Reducing bend scour using in-phase and out-of-phase hydraulic jets

2019 ◽  
Vol 19 (5) ◽  
pp. 1446-1453
Author(s):  
Zeinab Tamoradi ◽  
Javad Ahadiyan ◽  
Mohsen Najarchi ◽  
Houshang Hasounizadeh ◽  
Mohammad Mahdi Najafizadeh
Keyword(s):  
Outer Wall ◽  
Water Jet ◽  
Secondary Flows ◽  
Scour Depth ◽  
Jet Injection ◽  
Air Jet ◽  
Bend Flow ◽  
River Bends ◽  
Injection Modes ◽  
Optimal Effect

Abstract This study investigated the effectiveness of a new method of reducing scour in river bends. In this method, a perforated tube was placed along the bend on the bed and water and air were separately injected into the bend flow from both ends of the tube. The goal was to make a water and air screen to block secondary flows and prevent them from reaching the outer bank. The air jet and water jet injection modes changed the location of maximum scour depth from the outer wall to the middle of the bend, which increased the navigable width. Increasing the spacing between tube ports decreased the maximum scour depth. A port spacing of 5 cm was determined to be the optimal amount. At a bend section of 90°, the decrease in maximum scour depth was estimated to be 85% and 91% under air jet injection (qa/Q = 2.74) and water jet injection (qw/Q = 0.17), respectively. At 170°, the decrease in maximum scour depth was 79% and 86% for the air jet and water jet, respectively. The results show that the optimal effect was obtained by water jet injection.

Effect of water and air injection on reduction of bend scour

2020 ◽  
Author(s):  
Zeinab Tamoradi ◽  
Javad Ahadiyan
Keyword(s):  
Outer Wall ◽  
Secondary Flows ◽  
Experimental Results ◽  
Air Injection ◽  
The Other ◽  
Scour Depth ◽  
Rigid Barrier ◽  
Effect Of Water ◽  
Bend Flow ◽  
Perforated Tube

In the proposed method, air and water were injected into the 180° bend flow from both sides of a perforated tube to overcome curvature-induced secondary flows by creating a non-rigid barrier. The experimental results showed that the secondary flows were deviated from the outer bend causing a reduction in the maximum scour depth along the bend. The navigable width may also be increased by shifting the maximum scour depth from the outer wall to the centerline. On the other hand, the maximum scour depth was reduced by decreasing the distance between the perforated tube and the outer wall. For example, the maximum scour depth in the water and air injection main experiments at 130° section of the bend and two tube distances of 2.5 cm and 5 cm decreased by 88%, 91%, 63% and 45%, respectively. With the increase in the Froude numbers, the maximum scour depth has increased.

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.

Influence of runner cone profile and axial water jet injection in a low head Francis turbine at part load

2022 ◽  
Vol 50 ◽  
pp. 101810
Author(s):  
Subodh Khullar ◽  
Krishna M. Singh ◽  
Michel J. Cervantes ◽  
Bhupendra K. Gandhi
Keyword(s):  
Water Jet ◽  
Francis Turbine ◽  
Jet Injection ◽  
Part Load ◽  
Low Head

scholarly journals Suppression of Mixed-Flow Pump Instability and Surge by the Active Alteration of Impeller Secondary Flows

1993 ◽  
Author(s):  
Akira Goto
Keyword(s):  
Flow Characteristic ◽  
Secondary Flows ◽  
Wake Flow ◽  
Streamwise Vorticity ◽  
Jet Injection ◽  
Positive Slope ◽  
Suction Surface ◽  
Mixed Flow ◽  
Pump System ◽  
Flow Pump

An active method for enhancing pump stability, featuring water jet injection at impeller inlet, was applied to a mixed-flow pump. The stall margin, between the design point and the positive slope region of the head-flow characteristic, was most effectively enlarged by injecting the jet in the counter-rotating direction of the impeller. The counter-rotating streamwise vorticity along the casing, generated by the velocity discontinuity due to the jet injection, altered the secondary flow pattern in the impeller by opposing the passage vortex and assisting the tip leakage vortex motion. The location of the wake flow was displaced away from the casing-suction surface corner of the impeller, thus avoiding the onset of the extensive corner separation, the cause of positive slope region of the head-flow characteristic. This method was also confirmed to be effective for stabilizing a pump system already in a state of surge.

