Wave Energy Transmission Research Articles

Homogenous asymptotic analysis on vibration energy dissipation characteristics of periodical honeycomb reinforced composite laminate filled with viscoelastic damping material

In this paper, free transverse vibration energy dissipation properties of honeycomb reinforced composite laminated structures are studied. By applying the homogenous asymptotic method (HAM) and representative unit cell (RUC) approach, considering the frequency- and temperature-dependent properties of the viscoelastic damping material (VDM), the constitutive equations of the laminated composite structure is obtained. Based on the transverse wave energy propagation and transmission theory in solid structures, the structural loss factor (SLF) of the composite structure can be ultimately determined, which is a frequency- and temperature-dependent variable according to the same properties of VDM’s physical parameters that were applied. Several geometry factors including the thickness of the VDM layer, the width and the inner angle of the honeycomb reinforcements, influence on the vibration energy dissipation characteristics of the composite structure are investigated qualitatively and quantitatively. The results are validated by the Galerkin method based asymptotic approach, which shows consistency with each other, especially when the external excitation frequency larger than 500 Hz in the considered frequency ranges.

Hydrodynamic characteristics of curved and vertical front face pile-supported breakwaters in regular waves

The hydrodynamic performance characteristics of curved and vertical front face pile-supported breakwaters are evaluated in this paper. Two curved profiles, viz. Galveston wall shape (GS) and circular-cum parabola shape (CPS) are adopted as the seaward face for pile-supported breakwaters designated as GS-PSB & CPS-PSB, respectively. A comparison of the hydrodynamic performance characteristics of the said two types with a vertical face type (VW-PSB) is carried out. Experimental investigations on the three models were carried out in a wave flume under the action of regular harmonic waves. Wave energy transmission past the GS-PSB and CPS-PSB models were found to be lesser than that past the VW-PSB. The reflection of incident wave energy was found to be the least for CPS-PSB followed by GS-PSB and VW-PSB. The energy dissipation was observed to be a maximum for CPS-PSB, moderate in GS-PSB, whereas, the minimum was experienced by the VW-PSB. The dynamic pressures induced by long waves are observed to be more for CPS-PSB and GS-PSB than those exerted on the VW-PSB model. The run-up on the GS-PSB and CPS-PSB models are compared and a qualitative assessment of overtopping is reported.

Wave transmission through living shoreline breakwalls

Living shorelines are being widely implemented to mitigate shoreline erosion and provide ecosystem services, but how they interact with waves remains poorly understood. Wave transmission through living shoreline breakwalls is studied using field observations and theoretical approaches. The following hypotheses are tested: (i) living shoreline breakwalls can act as buffers against waves; (ii) wave transmission through these nature-based solutions is modulated by tides; and (iii) wave transmission through living shoreline breakwalls is similar to the behavior observed in waves through porous breakwaters. Observations were collected in intertidal settings where boat wakes and tides are the major flow components. Nearly 1000 boat wakes were identified in the observations using advanced time-frequency data analysis methods. Wave transmission through the breakwalls composed of tree branches was quantified and modulation of this process by tides was investigated. The two tested breakwall designs provided different behaviors of wave transmission. In the first design with an estimated porosity of 0.7 where the tree branches were bundled, transmission rates were found to vary mostly between 9% and 70% and had an average of 53%. Transmission increased with increasing water depth especially at mid-tide and low-tide where the height of the breakwall relative to depth was between 0.5 and 1. In the second design with an estimated porosity of 0.9 where the tree branches were not bundled, transmission rates exceeded 70% in 84% of the cases, sometimes reaching 100% transmission, and had an average of 83% with much less variability with depth compared to the first design. Wave transmission estimates based on theory of porous media were found to be most sensitive to breakwall porosity and the friction coefficient. Best agreement between the observed and theoretical estimates of wave transmission was found using a turbulent friction coefficient of 2.7, the median value of the most common range given in the literature on waves through porous media. The highest discrepancy between observed and theoretical estimates of wave transmission occurs at shallow depths when the breakwall emerged. In these conditions, the theory overestimates transmitted wave energy, most likely due to significant wave breaking and bottom friction in shallow water. The findings support our hypotheses that well-engineered semi-porous living shorelines act as buffers against human-mediated boat traffic and waves, and their related performance in dissipating wave energy and sustaining coastal ecosystems is modulated by depth. The results can be used as guidelines for design of living shorelines for given wave climate and breakwall properties.

