Effect of bridge pier induced turbulence on vegetated meander river morphology

2021 ◽  
Author(s):  
Suresh Modalavalasa ◽  
Vinay Chembolu ◽  
Ketan Kumar Nandi ◽  
Vinayak Kulkarni ◽  
Subashisa Dutta
Keyword(s):  
Transverse Velocity ◽  
Three Dimensional ◽  
Main Channel ◽  
Bridge Pier ◽  
Bridge Piers ◽  
Turbulent Structures ◽  
Meandering Channel ◽  
Turbulent Characteristics ◽  
Sinuous Channel ◽  
The Difference

<p>A natural riverine corridor has several curls based on its physical and geomorphological characteristics. In most of the scenarios, the bridge construction on a meandering channel aligns along the convergent section. The enhanced secondary flow at convergent sections and the effect of meandering curvature bring the complexity in river turbulent characteristics. This effect may become predominant inside the main channel with variability in size and shape of the bridge pier. The present work discusses the turbulent structures in the main channel due to the variability in pier diameter (1inch and 2 inch ϕ) and a number of bridge piers on floodplain with inclusive of vegetation. Three-dimensional flow vertical and transverse velocity measurements were carried with acoustic Doppler velocimeter (ADV) 100Hz, at apex cross-section in a low sinuous channel. The results of the analysis showed that the combined effect of pier and vegetation on floodplain significantly altered the shear layer mechanisms in the channel with varying flow patterns. The comparison of the difference in secondary velocities between the pier with 1 inch and 2 inch ϕ  is 57% more in the case of lesser diameter pier. Further, the effect of size and number of piers on transverse velocity, Reynold’s shear stress is more susceptible to the mainstream. The convergence induced contraction of the meandering channel along with the bridge pier on its floodplain is observed to affect the turbulent structures formed in the main channel.</p>

scholarly journals Turbulent Characteristics and Air Entrainment Patterns in Breaking Surge Waves

Fluids ◽  
2021 ◽  
Vol 6 (12) ◽  
pp. 422
Author(s):  
Zhuoran Li ◽  
Akash Venkateshwaran ◽  
Shooka Karimpour
Keyword(s):  
Sudden Change ◽  
Three Dimensional ◽  
Air Entrainment ◽  
Quadrant Analysis ◽  
Concentration Profiles ◽  
Air Concentration ◽  
Turbulent Structures ◽  
Eddy Simulation ◽  
Turbulent Characteristics ◽  
3D Flows

Breaking surge waves are highly turbulent three-dimensional (3D) flows, which occur when the water flow encounters a sudden change in depth or velocity. The 3D turbulent structures across a breaking surge are induced by the velocity gradient across the surge and phase discontinuity at the front. This paper examined the turbulent structures in breaking surge waves with Froude numbers of 1.71 and 2.13 by investigating the air entrainment and perturbation patterns across the surge front. A combination of the Volume Of Fluid (VOF) method and Large Eddy Simulation (LES) was utilized to capture air entrainment and turbulent structures simultaneously. The 3D nature of the vortical structures was simulated by implementing a spanwise periodic boundary. The water surface perturbation and air concentration profiles were extracted, and the averaged air concentration profiles obtained from the numerical simulations were consistent with laboratory observations reported in the literature. The linkage between turbulent kinetic energy distribution and air entrainment was also explored in this paper. Finally, using quadrant analysis and the Q-criterion, this paper examined the role of the spanwise perturbations in the development of turbulent structures in the surge front.

scholarly journals Velocity profiles and turbulence intensities around side-by-side bridge piers under ice-covered flow condition

2020 ◽  
Vol 68 (1) ◽  
pp. 70-82
Author(s):  
Mohammad Reza Namaee ◽  
Jueyi Sui
Keyword(s):  
Flow Condition ◽  
Three Dimensional ◽  
Velocity Profiles ◽  
Local Scour ◽  
Bridge Piers ◽  
Scour Depth ◽  
Measured Velocity ◽  
Acoustic Doppler Velocimetry ◽  
The Difference ◽  
Do So

