scholarly journals Modelling the Wave Overtopping Flow over the Crest and the Landward Slope of Grass-Covered Flood Defences

2020 ◽  
Vol 8 (7) ◽  
pp. 489
Author(s):  
Vera M. van Bergeijk ◽  
Jord J. Warmink ◽  
Suzanne J. M. H. Hulscher
Keyword(s):  
Shear Stress ◽  
Numerical Model ◽  
Flow Velocity ◽  
Normal Stress ◽  
High Pressures ◽  
Maximum Shear Stress ◽  
Maximum Flow ◽  
Maximum Pressure ◽  
Grass Cover ◽  
Wave Overtopping

The wave overtopping flow can exert high hydraulic loads on the grass cover of dikes leading to failure of the cover layer on the crest and the landward slope. Hydraulic variables such as the near bed velocity, pressure, shear stress and normal stress are important to describe the forces that may lead to cover erosion. This paper presents a numerical model in the open source software OpenFOAM® to simulate the overtopping flow on the grass-covered crest and slope of individual overtopping waves for a range of landward slope angles. The model provides insights on how the hydraulic forces change along the profile and how irregularities in the profile affect these forces. The effect of irregularities in the grass cover on the overtopping flow are captured in the Nikuradse roughness height calibrated in this study. The model was validated with two datasets of overtopping tests on existing grass-covered dikes in the Netherlands. The model results show good agreement with measurements of the flow velocity in the top layer of the wave, as well as the near bed velocity. The model application shows that the pressure, shear stress and normal stress are maximal at the wave front. High pressures occur at geometrical transitions such as the start and end of the dike crest and at the inner toe. The shear stress is maximal on the lower slope, and the normal stress is maximal halfway of the slope, making these locations vulnerable to cover failure due to high loads. The exact location of the maximum forces depends on the overtopping volume. Furthermore, the model shows that the maximum pressure and maximum normal stress are largely affected by the steepness of the landward slope, but the slope steepness only has a small effect on the maximum flow velocity and maximum shear stress compared to the overtopping volume. This new numerical model is a useful tool to determine the hydraulic forces along the profile to find vulnerable points for cover failure and improve the design of grass-covered flood defences.

scholarly journals How do transitions affect the wave overtopping flow locally as well as downstream?

2021 ◽  
Author(s):  
Vera van Bergeijk ◽  
Jord Warmink ◽  
Suzanne Hulscher
Keyword(s):  
Shear Stress ◽  
Flow Velocity ◽  
Normal Stress ◽  
Maximum Shear Stress ◽  
Velocity Shear ◽  
Maximum Pressure ◽  
Wave Overtopping ◽  
Jet Impact ◽  
Hydraulic Load ◽  
Geometric Transitions

<p>Wave overtopping on grass-covered dikes results in erosion of the dike cover. Once the dike cover is eroded, the core will be washed away and the dike breaches, leading to flooding of the hinterland. Transitions between grass covers and revetments or geometric transitions are vulnerable for cover erosion and are therefore the most likely locations to initiate dike breach. These transitions affect the overtopping flow and thereby the hydraulic load on the dike cover. For example, bed roughness differences can create additional turbulence and slope changes can result in the formation of a jet that increases the load at the jet impact location. Although it is known that dike cover failure often starts at transitions, the effect of transitions on the hydraulic load remains unknown.</p><p>We developed a detailed numerical 2DV model in OpenFOAM for the overtopping flow over the crest and the landward slope of a grass-covered dike. This model is used to study the effects of transitions on the overtopping flow variables including the flow velocity, shear stress, normal stress and pressure. Several types of transitions are studied such as revetment transitions, slope changes and height differences. </p><p>The results show that the shear stress, normal stress and pressure increase significantly at geometric transitions such as the transition from the crest to the slope and at the landward toe. The increase depends on the wave volume and the geometry of the dike such as the steepness and length of the landward slope. Furthermore, the results show that roughness changes at revetment transition on a grass-covered crest has no influence on the maximum shear stress, maximum normal stress and maximum pressure. The flow velocity increases from a rough to a smooth revetment, while the opposite occurs for the transition from a smooth to a rough revetment. The variation in the flow velocity is well described by analytical formulas for the maximum flow velocity along the dike profile. These formulas are also able to describe the variation in flow velocity for a revetment transition on a berm on the landward slope. In this case, the shear stress increases from a smooth to a rough revetment and decreases from a rough to a smooth revetment. This means that a rough revetment can locally reduce the shear stress, however the transitions have no effect on the shear stress downstream.</p><p>These model results are used to obtain relations for the increase in the hydraulic variables at transitions. These relations can be used to describe the effect of transitions on the hydraulic load in models for grass cover failure by overtopping waves. Accurate descriptions of the hydraulic load in these models will improve the failure assessment of grass-covered dikes with transitions.</p>

