Wave Trapping Efficiency of a Flexible Membrane Near a Partially Reflecting Seawall

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
V. Venkateswarlu ◽  
K. G. Vijay ◽  
R. Raja Pandi ◽  
Chandra Shekhar Nishad
Keyword(s):  
Domain Boundary ◽  
Wave Interaction ◽  
Cost Effective ◽  
Wave Theory ◽  
Trapping Efficiency ◽  
Maximum Deflection ◽  
Wave Regime ◽  
Flexible Membrane ◽  
Wave Trapping ◽  
Submergence Depth

Abstract The gravity wave interaction with a flexible membrane placed at a finite distance from the partially reflecting seawall is analyzed under the framework of linear water wave theory using the multi-domain boundary element method (BEM). The flow through a flexible membrane is assumed to follow Darcy’s law in addition to membrane displacements. As a viable alternative to the existing wave dampers, the flexible membrane is examined for the effective dampening of incident waves. The correctness of the numerical results is affirmed with the known results available in the literature. The effect of membrane tension, submergence depth, membrane width, porosity, angle of inclination, and confined chamber spacing on hydrodynamic coefficients is discussed as a function of dimensionless wavenumber. The partially reflecting harbor wall diminishes the wave reflection coefficient in the long-wave regime. The increase in the flexible membrane width does not necessarily ensure the ideal wave capturing performance. A shift in the peak of the maximum deflection is observed with the increase of membrane width while there is a shift in peak outward for the increase in the submergence depth. Moreover, the maximum deflection is found to decrease with the increase in porosity, and it is 62% reduction for membrane porosity b = 1 due to the significant wave damping. The wave run-up and the wall force coefficients are found to be minimum when the relative plate width is B/h = 1. The present study is expected to be useful for the design of cost-effective wave attenuating systems.

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.

Microactuator based on electroplated permanent magnets and flexible polydimethyl siloxane diaphragm

2008 ◽  
Vol 222 (3) ◽  
pp. 517-524 ◽  
Author(s):  
Y Su ◽  
H Wang ◽  
W Chen
Keyword(s):  
Permanent Magnets ◽  
Magnetic Energy ◽  
Optical Switch ◽  
Geometrical Parameters ◽  
Maximum Deflection ◽  
Polydimethyl Siloxane ◽  
Flexible Membrane ◽  
Microelectromechanical System ◽  
Planar Coil ◽  
A Current

The design, fabrication, and testing of a novel bidirectional magnetic microactuator were presented in the paper. The microactuator is composed of an integrated planar coil and a flexible polydimethyl siloxane (PDMS) diaphragm with embedded CoNiMnP-based permanent magnet arrays. There is a 7 × 7 array of magnets in a unit. The PDMS diaphragm is 2 mm × mm × 40 μm and the magnet post is 50 × 50 × 20 μm. Computer simulation was applied to verify the geometrical parameters. Electroplating under external magnetic field is carried out to improve the magnetic properties of the electroplated magnet, including coercivity, remanence and magnetic energy, and so on. The measured maximum coercivity, remanence and maximum magnetic energy were 2623 Oe (208.73 kA/m), 0.2 T (2000 G), and 10.15 kJ/m3 with the magnetic post, respectively. Moreover, and the deflection of the PDMS membrane is proportional to the exciting current. In a case of 0.35 A current, the maximum deflection of the membrane is 45 μm. Adjusting the electroplating mould results in the variation of the electroplated structure, thus the calibration of the microactuator. Due to the biomedical compatibility and simplicity of the fabrication, the flexible membrane-based microactuator is potential to be used as micropump and optical switch, the microelectromechanical system applications.

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.

Numerical Simulation of Non-Gaussian Wave Elevation and Kinematics Based on Two-Dimensional Fourier Transform

2006 ◽  
Author(s):  
Xiang Yuan Zheng ◽  
Torgeir Moan ◽  
Ser Tong Quek
Keyword(s):  
Fourier Transform ◽  
Wave Interaction ◽  
Wave Theory ◽  
Two Dimensions ◽  
Second Order ◽  
Interaction Matrix ◽  
Random Wave ◽  
Two Dimensional ◽  
Near Surface ◽  
Wave Elevation

The one-dimensional Fast Fourier Transform (FFT) has been extensively applied to efficiently simulate Gaussian wave elevation and water particle kinematics. The actual sea elevation/kinematics exhibit non-Gaussianities that mathematically can be represented by the second-order random wave theory. The elevation/kinematics formulation contains double-summation frequency sum and difference terms which in computation make the dynamic analysis of offshore structural response prohibitive. This study aims at a direct and efficient two-dimensional FFT algorithm for simulating the frequency sum terms. For the frequency difference terms, inverse FFT and FFT are respectively implemented across the two dimensions of the wave interaction matrix. Given specified wave conditions, not only the wave elevation but kinematics and associated Morison force are simulated. Favorable agreements are achieved when the statistics of elevation/kinematics are compared with not only the empirical fits but the analytical solutions developed based on modified eigenvalue/eigenvector approach, while the computation effort is very limited. In addition, the stochastic analyses in both time-and frequency domains show that the near-surface Morison force and induced linear oscillator response exhibits stronger non-Gaussianities by involving the second-order wave effects.

