scholarly journals IMPROVEMENTS IN DESCRIBING WAVE OVERTOPPING PROCESSES

2012 ◽  
Vol 1 (33) ◽  
pp. 35 ◽  
Author(s):  
Steven A Hughes ◽  
Christopher I Thornton ◽  
Jentsje W Van der Meer ◽  
Bryan N Scholl
Keyword(s):  
Weibull Distribution ◽  
Shape Factor ◽  
Empirical Relation ◽  
Maximum Velocity ◽  
Maximum Flow ◽  
Empirical Relationships ◽  
Wave Overtopping ◽  
Hydrodynamic Parameters ◽  
Applicable Range

This paper presents a new empirical relation for the shape factor in the Weibull distribution that describes the distribution of overtopping wave volumes. This improvement increases the applicable range of the Weibull distribution from very low average overtopping discharges to large discharges resulting from combined wave overtopping and steady surge overflow at negative freeboards. The effect this improvement has on wave overtopping simulation is also discussed. Measured maximum flow thicknesses, velocities, and discharges from experiments of combined wave and surge overtopping are examined to learn more about the variability of these key parameters as a function of individual overtopping wave volumes. A key finding is that wave volumes containing the 2%-exceedance value of maximum velocity typically have maximum flow thicknesses well below the 2%-exceedance level, and vice-versa. Furthermore, the 2%-exceedance hydrodynamic parameters do not occur in the 2%-exceedance wave volumes. Finally, empirical relationships are developed for several parameters that showed strong trends.

scholarly journals DISTRIBUTION OF INDIVIDUAL WAVE OVERTOPPING VOLUMES ON A SLOPING STRUCTURE WITH A PERMEABLE FORESHORE

2020 ◽  
pp. 54
Author(s):  
Md Salauddin ◽  
John O'Sullivan ◽  
Soroush Abolfathi ◽  
Shudhi Dong ◽  
Jonathan Pearson
Keyword(s):  
Weibull Distribution ◽  
Shape Factor ◽  
Shape Parameter ◽  
Accurate Estimation ◽  
Coastal Structures ◽  
Wave Overtopping ◽  
Scale Parameters ◽  
Distribution Shape ◽  
Individual Wave ◽  
Set Up

Maximum wave overtopping volumes on sea defences are an indicator for identifying risks to people and properties from wave hazards. The probability distribution of individual overtopping volumes can generally be described by a two-parameter Weibull distribution function (shape and scale parameters). Therefore, the reliable prediction of maximum individual wave overtopping volumes at coastal structures relies on an accurate estimation of the shape factor in the Weibull distribution. This study contributes to an improved understanding of the distribution of individual wave overtopping volumes at sloping structures by analysing the wave-by-wave overtopping volumes obtained from physical model experiments on a 1V:2H sloped impermeable structure with a permeable shingle foreshore of slope 1V:20H. Measurements of the permeable shingle foreshore were benchmarked against those from an identical experimental set-up with a smooth impermeable foreshore (1V:20H) of the same geometry. Results from both experimental set-ups were compared to commonly used empirical formulations, underpinned by the assumption that an impermeable foreshore exists in front of the sea structure. The effect on the shape factor in the Weibull distribution of incident wave steepness, relative crest freeboard, probability of overtopping waves and discharge are examined to determine the variation of individual overtopping volumes with respect to these key parameters. A key finding from the study is that no major differences in Weibull distribution shape parameter were observed for the tested impermeable and permeable sloped foreshores. Existing empirical formulae were also shown to predict reasonably well the Weibull distribution shape parameter, b, at sloping structures with both impermeable and permeable slopes.

scholarly journals An Experimental Study on the Influence of Drastically Varying Discharge Ratios on Bed Topography and Flow Structure at Urban Channel Confluences

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1147
Author(s):  
Zhiyuan Zhang ◽  
Yuqing Lin
Keyword(s):  
Transition Period ◽  
Maximum Velocity ◽  
Maximum Flow ◽  
River Network ◽  
Morphological Alteration ◽  
Minor Role ◽  
Material Transport ◽  
Lateral Velocity ◽  
Basic Work ◽  
Discharge Ratio

The confluences of rivers are important nodes for energy conversion and material transport in the river network. A slight morphological alteration of the confluences may trigger the “butterfly effect”, which will bring about changes in the ecology and environment of the entire river network. During the transition period of the wet and dry seasons, the variation of discharge ratio will make the originally balanced river bed change again, which will bring a series of follow-up effects. This research mainly studied the features of water flow itself and results showed that the variation of discharge ratio caused secondary erosion of the balanced bed surface and transported the sediment downstream. Thus, the zone of maximum velocity was enlarged and the maximum flow velocity at the equal discharge was reduced, and more intense vortex and turbulence were generated. The lateral velocity, vertical velocity, and turbulent structure were mainly controlled by the quantity and ratio of the discharge, and the varying topography only played a minor role in local areas. Nowadays, some scholars have been studying the combination of flow field features and various environmental substances and biological habitats, and the basic work done in this article has laid the foundation for these studies.

