Verification of equations for incipient motion studies for a rigid rectangular channel

2013 ◽  
Vol 67 (2) ◽  
pp. 395-403 ◽  
Author(s):  
Charles Hin Joo Bong ◽  
Tze Liang Lau ◽  
Aminuddin Ab. Ghani
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Experimental Work ◽  
Rectangular Channel ◽  
Incipient Motion ◽  
Deposit Thickness ◽  
Motion Studies ◽  
New Equation ◽  
Discrepancy Ratio ◽  
Sediment Deposit

The current study aims to verify the existing equations for incipient motion for a rigid rectangular channel. Data from experimental work on incipient motion from a rectangular flume with two different widths, namely 0.3 and 0.6 m, were compared with the critical velocity value predicted by the equations of Novak & Nalluri and El-Zaemey. The equation by El-Zaemey performed better with an average discrepancy ratio value of 1.06 compared with the equation by Novak & Nalluri with an average discrepancy ratio value of 0.87. However, as the sediment deposit thickness increased, the equation by El-Zaemey became less accurate. A plot on the Shields Diagram using the experimental data had shown the significant effect of the sediment deposit thickness where, as the deposit becomes thicker, the dimensionless shear stress θ value also increased. A new equation had been proposed by incorporating the sediment deposit thickness. The new equation gave improved prediction with an average discrepancy ratio value of 1.02.

scholarly journals Studying Disturbance Wave Velocity and Wall Shear Stress of Vertical Upward Annular Flow in Narrow Rectangular Channel

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Antai Liu ◽  
Changqi Yan ◽  
Fuqiang Zhu ◽  
Haifeng Gu ◽  
Suijun Gong
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Wave Velocity ◽  
Annular Flow ◽  
Rectangular Channel ◽  
Disturbance Wave ◽  
New Correlation ◽  
Current Experimental Data ◽  
Wall Shear

As two important parameters, the velocity of disturbance wave and the wall shear stress in annular flow are very important to solve the closed equations of the mechanical model for annular flow. In this study, the disturbance wave velocity and wall shear stress of annular flow in a vertical narrow rectangular channel with a cross section of 70 mm × 2 mm were studied. According to the experimental results, it is found that the wave velocity and wall shear stress of disturbance wave increase with increasing gas phase velocity and liquid phase velocity. Also, existing correlations for predicting the velocity of disturbance wave were summarized and evaluated using the current experimental data. A new correlation for wall shear stress based on the disturbance wave velocity has been proposed. Compared with the existing correlation for predicting wall shear stress, this new correlation can well predict the current experimental data and MAPE is only 7.32%.

scholarly journals Experimental study on incipient shear stress of consolidated cohesive sediment

2020 ◽  
Vol 13 (18) ◽  
Author(s):  
Caiwen Shu ◽  
Guangming Tan ◽  
Peng Chen ◽  
Jun Wang ◽  
Ping Lv
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Bulk Density ◽  
Cohesive Sediment ◽  
Experimental Results ◽  
Incipient Motion ◽  
Motion Mechanism ◽  
Cohesive Particles ◽  
Sediment Mixtures ◽  
Consolidation Time

Abstract This paper analyzes the incipient motion mechanism of consolidated cohesive sediment. An experimental device based on previous studies was designed to investigate the influencing factors of the incipient shear stress, including the consolidation time, the density of dry bulk, cohesive particles content, and the composition of sediment mixtures. The experimental results indicated that the incipient shear stress of cohesive sediment increased with the increase of consolidation time, dry bulk density, and content of cohesive particles. The incipient motion mechanism of cohesive particles was further investigated using experimental data and theoretical analysis. A formula of the incipient shear stress for cohesive sediment was proposed herein, which is related to both the content of cohesive particles and the relative dry bulk density. The proposed formula was validated by the experimental data, and the calculated values of incipient shear stress using the formula were in good agreement with the experimental results.

scholarly journals Experimental Investigation of Erosion Characteristics of Fine-Grained Cohesive Sediments