Scattering of Waves by Two-Dimensional Circular Obstacles in Finite Water Depths

1979 ◽  
Vol 23 (01) ◽  
pp. 32-42 ◽  
Author(s):  
Robert A. Naftzger ◽  
Subrata K. Chakrabarti
Keyword(s):  
Wave Interaction ◽  
Wave Theory ◽  
Finite Depth ◽  
Wave Forces ◽  
Linear Wave ◽  
Two Dimensional ◽  
Linear Wave Theory ◽  
Dimensional Object ◽  
Limiting Case ◽  
Water Depths

The wave forces on a fixed two-dimensional object submerged in water of finite depth are obtained under the assumptions of linear wave theory. The far-field characteristics of the wave interaction with the object are also examined. The boundary-value problem for the wave potential is formulated in terms of Green's theorem, and the resulting integral equation is solved numerically. Results for a submerged and half-submerged circular cylinder and a bottom-seated half cylinder are presented. In the limiting case of infinite depth the numerical results compare quite well with known solutions.

scholarly journals Complete Hamiltonian formalism for inertial waves in rotating fluids

2017 ◽  
Vol 831 ◽  
pp. 128-150 ◽  
Author(s):  
A. A. Gelash ◽  
V. S. L’vov ◽  
V. E. Zakharov
Keyword(s):  
Hamiltonian Formalism ◽  
Wave Interaction ◽  
Wave Theory ◽  
Incompressible Fluids ◽  
Hamiltonian Approach ◽  
Inertial Waves ◽  
Rotating Fluids ◽  
Weakly Nonlinear ◽  
Interaction Processes ◽  
Inertial Wave

A complete Hamiltonian formalism is suggested for inertial waves in rotating incompressible fluids. Resonance three-wave interaction processes – decay instability and confluence of two waves – are shown to play a key role in the weakly nonlinear dynamics and statistics of inertial waves in the rapid rotation case. Future applications of the Hamiltonian approach to inertial wave theory are investigated and discussed.

scholarly journals Three Dimensional Radiated Water Wave with a Submerged Cylinder in Presence of Circular Plate

2019 ◽  
Vol 9 (1) ◽  
pp. 6665-6670
Keyword(s):  
Separation Of Variables ◽  
Surface Condition ◽  
Three Dimensional ◽  
Wave Interaction ◽  
Wave Theory ◽  
Linear Wave ◽  
Energy Device ◽  
Linear Wave Theory ◽  
Bernoulli’S Equation ◽  
Submerged Cylinder

This work deals with the problem of radiated by wave interaction with a couple of submerged cylinders in water which can be considered as a wave energy device and the problem arising from the rotational motion of submerged upper cylinder which one contains in the device. In this work, we approach theoretically to solve the problem based on the method of separation of variables and we derive the radiated velocity potentials numerically based on linear wave theory and eigenfunctions are introduced for each region by using free surface condition. Then we calculate the hydrodynamic coefficients due to rotational of the upper cylinder by using Bernoulli’s equation of pressure by neglecting the atmospheric pressure and unknown constants are calculate by using matched conditions between the regions Finally, we present all numerical results graphically for different radii of the cylinders

Long-wave theory for a new convective instability with exponential growth normal to the wall

2005 ◽  
Vol 363 (1830) ◽  
pp. 1119-1130 ◽  
Author(s):  
J.J Healey
Keyword(s):  
Numerical Solutions ◽  
Flow Instability ◽  
Cross Flow ◽  
Wave Theory ◽  
Linear Stability Theory ◽  
Wave Regime ◽  
Long Wave ◽  
Point Analysis ◽  
New Type ◽  
Layer Flow

A linear stability theory is presented for the boundary-layer flow produced by an infinite disc rotating at constant angular velocity in otherwise undisturbed fluid. The theory is developed in the limit of long waves and when the effects of viscosity on the waves can be neglected. This is the parameter regime recently identified by the author in a numerical stability investigation where a curious new type of instability was found in which disturbances propagate and grow exponentially in the direction normal to the disc, (i.e. the growth takes place in a region of zero mean shear). The theory describes the mechanisms controlling the instability, the role and location of critical points, and presents a saddle-point analysis describing the large-time evolution of a wave packet in frames of reference moving normal to the disc. The theory also shows that the previously obtained numerical solutions for numerically large wavelengths do indeed lie in the asymptotic long-wave regime, and so the behaviour and mechanisms described here may apply to a number of cross-flow instability problems.

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