimensional Analysis ◽  
Local Scour ◽  
Bridge Piers ◽  
Scour Depth ◽  
Regression Analyses ◽  
Clear Water ◽  
Design Engineers ◽  
Water Conditions ◽  
Scouring Depth

The aim of this experimental study is to examine the effect of inclination of dual bridge piers on scour depth under clear-water conditions for various uniform flow depths. Duration of 4 h was used in the experiments for each run. Scour depths were measured at four different points around the piers. The depths of local scour around inclined piers were found to be substantially smaller than the scour depths around vertical piers. Dimensional and nondimensional curves were developed and presented to show the variation of scour depth with relevant parameters obtained in the dimensional analysis. Results of the study were compared to those obtained from a similar study performed with single inclined piers to see the effect of the second pier on scour depths. Useful equations for the design engineers were developed based on multiple regression analyses, to be used for predicting local scour depths around vertical and (or) inclined piers in uniform and (or) nonuniform sediments. Normalized scour depths measured around the vertical piers in the present study were compared with those computed by an equation suggested by Melville and Sutherland (1988), and also by an equation developed in the present study.

Clear-water local scour at wide piers in shallow-water flow

2014 ◽  
Vol 9 (3) ◽  
pp. 331-343 ◽  
Author(s):  
N. Ahmad ◽  
T. Mohamed ◽  
F. H. Ali ◽  
B. Yusuf
Keyword(s):  
Laboratory Data ◽  
Local Scour ◽  
The Other ◽  
Scour Depth ◽  
Temporal Development ◽  
Clear Water ◽  
Shallow Water Flow ◽  
Equilibrium Time ◽  
Sediment Size ◽  
Flow Intensity

Laboratory data for local scour depth regarding the size of wide piers are presented. Clear water scour tests were performed for various pier widths (0.06, 0.076, 0.102, 0.14 and 0.165 m), two types of pier shapes (circular and rectangular) and two types of uniform cohesionless bed sediment (d50 = 0.23 and d50 = 0.80 mm). New data are presented and used to demonstrate the effects of pier width, pier shape and sediment size on scour depth. The influence of equilibrium time (te) on scouring processes is also discussed. Equilibrium scour depths were found to decrease with increasing values of b/d50. The temporal development of equilibrium local scour depth with new laboratory data is demonstrated for flow intensity V/Vc = 0.95. On the other hand, the results of scour mechanism have shown a significant relationship between normalized volume of scoured and deposited with pier width, b. The experimental data obtained in this study and data available from the literature for wide piers are used to evaluate predictions of existing methods.

scholarly journals Investigation of local scour around tandem piers for different skew-angles

2018 ◽  
Vol 40 ◽  
pp. 03008 ◽  
Author(s):  
Sargol Memar ◽  
Mohammad Zounemat-Kermani ◽  
Ali-Asghar Beheshti ◽  
Giovanni De Cesare ◽  
Anton J. Schleiss
Keyword(s):  
Flow Direction ◽  
Local Scour ◽  
Scour Depth ◽  
Skew Angle ◽  
Approach Velocity ◽  
Sheltering Effect ◽  
Skew Angles

In the present study the effect of the skew-angle of the alignment of tandem piers on local scour depth around them is investigated. The tandem piers were aligned with different skew-angles of θ=0°,30°,45°,60°,90° with respect to the flow direction. The results indicatethat with the increment of the skew-angle, the influence of sheltering effects is decreased. In other word, since the sheltering effect of the upstream pier is declined (which reduces the approach velocity for the downstream pier) the scour depth around downstream pier increases. The results show that the maximum scour depth occurs at both piers for the skew-angle of θ=45°.Furthermore, the best configuration to aligned tandem piers was achieved at the skew-angle of θ=30°.

scholarly journals Scour around Bridge Piers: Numerical Investigations of the Longitudinal Biconcave Pier Shape

2018 ◽  
Vol 62 (4) ◽  
pp. 298-304 ◽  
Author(s):  
Bouabdellah Guemou ◽  
Abdelali Seddini ◽  
Abderrahmane Nekkache Ghenim
Keyword(s):  
Shear Stress ◽  
Flow Direction ◽  
Basic Mechanism ◽  
Horseshoe Vortex ◽  
Local Scour ◽  
Bridge Pier ◽  
Bed Shear Stress ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
The Rich

