Discussion of “Secondary Flow and Shear Stress at River Bends”

1980 ◽  
Vol 106 (10) ◽  
pp. 1710-1710
Author(s):  
Werner Götz
Keyword(s):  
Shear Stress ◽  
Secondary Flow ◽  
River Bends

Closure to “Secondary Flow and Shear Stress at River Bends”

1981 ◽  
Vol 107 (5) ◽  
pp. 644-644
Author(s):  
James C. Bathurst ◽  
Richard D. Hey ◽  
Colin R. Thorne
Keyword(s):  
Shear Stress ◽  
Secondary Flow ◽  
River Bends

Secondary Flow and Shear Stress at River Bends

1979 ◽  
Vol 105 (10) ◽  
pp. 1277-1295 ◽  
Author(s):  
James C. Bathurst ◽  
Richard D. Hey ◽  
Colin R. Thorne
Keyword(s):  
Shear Stress ◽  
Secondary Flow ◽  
River Bends

scholarly journals A Review of Numerical Simulations of Secondary Flows in River Bends

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 884
Author(s):  
Rawaa Shaheed ◽  
Abdolmajid Mohammadian ◽  
Xiaohui Yan
Keyword(s):  
Numerical Modeling ◽  
Numerical Simulations ◽  
Secondary Flow ◽  
Cross Section ◽  
Turbulence Models ◽  
Main Flow ◽  
Secondary Flows ◽  
River Bends ◽  
River Cross Section ◽  
River Bend

River bends are one of the common elements in most natural rivers, and secondary flow is one of the most important flow features in the bends. The secondary flow is perpendicular to the main flow and has a helical path moving towards the outer bank at the upper part of the river cross-section, and towards the inner bank at the lower part of the river cross-section. The secondary flow causes a redistribution in the main flow. Accordingly, this redistribution and sediment transport by the secondary flow may lead to the formation of a typical pattern of river bend profile. It is important to study and understand the flow pattern in order to predict the profile and the position of the bend in the river. However, there are a lack of comprehensive reviews on the advances in numerical modeling of bend secondary flow in the literature. Therefore, this study comprehensively reviews the fundamentals of secondary flow, the governing equations and boundary conditions for numerical simulations, and previous numerical studies on river bend flows. Most importantly, it reviews various numerical simulation strategies and performance of various turbulence models in simulating the flow in river bends and concludes that the main problem is finding the appropriate model for each case of turbulent flow. The present review summarizes the recent advances in numerical modeling of secondary flow and points out the key challenges, which can provide useful information for future studies.

scholarly journals Diagnosis of Erodible Locations in River Bends Using a Combined Method (GIS, RS and the CCHE2D Model) (Case Study: The Karkheh River in Iran)

2018 ◽  
Vol 26 (4) ◽  
pp. 78-88 ◽  
Author(s):  
Arash Adib ◽  
Hamid Reza Gafouri ◽  
Ali Liaghat
Keyword(s):  
Shear Stress ◽  
Maximum Shear Stress ◽  
Combined Method ◽  
Model Case ◽  
River Bends ◽  
The Karkheh River ◽  
River Bend

Abstract In this research, a combined method was developed to determine the erodibility of bends in the Karkheh River. For this purpose, a 40 km reach of the Karkheh River downstream of the Karkheh Dam was considered. The value of the shear stress was the calculated using the CCHE2D model. The results from the model show that in 1996 (before construction of the Karkheh dam), the length of the erodible reach was 1314 m; in 2011 (after construction of the Karkheh dam), this length was reduced to 840 m. Furthermore, the model illustrates that the location of the maximum shear stress is a function of the relative curvature (R/W) in the bends. For small values of the R/W (less than 1.5), the maximum shear stress occurs on the convex bank of a river bend. By increasing the R/W, the location of the maximum shear stress transfers to the concave bank of the river bend. Also, this location is displaced towards downstream by increasing the R/W.

scholarly journals Secondary Flow Development Downstream of a Blade Endwall Corner

1994 ◽  
Author(s):  
A. Karim Abdulla-Altaii ◽  
Rishi S. Raj
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Flat Plate ◽  
Secondary Flow ◽  
Total Pressure ◽  
Static Pressure ◽  
Horseshoe Vortex ◽  
Chord Length ◽  
Trailing Edge

The flow downstream of the corner formed by a blade and a flat plate was investigated experimentally. A single dominant horseshoe vortex was identified which persisted more than one chord length downstream of the blade trailing edge. A smaller and weaker corner vortex was also identified. It dissipated and ceased to exist by a downstream axial location of approximately 0.2C (C= chord length). There was no evidence of stress induced vortices in the region of this investigation. The secondary flow system redistributes the mean flow momentum and distorts total pressure profiles and contours. In planes parallel to the flat plate, total pressure values were found to be higher than the undisturbed two-dimensional boundary layer at that height. Surface static pressure was found to be at its maximum at the blade trailing edge location and it decreased in both the downstream and transverse directions. There was no significant static pressure variation in the spanwise direction. Downstream of the blade trailing edge, under the domain of the horseshoe vortex, local wall shear stress increased to values exceeding the values found in the undisturbed boundary layer at that axial location. However, a 20% reduction in the net wall skin-friction (wall shear stress integrated over the flat plate surface) was observed.

