Gravity Wave Trapping by Series of Horizontally Stratified Wave Absorbers Away From Seawall

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
V. Venkateswarlu ◽  
D. Karmakar
Keyword(s):  
Dynamic Pressure ◽  
Vertical Wall ◽  
Expansion Method ◽  
Wave Theory ◽  
Middle Layer ◽  
Bottom Layer ◽  
Rigid Wall ◽  
Wave Trapping ◽  
Chamber Length ◽  
Eigenfunction Expansion Method

Abstract The fluid oscillation between the rigid wall and stratified wave absorber is analyzed in the context of the linearized water wave theory. The stratified wave absorber is composed of multiple horizontal layers considering higher porosity in the surface layer, moderate porosity in the middle layer, and zero porosity in the bottom layer. The study examined the wave motion through multiple horizontally stratified wave absorbers on solving the multilayer dispersion relation. The eigenfunction expansion method is used to form the system of analytical equations using the property of orthogonal mode-coupling relation with continuity of dynamic pressure and velocity at each of the interfaces. The free spacing available between leeward porous wave absorber and the rigid wall is termed as “trapping chamber.” The effect of the trapping chamber on wave reflection and fluid force experienced by a rigid wall is discussed. The analytical results formulated for the physical problem are validated with the available experimental and numerical results. The wave trapping is examined and compared for three types of seawalls such as vertical wall, permeable wall, and stepped wall. The change in trapping chamber length shows the harmonic peaks and troughs in the trapping coefficients and the harmonic oscillations help in the design and development of the stratified porous wave absorbers for the protection of marine infrastructure.

Analysis of Wave Action Through Multiple Submerged Porous Structures

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Mohamin B. M. Khan ◽  
Harekrushna Behera
Keyword(s):  
Wave Energy ◽  
Structural Parameters ◽  
Wave Interaction ◽  
Expansion Method ◽  
Wave Theory ◽  
Rigid Wall ◽  
Porous Structures ◽  
Wave Trapping ◽  
Linear Water Wave Theory ◽  
Multiple Structures

Abstract Wave interaction with multiple bottom-standing rectangular porous structures of different structural parameters is numerically modeled using the multidomain boundary element method and the matched eigenfunction expansion method, while assuming linear water wave theory. The sensitivity of wave reflection and transmission to the wave and structural parameters is analyzed with the objective to maximize wave energy attenuation. Different configurations of multiple structures are tested for maximizing the efficiency of dissipation. Furthermore, wave trapping by multiple porous structures near a sloping rigid wall is studied. Bragg resonance is observed in the case of wave scattering by multiple structures irrespective of wave and structural parameters and is found as proportional to the number of structures deployed. In addition, the study reveals that in the presence of multiple structures, due to more wave energy dissipation, wave transmission in the lee side of the structures is reduced significantly when compared with that observed for a single structure.

scholarly journals A Theoretical Study of the Hydrodynamic Performance of an Asymmetric Fixed-Detached OWC Device

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2637
Author(s):  
Ayrton Alfonso Medina Rodríguez ◽  
Rodolfo Silva Casarín ◽  
Jesús María Blanco Ilzarbe
Keyword(s):  
Vertical Wall ◽  
Expansion Method ◽  
Wave Theory ◽  
Hydrodynamic Performance ◽  
Linear Wave ◽  
Low Frequencies ◽  
Linear Wave Theory ◽  
Hydrodynamic Efficiency ◽  
Eigenfunction Expansion Method ◽  
Good Agreement