Effect of shielding gas flow rate on arc behaviors in GMAW with single cable-typed wire

2019 ◽  
Vol 34 (01n03) ◽  
pp. 2040059
Author(s):  
Qingxian Hu ◽  
Lei Zhang ◽  
Juan Pu ◽  
Caichen Zhu
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Gas Metal Arc Welding ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Maximum Flow ◽  
Maximum Pressure ◽  
Arc Plasma ◽  
Shielding Gas ◽  
Gas Flow Rate

A three-dimensional numerical model of arc in gas metal arc welding (GMAW) with single cable-typed wire was established based on the theory of arc physics. The influences of different shielding gas flow rates on the features of temperature field, velocity field and pressure field were investigated. The results showed that the maximum velocity of arc plasma along radial direction and the arc pressure on the surface of workpieces were increased obviously with the increase of the shielding gas flow rate, while the arc temperature was changed little. This phenomenon was mainly attributed to the increasing collisions between arc plasmas and the self-rotation action of cable-typed wires. The arc temperature at the tip of the cable-typed wire reached the maximum. The maximum flow velocity of arc plasma was located at the tip of wire (2–8 mm). The arc pressures in the central axis reached the maximum pressure. The simulation results were in agreement with the experimental results.

Proposal for an Empirical Evaluation of Rotation Capacity of RHS Aluminium Alloy Beams Based on FEM Simulations

2016 ◽  
Vol 710 ◽  
pp. 231-237 ◽  
Author(s):  
Paolo Castaldo ◽  
Elide Nastri ◽  
Vincenzo Piluso
Keyword(s):  
Aluminium Alloy ◽  
Shape Factor ◽  
Parametric Analysis ◽  
Empirical Relationship ◽  
Empirical Evaluation ◽  
Regression Analyses ◽  
Empirical Relationships ◽  
Rotation Capacity ◽  
Moment Gradient ◽  
Insight Into

The aim of this work is the development of an empirical relationship for evaluating the rotation capacity of RHS aluminium alloy beams, for temper T4 and T6. The proposed relationships are based on the numerical results coming from an extensive parametric analysis performed by means of FE code ABAQUS for different materials, which gain insight into the influence of all the geometrical and mechanical parameters affecting the ultimate behaviour. In particular, the influence of the materials strain hardening, flange slenderness, web stiffness, shape factor and moment gradient the on the plastic behaviour of such beams has been investigated. Successively, by means of monovariate and multivariate non linear regression analyses, empirical relationships are provided in order to predict the rotation capacity of RHS aluminium alloy beams starting from their geometrical and mechanical properties. This paper is focused on this issue.

scholarly journals Pressure and Water Flow Patterns in the Respiratory Tract of the Bass (Micropterus Salmoides)

1984 ◽  
Vol 113 (1) ◽  
pp. 151-164 ◽  
Author(s):  
GEORGE V. LAUDER
Keyword(s):  
Respiratory Tract ◽  
Flow Velocity ◽  
Buccal Cavity ◽  
Micropterus Salmoides ◽  
Maximum Velocity ◽  
Maximum Flow ◽  
Wave Form ◽  
Dimensional Changes ◽  
Velocity Wave ◽  
Phase Differences

Instantaneous water velocities in the respiratory tract of bass, Micropterus salmoides (Lacepéde), were measured using a fast-responding hot-filmanemometer. The flow velocity wave form varied within the buccal cavity, with lower peak velocities at the back than at the front. Flow velocity in both the buccal and opercular cavities varied over the respiratory cycle, and 80% of signal power in the velocity wave form was between 1 and 10 Hz. Flow within the buccal cavity reached a maximum velocity of 50cms−1 and did not decline to zero, even when differential pressure across the gills was negative. Simultaneous measurement of dimensional changes in the branchial apparatus, pressure and velocity fluctuations showed that gill bar adduction coincides both with the pressure reversal across the gills and with maximum flow velocities in the opercular cavity. The movement of the gillbars during respiration causes flow velocity fluctuation just in front of the primary lamellae and may be an important component of intraoral resistance contributing to the phase differences between pressure and velocity waveforms.

scholarly journals Correlation between Electrical Resistivity and Cone Penetrometer Test Data for Geotechnical Site Investigation

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
I. A. Akinlabi
Keyword(s):  
Electrical Resistivity ◽  
Bearing Capacity ◽  
Test Data ◽  
Empirical Relation ◽  
Site Investigation ◽  
Cone Penetrometer ◽  
Soil Resistivity ◽  
Empirical Relationships ◽  
Cone Resistance ◽  
Allowable Bearing Capacity