Uniform large­sized lumber drying system using mw radiation and basing on a single­wire E00 wave energy transmission line

In order to generalize the possibilities of using MW radiation in industrial processes, the given paper considers and analyzes various methods of wood drying. Technological and economic advantages of wood drying in an ultra-high frequency electromagnetic field are well justified. Wood drying in the ultra-high frequency range is considered as the most optimal in contrast to traditional methods. This method is based on the penetration of electromagnetic energy into the material and converting it into heat. The paper reveals the possibility of more effective use of MW radiation. It proposes a method for drying wood and large-sized lumber basing on a single-wire transmission line of electromagnetic energy of the surface wave. The paper also describes the advantages of the proposed method: the use of a single wire covered with a thin layer of dielectric material, the use of a vibratory system for surface wave excitation, and the use of a flat reflector. Special attention is paid to the contact area of the wire with a flat reflector since the perfection of this contact largely determines the efficiency of surface wave excitation. The conducted research estimated the influence of the parameters of the vibratory surface wave excitation system in a single waveguide on the efficiency of its excitation. The proposed vibratory excitation device allows quite a simple step-by-step adjustment of the thermal power in the irradiated object. The design of the dissipation load for surface wave lines has been successfully tested during the laboratory works where certain ways of unclaimed electromagnetic energy utilization were suggested. Following the results of the conducted research, we proposed a physical model of a system for microwave drying of wood and large-sized lumber

Tunable unidirectional compact acoustic amplifier via space-time modulated membranes

Space-time modulation has recently attracted considerable attention as it enables new possibilities in wave manipulation and control. Here we propose a tunable unidirectional acoustic amplifier based on a space-time modulated membrane system. The transfer matrix method is applied to design this system and optimize the modulation parameters for the realization of unidirectional amplification. Efficient one-way amplification of acoustic waves is demonstrated theoretically and numerically within a frequency range from 2260 to 2520 Hz, with overall dimension being less than $1/3$ of the corresponding wavelength. Across this operation band, the amplification factor in the positive direction varies smoothly from 3.0 to 5.8, while the transmitted wave energy in the negative direction does not change significantly. Our work identifies a feasible approach to realize a tunable unidirectional acoustic amplifier via space-time modulated membranes, which offers a design platform for a number of applications in sensing, imaging, and communication.

Hydrodynamic performance of a novel WEC-breakwater integrated system consisting of triple dual-freedom pontoons

A breakwater consisting of three pontoon-type wave energy converters equipped with Power Take-Off (PTO) systems to extract wave energy from pitch and heave motions is proposed. The proposed integrated system has the potential to reduce the cost of the wave energy conversion system by sharing the essential infrastructure with the floating breakwater. In the model, the eigenfunction expansion matching method and technique of variables separation are used. The effects of the geometrical parameters (including pontoon width, draft and spacing) on the hydrodynamic performance characterized by the wave energy conversion efficiency, transmission and reflection coefficients are investigated, respectively. It is found that the effective bandwidth (transmission coefficient KT < 0.5 and hydrodynamic efficiency Cw > 0.3) and the peak efficiency are enhanced when the pitch and heave motions are considered simultaneously, compared with the single DoF motion system. The effective bandwidth increases with the decrease of width and draft of the front pontoon. And the variation of pontoon spacing affects significantly the distribution of the efficiency due to the Bragg-type reflection. Additionally, it is found that the variation of the geometrical parameters of the front pontoon on wave transmission is limited by changing the geometrical parameters of the front pontoon only.

Diffraction waves on large aspect ratio rectangular submerged breakwaters

In this paper, hydrodynamic characteristics of two-dimensional submerged breakwaters in water of finite depth and infinite domain interacting with sinusoidal waves are studied from both analytical and numerical approaches. Added mass and damping coefficients are obtained following the determination of radiation potentials in three degrees of freedom (sway, heave and roll). Diffraction problem is then solved according to the linear wave theory and the resulting forces are derived. To verify the results, a comparison of the solution from the analytical method with those obtained by the boundary element method is made and a good agreement is observed. Additionally, high aspect ratio horizontal and vertical flat submerged breakwaters are proposed and their hydrodynamic characteristics are analysed using the numerical and analytical methods. Results show that the horizontal flat submerged breakwater generates low transmitted waves. However, the vertical flat submerged breakwater transmits almost the entire incident wave energy. A parametric study on the effect of submergence depth and the width of the structure on the maximum diffraction wave amplitude, which is responsible for the transmitted wave energy, is carried out and a better understanding of the variation of diffraction wave amplitudes with respect to dominant parameters and wave frequency is achieved.