The chamber configuration of an asymmetric, fixed-detached Oscillating Water Column (OWC) device was investigated theoretically to analyze its effects on hydrodynamic performance. Two-dimensional linear wave theory was used, and the solutions for the associated radiation and scattering boundary value problems (BVPs) were derived through the matched eigenfunction expansion method (EEM) and the boundary element method (BEM). The results for the hydrodynamic efficiency and other important hydrodynamic properties were computed and analyzed for various cases. Parameters, such as the length of the chamber and the thickness and submergence of the rear and front walls, were varied. The effects on device performance of adding a step under the OWC chamber and reflecting wall in the downstream region were also investigated. A good agreement between the analytical and numerical results was found. Thinner walls and low submergence of the chamber were seen to increase the efficiency bandwidth. The inclusion of a step slightly reduced the frequency at which resonance occurs, and when a downstream reflecting wall is included, the hydrodynamic efficiency is noticeably reduced at low frequencies due to the near trapped waves in the gap between the OWC device and the rigid vertical wall.

Wave motion over stratified porous absorber combined with seaward vertical barrier

2020 ◽  
Vol 234 (4) ◽  
pp. 830-845
Author(s):  
Valliboina Venkateswarlu ◽  
Debabrata Karmakar
Keyword(s):  
Wave Reflection ◽  
Single Layer ◽  
Expansion Method ◽  
Wave Theory ◽  
Wave Trapping ◽  
Eigenfunction Expansion Method ◽  
Vertical Barrier ◽  
Friction Factors ◽  
Structural Configurations ◽  
Analytical Relations

The oblique wave reflection by horizontally stratified porous absorber having two horizontal porous bars of different porosities and friction factors placed on step-type bottom is studied using eigenfunction expansion method based on linearised wave theory. The present study examines several structural configurations such as porous absorber consisting of finite and semi-infinite thickness with/without seaward vertical barrier. The present study derived the direct analytical relations to determine wave reflection by each of the structural configuration for plane-wave assumption using potential flow theory. Initially, the porous absorber considering uniform porosity and friction factor is examined and validated with available numerical results, and the direct analytical relations are also validated with available relations of possible structural configurations. In addition, the present study reported wave reflection performance of submerged single-layer and double-layer porous absorbers with/without seaward vertical barrier. The effect of bottom rigid bar, surface porous bar, middle porous bar depth, multiple porosities, friction factors, incident wave angle and porous effect parameter on wave reflection coefficient is presented in detail for various structural configurations. The significance of seaward vertical barrier on wave reflection and wave trapping is reported. The point of wave trapping, critical angle of impinging, resonating peaks and troughs due to various structural configurations are presented against structural thickness.

scholarly journals Radiated Force due to Surge Motion by a Pair of Submerged Cylinder in Water

2019 ◽  
Vol 8 (10) ◽  
pp. 3205-3210
Keyword(s):  
Water Wave ◽  
Expansion Method ◽  
Wave Theory ◽  
Finite Depth ◽  
Added Mass ◽  
Damping Coefficient ◽  
Hydrodynamic Coefficients ◽  
Linear Water Wave Theory ◽  
Eigenfunction Expansion Method ◽  
Submerged Cylinder

Evaluation of hydrodynamic coefficients due to surge of submerged structure is great significant to designing a device which can be consider as a device of wave energy. In the present work, a theoretical approach is developed to describe radiation of water wave by fully submerged cylinder placed above a submerged circular plate in water of finite depth which is based on linear water wave theory The radiation problem due to surge motion by this pair of cylinders have investigated with the suspicion of linear water wave theory. To determine the radiated potentials in every area, we utilize the eigenfunction expansion method and variables separation method. Finally, we derived the analytical expressions of Hydrodynamic coefficients i. e. added mass and damping coefficient due to surge and associated unknown coefficients are calculated by utilizing the matching conditions between the physical and virtual boundaries. A set of added mass and damping coefficient have presented graphically for various radius of the submerge cylinder.

scholarly journals Theoretical Hydrodynamic Analysis of a Surface-Piercing Porous Cylindrical Body