Stress in Bonded Adherends for Single Lap Joints

1996 ◽  
Vol 12 (03) ◽  
pp. 167-171
Author(s):  
G. Bezine ◽  
A. Roy ◽  
A. Vinet
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Numerical Model ◽  
Stress Distribution ◽  
Normal Stress ◽  
Lap Joints ◽  
Axial Loads ◽  
Normal Stress Distribution ◽  
Single Lap Joints ◽  
Element Technique

A finite-element technique is used to predict the shear stress and normal stress distribution in adherends for polycarbonate/polycarbonate single lap joints subjected to axial loads. Numerical and photoelastic results are compared so that a validation of the numerical model is obtained. The influences on stresses of the overlap length and the shape of the adherends are studied.

Investigation of Design Parameters and Failure Criteria of O-Ring Seal Structure

2005 ◽  
Author(s):  
Dianyin Hu ◽  
Rongqiao Wang ◽  
Quanbin Ren ◽  
Jie Hong
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Shear Stress ◽  
Normal Stress ◽  
Maximum Shear Stress ◽  
Design Parameters ◽  
Element Analysis ◽  
Axisymmetric Model ◽  
Sealing Performance ◽  
Maximum Contact

First, this paper established the seal structural 2D axisymmetric model of a certain Solid Rocket Booster (SRB) and calculated the deformation and stresses at ignition through a large displacement, incompressible, contact finite element analysis. The results show that the maximum contact stress appears at the contact area and the maximum shear stress at groove notch. Then, some typical parameters of the seal structure which might have the impact on the sealing performance, such as the gap breadth, initial compressibility, fillets of the groove notch and bottom, groove width, were analyzed. We can find that the gap breadth and initial compressibility do great contributions to the maximum contact normal stress, and the groove notch and bottom fillets act upon the maximum shear stress obviously. In order to verify the validity of the 2D axisymmetric model, 3D structural finite element analysis of the structure was conducted, and the results indicate that in service, the upper flange is inclined relative to the nether flange, which seems to mean that the gap breadth can not be considered as a constant during the 2D axisymmetric analysis. However further calculations say that if using the minimum gap breadth gotten in 3D analysis as its constant gap value, the above 2D axisymmetric model can rationally take the place of 3D model to analyze the sealing performance. Finally, the failure modes & criteria of the O-ring seals based on the maximum contact normal stress and shear stress were determined to ensure the reliability of this structure.

Design of a Nozzle for the Production of Metal Powder via Gas Atomization

2013 ◽  
Author(s):  
Mehmet Alper Sofuoglu ◽  
Murat Erbas ◽  
Ibrahim Uslan ◽  
Atilla Biyikoglu
Keyword(s):  
Numerical Model ◽  
Flow Velocity ◽  
Metal Powder ◽  
Nozzle Exit ◽  
Maximum Pressure ◽  
Gas Atomization ◽  
Exit Angle ◽  
Second Stage ◽  
Empirical Relations ◽  
Two Stages

In this study, a nozzle has been designed in order to produce metal powder via the method of gas atomization. The design has been performed in two stages. At the first stage of design, the size and geometry of the nozzle have been determined using empirical relations as a pre-design. At the second stage, a parametrical analysis has been done using a CFD code. As a parametrical study, the effects of nozzle exit angle, throat distance and protrusion length on pressure and flow velocity at the nozzle exit are investigated with the numerical model. Appropriate values for the investigated parameters have been determined to get maximum pressure in vacuum condition at the tip of the melt. The nozzle has been designed based on the determined parameters.