AbstractRecent studies have shown that the presence of ice cover leads to an intensified local scour pattern in the vicinity of bridge piers. To investigate the local scour pattern in the vicinity of bridge pier under ice-covered flow condition comparing to that under open channel flow condition, it is essential to examine flow field around bridge piers under different flow conditions. In order to do so, after creation of smooth and rough ice covers, three-dimensional timeaveraged velocity components around four pairs of bridge piers were measured using an Acoustic Doppler velocimetry (ADV). The ADV measured velocity profiles describe the difference between the velocity distributions in the vicinity of bridge piers under different covered conditions. Experimental results show that the vertical velocity distribution which represents the strength of downfall velocity is the greatest under rough covered condition which leads to a greater scour depth. Besides, results show that the turbulent intensity increases with pier size regardless of flow cover, which implies that larger scour depth occurs around piers with larger diameter.

Reduction of local scour around a bridge pier by using different shapes of pier slots and collars

2020 ◽  
Vol 20 (3) ◽  
pp. 1006-1015 ◽  
Author(s):  
A. Bestawy ◽  
T. Eltahawy ◽  
A. Alsaluli ◽  
A. Almaliki ◽  
M. Alqurashi
Keyword(s):  
Three Dimensional ◽  
Laser Scanner ◽  
Local Scour ◽  
Bridge Pier ◽  
Bridge Piers ◽  
Scour Depth ◽  
Contour Maps ◽  
Reduction Methods ◽  
Analysis System ◽  
Bridge Failure

Abstract Local scour around bridge piers is one of the main causes of bridge failure all over the world. Experimental and hydraulic models were carried out to investigate two types of scour reduction methods around a single cylindrical pier, namely the pier's slots and collars. The efficiency of various types of pier slots and circular collars around the pier's base in reducing scour were studied. A new shape of a conical collar was developed by the authors and examined along with other shapes. The results revealed that collars, in general, have more influence in reducing scour depth than slots made in the front and rear of bridge piers. The sigma-slot acts better than other tested slots, with a reduction in the scour depths of 59.3% and 52.8% at the upstream and downstream of the pier, respectively. On the other hand, the conical collar appeared to be the most effective collar shape in reducing the scour around the bridge pier, with a 61.1% reduction in the scour depth downstream of the pier. A three-dimensional laser scanner was used to capture the bed topography at the end of each experiment and contour maps of the deformed bed were produced. A one-dimensional Hydrologic Engineering Center-River Analysis System model was developed with a single bridge pier to predict the scour depth around the pier in an attempt to introduce new values for the pier nose shape factor, , which describes the tested piers.

scholarly journals CFD Simulation of Local Scouring Around Bridge Pier

2019 ◽  
Vol 9 (1) ◽  
pp. 1870-1880
Keyword(s):  
Cfd Simulation ◽  
Flow Behavior ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Local Scour ◽  
Bridge Pier ◽  
Bridge Piers ◽  
Multiphase Model ◽  
Model Studies ◽  
Dimensional Simulation

The threat of local scour around bridge piers has been in research for many years. According to the various studies, local scour around the bridge pier is the prime cause for most of the bridge failures. The main objective of the present study was to investigate the flow behavior and the scour phenomenon around the bridge piers of various shapes namely Circular, Elliptical, Square and Streamlined. Local scouring depends on various factors like depth of flow, upstream flow conditions, pier shape and dimensions. Here, we have taken only pier shape as the primary factor and kept other factors constant. The numerical simulations were even carried out using CFDFluent, Eulerian multiphase model, k–epsilon turbulence model, to elaborate the physics behind the scour formation. CFD simulation tool can be used for wide understanding of the flow behavior around the bridge piers even without physical model studies because it saves time and money as compared to experimental studies. Three dimensional simulation of flow behavior around four pier shapes indicates that the streamlined pier is the most efficient pier to use as it allows the flow to pass smoothly around it creating less obstruction to the flow and hence creating less chances of local scouring near the pier toe.

