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1
Gomes, M. N., C. R. Olinto, L. A. O. Rocha, J. A. Souza, and L. A. Isoldi. "COMPUTATIONAL MODELING OF A REGULAR WAVE TANK." Revista de Engenharia Térmica 8, no. 1 (June 30, 2009): 44. http://dx.doi.org/10.5380/reterm.v8i1.61881.
Анотація:
This paper presents two different numerical methodologies to generate regular gravity waves in a wave tank. We performed numerical simulations of wave generation through the FLUENT® package, using the Volume of Fluid (VOF) multiphase model to reproduce the wave propagation in the tank. Thus it was possible to analyze two methods for generating regular waves that could be used in future work, especially in the study of devices of energy conversion from ocean waves into electrical energy.
2
Eldrup, Mads Røge, and Thomas Lykke Andersen. "Applicability of Nonlinear Wavemaker Theory." Journal of Marine Science and Engineering 7, no. 1 (January 14, 2019): 14. http://dx.doi.org/10.3390/jmse7010014.
Анотація:
Generation of high-quality waves is essential when making numerical or physically model tests. When using a wavemaker theory outside the validity area, spurious waves are generated. In order to investigate the validity of different wave generation methods, new model test results are presented where linear and nonlinear wave generation theories are tested on regular and irregular waves. A simple modification to the second-order wavemaker theory is presented, which significantly reduces the generation of spurious waves when used outside its range of applicability. For highly nonlinear regular waves, only the ad-hoc unified wave generation based on stream function wave theory was found acceptable. For irregular waves, similar conclusions are drawn, but the modified second-order wavemaker method is more relevant. This is because the ad-hoc unified generation method for irregular waves requires the wave kinematics to be calculated by a numerical model, which might be quite time-consuming. Finally, a table is presented with the range of applicability for each wavemaker method for regular and irregular waves.
3
Wang, Gang, and Jin-Hai Zheng. "SUBHARMONIC GENERATION OF TRANSVERSE OSCILLATIONS INDUCED BY INCIDENT REGULAR WAVES." Coastal Engineering Proceedings 1, no. 33 (September 27, 2012): 11. http://dx.doi.org/10.9753/icce.v33.waves.11.
Анотація:
It is generally accepted that there are transverse oscillation, which are concentrated and confined to the backwall and decay asymptotically offshore, existed in the harbor of constant slope, however, whether these oscillations can be induced by the normally incident waves is not clear. This numerical investigation aims at providing the subharmonic generations of transverse oscillations within the harbor of a plane slope by waves normally impacting on. For the harbor of perfectly plane slopes, the subharmonic transverse oscillations are small on the mild and moderate slopes but evident on the steep slope. This instability can take place only if the incident wave amplitude exceeds a threshold value, and transverse oscillations can even grow up to a larger value than that of longitudinal oscillations. The magnitudes of transverse oscillations are approximately the same, only their growth rates are affected by the incident wave amplitude.
4
Vasarmidis, Panagiotis, Vasiliki Stratigaki, Tomohiro Suzuki, Marcel Zijlema, and Peter Troch. "Internal Wave Generation in a Non-Hydrostatic Wave Model." Water 11, no. 5 (May 10, 2019): 986. http://dx.doi.org/10.3390/w11050986.
Анотація:
In this work, internal wave generation techniques are developed in an open source non-hydrostatic wave model (Simulating WAves till SHore, SWASH) for accurate generation of regular and irregular long-crested waves. Two different internal wave generation techniques are examined: a source term addition method where additional surface elevation is added to the calculated surface elevation in a specific location in the domain and a spatially distributed source function where a spatially distributed mass is added in the continuity equation. These internal wave generation techniques in combination with numerical wave absorbing sponge layers are proposed as an alternative to the weakly reflective wave generation boundary to avoid re-reflections in case of dispersive and directional waves. The implemented techniques are validated against analytical solutions and experimental data including water surface elevations, orbital velocities, frequency spectra and wave heights. The numerical results show a very good agreement with the analytical solution and the experimental data indicating that SWASH with the addition of the proposed internal wave generation technique can be used to study coastal areas and wave energy converter (WEC) farms even under highly dispersive and directional waves without any spurious reflection from the wave generator.