Poisson Ratio Effects on the Von Mises and Maximum Shear Stresses in Cylindrical Contacts

2005 ◽  
Author(s):  
Itzhak Green
Keyword(s):  
Shear Stress ◽  
Poisson Ratio ◽  
Unit Length ◽  
Maximum Shear Stress ◽  
Critical Force ◽  
Von Mises Stress ◽  
Maximum Pressure ◽  
Shear Stresses ◽  
Wide Range ◽  
Von Mises

This work determines the location of the greatest elastic distress in cylindrical contacts based upon the distortion energy and the maximum shear stress theories. The ratios between the maximum pressure, the von Mises stress, and the maximum shear stress are determined and fitted by empirical formulations for a wide range of Poisson ratios, which represent material compressibility. Some similarities exist between cylindrical and spherical contacts, where for many metallic materials the maximum von Mises or shear stresses emerge beneath the surface. However, if any of the bodies in contact is excessively compressible the maximum von Mises stress appears at the surface. That transitional Poisson ratio is found. The critical force per unit length that causes yielding onset, along with its corresponding interference and half-width contact are derived.

scholarly journals ANALISA HIDROLIS JARINGAN PIPA DISTRIBUSI UTAMA DAN DISTRIBUSI BAGI PADA SISTEM PENYEDIAAN AIR MINUM (SPAM) IKK WASILE TIMUR

2018 ◽  
Vol 1 (1) ◽  
Author(s):  
Robbi Harisman ◽  
Zulkarnain K Misbah ◽  
Edward Risky Ahadian
Keyword(s):  
Water Resources ◽  
Flow Velocity ◽  
Management System ◽  
Water Resource Management ◽  
Maximum Flow ◽  
Maximum Pressure ◽  
Research Activity ◽  
Resource Management System ◽  
Distribution Network Planning ◽  
Maximum Flow Velocity

The existing water resources need to be sustainably managed. Sustainable water resource management system is a managed and managed water resources management system that fully contributes to current and future societal and economic goals while maintaining its ecological sustainability. This research was conducted by direct observation in the field. Then the data obtained from the field in though by using a computer program. This research activity was conducted in East Wasile Sub-district of East Halmahera Regency of North Maluku Province. The results of this study indicate that the diameter of the pipe used is 300 mm diameter, 250 mm, 200 mm, 150 mm, 100 mm, and 63 mm. From the variation of the pipe obtained Maximum pressure 49.37 m or equal to 4.937 bar while minimum pressure of 26.39 m or equal to 2,639 bar. The pressure of the analysis result meets the criteria of distribution network planning that is maximum 9.0 - 12.4 bar and minimum 0.5 - 1.0 bar. Maximum flow velocity of 0.60 m/s and a minimum speed of 0.30 m/s flow velocity on the analysis results meets the planning criteria which according to the provisions of a maximum of 2.5 m/s and a minimum of 0.25 m/s.

Experimental Analysis on Shear Behavior of Sand-Concrete Interface

2012 ◽  
Vol 204-208 ◽  
pp. 893-898
Author(s):  
Chun Feng Zhao ◽  
Bao Lai Yu ◽  
Cheng Zhao
Keyword(s):  
Shear Stress ◽  
Friction Coefficient ◽  
Normal Stress ◽  
Maximum Shear Stress ◽  
Relative Displacement ◽  
Shear Behavior ◽  
Tangential Displacement ◽  
Interface Shear ◽  
Direct Shear Tests ◽  
Concrete Interface

