scholarly journals Characteristics of Positive Surges in a Rectangular Channel

Water ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1473 ◽  
Author(s):  
Feidong Zheng ◽  
Yun Li ◽  
Guoxiang Xuan ◽  
Zhonghua Li ◽  
Long Zhu
Keyword(s):  
Rectangular Channel ◽  
Experimental Studies ◽  
Wave Theory ◽  
Progressive Increase ◽  
Wave Crest ◽  
Linear Wave ◽  
Sudden Increase ◽  
Initial Profile ◽  
Increasing Trend ◽  
Flow Motion

A positive surge is an unsteady open channel flow motion characterized by an increase of flow depth. In previous experimental studies, a positive surge was typically induced by either a sudden increase of discharge in a channel or by the rapid closure of a downstream sluice gate, thus leading to a steep initial profile. However, in many instances, the evolution of a positive surge is of a progressive manner (e.g., in the downstream navigation canal during the emptying operation of lock chambers). In the present work, the inception and development of a positive surge induced by a progressive increase of discharge was investigated in a rectangular channel with a smooth bed. Both undular and breaking surges were studied. The results demonstrate that the maximum wave height at the first wave crest of an undular surge is in very close agreement with the McCowan theory. Additionally, the wave amplitude essentially shows a linearly increasing trend with an increasing surge Froude number up to Fr0 = 1.26 to 1.28, whereas it tends to suggest a power law reduction for larger surge Froude numbers. Moreover, the dispersion of undular surges is consistent with the linear wave theory only for surge Froude numbers close to unity. Overall, the present study demonstrates the unique features of positive surges induced by a progressive increase of discharge.

Crest-Height Distribution in Nonlinear Random Wave

2009 ◽  
Author(s):  
Cuilin Li ◽  
Dingyong Yu ◽  
Yangyang Gao ◽  
Junxian Yang
Keyword(s):  
Nonlinear Wave ◽  
Wave Theory ◽  
Distribution Functions ◽  
Theoretical Distribution ◽  
Distribution Model ◽  
Stokes Wave ◽  
Wave Crest ◽  
Linear Wave ◽  
Height Distribution ◽  
Crest Height

Many empirical and theoretical distribution functions for wave crest heights have been proposed, but there is a lack of agreement. With the development of ocean exploitation, waves crest heights represent a key point in the design of coastal structures, both fixed and floating, for shoreline protection and flood prevention. Waves crest height is the dominant parameter in assessing the likelihood of wave-in-deck impact and its resulting severe damage. Unlike wave heights, wave crests generally appear to be affected by nonlinearities; therefore, linear wave theory could not be satisfied to practical application. It is great significant to estimate a new nonlinear wave crest height distribution model correctly. This paper derives an approximation distribution formula based on Stokes wave theory. The resulting theoretical forms for nonlinear wave crest are compared with observed data and discussed in detail. The results are shown to be in good agreement. Furthermore, the results indicate that the new theoretical distribution has more accurate than other methods presented in this paper (e.g. Rayleigh distribution and Weibull distribution) and appears to have a greater range of applicability.

Investigation of Shallow Water Kinematics and Local Loading Effects on Reliability of Minimum Structures

2001 ◽  
Vol 124 (1) ◽  
pp. 41-47
Author(s):  
Suhartodjo Tuty ◽  
Mark J. Cassidy ◽  
Beverley F. Ronalds
Keyword(s):  
Shallow Water ◽  
Stream Function ◽  
Function Theory ◽  
Strong Relationship ◽  
Wave Theory ◽  
Wave Crest ◽  
Linear Wave ◽  
North West ◽  
Wave Kinematics ◽  
The North

In shallow water, and specifically for minimum structures, the critical wave height exponent α has been shown to vary significantly with structural configuration. Because of the strong relationship to the wave kinematics, α is also sensitive to the wave theory chosen. The North West Shelf offshore Australia has numerous minimum structures located in relatively shallow water, which requires non-linear wave theory. In the near-breaking condition, estimation of the wave crest kinematics is difficult, with Stream Function theory being the most widely used. However, various other wave theories and nonlinear numerical techniques have been developed to predict wave kinematics for shallow water conditions. The following wave theories are compared: regular Stream Function theory, Cnoidal wave theory, Stokes’ theory, NewWave theory, and a second-order correction to NewWave theory. Kinematics, loads and α results are presented for a cylinder in three different water depths.

scholarly journals INDIVIDUAL WAVE EFFECTS ON COASTAL STRUCTURE DAMAGE DURING WINDSTORMS

2018 ◽  
pp. 14
Author(s):  
Gregory Westcott ◽  
Annette R. Grilli ◽  
Stephan Grilli ◽  
James T. Kirby ◽  
Fengyan Shi
Keyword(s):  
Structural Damage ◽  
Wave Interaction ◽  
Wave Theory ◽  
Conservation Equation ◽  
Wave Crest ◽  
Linear Wave ◽  
Structure Damage ◽  
Interaction Terms ◽  
Structural Loading ◽  
Set Up

