scholarly journals WAVE REFLECTION AND TRANSMISSION FOR PILE ARRAYS

1972 ◽  
Vol 1 (13) ◽  
pp. 106 ◽  
Author(s):  
Brian J. Van Weele ◽  
John B. Herbich
Keyword(s):  
Wave Height ◽  
Wave Reflection ◽  
Wave Transmission ◽  
Pile Groups ◽  
Wave Reflections ◽  
Reflection And Transmission ◽  
Wave Characteristics ◽  
Staggered Arrangement ◽  
Sea Wall ◽  
Reflection Characteristics

A group of piles in a specific geometric pattern may represent a part of a foundation supported by multiple pilings or a porous sea wall or other type of porous coastal structure. "Wave characteristics" of such a structure will include not only the wave transmission but also wave reflection characteristics. Most of the experiments in the past on pile groups were mainly concerned with wave transmission characteristics as a function of wave height and period. The main purpose of these previous studies was to evaluate the absorption characteristics of pile groups, and wave reflections were generally not measured, or evaluated. Variables in this study included wave characteristics such as wave height and length and three types of symmetric pile arrays, two providing clear spacing in the direction of the wave between pile rows and one with a staggered arrangement. The results presented in dimensionless form show the effect of pile geometry and wave steepness on the coefficient of reflection and transmissibility.

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.

Numerical Simulation of Water Wave Propagation Over Porous Slope Bottom by Using Two-Domain Method

2019 ◽  
Author(s):  
Eun-Hong Min ◽  
Weoncheol Koo
Keyword(s):  
Wave Reflection ◽  
Computational Domain ◽  
Numerical Wave Tank ◽  
Flow Conditions ◽  
Reflection And Transmission ◽  
Wave Characteristics ◽  
Boundary Interaction ◽  
Domain Method ◽  
Propagating Waves ◽  
Numerical Wave

Abstract This study aims at the numerical analysis of wave characteristics when a wave propagates on the porous slope seabed. Numerical wave tank technique was developed using boundary element method with constant panels on the boundary. The fluid was satisfied with potential flow conditions and Darcy’s law was applied for porous intersection. Two computational domain method, which consists of fluid and porous domains, was used to simulate the propagating waves over a sloped seabed having a permeability. To consider fluid-porous boundary interaction, three-step boundary value problems were calculated. The wave amplitude decreased along the free surface as the wave propagated over a sloped bottom. The wave reflection and transmission by subsea structures were also analyzed.

scholarly journals APPLYING PIV MEASUREMENTS ON FLOW FIELD OF WAVES PROPAGATING OVER A SINGLE SUBMERGED POROUS ELASTIC BREAKWATER

2012 ◽  
Vol 1 (33) ◽  
pp. 29
Author(s):  
Tai-Wen Hsu ◽  
Yuan-Jyh Lan ◽  
Jian-Wu Lai ◽  
Yung-Han Cheng ◽  
Shan-Hwei Ou
Keyword(s):  
Flow Field ◽  
Wave Reflection ◽  
Surface Friction ◽  
The Other ◽  
Pressure Gradients ◽  
Wave Reflections ◽  
Reflection And Transmission ◽  
Submerged Breakwater ◽  
Piv Measurements ◽  
Image Velocimetry

The objective of the present study is to investigate the flow field for waves propagating over a submerged poro-elastic breakwater. Particle Image Velocimetry (PIV) measurements were performed in wave conditions with breakwaters made of different materials. The experimental results were compared for various rigid and impermeable, elastic and impermeable, as well as poro-elastic cases. Measurements of wave reflection and transmission induced by soft and permeable submerged breakwaters are both carried out. The results show that the oscillatory motion of elastic submerged breakwater can induce extra reflective waves and result in a larger reflection coefficient. Positive (counterclockwise) and negative (clockwise) vortices are generated due to corner separation and pressure gradients. The negative vortex obtained in a poro-elastic breakwater is generated by the surface friction at the top of the structure. Because of the permeability, it is found that the negative vortex at the upstream side of the elastic and permeable case is smaller than that of the rigid and impermeable one. In contrast, the positive vortex at the downstream side of the poro-elastic case is larger than that seen with the other two cases. It is concluded that a poro-elastic breakwater would induce different wave reflections and flow patterns from those seen with the other cases due to its particular wave and structure interactions.