In order to study the shear behavior of sand-concrete structure interface, shear stress and relative displacement curves were obtained through a series of direct shear tests, in the procedure of which the roughness of interfaces was quantified into 3 grades and the stress history can be achieved by loading the sand to an initial normal stress and then unloading to a normal stress to shear. Through analyzing the curves, several conclusions can be obtained as follows: Shear stress increases with the initial normal stress and roughness at the same tangential displacement. The initial shear modulus can be improved in case of the increase of initial normal stress and roughness. The friction coefficient can be obtained by fitting the curve of the maximum shear stress and normal stress corresponded to Mohr-Coulomb Criterion linearly. The friction coefficient of sand-concrete interface increases with roughness as well as its increase range.

scholarly journals Some Observations on the Banding of Glacier Ice

1955 ◽  
Vol 2 (17) ◽  
pp. 502-506 ◽  
Author(s):  
N. Untersteiner
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Maximum Shear Stress ◽  
Stress System ◽  
Outward Appearance ◽  
Glacier Tongue ◽  
Maximum Normal Stress ◽  
Glacier Ice

AbstractThe distribution of fine banding (foliation) on the surface of a flat glacier tongue was studied. The conclusions reached are that fine banding seems to be neither of sedimentary origin nor to be the representation of a straightforward stress system. In the present case, foliation seems to be connected with ice falls.Other bands definitely not belonging to the fine banding system were plotted irrespective of their outward appearance. Statistically, their preferred spacial directions correspond to the directions of either maximum shear stress or maximum normal stress (tension).

scholarly journals Study of Flow-Assisted Corrosion of AZ91D Magnesium Alloy in Loop System Based on Array Electrode Technology

2015 ◽  
Vol 2015 ◽  
pp. 1-8
Author(s):  
Hualiang Huang ◽  
Guoan Zhang ◽  
Jiakuan Yang ◽  
Zhiquan Pan ◽  
Xingpeng Guo
Keyword(s):  
Shear Stress ◽  
Magnesium Alloy ◽  
Corrosion Rate ◽  
Flow Velocity ◽  
Maximum Flow ◽  
Outer Wall ◽  
Loop System ◽  
Dynamics Simulation ◽  
Az91d Magnesium Alloy ◽  
Array Electrode

A loop system was used to investigate flow-assisted corrosion (FAC) of AZ91D magnesium alloy at an elbow based on array electrode technology by potentiodynamic polarization, computational fluid dynamics, simulation and surface analysis. The experimental results demonstrate the fluid hydrodynamics plays a significant role in the FAC of AZ91D magnesium alloy. The corrosion rate increases from the outer wall to the inner wall of the elbow, with the higher corrosion rate corresponding to the higher flow velocity and larger shear stress at the elbow. The maximum corrosion rate appears at the innermost wall of the elbow, the location with the maximum flow velocity and shear stress.

scholarly journals Effect of Loading Frequency Ratio on Multiaxial Asynchronous Fatigue Failure of 30CrMnSiA Steel

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3968
Author(s):  
Tianqi Liu ◽  
Xinxin Qi ◽  
Xinhong Shi ◽  
Limin Gao ◽  
Tian Zhang ◽  
...  
Keyword(s):  
Shear Stress ◽  
Fatigue Life ◽  
Normal Stress ◽  
Frequency Ratio ◽  
Prediction Models ◽  
Maximum Shear Stress ◽  
Fatigue Crack Initiation ◽  
Loading Frequency ◽  
Obvious Effect ◽  
Maximum Normal Stress

Multiaxial asynchronous fatigue experiments were carried out on 30CrMnSiA steel to investigate the influence of frequency ratio on fatigue crack initiation and propagation. Test results show that the surface cracks initiate on the maximum shear stress amplitude planes with larger normal stress, propagate approximately tens of microns, and then propagate along the maximum normal stress planes. The frequency ratio has an obvious effect on the fatigue life. The variation of normal and shear stress amplitudes on the maximum normal stress plane induces the crack retardation, and results in that the crack growth length is longer for the constant amplitude loading than that for the asynchronous loading under the same fatigue life ratio. A few fatigue life prediction models were employed and compared. Results show that the fatigue life predicted by the model of Bannantine-Socie cycle counting method, section critical plane criterion and Palmgren-Miner’s cumulative damage rule were more applicable.

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