Inclined space-coiling metamaterials for highly efficient sound energy transmission at various incident angles

In many acoustic components, strong directional response exerts considerable influence on sound wave energy transmission, restricting their widespread applications. Here, we report new designs of an inclined metamaterial channel that enable improved transmission behaviors and broadband performance under variable-angle incident radiation. For the two-dimensional sound wave guide, the tilt angle is tuned to cater for oblique incidences. The inclined metamaterial is modified based on the normal space-coiling sound wave guide with impedance matching layers. At different incident angles, the inclined waveguides are capable of providing proper gradient parameter distributions to match the impedance value of the outside environment and the inner structure. Both experimental and numerical results show that the inclined metamaterial designs improve the broadband transmission efficiency for 2 kHz with specific incident angles. The anomalous refraction behaviors are demonstrated based on the inclined metamaterial units, showing a huge potential for wavefront engineering and acoustic transparency.

An experimental investigation of the Rossby two-slit problem

The problem of the transmission of wave energy through small gaps arises in a variety of physical contexts. Here we consider the problem of Rossby waves encountering a barrier with two small gaps. In contrast to waves encountering a barrier with one small gap, in which very little wave energy is predicted to transmit across the barrier, when there are two or more gaps linear theory predicts that the barrier may be surprisingly inefficient at blocking the transmission of Rossby wave energy, owing to the requirement that circulation be conserved around individual segments of the barrier. However, the theory neglects viscosity in the main basin interiors and nonlinear effects in the basins and the gaps. To examine these effects, here we present the results of a series of laboratory experiments in which Rossby basin modes interact with a barrier with zero, one or two gaps. We find that the large-scale waves are able to transmit across the barrier with two gaps as predicted by the theory. However, while the linear theory captures the large-scale flow structures, viscosity and nonlinearity significantly affect the flow along the boundaries and near the gaps in the barrier.

Wave propagation in elastic bi-materials with a doubly periodic array of interface cracks

In the present study, the scattering of plane elastic waves by a doubly periodic array of planar interface cracks is investigated. The problem is solved using the boundary integral equation method. The influences of the shape of cracks and lattice in the periodic array on wave transmission through an interface are studied. It is revealed that introduction of the periodic array of interface cracks allows to increase wave energy transmission compared to the interface without cracks. It is shown that the phenomenon is related to cut-off frequencies location and decrease in the amplitudes of the crack-opening-displacements.

Optimized modelling on lateral separation of twin pontoon-net floating breakwater

Since the attribute of wave energy transmission is susceptible to lateral separation (S/D) between twin pontoons of floating breakwater, employing improper S/D may cause ineffective attenuation in the amount of wave energy. This paper presents a numerical optimization modelling aimed at obtaining the optimum S/D through Genetic Algorithm (GA) approach. The artificial intelligence is primarily employed to minimize transmission of wave energy coefficients ( ) whereas maximize energy dissipation coefficient ( ). To achieve such demand, a numerical simulation implementing a MATLAB code as an interface between the Genetic Algorithm and a CFD program is applied. Several parameters for the effects of various wavelengths and ratios of S/D including a set of criteria have been considered in the simulation, where the optimum solution is chosen from various populations. The results demonstrated that the current GA analysis is efficient that can search a global trade-offs between and to determine an optimum S/D. The was minimized to less than 0.3 as compared to existing model ( ) while maximizing to greater than 0.95. Hence, the optimisation algorithm can serve as a useful engineering tool for a conceptual design to determine an optimum S/D for twin pontoons of floating breakwater.&#x0D; &#x0D;

Application of Genetic Algorithm for Optimum Hydrodynamic Performance of Twin Pontoon Floating Breakwater

AbstractThe lateral separation ratio (S/D) between the twin pontoons of a floating breakwater (TPFB) is one of the prominent factors that attenuate wave energy transmission and reflection. In fact,...