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1511
Author(s):  
Bommanna Gounder Krishnappan ◽  
Mike Stone ◽  
Steven Granger ◽  
Hari Upadhayay ◽  
Qiang Tang ◽  
...  
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Critical Shear Stress ◽  
River System ◽  
Cohesive Sediment ◽  
Erosion Process ◽  
Fine Grained ◽  
Annular Flume ◽  
Two Factors ◽  
Sediment Deposit

In this short communication, the erosion process of the fine, cohesive sediment collected from the upper River Taw in South West England was studied in a rotating annular flume located in the National Water Research Institute in Burlington, Ontario, Canada. This study is part of a research project that is underway to model the transport of fine sediment and the associated nutrients in that river system. The erosion experimental data show that the critical shear stress for erosion of the upper River Taw sediment is about 0.09 Pa and it did not depend on the age of sediment deposit. The eroded sediment was transported in a flocculated form and the agent of flocculation for the upper River Taw sediment may be due to the presence of fibrils from microorganisms and organic material in the system. The experimental data were analysed using a curve fitting approach of Krone and a mathematical model of cohesive sediment transport in rotating circular flumes developed by Krishnappan. The modelled and measured data were in good agreement. An evaluation of the physical significance of Krone’s fitting coefficients is presented. Variability of the fitting coefficients as a function of bed shear stress and age of sediment deposit indicate the key role these two factors play in the erosion process of fluvial cohesive sediment.

Sediment deposit thickness and its effect on critical velocity for incipient motion

2016 ◽  
Vol 74 (8) ◽  
pp. 1876-1884 ◽  
Author(s):  
C. H. J. Bong ◽  
T. L. Lau ◽  
A. Ab. Ghani ◽  
N. W. Chan
Keyword(s):  
Boundary Conditions ◽  
Critical Velocity ◽  
Sediment Deposition ◽  
Incipient Motion ◽  
Rigid Boundary ◽  
Densimetric Froude Number ◽  
Deposit Thickness ◽  
Velocity Equation ◽  
Deposition Thickness ◽  
Sediment Deposit

The understanding of how the sediment deposit thickness influences the incipient motion characteristic is still lacking in the literature. Hence, the current study aims to determine the effect of sediment deposition thickness on the critical velocity for incipient motion. An incipient motion experiment was conducted in a rigid boundary rectangular flume of 0.6 m width with varying sediment deposition thickness. Findings from the experiment revealed that the densimetric Froude number has a logarithmic relationship with both the thickness ratios ts/d and ts/y0 (ts: sediment deposit thickness; d: grain size; y0: normal flow depth). Multiple linear regression analysis was performed using the data from the current study to develop a new critical velocity equation by incorporating thickness ratios into the equation. The new equation can be used to predict critical velocity for incipient motion for both loose and rigid boundary conditions. The new critical velocity equation is an attempt toward unifying the equations for both rigid and loose boundary conditions.

DEPOSITION THICKNESS AND ITS EFFECT ON CRITICAL SHEAR STRESS FOR INCIPIENT MOTION OF SEDIMENTS

2016 ◽  
Vol 78 (9-4) ◽  
Author(s):  
Charles Hin Joo Bong ◽  
Frederik Josep Putuhena ◽  
Tze Liang Lau ◽  
Aminuddin Ab. Ghani
Keyword(s):  
Boundary Condition ◽  
Shear Stress ◽  
Linear Regression Analysis ◽  
Critical Shear Stress ◽  
Multiple Linear Regression Analysis ◽  
Incipient Motion ◽  
Rigid Boundary ◽  
Sediment Deposits ◽  
Deposition Thickness ◽  
New Equation