The flow pattern around a bridge pier and the scouring phenomenon are very complicated. The basic mechanism causing local scour is the down-flow at the upstream face of the pier. It is understood that the horseshoe vortex is the key mechanism that leads to the local scour around pier; existing literature revealed that the strength of the down-flow, horseshoe vortex and the wake vortex are greater in the case of square piers compared to circular piers. In this paper we have investigated a new longitudinal biconcave bridge pier shape that reduces better the bed shear stress. For that purpose, a number of numerical simulations have been carried out using a Finite Volume Method (FVM) and for the turbulence model we have chosen the Detached Eddy Simulation (DES) for its capability to capture the rich dynamics of the horseshoe vortex at the upstream junction between the pier and the bed.The present study shows that the new longitudinal biconcave bridge pier shape reduces 10 % to 12 % the bed shear stress at the junction between the pier and the bed in other hand this shape increases the bed shear stress about 20 % but at a distance of D downstream the bridge pier in the flow direction.

scholarly journals Reduction of Local Scour Around A Bridge Pier Using Triple Rectangular Plates

2015 ◽  
Vol 10 (Special-Issue1) ◽  
pp. 47-55 ◽  
Author(s):  
Alireza Arabani ◽  
Human Hajikandi
Keyword(s):  
Water Flow ◽  
Flow Direction ◽  
Side Wall ◽  
Local Scour ◽  
Maximum Efficiency ◽  
Rectangular Plates ◽  
Clear Water ◽  
The Third ◽  
Different Depths ◽  
Lateral Plates

The performance of vertical triple plates as a new countermeasure in control of local scour around a cylindrical model pier is studied. Two ones of the plates are attached to the side wall one of the pier at one pier diameter distance, extending toward upstream distance and the third one is located in the middle, attached to the pier nose. All the three plates are parallel to flow direction. Experiments are conducted for five different depths of flow and two different lengths of the lateral plates, namely 8 and 14 cm. all the runs are performed under the clear water flow over uniform sediment. The results showed a maximum efficiency of 76% in scour reduction for 8 cm long side plates and 85% for 14 cm long ones.it is also found that the proposed setup act simultaneously as both the bed armoring and flow altering countermeasure.

Effect of Reynolds Number on Local Scour Around a Monopile in Steady Current

2019 ◽  
Author(s):  
Xiaofan Lou ◽  
Kaibing Zhang ◽  
Zhenhong Chen
Keyword(s):  
Reynolds Number ◽  
Time Scale ◽  
Time History ◽  
Local Scour ◽  
Circular Cylinders ◽  
Scour Depth ◽  
Clear Water ◽  
Number Range ◽  
Steady Current ◽  
Equilibrium Scour Depth

Abstract The effect of Reynolds number (Re) on the local scour around a monopile encountering steady current was investigated experimentally in a water flume. The experiment was performed using circular cylinders with different diameters under two different freestream velocities, covering both clear-water and live-bed scours and a Reynolds number range of approximately 9,000–60,000. The time-series of the scour depth was recorded during the whole scour process and the scour pit was scanned after the scour process reached equilibrium. Results are presented in terms of the equilibrium scour depth, the time-scale of the scour process and the three-dimensional scour profile at different Reynolds numbers. For both clear-water and live-bed scours, the time history of the scour process indicate that the time-scale becomes larger as Re increases. It is also found that the normalized equilibrium scour depth, as well as the normalized scour radius, decrease with the increasing Re. An empirical equation of the equilibrium scour depth is derived as a function of Reynolds number based on the experimental results so as to better account for Re effect in the scour design.

scholarly journals Optimal Octagonal Hooked Collar Countermeasure to Reduce Scour Around a Single Bridge Pier

2020 ◽  
Author(s):  
Rashid Farooq ◽  
Abdul Razzaq Ghumman ◽  
Muhammad Atiq Ur Rehman Tariq ◽  
Afzal Ahmed ◽  
Khan Zaib Jadoon
Keyword(s):  
Cross Section ◽  
Vital Role ◽  
Bridge Pier ◽  
Scour Depth ◽  
Clear Water ◽  
Action Current ◽  
Pier Scour ◽  
Uniform State ◽  
Scour Hole ◽  
New Equation

Pier modification countermeasures are essential as they play a vital role in protecting pier against local scour action. Current study investigates experimentally the scour around vertical pier of octagonal cross section with pier modification such as newly proposed octagonal hooked collar is explored, in steady uniform state, under clear water condition. The results of pier scour without any modification were used as a reference to compute the efficiency of hooked collar provision around octagonal pier. The results show that by increasing the hooked collar width up to 2.5 Wp reduced maximum scour depth significantly. However, the experimental investigation revealed that the best combination to be with a hooked collar width of 2.5 Wp, having sidewall height 0.45 Wp. The best combination minimized around 73.3 % of scour hole depth, compared to octagonal pier without any modification. Using experimental results, a new equation is proposed to predict the scour depth around a bridge pier fitted with hooked collar. Moreover, a relation was developed for maximum scour depth and scour hole volume. Results indicate that the scour hole volume around a bridge pier increases quadratically with maximum scour depth.