A novel oscillating buoy wave energy harvester based on a spatial double X-shaped mechanism for self-powered sensors in sea-crossing bridges

With the sharp increase in the number of sea-crossing bridges, various sensors have been widely used in bridge monitoring systems in order to ensure safety and prevent accidents during the use of sea-crossing bridges. In this paper, an oscillating buoy wave energy harvester (WEH) based on a spatial double X-shaped mechanism is proposed for self-powered sensors in sea-crossing bridges. Fixed to the side of pillars in sea-crossing bridges, the proposed WEH can convert wave energy with high energy density into electricity. The system consists of four modules: wave energy capture module, transmission module, generator module, and energy storage module. The wave energy capture module collects wave energy through a cylindrical buoy. The transmission module converts the up and down motion of the buoy into a unidirectional rotational motion of the generator input shaft in the generator module to produce electricity. The super-capacitors in the energy storage module store this electrical energy, which is applied to the self-powered sensors. A max efficiency of 57% and an average efficiency of 46.17% can be obtained through MTS bench tests. In field tests, the system’s voltage can reach approximately 3 V, given wave excitation of 1.2 Hz frequency and 15 mm amplitude, which indicates that the proposed WEH is feasible and practical for generating energy used for self-powered sensors in sea-crossing bridges.

Experimental study on the influence of draft relative due to wave transmission energy coefficient on hanging sheet pile breakwater

Rubble mount breakwateris recently become the most widely used breakwater, consist both of natural and artificial stone. It required a large dimension of structure so that the investment costs become more and more expensive. One of the solutions that can be implemented is Hanging Sheet Pile breakwater. Unfortunately, the performance of this type of breakwater has not been known yet. Performance of this breakwater represented by wave energy transmission coefficient (KEt). Therefore, this study aims to examine the effect of relative draft (s/d) and relative wave height (H/s) to KEt. This study conducted in Ocean Technology Laboratory of Universitas Hasanuddin. The parameters studied are structure dimensions and wave parameters. Wave parameters consist of wave height (H) and wave period (T), while the structure parameter is the draft structure (D). The result of this study shows that the greater value of both incident wave steepness (Hi/gT2) and structure relative draft (s/d), then the smaller of KEt value will be achieved. Also, the greater relative H/s, the smaller KEt will be achieved. For all cases of study, the transmission coefficient ranges from 0.122 – 0.786.

Time-Domain Full Waveform Inversion Using the Gradient Preconditioning Based on Transmitted Wave Energy

The gradient preconditioning approach based on seismic wave energy can effectively avoid the huge memory consumption of the gradient preconditioning algorithms based on the Hessian matrix. However, the accuracy of this approach is prone to be influenced by the energy of reflected waves. To tackle this problem, the paper proposes a new gradient preconditioning method based on the energy of transmitted waves. The approach scales the gradient through a precondition factor, which is calculated by the ‘approximate transmission wavefield’ simulation based on the nonreflecting acoustic wave equation. The method requires no computing nor storing of the Hessian matrix and its inverse matrix. Furthermore, the proposed method can effectively eliminate the effects of geometric spreading and disproportionality in the gradient illumination. The results of model experiments show that the time-domain full waveform inversion (FWI) using the gradient preconditioning based on transmitted wave energy can achieve higher inversion accuracy for deep high-velocity bodies and their underlying strata in comparison with the one using the gradient preconditioning based on seismic wave energy. The field marine seismic data test shows that our proposed method is also highly applicable to the FWI of field marine seismic data.

On the wave propagation analysis and supratransmission prediction of a metastable modular metastructure for non-reciprocal energy transmission

In this research, we investigate in-depth the nonlinear energy transmission phenomenon in a metastable modular metastructure and develop efficient tools for the design of such systems. Previous studies on a one-dimensional (1D) reconfigurable metastable modular chain uncover that when the driving frequency is within the stopband of the periodic structure, there exists a threshold input amplitude, beyond which sudden increase in the energy transmission can be observed. This onset of transmission is caused by nonlinear instability and is known as supratransmission. Due to spatial asymmetry of strategically configured constituents, such transmission thresholds could shift considerably when the structure is excited from different ends and therefore enabling the non-reciprocal energy transmission. This one-way propagation characteristic can be adaptable via reconfiguring the metastable modular system. In this new study, we build upon these findings and advance the state of the art by (a) exploring the different mechanisms that are able to activate the onset of supratransmission and their implications on wave energy transmission potential, and (b) developing an effective design tool - a localized nonlinear-linear model combined with harmonic balancing and transfer matrix analyses to analytically and efficiently predict the critical threshold amplitude of the metastable modular chain. These investigations provide important new understandings of the rich and intricate dynamics achievable by nonlinearity, asymmetry, and metastability, and create opportunities to accomplish adaptable non-reciprocal wave energy transmission.