The use of the electrical resistivity method provides cost-effective subsurface information faster and allows reliable interpolation to be made between the tested points. It is therefore desirable to generate consistent data from resistivity measurements by using empirical relationships while only few zones of interest will require testing. This study, therefore, developed empirical relationships between electrical resistivity sounding and cone penetrometer test data for engineering site investigation using a case study from the Basement Complex Terrain of Southwestern Nigeria. Regression analysis was used to assess the correlation between the soil resistivity and cone resistance and the validity of the empirical relation was evaluated by comparing values estimated from the soil resistivity vs. cone resistance cross plot with field values obtained from cone penetration tests. The values of allowable bearing pressure computed by using both values in Meyerhof’s equation were also compared with the allowable bearing capacity deduced with laboratory values of soil strength parameters (cohesion, angle of internal friction, soil unit weight) in Terzaghi’s general formula. The results show close agreement between the measured and estimated values with the differences typically less than 10%. The standard errors of the estimates for the cone resistance and allowable bearing capacity are 2.70 and 4.16 respectively, implying reliability of the estimates. The proposed empirical relationships, therefore, appear to provide reasonable estimation of soil cone resistance and allowable bearing capacity from soil resistivity. Few complimentary cone penetrometer and laboratory tests will thus be required while the cost and duration of site investigation for engineering structures are expected to reduce.

scholarly journals Experimental Study of Overland Flow through Rigid Emergent Vegetation with Different Densities and Location Arrangements

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1638 ◽  
Author(s):  
Yuting Wang ◽  
Huilan Zhang ◽  
Pingping Yang ◽  
Yunqi Wang
Keyword(s):  
Water Depth ◽  
Overland Flow ◽  
Maximum Velocity ◽  
Two Dimensions ◽  
Emergent Vegetation ◽  
Vegetation Density ◽  
Hydrodynamic Parameters ◽  
Flow Through ◽  
Rigid Emergent Vegetation ◽  
Vegetated Slopes

The effect of vegetation density on overland flow dynamics has been extensively studied, yet fewer investigations have focused on vegetation arrangements with different densities and position features. Flume experiments were conducted to investigate the hydrodynamics of flow through rigid emergent vegetation arranged in combinations with three densities (Dense, Middle, and Sparse) and three positions (summit, backslope, and footslope). This study focused on how spatial variations regulated hydrodynamic parameters from two dimensions: direction along the slope and water depth. The total hydrodynamic parameters of bare slopes were significantly different from those of vegetated slopes. The relationship between Re and f illustrated that Re was not a unique predictor of hydraulic roughness on vegetated slopes. In the slope direction, all hydrodynamic parameters on vegetated slopes exhibited fluctuating downward/upward trends due to the clocking effect before the vegetated area and the rapid conveyance effect in the vegetated area, whereas constant values were observed on bare slopes. The performance of hydrodynamics parameters suggested that the dense rearward arrangement (SMD) was the optimal vegetation pattern to regulate flow conditions. Specifically, the vertical profiles of the velocity and turbulence features of the SMD arrangement at different sections demonstrated the significant role of vegetation density in identifying the velocity layers along the water depth. The maximum velocity and Reynolds Stress Number (RSN) indicated the position where local scour was most likely to occur, which would improve our basic understanding of the mechanisms underlying hydraulic and soil erosion processes.

A NUMERICAL SIMULATION OF THE WOS AND THE WAVE PROPAGATION ALONG A COASTAL DIKE

2012 ◽  
Vol 1 (33) ◽  
pp. 49 ◽  
Author(s):  
Panayotis Prinos ◽  
Maria Tsakiri ◽  
Dimitris Souliotis
Keyword(s):  
Numerical Simulation ◽  
Wave Propagation ◽  
Free Surface ◽  
Numerical Models ◽  
Field Measurements ◽  
Air Entrainment ◽  
Empirical Relationships ◽  
Wave Overtopping ◽  
Unsteady Rans ◽  
The Waves

Wave overtopping and the propagation of the waves on the crest and the landward slope of a coastal dike is investigated numerically. Wave overtopping conditions are simulated using the concept of the Wave Overtopping Simulator (WOS). Two numerical models of the WOS are constructed using the FLUENT 6.0.12 (FLUENT Inc. 2001) and the FLOW 3D 9.4 (FLOW 3D 2010) CFD codes. The former simulates the WOS without accounting for air entrainment while the latter accounts for air entrainment. The unsteady RANS equations, the RNG k-ε turbulence model and the VOF method are solved numerically, for "tracking" the free surface and the head of the "current" from the dike crest to the landward dike slope. The computed results from the two models are compared with each other and also against field measurements and proposed empirical relationships (Van der Meer et al. 2010).

scholarly journals RELATIONS BETWEEN THE RUN-UP AND OVERTOPPING OF WAVES

1972 ◽  
Vol 1 (13) ◽  
pp. 108 ◽  
Author(s):  
Shoshichiro Nagai ◽  
Akira Takada
Keyword(s):  
Standing Waves ◽  
Empirical Relationships ◽  
Wave Overtopping ◽  
Run Up ◽  
Reflection Of Waves

The quantitative relationships among run-up, overtopping and reflection of waves are presented in this paper. In addition, the authors have proposed several empirical relationships to calculate the height of wave run-up and the quantity of wave overtopping in the region of standing waves.

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