On the Interaction of Waves With an Array of Open Chambered Structures: Application to Wave Energy Converters

2010 ◽  
Author(s):  
V. Venugopal ◽  
I. G. Bryden ◽  
A. R. Wallace
Keyword(s):  
Wave Height ◽  
Wave Energy ◽  
Significant Wave Height ◽  
Wave Reflection ◽  
Wave Climate ◽  
Random Waves ◽  
Maximum Increase ◽  
Reflection And Transmission ◽  
Significant Wave ◽  
Adjacent Structures

The results of a study carried out to determine the modification of wave climate around an array of open chambered structures, which could represent an array of wave power devices are presented in this paper. The wave-structure interaction is studied using the Boussinesq wave model within the MIKE 21 suite software. The spacing between two adjacent structures within the array is varied from 1S to 5S, where S is equal to 20 m. The effect of varying the spacing between individual structures and the resulting wave reflection and transmission around the array is illustrated using simulated random waves. The results show that the degree of reflection and transmission mainly depends on the spacing between individual structures and the peak wave periods. The maximum increase in significant wave height due to wave reflection in front of the array reached about 39% and the maximum reduction in significant wave height downstream the array is found to be about 41%. The results presented in this paper should be of interest to the wave energy industry.

Reducing Undesired Wave Reflection at Domain Boundaries in 3D Finite Volume-Based Flow Simulations via Forcing Zones

2020 ◽  
Vol 64 (01) ◽  
pp. 23-47
Author(s):  
Robinson Peric ◽  
Moustafa Abdel-Maksoud
Keyword(s):  
Finite Volume ◽  
Wave Reflection ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Special Focus ◽  
Computational Domain ◽  
Wave Reflections ◽  
Flow Simulations ◽  
Large Eddy ◽  
Domain Boundaries

This article reviews different types of forcing zones (sponge layers, damping zones, relaxation zones, etc.) as used in finite volume-based flow simulations to reduce undesired wave reflections at domain boundaries, with special focus on the case of strongly reflecting bodies subjected to long-crested incidence waves. Limitations and possible sources of errors are discussed. A novel forcing-zone arrangement is presented and validated via three-dimensional (3D) flow simulations. Furthermore, a recently published theory for predicting the forcing-zone behavior was investigated with regard to its relevance for practical 3D hydrodynamics problems. It was found that the theory can be used to optimally tune the case-dependent parameters of the forcing zones before running the simulations. 1. Introduction Wave reflections at the boundaries of the computational domain can cause significant errors in flow simulations, and must therefore be reduced. In contrast to boundary element codes, where much progress in this respect has been made decades ago (see e.g., Clement 1996; Grilli &Horillo 1997), for finite volume-based flow solvers, there are many unresolved questions, especially:How to reliably reduce reflections and disturbances from the domain boundaries?How to predict the amount of undesired wave reflection before running the simulation? This work aims to provide further insight to these questions for flow simulations based on Navier-Stokes-type equations (Reynolds-averaged Navier-Stokes, Euler equations, Large Eddy Simulations, etc.), when using forcing zones to reduce undesired reflections. The term "forcing zones" is used here to describe approaches that gradually force the solution in the vicinity of the boundary towards some reference solution, as described in Section 2; some examples are absorbing layers, sponge layers, damping zones, relaxation zones, or the Euler overlay method (Mayer et al. 1998; Park et al. 1999; Chen et al. 2006; Choi &Yoon 2009; Jacobsen et al. 2012; Kimet al. 2012; Schmitt & Elsaesser 2015; Perić & Abdel-Maksoud 2016a; Vukčević et al. 2016).

Distribution of Wave Impact Forces From Breaking and Non-Breaking Waves

2009 ◽  
Author(s):  
Anne M. Fullerton ◽  
Thomas C. Fu ◽  
Edward S. Ammeen
Keyword(s):  
Free Surface ◽  
Wave Height ◽  
Breaking Waves ◽  
Qualitative Assessment ◽  
Total Force ◽  
Impact Loads ◽  
Wave Impact ◽  
Data Set ◽  
Wave Characteristics ◽  
Wide Range