Aerothermal Characterization of a Rotating Ribbed Channel at Engine Representative Conditions: Part II — Detailed LCT Measurements

2015 ◽  
Author(s):  
Ignacio Mayo ◽  
Aude Lahalle ◽  
Gian Luca Gori ◽  
Tony Arts
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Cross Section ◽  
Flow Direction ◽  
Channel Cross Section ◽  
Wall Region ◽  
Static Case ◽  
Ribbed Channel ◽  
Static Conditions

The present two-part work deals with a detailed characterization of the flow field and heat transfer distribution in a model of a rotating ribbed channel performed in a novel setup which allows test conditions at high Rotation numbers (Ro). The tested model is mounted on a rotating frame with all the required instrumentation, resulting in a high spatial resolution and accuracy. The channel has a cross section with an aspect ratio of 0.9 and a ribbed wall with 8 ribs perpendicular to the main flow direction. The blockage of the ribs is 10% of the channel cross section, whereas the rib pitch to height ratio is 10. In this second part of the study, the heat transfer distribution over the wall region between the 6th and 7th ribs is obtained by means of Liquid Crystal Thermography (LCT). Tests were firstly carried out at a Reynolds number of 15000 and a maximum Ro of 1.00 to evaluate the evolution of the heat transfer with increasing rotation. On the trailing side, the overall Nusselt number increases with rotation until a limit value a 50% higher than in the static case, which is achieved after a value of the Rotation number of about 0.3. On the leading side, the overall Nusselt number decreases with increasing rotation speed to reach a minimum which is approximately 50% of the one found in static conditions. The velocity measurements at Re=15000 and Ro=0.77 provided in Part I of this paper are finally merged to provide a consistent explanation of the heat transfer distribution in this model. Moreover, heat transfer measurements were performed at Reynolds numbers of 30000 and 55000, showing approximately the same trend.

scholarly journals A laboratory study of the effect of asymmetric-lattice collar shape and placement on scour depth and flow pattern around the bridge pier

2021 ◽  
Author(s):  
Narges Raeisi ◽  
Mehdi Ghomeshi
Keyword(s):  
Flow Pattern ◽  
Flow Characteristics ◽  
Bridge Pier ◽  
Scour Depth ◽  
Front Part ◽  
Clear Water ◽  
Scouring Depth ◽  
Level 1 ◽  
Downstream Flow ◽  
The Cost

Abstract In this study, the effect of collar shape and its alignment on reducing scour depth in the front part of the structure, with the pier under clear water conditions, was investigated to determine changes in the flow pattern around the structure. The collars were examined in two asymmetrical shapes with dimensions of and at three levels of installation relative to the bed: bed level, 1 and 2 cm above the bed. The results revealed that the presence of the collar not only reduced the ultimate scouring depth but also delayed the formation of the scouring hole. This impact was observed to be greater as the size of the collar increased. In addition, reducing the alignment of the collars can lead to better performance of the collar and its efficiency in the cost of the design. Therefore, collars installed on the bed surface indicated good performance in controlling scour. On the other hand, once the flow characteristics around the bridge pier with and without collar were examined, it was determined that affecting the downstream flow reduces the strength of the vortices and changes the reciprocating behavior and the displacement of the vortices.

Numerical investigation on the effect of bluntness factor on scouring mechanism by using lenticular geometry piers

2020 ◽  
Vol 47 (3) ◽  
pp. 279-290
Author(s):  
Yousef Hassanzadeh ◽  
Milad Khosravi ◽  
Nazila Kardan
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Flow Separation ◽  
Width Ratio ◽  
Scour Depth ◽  
Clear Water ◽  
Eddy Simulation ◽  
Water State ◽  
Large Eddy ◽  
Scouring Process

Local scour and flow field around cylinders with lenticular geometry and different bluntness factors under the clear-water state were investigated numerically. To examine the scouring, large eddy simulation with a WMLES-Omega sub-grid model incorporating the sediment transport and morphodynamic model was applied. Streamlined geometry of the pier significantly affected the scour pattern and flow field in the lenticular model with length to width ratio of 5 and bluntness factor of zero. In the mentioned case, a very small scoured region was estimated at the sides of the pier, so it can be concluded that scour depth and scoured region decreases as the length to width ratio increases. Investigation of the scouring process and the flow field revealed that, the flow separation can affect the scour mechanism more in comparison to down-flow.

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