Diffraction of water waves by an array of vertical barriers and heterogeneous bottom

The interaction of head waves with an infinite row of identical, equally spaced, rectangular breakwaters is investigated in the presence of uneven bottom topography. Using linear water wave theory and matched eigenfunction expansion method, the boundary value problem is transformed into a system of linear algebraic equations which are numerically solved to know the velocity potentials completely. Utilizing this method, reflected and transmitted wave energy are computed for different physical parameters along with the wave field in the vicinity of breakwaters. It is observed that the wave field becomes more complicated when the incoming wavelength becomes smaller than the channel width. A critical ratio of the gap width to the channel width, corresponding to the inflection point of the transmitted energy variation, is identified for which 1/3 of the total energy is transmitted. Similarly, depending on the incident wavelength, there is a critical breakwater width for which a minimum energy is transmitted. Further, the accuracy of the computed results is verified by using the derived energy relation.

3D numerical simulation of wave transmission for low-crested and submerged breakwaters

Low-crested and submerged breakwaters, serving as one of the coastal defensive structures, are usually used to dissipate wave energy and help reduce wave impacts on coastal infrastructures and communities especially during extreme weather events, such as hurricanes or tsunamis. Many recent post disaster surveys indicated that breakwaters did not perform as designed during some extreme weather events. The performance of the breakwaters subjected to strong waves is still not clear especially when the breakwaters turn into the submerged condition. Meanwhile, many researches on the breakwaters are usually carried out in a two-dimensional wave flume either experimentally or numerically. However, the incident wave could impact the breakwaters from any directions instead of only from the head-on direction, which should be a three-dimensional physical process of wave and breakwater interactions. Therefore, it is essential to conduct a three-dimensional numerical study to investigate the breakwater performance in reducing the transmitted wave energy behind it and compare the results with those from a two-dimensional study. This study is to investigate the effect of three-dimensional interactions of obliquely incident waves and breakwaters on wave potential energy reduction based on the proposed energy transmission coefficient. Computational fluid dynamics (CFD) simulations are carried out in OpenFOAM to simulate the interactions between the wave and breakwater using a three-dimensional Reynolds-averaged Navier-Stokes (RANS) model together with the k-ω SST turbulence model. Two validation studies are performed to validate the applicability of the proposed numerical model in two-dimensional and three-dimensional numerical simulations. Sensitivity analyses are performed to investigate the effect of different parameters associated with breakwater geometries and incident wave properties on a two-dimensional submerged breakwater performance in reducing the transmitted wave height. The effects of incident wave angle on the transmitted wave energy reduction for a three-dimensional submerged and surface breakwater are then investigated and compared with the two-dimensional simulation results. The numerical studies indicate that a three-dimensional simulation is more appropriate to describe a breakwater behavior in the real-world scenario.

Load shedding characteristics of an oscillating surge wave energy converter with variable geometry

This study investigates performance and load shedding capabilities of an oscillating surge wave energy converter (OSWEC) that utilizes adjustable geometry to control hydrodynamic coefficients. The body consists of a bottom-hinged rectangular paddle in which the frame holds five horizontal flaps spanning the interior of the frame. Each flap can rotate independently about its center of rotation to alter hydrodynamic coefficients. A 1:14 scale model was built for wave tank tests where the OSWEC's natural response to regular waves was measured. Tests with the paddle fixed vertically were conducted to measure the moment induced by incident waves. Results were compared to numerical simulations which determined that flap orientation significantly affected wave energy transmission past the device. Numerical simulations with the addition of a linear rotational damper power take-off (PTO) suggested that with flaps open, the resistive moment was reduced by up to 47%, the surge force on the foundation up to 55%, and the capture width up to 72% over a range of wave periods and PTO damping values. The experimental nondimensional excitation moments and reflection coefficients were reduced by up to 54%. Overall, the flaps provide mechanical means to reduce loads, thus improving the design life of a WEC system.

Simulation of EM wave propagation along a femtosecond laser plasma filament

Abstract The propagation of electromagnetic (EM) wave along a plasma filament induced by the sufficiently intense femtosecond laser pulse is studied with the commercial simulation software XFDTD. The simulated results show that the EM wave can propagate along the plasma filament, with the electric field enhanced out of the waveguide and attenuated in the waveguide. Besides, we can conclude that the relative direction between the plasma filament and the electric field can influence the guiding performance of the plasma filament. Furthermore, a maximum EM wave intensity enhancement more than threefold the free space propagation is realized. The research results imply that the laser-induced plasma filament can provide efficient transmission of the EM wave energy.