Investigation of the Effects of Dynamic Change in Curvature and Torsion on Pulsatile Flow in a Helical Tube

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
N. K. C. Selvarasu ◽  
Danesh K. Tafti
Keyword(s):  
Shear Stress ◽  
Coronary Artery ◽  
Wall Shear Stress ◽  
Secondary Flow ◽  
Pulsatile Flow ◽  
Flow Patterns ◽  
Shear Stresses ◽  
Wall Shear ◽  
Vorticity Flux ◽  
Curvature And Torsion

Cardiovascular diseases are the number one cause of death in the world, making the understanding of hemodynamics and the development of treatment options imperative. The effect of motion of the coronary artery due to the motion of the myocardium is not extensively studied. In this work, we focus our investigation on the localized hemodynamic effects of dynamic changes in curvature and torsion. It is our objective to understand and reveal the mechanism by which changes in curvature and torsion contribute towards the observed wall shear stress distribution. Such adverse hemodynamic conditions could have an effect on circumferential intimal thickening. Three-dimensional spatiotemporally resolved computational fluid dynamics (CFD) simulations of pulsatile flow with moving wall boundaries were carried out for a simplified coronary artery with physiologically relevant flow parameters. A model with stationary walls is used as the baseline control case. In order to study the effect of curvature and torsion variation on local hemodynamics, this baseline model is compared to models where the curvature, torsion, and both curvature and torsion change. The simulations provided detailed information regarding the secondary flow dynamics. The results suggest that changes in curvature and torsion cause critical changes in local hemodynamics, namely, altering the local pressure and velocity gradients and secondary flow patterns. The wall shear stress (WSS) varies by a maximum of 22% when the curvature changes, by 3% when the torsion changes, and by 26% when both the curvature and torsion change. The oscillatory shear stress (OSI) varies by a maximum of 24% when the curvature changes, by 4% when the torsion changes, and by 28% when both the curvature and torsion change. We demonstrate that these changes are attributed to the physical mechanism associating the secondary flow patterns to the production of vorticity (vorticity flux) due to the wall movement. The secondary flow patterns and augmented vorticity flux affect the wall shear stresses. As a result, this work reveals how changes in curvature and torsion act to modify the near wall hemodynamics of arteries.

scholarly journals Mechanism for initiating secondary currents in channel flows

2009 ◽  
Vol 36 (9) ◽  
pp. 1506-1516 ◽  
Author(s):  
Shu-Qing Yang
Keyword(s):  
Shear Stress ◽  
Secondary Flow ◽  
Flow Region ◽  
Streamwise Velocity ◽  
Vortex Center ◽  
Duct Flow ◽  
Secondary Currents ◽  
Total Shear Stress ◽  
Underlying Mechanisms ◽  
Total Shear

This study investigates the underlying mechanisms that initiate secondary flow in developing turbulent flow along a corner. This is done by theoretical examination of the total shear stress, which is the time-averaged product of instantaneous streamwise velocity U and the velocity Vn normal to the interface. The study shows that lines of zero total shear stress exist in the flow region, which delineate the region of secondary flow. Therefore, the flow region is dividable and eight vortices occur in a duct flow. The theoretical and experimental results show that the division line, separating the neighboring secondary currents in a corner, is not always identical to the bisector of the corner, but deviates from the corner bisector if the aspect ratio is b/h ≠ 1. By simplifying Reynolds equation in the near-bed region, we find that theoretically a lateral variation of streamwise velocity initiates the wall-tangent flow that drives the vortex in the region bounded by zero total shear stress. A simplified method for estimating the vortex center, near-bed secondary velocity, and shape of secondary currents has been proposed, and a good agreement between the measured and predicted features is achieved.

scholarly journals ANALYSIS OF CHARACTERISTICS OF SEVERAL BENDS ON SIDOAN RIVER

2021 ◽  
Vol 8 (4) ◽  
pp. 46-57
Author(s):  
Rinawati ◽  
M. Galib Ishak ◽  
Rudi Herman
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Shear Velocity ◽  
High Water ◽  
Sliding Velocity ◽  
Hydraulic Simulation ◽  
Velocity Relationship ◽  
Riverbed Sediment ◽  
River Bends ◽  
The Stability

Researching the behavior of the river. Especially at the bend, where the morphology of the river is not always straightforward. Flow velocity high water and grinding at river bends occur at different points. This research was conducted on five adjacent bends on the Sidoan River section. This study examined the condition of riverbed sediment, knowing the stability of riverbed sediment granules based on shearing velocity, and stability of riverbed sediment granules based on shear stress. The method used in this study is geometric measurement. Q50 discharge calculation. produces hydraulic simulation. d50 sediment diameter. HEC-RAS software simulation and Shields graphs analysis. The results of the study on five bends for Q50 discharge are the condition of the riverbed in five bends all moving, the critical shear velocity relationship and flow depth are directly proportional, the highest condition at bend 2, otherwise the lowest condition at bend 3. The relationship between particle dimensions and shear velocity is inversely proportional to the value of sliding velocity. if the particle dimensions are small then the large shear stress occurs at bend 5 and vice versa, the dimensions of large particles then the small shear velocity occurs at bend 4, sliding velocity is directly proportional to the shear stress. The highest critical shear stress at bend 2, while the lowest condition at bend 4, the greater the radius of the bend the scouring was deeper.

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