Impact loads from waves on vessels and coastal structures are highly complex and may involve wave breaking, making these changes difficult to estimate numerically or empirically. Results from previous experiments have shown a wide range of forces and pressures measured from breaking and non-breaking waves, with no clear trend between wave characteristics and the localized forces and pressures that they generate. In 2008, a canonical breaking wave impact data set was obtained at the Naval Surface Warfare Center, Carderock Division, by measuring the distribution of impact pressures of incident non-breaking and breaking waves on one face of a cube. The effects of wave height, wavelength, face orientation, face angle, and submergence depth were investigated. A limited number of runs were made at low forward speeds, ranging from about 0.5 to 2 knots (0.26 to 1.03 m/s). The measurement cube was outfitted with a removable instrumented plate measuring 1 ft2 (0.09 m2), and the wave heights tested ranged from 8–14 inches (20.3 to 35.6 cm). The instrumented plate had 9 slam panels of varying sizes made from polyvinyl chloride (PVC) and 11 pressure gages; this data was collected at 5 kHz to capture the dynamic response of the gages and panels and fully resolve the shapes of the impacts. A Kistler gage was used to measure the total force averaged over the cube face. A bottom mounted acoustic Doppler current profiler (ADCP) was used to obtain measurements of velocity through the water column to provide incoming velocity boundary conditions. A Light Detecting and Ranging (LiDAR) system was also used above the basin to obtain a surface mapping of the free surface over a distance of approximately 15 feet (4.6 m). Additional point measurements of the free surface were made using acoustic distance sensors. Standard and high-speed video cameras were used to capture a qualitative assessment of the impacts. Impact loads on the plate tend to increase with wave height, as well as with plate inclination toward incoming waves. Further trends of the pressures and forces with wave characteristics, cube orientation, draft and face angle are investigated and presented in this paper, and are also compared with previous test results.

scholarly journals Wave Transformation for International Hub Port Planning (Transformasi Gelombang untuk Perencanaan Pelabuhan Hub Internasional)

2015 ◽  
Vol 20 (1) ◽  
pp. 9
Author(s):  
Denny Nugroho Sugianto ◽  
Purwanto Purwanto ◽  
Andika B Candra
Keyword(s):  
Wave Height ◽  
Vital Role ◽  
Ocean Wave ◽  
Wave Transformation ◽  
Wave Refraction ◽  
Wave Characteristics ◽  
Maximum Period ◽  
Wave Patterns ◽  
Port Planning ◽  
North Sumatra

Indonesia merupakan salah satu negara kepulauan terbesar di dunia sehingga peran pelabuhan sangat vital dalam pembangunan ekonomi. Pelabuhan bukan hanya sekedar sebagai pelengkap infrastruktur, melainkan harus direncanakan dan dikelola dengan baik serta memperhatikan fenomena dinamika perairan laut seperti pola gelombang laut. Data gelombang laut menjadi faktor penting dalam perencanaan tata letak dan tipe bangunan pantai karena dipengaruhi oleh tinggi gelombang signifikan, tunggang pasang surut dan transformasi gelombang. Penelitian ini mengalisis karaketristrik dan bentuk transformasi gelombang untuk perencanaan Pelabuhan Hub Internasional, sebagai studi kasus adalah pelabuhan di Kuala Tanjung, Kabupaten Batu Bara. Pelabuhan di Kuala Tanjung merupakan salah satu dari 2 pelabuhan hub internasional yang direncanakan akan dibangun oleh pemerintah Indonesia. Metode yang digunakan adalah metode kuantitatif yang dilakukan dengan perhitungan statistik dan pemodelan matematik dengan modul hydrodinamic dan spectral wave untuk mengetahui arah penjalaran dan transformasi gelombang. Hasil dari data ECMWF selama 1999–Juni 2014, diketahui tinggi gelombang signifikan (Hs) maksimum mencapai 1,69 m dan periode maksimum 8 detik. Karakteristik gelombang termasuk klasifikasi gelombang laut transisi dengan nilai d.L-1 berkisar anrata 0,27–0,48 dan berdasarkan periodenya diklasifikasikan sebagai gelombang gravitasi.Transformasi gelombang terjadi akibat pendangkalan dengan koefesian pendangkalan Ks 0,93–0,98 dan proses refraksi gelombang dengan koefesien Kr 0,97–0,99. Tinggi gelombang pecah Hb sebesar 1,24 meter dengan kedalaman gelombang pecah db sebesar 1,82 meter. Efektifitas desain bangunan terminal di Pelabuhan Kuala Tanjung secara keseluruhan untuk sepanjang musim sebesar 79,8% atau dapat dikatakan cukup efektif dalam meredam gelombang. Kata kunci: transformasi gelombang, tinggi dan periode gelombang, pelabuhan Indonesia is one of the largest archipelagic countries in the world, therefore port has vital role in economic development. Port is not just as a complement to the infrastructure, but it must be planned and managed properly and attention to the dynamics of marine phenomena such as ocean wave patterns. Ocean wave data become important factors in planning coastal building, since it is influenced by wave height, tides and waves transformation. The purpose of this study was to analyse characteristic and forms wave transformations for planning of international hub port at Kuala Tanjung, Baru Bara District North Sumatra. This port is one of two Indonesian government's plan in the development of international hub port. Quantitative method was used in this study by statistical calculations and mathematical modeling with hydrodinamic modules and spectral wave to determine the direction of wave propagation and transformation. Results show that based on ECMWF data during 1999-June 2014, known significant wave height (Hs) maximum of 1.69 m and maximum period (Ts) of 8 secs. The classification wave characteristics iswave transition (d.L-1: 0.27–0.48) and by the period are classified as gravitational waves. Wave transformation occurs due to the soaling, withKs 0.93–0.98 and the wave refraction Kr 0.97–0.99. Whereas Hb of 1.24 meters anddb 1.82 meters. The effectiveness of the design of the terminal building at the Port of Kuala Tanjung overall for the season amounted to 79.8%, which is quite effective in reducing the wave. Keywords: wave transformation, wave height and period, Port of Kuala Tanjung