There are evidences in existing literatures suggesting the incipient motion values for any particle size is substantially lower for rigid boundary condition as compared to loose boundary condition.  The objective of the current study is to determine the effect of sediment deposition thickness on the critical shear stress for incipient motion. Experimental works for incipient motion were carried out in a rectangular flume with varying sediment deposits thickness. Results showed that the sediment deposits thickness has effect on the critical shear stress at low sediment deposits thickness and the effect will slowly diminish as the sediment deposits thickness increases. Multiple linear regression analysis was performed on the experimental data to develop a new critical shear stress equation.  The best regression model has   value of 0.69;    value of 0.60;  value of 0.009 and Mallow’s  value of 3.00. The new equation appears to be more consistent as compared to existing incipient motion equations for rigid boundary condition by having 80% of the predicted data falls within the acceptable discrepancy ratio when tested with data from other authors. The new equation can be used to determine critical shear stress values for self-cleansing sewerage design and other related engineering applications

scholarly journals Assessing Machine Learning versus a Mathematical Model to Estimate the Transverse Shear Stress Distribution in a Rectangular Channel

Mathematics ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 596
Author(s):  
Babak Lashkar-Ara ◽  
Niloofar Kalantari ◽  
Zohreh Sheikh Khozani ◽  
Amir Mosavi
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Fuzzy Inference ◽  
Rectangular Channel ◽  
Tsallis Entropy ◽  
Shear Stress Distribution ◽  
Data Series ◽  
Shear Stresses ◽  
Inference System ◽  
Aspect Ratios

One of the most important subjects of hydraulic engineering is the reliable estimation of the transverse distribution in the rectangular channel of bed and wall shear stresses. This study makes use of the Tsallis entropy, genetic programming (GP) and adaptive neuro-fuzzy inference system (ANFIS) methods to assess the shear stress distribution (SSD) in the rectangular channel. To evaluate the results of the Tsallis entropy, GP and ANFIS models, laboratory observations were used in which shear stress was measured using an optimized Preston tube. This is then used to measure the SSD in various aspect ratios in the rectangular channel. To investigate the shear stress percentage, 10 data series with a total of 112 different data for were used. The results of the sensitivity analysis show that the most influential parameter for the SSD in smooth rectangular channel is the dimensionless parameter B/H, Where the transverse coordinate is B, and the flow depth is H. With the parameters (b/B), (B/H) for the bed and (z/H), (B/H) for the wall as inputs, the modeling of the GP was better than the other one. Based on the analysis, it can be concluded that the use of GP and ANFIS algorithms is more effective in estimating shear stress in smooth rectangular channels than the Tsallis entropy-based equations.

In Reply: Combinations of Antibiotics

PEDIATRICS ◽  
1960 ◽  
Vol 26 (3) ◽  
pp. 499-499
Author(s):  
Robert J. Haggerty
Keyword(s):  
Experimental Data ◽  
Clinical Data ◽  
Experimental Work ◽  
The Subject ◽  
Antimicrobial Combinations

I am delighted to have Dr. Jawetz again bring to the attention of your readers his definitive work on the subject of antimicrobial combinations. We certainly have no quarrel with the points he reiterates. Our choice of words, "It is not clear why these results are at variance with the experimental data of Jawetz or the clinical data of Lepper and Dowling," was probably unfortunate, for Dr. Jawetz points out why the results did differ from his experimental work.

Experimental Study on Critical Shear Stress of Cohesive Soils and Soil Mixtures

2021 ◽  
Vol 64 (2) ◽  
pp. 587-600
Author(s):  
Xiaojing Gao ◽  
Qiusheng Wang ◽  
Chongbang Xu ◽  
Ruilin Su
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Critical Shear Stress ◽  
Cohesive Soil ◽  
Future Research ◽  
Cohesive Soils ◽  
List Type ◽  
Soil Mixture ◽  
Linear Relationships ◽  
Soil Mixtures