Fluids ◽  
2021 ◽  
Vol 6 (9) ◽  
pp. 320
Author(s):  
Dimitrios N. Konispoliatis ◽  
Ioannis K. Chatjigeorgiou ◽  
Spyridon A. Mavrakos
Keyword(s):  
Water Waves ◽  
Wave Attenuation ◽  
Three Dimensional ◽  
Cylindrical Body ◽  
Expansion Method ◽  
Wave Theory ◽  
Linear Wave ◽  
Wave Loads ◽  
Dimensional Solution ◽  
Eigenfunction Expansion Method

In the present study, the diffraction and the radiation problems of water waves by a surface-piercing porous cylindrical body are considered. The idea conceived is based on the capability of porous structures to dissipate the wave energy and to minimize the environmental impact, developing wave attenuation and protection. In the context of linear wave theory, a three-dimensional solution based on the eigenfunction expansion method is developed for the determination of the velocity potential of the flow field around the cylindrical body. Numerical results are presented and discussed concerning the wave elevation and the hydrodynamic forces on the examined body for various values of porosity coefficients. The results revealed that porosity plays a key role in reducing/controlling the wave loads on the structure and the wave run-up, hence porous barriers can be set up to protect a marine structure against wave attack.

Wave scattering by a fixed submerged platform over a step bottom

2017 ◽  
Vol 233 (1) ◽  
pp. 93-107 ◽  
Author(s):  
Ramnarayan Mondal ◽  
Ken Takagi
Keyword(s):  
Water Wave ◽  
Wave Scattering ◽  
Rectangular Cross Section ◽  
Vertical Wall ◽  
Expansion Method ◽  
Wave Theory ◽  
Geometrical Parameters ◽  
Linear Water Wave Theory ◽  
Expansion Formulae ◽  
Submerged Body

This study deals with oblique and normal water wave scattering by a fixed submerged body of rectangular cross section which is infinite in length and finite in width. The fluid domain is considered as infinite as well as semi-infinite in nature. The study is carried out under the assumption of small amplitude linear water wave theory. It is considered that the bottom has a step and the submerged body is considered in shallower water depth region. The velocity potential is derived using the eigenfunction expansion method. The unknown constants, which appear in the expansion formulae, are obtained using orthogonal relation along with the boundary conditions at the interfaces. The wave-induced hydrodynamic forces acting on the submerged body and vertical wall are computed for different geometrical parameters. The wave reflection coefficient and the free surface motion are also calculated to see the wave phenomena around the submerged body.

scholarly journals High-Gain Vivaldi Antenna with Wide Bandwidth Characteristics for 5G Mobile and Ku-Band Radar Applications

Electronics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 667
Author(s):  
Raza Ullah ◽  
Sadiq Ullah ◽  
Farooq Faisal ◽  
Rizwan Ullah ◽  
Dong-you Choi ◽  
...  
Keyword(s):  
Mobile Communication ◽  
Middle Layer ◽  
Bottom Layer ◽  
High Gain ◽  
Mirror Image ◽  
Radar Applications ◽  
Vivaldi Antenna ◽  
5G Mobile Communication ◽  
Element Array ◽  
Ku Band

In this paper, antipodal Vivaldi antenna is designed for 5th generation (5G) mobile communication and Ku-band applications. The proposed designed has three layers. The upper layer consists of eight-element array of split-shaped leaf structures, which is fed by a 1-to-8 power divider network. Middle layer is a substrate made of Rogers 5880. The bottom layer consists of truncated ground and shorter mirror-image split leaf structures. The overall size of the designed antenna is confined significantly to 33.31 × 54.96 × 0.787 (volume in mm3), which is equivalent to 2λo× 3.3λo× 0.05λo (λo is free-space wavelength at 18 GHz). Proposed eight elements antenna is multi-band in nature covering Ku-bands (14.44–20.98 GHz), two millimeter wave (mmW) bands i.e., 24.34–29 GHz and 33–40 GHz, which are candidate frequency bands for 5G communications. The Ku-Band is suitable for radar applications. Proposed eight elements antenna is very efficient and has stable gain for 5G mobile communication and Ku-band applications. The simulation results are experimentally validated by testing the fabricated prototypes of the proposed design.