scholarly journals Effects of pacing modality on noninvasive assessment of heart rate dependency of indices of large artery function

2016 ◽  
Vol 121 (3) ◽  
pp. 771-780 ◽  
Author(s):  
Isabella Tan ◽  
Hosen Kiat ◽  
Edward Barin ◽  
Mark Butlin ◽  
Alberto P. Avolio
Keyword(s):  
Heart Rate ◽  
Arterial Stiffness ◽  
Pulse Pressure ◽  
Wave Reflection ◽  
Pulse Wave ◽  
Augmentation Index ◽  
Large Artery ◽  
Rate Dependency ◽  
Wave Reflections

Studies investigating the relationship between heart rate (HR) and arterial stiffness or wave reflections have commonly induced HR changes through in situ cardiac pacing. Although pacing produces consistent HR changes, hemodynamics can be different with different pacing modalities. Whether the differences affect the HR relationship with arterial stiffness or wave reflections is unknown. In the present study, 48 subjects [mean age, 78 ± 10 (SD), 9 women] with in situ cardiac pacemakers were paced at 60, 70, 80, 90, and 100 beats per min under atrial, atrioventricular, or ventricular pacing. At each paced HR, brachial cuff-based pulse wave analysis was used to determine central hemodynamic parameters, including ejection duration (ED) and augmentation index (AIx). Wave separation analysis was used to determine wave reflection magnitude (RM) and reflection index (RI). Arterial stiffness was assessed by carotid-femoral pulse wave velocity (cfPWV). Pacing modality was found to have significant effects on the HR relationship with ED ( P = 0.01), central aortic pulse pressure ( P = 0.01), augmentation pressure ( P < 0.0001), and magnitudes of both forward and reflected waves ( P = 0.05 and P = 0.003, respectively), but not cfPWV ( P = 0.57) or AIx ( P = 0.38). However, at a fixed HR, significant differences in pulse pressure amplification ( P < 0.001), AIx ( P < 0.0001), RM ( P = 0.03), and RI ( P = 0.03) were observed with different pacing modalities. These results demonstrate that although the HR relationships with arterial stiffness and systolic loading as measured by cfPWV and AIx were unaffected by pacing modality, it should still be taken into account for studies in which mixed pacing modalities are present, in particular, for wave reflection studies.

Wave Propagation Analysis of an Axially Strained, Rotating Timoshenko Shaft: Part II

1997 ◽  
Author(s):  
Bongsu Kang ◽  
Chin An Tan
Keyword(s):  
Boundary Conditions ◽  
Wave Reflection ◽  
Axial Strain ◽  
Free Vibration Analysis ◽  
Reflection And Transmission ◽  
Transmission Coefficients ◽  
Propagation Analysis ◽  
Geometric Discontinuities ◽  
Bernoulli Models ◽  
Incident Waves

Abstract In this paper, the wave reflection and transmission characteristics of an axially strained, rotating Timoshenko shaft under general support and boundary conditions, and with geometric discontinuities are examined. As a continuation to Part I of this paper (Kang and Tan, 1997), the wave reflection and transmission at point supports with finite translational and rotational constraints are further discussed. The reflection and transmission matrices for incident waves upon general supports and geometric discontinuities are derived. These matrices are combined, with the aid of the transfer matrix method, to provide a concise and systematic approach for the free vibration analysis of multi-span rotating shafts with general boundary conditions. Results on the wave reflection and transmission coefficients are presented for both the Timoshenko and the Euler-Bernoulli models to investigate the effects of the axial strain, shaft rotation speed, shear and rotary inertia.

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