scholarly journals THE SIGNIFICANCE OF WAVE REFLECTION ON THE MORPHOLOGY OF INTERTIDAL MUDFLATS

2011 ◽  
Vol 1 (32) ◽  
pp. 50
Author(s):  
Elizabeth Chellew ◽  
Kate Rossington ◽  
Ian Townend ◽  
Carl Amos ◽  
Stephen Richardson
Keyword(s):  
Numerical Model ◽  
Wave Reflection ◽  
Wave Interaction ◽  
Equilibrium Form ◽  
Southampton Water ◽  
Intertidal Mudflats ◽  
Reflected Wave

The influence of seawalls in modifying the equilibrium form of a shoreline has previously caused extensive debate. A numerical model was used to predict the equilibrium form of muddy intertidal profiles, along a shoreline in Southampton Water, UK. It was found that the profile containing a seawall had a very different profile form to the undefended sites, and that this seawall profile could not be accurately represented in the model. The model was extended to include wave reflection from the seawall, producing a new prediction with a much improved resemblance of the observed profile. It was concluded that the likely cause of the different profile form at the site of the seawall in this case, is due incident and reflected wave interaction.

Abstract 2994: Gender-Related Differences in the Central Arterial Pressure Waveform Begin in Childhood and are Independent of Height

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Julian G Ayer ◽  
Albert Avolio ◽  
Guy Marks ◽  
Jason A Harmer ◽  
David S Celermajer
Keyword(s):  
Arterial Pressure ◽  
Wave Reflection ◽  
Augmentation Index ◽  
Systolic Pressure ◽  
Pressure Rise ◽  
Radial Pressure ◽  
Applanation Tonometry ◽  
Stiffness Index ◽  
Reflected Wave ◽  
Age Related

Introduction Women develop age-related LV hypertrophy and symptomatic heart failure to a greater extent than men. Contributing to this may be a higher pulsatile afterload in women, with a higher central arterial systolic augmentation pressure (AP, peak pressure minus pressure at systolic shoulder) and augmentation index (AIx, ratio of AP to pulse pressure). It is unclear if these differences are due to gender per se or shorter female stature. We studied 8-year old children to determine if gender-related differences in carotid pressure augmentation are present in early life and if so, whether they are independent of height (Ht). Methods 406 children (age 8.0 ± 0.1, 49% girls) had anthropometry, brachial systolic and diastolic BP (SBP, DBP), heart rate (HR) and carotid and radial pressure waveforms (by applanation tonometry, calibrated to mean BP and DBP) assessed. Carotid ultrasound evaluated arterial elasticity [Carotid Artery Compliance (CAC), Stiffness Index (SI) and Young’s Elastic Modulus (YEM)]. Results Boys and girls had a similar Ht (129 ± 6 v 128 ± 6 cm), BMI (17.6 ± 3.1 v 17.5 ± 3.0), SBP (100 ± 7 v 101 ± 5 mmHg), DBP (59 ± 6 v 60 ± 5 mmHg) and HR (80 ± 10 v 82 ± 10 bpm). The carotid AP and AIx were significantly higher in girls (−4 ± 3 v −6 ± 4 mmHg and −12 ± 8 v −16 ± 9 respectively, p < 0.001), indicating greater systolic pressure augmentation. Time to onset of the reflected wave ( Tr ) and time to peak of the reflected wave were shorter in girls (154 ± 19 v 163 ± 18 msec, p < 0.001 and 206 ± 23 v 212 ± 22 msec, p = 0.03 respectively), indicating earlier wave reflection. Girls had a higher velocity index (Vr) estimated from Ht ( Vr = Ht /Tr , 8.4 ± 1.0 v 8.0 ± 0.9 m/sec, p = 0.001). Ejection duration, maximum rate of pressure rise and time to systolic peak (indicating effect of ventricular ejection on the carotid waveform) were not significantly different between genders. Boys, however, had stiffer carotid arteries than girls [lower CAC (5.8 ± 1.5 v 6.2 ± 1.8 %/10 mmHg, p = 0.016), higher SI (2.7 ± 0.7 v 2.5 ± 0.7, p = 0.012) and YEM (735 ± 217 v 681 ± 237, p = 0.021)]. Conclusion Even in the first decade of life, girls demonstrate greater central arterial pressure augmentation than boys, with earlier wave reflection. This is independent of height and may contribute to cardiovascular morbidity in females, later in life.