The Quasi-Static Analysis for Two-Dimensional Thin Plates

2011 ◽  
Vol 255-260 ◽  
pp. 166-169
Author(s):  
Li Chen ◽  
Yang Bai
Keyword(s):  
Boundary Conditions ◽  
Eigenfunction Expansion ◽  
Solution Space ◽  
Expansion Method ◽  
Fundamental Solutions ◽  
Thin Plates ◽  
Elastic Plates ◽  
Various Boundary Conditions ◽  
Eigenfunction Expansion Method ◽  
Concentration Phenomena

The eigenfunction expansion method is introduced into the numerical calculations of elastic plates. Based on the variational method, all the fundamental solutions of the governing equations are obtained directly. Using eigenfunction expansion method, various boundary conditions can be conveniently described by the combination of the eigenfunctions due to the completeness of the solution space. The coefficients of the combination are determined by the boundary conditions. In the numerical example, the stress concentration phenomena produced by the restriction of displacement conditions is discussed in detail.

Study on Dynamic Stability of Single Floating Pier Under Waves

2021 ◽  
Author(s):  
Yikuan He ◽  
Bing Han ◽  
Wenyu Ji
Keyword(s):  
Dynamic Stability ◽  
Expansion Method ◽  
Diffraction Effect ◽  
Exterior Region ◽  
Factors Affecting ◽  
Eigenfunction Expansion Method ◽  
Floating Bridge ◽  
Response Equation ◽  
Floating Pier ◽  
Wave Excitation Force

Abstract Considering the upper structure restraint effect of the floating bridge, the diffraction effect and radiation effect of linear monochromatic waves, the dynamic response equation of floating pier is derived and the factors affecting the dynamic stability of the floating pier are analyzed in this paper. Based on the theory of potential flow, the calculation domain is divided into the interior region and the exterior region. The wave diffraction and radiation problems are solved by the matched eigenfunction expansion method (MEEM). After obtaining the wave excitation force, additional mass and radiation damping coefficient, considering the restraint effect of the upper structure of the floating bridge, the motion differential equation of the floating pier is established, and the response amplitude operator (RAOs) of the floating pier is obtained. The effects of span, mass and stiffness of upper structure, as well as the draft depth, size and net height of floating pier on dynamic stability of floating pier under wave are analyzed. The results show that the increase in the span of upper structure will significantly increase the peak RAOs of sway and heave, and the increase in stiffness is helpful to reduce the peak RAOs of sway and heave. The increase of the floating pier radius can reduce the heave RAO, and the net height on the water surface of the floating pier increases the heave and roll.

Development of Intelligent Hierarchical Control for a Hydraulic Manipulator

2001 ◽  
Author(s):  
Roya Rahbari ◽  
Clarence W. deSilva
Keyword(s):  
Hierarchical Control ◽  
Middle Layer ◽  
Bottom Layer ◽  
Mechanical Processing ◽  
Pd Controller ◽  
Performance Parameters ◽  
Hydraulic Actuator ◽  
Intelligent Controller ◽  
Hydraulic Manipulator ◽  
Input Response

Abstract This paper presents the development of a hierarchical intelligent controller for a hydraulic manipulator, which has been designed to be an integral part of an automated machine for mechanical processing of salmon. The developed controller for this hydraulic actuator is a three-layer hierarchical system. In the bottom layer of the hierarchy, a conventional proportional plus derivative (PD) controller is used to control the position of the cutting blade. The middle layer monitors the performance of the manipulator, preprocesses the response signals, and extracts the performance parameters, based on a step-input response. The top layer infers the tuning actions for the PD servo. The knowledge base for tuning the low level controller has been developed and represented by fuzzy rulesbase modules. The development of this hierarchical control system is discussed and some experimental results are given.

Sign in / Sign up

Export Citation Format

Share Document