scholarly journals Effect of Meander on Bridge Pier Scour

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Mohammad Athar ◽  
M.K. Sabiree ◽  
H. Athar
Keyword(s):  
Angular Displacement ◽  
Bridge Pier ◽  
Bridge Piers ◽  
Bend Angle ◽  
Test Bed ◽  
Pier Scour ◽  
Meandering Channel ◽  
Channel Bend ◽  
Constant Diameter ◽  
Bridge Pier Scour

Lots of work regarding the scour around bridge piers in straight channelhave been done in the past by many researchers. Many factors which affectscour around piers such as shape of piers, size, positioning and orientationetc. have been studied in detail by them. However, similar studies inmeandering channels are scanty. Very few researchers have studied theeffect of angular displacement which has considerable effects of scouraround bridge piers.In this paper an attempt has been made to carry out a detailed study ofangular displacement on scour. A constant diameter bridge pier of circularshape has been tested in a meandering channel bend with bend angle as 800 .The test bed was prepared by using uniform sand having d50 as 0.27 mmand run was taken for a discharge of 2.5 l/s.

Defocus ramp correction in spot-scan imaging

1992 ◽  
Vol 50 (1) ◽  
pp. 130-131
Author(s):  
Kenneth H. Downing
Keyword(s):  
Computer Control ◽  
Three Dimensional ◽  
Sufficient Accuracy ◽  
Objective Lens ◽  
Electron Crystallography ◽  
Contrast Transfer Function ◽  
Tilt Axis ◽  
Specimen Height ◽  
The Difference ◽  
Envelope Functions

Three-dimensional structures of a number of samples have been determined by electron crystallography. The procedures used in this work include recording images of fairly large areas of a specimen at high tilt angles. There is then a large defocus ramp across the image, and parts of the image are far out of focus. In the regions where the defocus is large, the contrast transfer function (CTF) varies rapidly across the image, especially at high resolution. Not only is the CTF then difficult to determine with sufficient accuracy to correct properly, but the image contrast is reduced by envelope functions which tend toward a low value at high defocus.We have combined computer control of the electron microscope with spot-scan imaging in order to eliminate most of the defocus ramp and its effects in the images of tilted specimens. In recording the spot-scan image, the beam is scanned along rows that are parallel to the tilt axis, so that along each row of spots the focus is constant. Between scan rows, the objective lens current is changed to correct for the difference in specimen height from one scan to the next.

Simulation of Three-Dimensional Flow Field Around Unconventional Bridge Piers

2017 ◽  
Author(s):  
Adnan Ismael ◽  
Hamid Hussein ◽  
Mohammed Tareq ◽  
Mustafa Gunal
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Bridge Piers ◽  
Three Dimensional Flow ◽  
Dimensional Flow

The iron content of iron superoxide dismutase: determination by anomalous scattering

1983 ◽  
Vol 218 (1210) ◽  
pp. 119-126 ◽  
Keyword(s):  
Superoxide Dismutase ◽  
Iron Content ◽  
Three Dimensional ◽  
Anomalous Scattering ◽  
Total Iron Content ◽  
Iron Site ◽  
Iron Superoxide Dismutase ◽  
Density Map ◽  
The Difference ◽  
Electron Density Map

The number of iron atoms in the dimeric iron-containing superoxide dismutase from Pseudomonas ovalis and their atomic positions have been determined directly from anomalous scattering measurements on crystals of the native enzyme. To resolve the long-standing question of the total amount of iron per molecule for this class of dismutase, the occupancy of each site was refined against the measured Bijvoet differences. The enzyme is a symmetrical dimer with one iron site in each subunit. The iron position is 9 ņ from the intersubunit interface. The total iron content of the dimer is 1.2±0.2 moles per mole of protein. This is divided between the subunits in the ratio 0.65:0.55; the difference between them is probably not significant. Since each subunit contains, on average, slightly more than half an iron atom we conclude that the normal state of this enzyme is two iron atoms per dimer but that some of the metal is lost during purification of the protein. Although the crystals are obviously a mixture of holo- and apo-enzymes, the 2.9 Å electron density map is uniformly clean, even at the iron site. We conclude that the three-dimensional structures of the iron-bound enzyme and the apoenzyme are identical.

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