Numerical Simulation of Wave Interaction With a Pair of Fixed Large Tandem Cylinders Subjected to Regular, Non-Breaking Waves

2021 ◽  
Author(s):  
M. Mohseni ◽  
C. Guedes Soares
Keyword(s):  
Numerical Model ◽  
Wave Field ◽  
Circular Cross Section ◽  
Wave Interaction ◽  
Breaking Waves ◽  
Wave Loading ◽  
Two Phase ◽  
Wave Regime ◽  
Wave Amplification ◽  
Vof Model

Abstract The wave interaction with cylinders placed in proximity results in significant modification of the wave field, wave-induced processes, and wave loading. The evaluation of such a complex wave regime and accurate assessment of the wave loading requires an efficient and accurate numerical model. Concerning the wave scattering types identified by Swan et al. (2015) and lateral progressive edge waves, this paper presents the application of a two-phase Computational Fluid Dynamics (CFD) model to carry out a detailed investigation of nonlinear wave field surrounding a pair of columns placed in the tandem arrangement in the direction of wave propagation and corresponding harmonics. The numerical analysis is conducted using the Unsteady Reynolds-Averaged Navier-Stokes/VOF model based on the OpenFOAM framework combined with the olaFlow toolbox for wave generation/absorption. For the simulations, the truncated cylinders are assumed vertical and surface piercing with a circular cross-section subjected to regular, non-breaking fifth-order Stokes waves propagating with moderate steepness in deep water. Primarily, the numerical model is validated with experimental data provided by ITTC (OEC)[1] for a single cylinder. Future, the given simulations are conducted for different centre-to-centre distances between the tandem large cylinders. The results show the evolution of a strong wave diffraction pattern and consequently high wave amplification harmonics around cylinders are apparent.

scholarly journals Wave Interaction with Single and Twin Vertical and Sloped Slotted Walls

2020 ◽  
Vol 8 (8) ◽  
pp. 589
Author(s):  
Mohamad Alkhalidi ◽  
Noor Alanjari ◽  
S. Neelamani
Keyword(s):  
Energy Dissipation ◽  
Transmission Coefficient ◽  
Wave Height ◽  
Wave Reflection ◽  
Wave Length ◽  
Wave Interaction ◽  
Wave Transmission ◽  
Random Wave ◽  
Dissipation Coefficient ◽  
Energy Dissipation Coefficient

The interaction between waves and slotted vertical walls was experimentally studied in this research to examine the performance of the structure in terms of wave transmission, reflection, and energy dissipation. Single and twin slotted barriers of different slopes and porosities were tested under random wave conditions. A parametric analysis was performed to understand the effect of wall porosity and slope, the number of walls, and the incoming relative wave height and period on the structure performance. The main focus of the study was on wave transmission, which is the main parameter required for coastal engineering applications. The results show that reducing wall porosity from 30% to 10% decreases the wave transmission by a maximum of 35.38% and 38.86% for single and twin walls, respectively, increases the wave reflection up to 47.6%, and increases the energy dissipation by up to 23.7% on average for single walls. For twin-walls, the reduction in wall porosity decreases the wave transmission up to 26.3%, increases the wave reflection up to 40.5%, and the energy dissipation by 13.3%. The addition of a second wall is more efficient in reducing the transmission coefficient than the other wall parameters. The reflection and the energy dissipation coefficients are more affected by the wall porosity than the wall slope or the existence of a second wall. The results show that as the relative wave height increases from 0.1284 to 0.2593, the transmission coefficient decreases by 21.2%, the reflection coefficient decreases by 15.5%, and the energy dissipation coefficient increases by 18.4% on average. Both the transmission and the reflection coefficients increase as the relative wave length increases while the energy dissipation coefficient decreases. The variation in the three coefficients is more significant in deep water than in shallower water.

scholarly journals A Discussion of Ionospheric Demodulation Near Gyro Frequency

1959 ◽  
Vol 12 (2) ◽  
pp. 157 ◽  
Author(s):  
GL Goodwin
Keyword(s):  
Modulation Frequency ◽  
Wave Interaction ◽  
Radio Waves ◽  
Large Magnitude ◽  
Reflected Wave ◽  
Made In

Observations made in Adelaide of the ionospheric demodulation of radio waves near gyro frequency at vertical incidence are discussed. The effect occurs in the region of about 90 km, and does not appear to decrease through dawn. An F-Iayer reflected wave is demodulated by unequal amounts during its two passages through the region. The large magnitude of the effect and its lack of dependence on modulation frequency seem to be inconsistent with the theory of wave interaction.