5
Klein, Marco, Moritz Hartmann, and Franz von Bock und von Bock und Polach. "Note on the Application of Transient Wave Packets for Wave–Ice Interaction Experiments." Water 13, no. 12 (June 19, 2021): 1699. http://dx.doi.org/10.3390/w13121699.
Анотація:
This paper presents the transient wave packet (TWP) technique as an efficient method for wave–ice interaction experiments. TWPs are deterministic wave groups, where both the amplitude spectrum and the associated phases are tailor-made and manipulated, being well established for efficient wave–structure interaction experiments. One major benefit of TWPs is the possibility to determine the response amplitude operator (RAO) of a structure in a single test run compared to the classical approach by investigating regular waves of different wave lengths. Thus, applying TWPs for wave–ice interaction offers the determination of the RAO of the ice at specific locations. In this context, the determination of RAO means that the ice characteristics in terms of wave damping over a wide frequency range are obtained. Besides this, the wave dispersion of the underlying wave components of the TWP can be additionally investigated between the specific locations with the same single test run. For the purpose of this study, experiments in an ice tank, capable of generating tailored waves, were performed with a solid ice sheet. Besides the generation of one TWP, regular waves of different wave lengths were generated as a reference to validate the TWP results for specific wave periods. It is shown that the TWP technique is not only applicable for wave–ice interaction investigations, but is also an efficient alternative to investigations with regular waves.
6
Zhang, Huichen, and Markus Brühl. "GENERATION OF EXTREME TRANSIENT WAVES IN EXPERIMENTAL MODELS." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 51. http://dx.doi.org/10.9753/icce.v36.waves.51.
Анотація:
The transfer of natural waves and sea states into small- and large-scale model teste contributes to the proper design of offshore and coastal structure. Such shallow-water ocean surface waves are highly nonlinear and subject to wave transformation and nonlinear wave-wave interactions. However, the standard methods of wave generation according to conventional wave theories and wave analysis methods are limited to simple regular waves, simple sea states and low-order wave generation without considering the nonlinear wave-wave interactions. The research project Generation of Extreme Transient Waves in Experimental Models (ExTraWaG) aims to accurately generate target transient wave profile at a pre-defined position in the wave flume (transfer point) under shallow water conditions. For this purpose, the KdV-based nonlinear Fourier transform is introduced as a continuative wave analysis method and is applied to investigate the nonlinear spectral character of experimental wave data. Furthermore, the method is applied to generate transient nonlinear waves as specific locations in the wave flume, considering the nonlinear transformation and interactions of the propagating waves.
7
Jung, Jae-Sang, and Changhoon Lee. "An Analytical Study of Regular Waves Generated by Bottom Wave Makers in a 3-Dimensional Wave Basin." Journal of Korean Society of Coastal and Ocean Engineers 34, no. 4 (August 31, 2022): 93–99. http://dx.doi.org/10.9765/kscoe.2022.34.4.93.
Анотація:
Analytical solutions for regular waves generated by bottom wave makers in a 3-dimensional wave basin were derived in this study. Bottom wave makers which have triangular, rectangular and combination of two shapes were adopted. The 3-dimensional velocity potential was derived based on the linear wave theory with the bottom moving boundary condition, kinematic and dynamic free surface boundary conditions in a wave basin. Then, analytical solutions of 3-dimensional particle velocities and free surface displacement were derived from the velocity potential. The solutions showed physically valid results for regular waves generated by bottom wave makers in a wave basin. The analytical solution for obliquely propagating wave generation from bottom wave maker which works like a snake was also derived. Numerical results of the solution agree well with theoretically predicted results.
8
Ali Shehab Shams Eldeen, Ahmed M. R. El-Baz, and Abdalla Mostafa Elmarhomy. "CFD Modeling of Regular and Irregular Waves Generated by Flap Type Wave Maker." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 85, no. 2 (August 9, 2021): 128–44. http://dx.doi.org/10.37934/arfmts.85.2.128144.