In hazard assessment studies that evaluate the damage caused to coastal structures by windstorm-generated surge and waves, the standard approach has been to estimate structural loading by applying phase-averaged wave propagation models (e.g., SWAN, STWAVE) and storm surge models (e.g., ADCIRC), coupled or not with each other. Bare-earth “Digital Elevation Models” (DEMs) have typically been used as a basis for model grid development, with sometimes empirical adjustments being made to beach profiles or dune crest levels to account for storm-induced erosion. In recent work, the latter approach has been improved by including real time morphodynamic changes in simulations, using models such as XBeach (e.g., Schambach 2017; Schambach et al., 2017), which are still based on the wave action conservation equation, including semi-empirical parameterizations of wave breaking and many formulations based on linear wave theory (e.g., phase/group velocity, radiation stresses,…), as well as low-order wave-wave interaction terms. Finally, structural damage has typically been estimated based on empirical damage curves, developed based on field surveys, that use flow depth and controlling wave crest height as inputs (e.g., Grilli et al., 2017). Neglected in this modeling approach, however, are dynamic set-up and runup effects, as well as strongly nonlinear wave interactions that occur near and in the surf and swash zones.

scholarly journals 10-year trend analysis of atrioventricular node ablation in patient with atrial fibrillation: 2005–2014 United State hospitalization

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
L Wu ◽  
B Narasimhan ◽  
A.N Shah ◽  
Y.Y Zheng ◽  
K Bhatia ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Atrioventricular Node ◽  
Health Care Research ◽  
Progressive Increase ◽  
Pharmacological Therapy ◽  
Af Ablation ◽  
Diagnosis Codes ◽  
Increasing Trend ◽  
Quality Guideline ◽  
Pacemaker Insertion

Abstract Introduction Atrial fibrillation (AF) ablation and Atrioventricular Node (AVN) ablation are both important non-pharmacological therapy of AF. In spite of increased availability of AF ablation data, that of AVN ablation per se is limited. Method AF ablation was identified using ICD-9 procedure code with principle diagnosis of AF from United States National Inpatient Sample database 2005–2014. From procedure and diagnosis codes of pacemaker insertion followed by ablation, the cohort who underwent AVN ablation was identified. Patients hospitalization with any diagnosis of other type of arrythmia or epicardial ablation were excluded. Complications were defined as per the Agency for Health Care Research and Quality guideline. Results Total AF ablation was noted to increase from 2005- 2011, and declined steadily from 2011–2014. In contrast, the number of AVN ablations increased from 4505 cases to 5175 (Figure 1). AVN ablation were mainly performed in elderly patient (mean age 72), and increasingly in patient with higher Charlson Commobidity index (0.9 to 1.7)and higher CHA2DS2-VASc score (2.8 to 3.7) (Table 1). An increasing trend in procedure complications but no significant change in mortalitywere observed with AVN ablation. Progressive increase in the length of stay and the hospitalization cost were also observed over the years with AVN ablation. Conclusion AVN ablation is being performed at a steady volume, and increasingly in patients with multiple comorbidities. This trend although was not associated with increased mortality, it was associated with increased hospital complications. Funding Acknowledgement Type of funding source: None

A Second Order Lagrangian Model for Irregular Ocean Waves

2005 ◽  
Vol 128 (3) ◽  
pp. 177-183 ◽  
Author(s):  
Sébastien Fouques ◽  
Harald E. Krogstad ◽  
Dag Myrhaug
Keyword(s):  
Specular Reflection ◽  
Fluid Velocity ◽  
Equations Of Motion ◽  
Wave Theory ◽  
Ocean Waves ◽  
Second Order ◽  
Lagrangian Model ◽  
Lagrangian Description ◽  
Linear Wave ◽  
Irregular Solution

Synthetic aperture radar (SAR) imaging of ocean waves involves both the geometry and the kinematics of the sea surface. However, the traditional linear wave theory fails to describe steep waves, which are likely to bring about specular reflection of the radar beam, and it may overestimate the surface fluid velocity that causes the so-called velocity bunching effect. Recently, the interest for a Lagrangian description of ocean gravity waves has increased. Such an approach considers the motion of individual labeled fluid particles and the free surface elevation is derived from the surface particles positions. The first order regular solution to the Lagrangian equations of motion for an inviscid and incompressible fluid is the so-called Gerstner wave. It shows realistic features such as sharper crests and broader troughs as the wave steepness increases. This paper proposes a second order irregular solution to these equations. The general features of the first and second order waves are described, and some statistical properties of various surface parameters such as the orbital velocity, slope, and mean curvature are studied.

On nonlinear extrapolation of the linear wave theory for shallow flows

2002 ◽  
Author(s):  
E.L. Amromin ◽  
Yu.S. Timoshin ◽  
L.G. Stchemelinin
Keyword(s):  
Wave Theory ◽  
Linear Wave ◽  
Linear Wave Theory ◽  
Shallow Flows

Does linear wave theory support freak waves?

2006 ◽  
pp. 1023-1028
Author(s):  
Paulo Monica ◽  
Sara Cosme
Keyword(s):  
Wave Theory ◽  
Linear Wave ◽  
Freak Waves ◽  
Linear Wave Theory

Estimation of rogue wave loads on ship structures by exploiting linear wave theory

2021 ◽  
pp. 3-9
Author(s):  
M. Acanfora ◽  
T. Coppola ◽  
E. Fasano
Keyword(s):  
Rogue Wave ◽  
Wave Theory ◽  
Linear Wave ◽  
Wave Loads ◽  
Ship Structures ◽  
Linear Wave Theory

Three Dimensional Model of Snake-Type Wavemakers using Linear Wave Theory

2018 ◽  
Author(s):  
Zahnur Nurdin ◽  
Muarif Muarif ◽  
Said Munzir ◽  
Tulus Tulus ◽  
Mardiningsih Mardiningsih ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Wave Theory ◽  
Linear Wave ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Linear Wave Theory
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