scholarly journals Wave interaction with Floating platform of different shapes and supports using BEM approach

2017 ◽  
Vol 14 (2) ◽  
pp. 115-133
Author(s):  
Anoop I. Shirkol ◽  
Nasar Thuvanismail
Keyword(s):  
Numerical Model ◽  
Elastic Plate ◽  
Wave Interaction ◽  
Wave Force ◽  
Ocean Waves ◽  
Wave Forces ◽  
Thin Elastic Plate ◽  
Floating Platform ◽  
Floating Elastic Plate ◽  
Different Shapes

Wave interaction with a floating thin elastic plate which can be used as floating platform is analyzed using Boundary Element Method (BEM) for different shapes such as rectangular, circular and triangular. Different support conditions are considered and the performance of the floating platform under the action of ocean waves is explored. The study is performed under the assumption of linearized water wave theory and the floating elastic plate is modelled based on the Euler-Bernoulli beam theory. Using Galerkin’s approach, a numerical model has been developed and the hydrodynamic loading on the floating elastic plate of shallow draft (thickness) is investigated. The wave forces are generated by the numerical model for the analysis of the floating plate. The resulting bending moment and optimal deflection due to encountering wave force is analysed. The present study will be helpful in design and analysis of the large floating platform in ocean waves.

Numerical Modelling of Breaking Wave Interaction With a Group of Four Vertical Slender Cylinders in Square Arrangements

2016 ◽  
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs ◽  
Arun Kamath ◽  
Dag Myrhaug ◽  
Øivind Asgeir Arnsten
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Model ◽  
Numerical Modelling ◽  
Wave Interaction ◽  
Wave Force ◽  
Wave Forces ◽  
Breaking Wave ◽  
Square Configuration ◽  
Breaking Wave Forces

The main purpose of the study is to investigate the breaking wave interaction with a group of four circular cylinders. The physical process of wave breaking involves many parameters and an accurate numerical modelling of breaking waves and the interaction with a structure remain a challenge. In the present study, the open-source (Computational Fluid Dynamics) CFD model REEF3D is used to simulate the breaking wave interaction with the multiple cylinders. The numerical model is based on the incompressible Reynolds Averaged Navier-Stokes (RANS) equations, the level set method for the free surface and the k–ω model for turbulence. The model uses a 5th-order conservative finite difference WENO scheme for the convective discretization and a 3rd-order Runge-Kutta scheme for time discretization. The numerical model is validated with experimental data of large-scale experiments for the free surface elevation and the breaking wave force on a single cylinder. A good agreement is seen between the numerical results and experimental data. Two different configurations with four cylinders are examined: in-line square configuration and diamond square configuration. The breaking wave forces on each cylinder in the group are computed for the two cases and the results are compared with the breaking wave force on a single isolated cylinder. Further, the study investigates the water surface elevations and the free surface flow features around the cylinders. In general, the cylinders in both configurations experience the maximum forces lower than the maximum force on a single cylinder. The results of the present study show that the interference effects from the neighbouring cylinders in a group strongly influence the kinematics around and the breaking wave forces on them.

Reflection effects on wave field within a harbour

1993 ◽  
Vol 20 (3) ◽  
pp. 386-397 ◽  
Author(s):  
Michael Isaacson ◽  
Enda O'Sullivan ◽  
John Baldwin
Keyword(s):  
Numerical Model ◽  
Wave Field ◽  
Wave Reflection ◽  
Diffraction Theory ◽  
Specific Reference ◽  
Wave Source ◽  
Numerical Predictions ◽  
Diffraction Wave ◽  
Reflecting Boundaries ◽  
Reflection Boundary

The present paper outlines a numerical model for predicting the wave field in a harbour with partially reflecting boundaries, and describes laboratory tests undertaken to assess the model. The numerical model is based on linear diffraction theory and involves the application of a partial reflection boundary condition. By utilizing a wave doublet representation of the fluid boundaries instead of the usual wave source representation, the extension is made to general harbour configurations that include breakwaters. Numerical results are compared with known solutions for specific reference configurations. Laboratory measurements have been made of the wave field within a particular harbour model having portions of the boundary corresponding to different degrees of wave reflection. A comparison with the numerical predictions is summarized and highlights the importance of adequately modelling the partial reflections within the harbour. Key words: breakwaters, coastal engineering, harbours, waves, wave diffraction, wave reflection.