Two-Dimensional Miter-Bend Flow

1971 ◽  
Vol 93 (3) ◽  
pp. 433-443 ◽  
Author(s):  
G. Heskestad
Keyword(s):  
Reynolds Number ◽  
Constant Width ◽  
Outer Wall ◽  
Two Dimensional ◽  
Mean Flow ◽  
Internal Flows ◽  
Concave Corner ◽  
Reynolds Number Effects ◽  
Bend Flow ◽  
The Mean

Measurements have been made of the mean flow in a two-dimensional, constant-width, ninety-degree miter bend and compared with predictions of available free-streamline theories. Agreement is quite favorable, especially with a model incorporating separation ahead of the concave corner. Reynolds number effects observed in real flows are argued to be associated with changes in the location of the outer-wall separation point. Requirements for relevancy of free-streamline models of internal flows separating at a salient edge are suggested and confirmed for cases examined.

scholarly journals Theoretical and experimental study of scour depth by submerged water jet

2016 ◽  
Vol 8 (12) ◽  
pp. 168781401668239 ◽  
Author(s):  
Jiaoyi Hou ◽  
Lishan Zhang ◽  
Yongjun Gong ◽  
Dayong Ning ◽  
Zengmeng Zhang
Keyword(s):  
Mathematical Model ◽  
Experimental Study ◽  
Working Conditions ◽  
Curve Fitting ◽  
Functional Relationship ◽  
Water Jet ◽  
Scour Depth ◽  
Experiment Data ◽  
Fitting Method ◽  
Curve Fitting Method

The characteristics and working principles of the impinging by submerged water jet are analyzed, and the relevant mathematical model is optimized based on Rajaratnam’s theoretical and experimental study. A new mathematical model is constructed by adding an important parameter called impinging angle. A new experiment is designed according to the working conditions of various impinging distances and angles. In combination with the experiment data and with the use of the curve fitting method, the functional relationship between the impinging distance and angle as well as the coefficient C4 is obtained. The experiment results show that the scour depth decreases as impinging distance increases, followed by a trend from decline to rise before falling again; those two turning points occur within the range of 20d–25d. The scour depth constantly increases with rising impinging angle, and the maximum and minimum increasing ranges can reach 180% and 50%, respectively, with the impinging angle increasing from 40° to 90°.

SIMULATION OF VESSEL STRESS AND SECONDARY FLOWS FOR BLOOD FLOWS THROUGH A REALISTIC AORTA WITH THREE BRANCHES

2007 ◽  
Vol 19 (04) ◽  
pp. 215-223 ◽  
Author(s):  
Yang-Yao Niu ◽  
Pang-Chung Wu ◽  
Wen-Yih I. Tseng ◽  
Hsi-Yu Yu
Keyword(s):  
Secondary Flow ◽  
Aortic Arch ◽  
Three Dimensional ◽  
Wall Stress ◽  
Outer Wall ◽  
Secondary Flows ◽  
Blood Flows ◽  
Flow Recirculation ◽  
Dimensional Reconstruction

Blood secondary flows and vessel wall shear stress distributions in a human aortic arch have been predicted numerically for a Reynolds number of 4700 at entrance. The simulation geometry was derived from a three-dimensional reconstruction of a series of two-dimensional slices obtained in vivo. Numerical results demonstrate wall stresses were highly dynamic, but were generally high along the outer wall in the vicinity of the branches and low along the inner wall, particularly in the descending thoracic aorta. The maximum wall stress distribution is presented on the aortic arch in the systole. Extensive secondary flow motion was observed in the aorta, and the structure of these secondary flows was influenced considerably by the presence of the branches. Within the aorta, it is observed that clockwise secondary flow recirculation, also seen in the MRA scan data, appears in the downstream of aortic arch in the late systole and turn out to be a pair of counter-clockwise vortex in the downstream of the arch in the early diastole.

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