HighlightsErosion tests were performed to study the critical shear stress of cohesive soils and soil mixtures.Linear relationships were observed between critical shear stress and cohesion of cohesive soils.Mixture critical shear stress relates to noncohesive particle size and cohesive soil erodibility.A formula for calculating the critical shear stress of soil mixtures is proposed and verified.Abstract. The incipient motion of soil is an important engineering property that impacts reservoir sedimentation, stable channel design, river bed degradation, and dam breach. Due to numerous factors influencing the erodibility parameters, the study of critical shear stress (tc) of cohesive soils and soil mixtures is still far from mature. In this study, erosion experiments were conducted to investigate the influence of soil properties on the tc of remolded cohesive soils and cohesive and noncohesive soil mixtures with mud contents varying from 0% to 100% using an erosion function apparatus (EFA). For cohesive soils, direct linear relationships were observed between tc and cohesion (c). The critical shear stress for soil mixture (tcm) erosion increased monotonically with an increase in mud content (pm). The median diameter of noncohesive soil (Ds), the void ratio (e), and the organic content of cohesive soil also influenced tcm. A formula for calculating tcm considering the effect of pm and the tc of noncohesive soil and pure mud was developed. The proposed formula was validated using experimental data from the present and previous research, and it can reproduce the variation of tcm for reconstituted soil mixtures. To use the proposed formula to predict the tcm for artificial engineering problems, experimental erosion tests should be performed. Future research should further test the proposed formula based on additional experimental data. Keywords: Cohesive and noncohesive soil mixture, Critical shear stress, Erodibility, Mud content, Soil property.

scholarly journals β-γ and isomeric decay spectroscopy of 168Dy

2018 ◽  
Vol 178 ◽  
pp. 02023
Author(s):  
G.X. Zhang ◽  
H. Watanabe ◽  
F.G. Kondev ◽  
G.J. Lane ◽  
P.H. Regan ◽  
...  
Keyword(s):  
Experimental Data ◽  
Excited States ◽  
Experimental Work ◽  
Isomeric State ◽  
Level Structure ◽  
Primary Beam ◽  
Average Intensity ◽  
Experimental Procedure ◽  
Preliminary Results ◽  
Decay Spectroscopy

This contribution will report on the experimental work on the level structure of 168Dy. The experimental data have been taken as part of the EURICA decay spectroscopy campaign at RIBF, RIKEN in November 2014. In the experiment, a 238U primary beam is accelerated up to 345 MeV/u with an average intensity of 12 pnA. The nuclei of interest are produced by in-flight fission of 238U impinging on Be target with a thickness of 5 mm. The excited states of 168Dy have been populated through the decay from a newly identified isomeric state and via the β decay from 168Tb. In this contribution, scientific motivations, experimental procedure and some preliminary results for this study are presented.

3-D Simulation for Blood Flow and Artery Compression in Asymmetric Stenotic Arteries With Axial Stretch

2001 ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Shunnichi Kobayashi
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Shear Stress ◽  
Wall Stress ◽  
Small Strain ◽  
Rigid Wall ◽  
Severe Stenosis ◽  
Physiological Conditions ◽  
Oscillating Shear Stress ◽  
Stenotic Arteries

Abstract There has been increasing evidence that severe stenosis may cause artery compression and plaque cap rupture leading to heart attack and stroke. The physiological conditions under which that may occur and mechanisms involved are not well understood. It has been known that severe stenosis causes critical flow and wall mechanical conditions such as flow limitation, flow separation, low and oscillating shear stress distal to the stenosis, high shear stress and low or even negative flow pressure at the throat of stenosis, artery compression or even collapse. Those conditions are related to limitation of blood supply, intimal thickening and thrombosis formation, endothelism damage, platelet activation and aggregation, plaque cap rupture (for review, see [1,2]). Due to the complexity of the problem and lack of experimental data for mechanical properties of arteries under both expansion and compression, previous models were limited primarily to flow behaviors and with various limitations (axisymmetry, rigid wall, small strain, small pressure gradient). In this paper, experimental data for artery mechanical properties under physiological conditions were measured and a 3-d computational model is introduced to investigate flow behaviors and wall stress and strain distributions with fluid-structure interactions to better understand the mechanism involved in artery compression and plaque cap rupture.

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