SLIM: a numerical model to evaluate the factors controlling the evolution of intertidal mudflats in Venice Lagoon, Italy

2004 ◽  
Vol 51 (1-4) ◽  
pp. 257-280 ◽  
Author(s):  
Sergio Cappucci ◽  
Carl L. Amos ◽  
Taro Hosoe ◽  
Georg Umgiesser
Keyword(s):  
Numerical Model ◽  
Venice Lagoon ◽  
Intertidal Mudflats

Breaking Wave Interaction With a Group of Four Vertical Slender Cylinders in Two Square Arrangements

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs ◽  
Arun Kamath ◽  
Dag Myrhaug ◽  
Øivind Asgeir Arntsen
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Model ◽  
Wave Interaction ◽  
Wave Force ◽  
Maximum Force ◽  
Wave Forces ◽  
Breaking Wave ◽  
Square Configuration ◽  
Breaking Wave Forces

The main purpose of the study is to investigate the breaking wave interaction with a group of four circular cylinders. The physical process of wave breaking involves many parameters, and an accurate numerical modeling of breaking waves and the interaction with a structure remain a challenge. In the present study, the open-source computational fluid dynamics (CFD) model REEF3D is used to simulate the breaking wave interaction with multiple cylinders. The numerical model is based on the incompressible Reynolds-averaged Navier–Stokes (RANS) equations, the level set method for the free surface, and the k–ω model for turbulence. The numerical model is validated with experimental data of large-scale experiments for the free surface elevation and the breaking wave force on a single cylinder. A good agreement is obtained between the numerical results and experimental data. Two different configurations with four cylinders are examined: in-line square configuration and diamond square configuration. For both configurations, three different tank widths and four different spacings between the cylinders are investigated. The breaking wave forces on each cylinder in the group are computed for each case for the two configurations, and the results are compared with the breaking wave force on a single isolated cylinder. Furthermore, the study investigates the water surface elevations and the free surface flow features around the cylinders. For the closely spaced cylinders in a relatively narrower tank, the cylinders in both configurations experience the maximum forces lower than the maximum force on a single cylinder. But for the widely spaced cylinder in a relatively wider tank, the forces are higher and lower for the upstream cylinders and downstream cylinders, respectively, than the maximum force on a single isolated cylinder. The results of the present study show that the interference effects from the neighboring cylinders in a group strongly influence the kinematics around and the breaking wave forces on them.

THE INFLUENCES OF CARDIOVASCULAR PROPERTIES ON SUPRASYSTOLIC BRACHIAL CUFF WAVE STUDIED BY A SIMPLE ARTERIAL-TREE MODEL

2012 ◽  
Vol 12 (03) ◽  
pp. 1250040 ◽  
Author(s):  
FUYOU LIANG ◽  
SHU TAKAGI ◽  
HAO LIU
Keyword(s):  
Arterial Stiffness ◽  
Aortic Stiffness ◽  
Wave Reflection ◽  
Cuff Pressure ◽  
Time Lag ◽  
Wave Interaction ◽  
Tree Model ◽  
Arterial Tree ◽  
Physiological Conditions ◽  
Two Peaks

It has been found that a pronounced secondary systolic peak appears on the oscillometric wave recorded by a brachial oscillometric cuff as cuff pressure is raised to a suprasystolic level. This finding has accordingly motivated some studies aimed to explore the potential value carried by the cuff wave for assessing arterial stiffness. However, so far, there remain considerable controversies in the literature regarding the cardiovascular properties that dominate the characteristics of the cuff wave. In this context, we developed a simple arterial-tree model and applied it to investigate the respective influence on the cuff wave of various cardiovascular properties and the associated wave interaction phenomena. It was found that (1) neither aortic stiffness nor brachial arterial stiffness can uniquely determine the time lag (Δt) between the first and secondary peaks of the cuff wave, although both of them significantly influence Δt; and (2) the BAIx (an index that characterize the height of the secondary peak relative to the first) is sensitive to most of the investigated cardiovascular properties and physiological conditions, such as arterial stiffness, intensity of wave reflection in the lower body and heart rate, etc. These findings suggest that the reliability of assessing aortic stiffness based solely on the timings and heights of the two peaks is limited. Moreover, we argued that the controversial findings presented in previous model-based studies are likely to be caused by limitations related to the research objectives or computation conditions of the studies.

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