Анотація:
The improvement of wave generation in numerical tanks represents the key factor in ocean engineering development to save time and effort in research concerned with wave energy conversion. For this purpose, this paper introduces a numerical simulation method to generate both regular and irregular waves using Flap-Type wave maker. A 2D numerical wave tank model is constructed with a numerical beach technique, the independence of the numerical beach slope is tested to reduce the wave reflections. The different governing parameters of the Flap type wave maker were studied such as periodic time dependency and length of the flap stroke. The linear wave generated was validated against the wave maker theory WMT, the numerical results agreed with WMT. The Pierson-Moskowitz model is used to generate irregular waves with different frequencies and amplitudes. The numerical model succeeded to generate irregular waves which was validated against published experimental data and with Pierson-Moskowitz spectrum model using Fourier expansion theory in the frequency domain. Useful results are presented in this paper based on the numerical simulation to understand the characteristics of the waves. This paper produces a full guide to generate both regular and irregular waves numerically using ANSYS-CFX approach to solve the 2D Unsteady Reynolds Averaged Navier-Stokes Equation (URANS).
9
Naeser, Harald. "The Capillary Waves’ Contribution to Wind-Wave Generation." Fluids 7, no. 2 (February 10, 2022): 73. http://dx.doi.org/10.3390/fluids7020073.
Анотація:
Published theories and observations have shown that dissipation of gravity waves implies frequency downshifting of wave energy. Hence, for wind-waves, the wind energy input to the highest frequencies is of special interest. Here it is shown that this input is vital, because the direct wind energy input obtained by the air-pressure’s work on most gravity waves is slightly less than what the waves need to grow. Further, the wind’s input of the angular momentum that waves need to grow is found to be absent at most gravity wave frequencies. The capillary waves that appear at the surface of the sea when the wind is blowing solve these problems. To demonstrate this, an extension of linear wave theory is established to study possibilities and limitations for transfer of energy and angular momentum from the wind to waves through these frequencies. The theory describes regular, gravity–capillary waves with constant amplitude under laminar conditions. It includes surface tensions, viscosity, gravity and a wind-generated shear current, and shows that these waves—contrary to most gravity waves—receive more energy from the wind than they dissipate and angular momentum they cannot keep. Hence, the problem of the missing input of energy and angular momentum from wind to gravity waves is solved by transfers through the capillary waves. This implies that capillary waves are vital to obtain growing gravity waves.
10
Liu, Yi, Yuxi Zheng, Ruiyin Song, Junhua Chen, and Heng Jin. "Wave generation characteristic analysis of piston and flap type wave maker with rotary-valve-control vibrator." Journal of Vibration and Control 26, no. 15-16 (January 9, 2020): 1297–308. http://dx.doi.org/10.1177/1077546319895664.
Анотація:
Wave maker is one of the most important experimental equipment in marine engineering. To meet the demands of simulation of higher wave amplitude and compare the effect of piston and flap type wave generation, a new wave generation device was proposed and a new piston and flap type wave maker with a rotary-valve-control vibrator was developed. A mathematical model of the new wave maker was established and analysed by Simulink, and a series of experiments were conducted on the wave maker to analyze wave generation characteristics. The results show that the wave maker can adjust the distance of wave paddle and generate different regular waves. The bigger the axial opening size of the valve port, the larger the wave paddle amplitude and the wave amplitude; the higher the pressure, the higher the wave paddle amplitude and the wave amplitude. High frequency wave making is more efficient than the lower one, and piston type wave making is more efficient than those wave makers that generate waves by flap type.
11
Choi, Junwoo. "A PRELIMINARY EXPERIMENT OF NEARSHORE CURRENT GENERATED DUE TO TRANSVERSE PHASE DIFFERENCES." Coastal Engineering Proceedings, no. 36v (December 28, 2020): 25. http://dx.doi.org/10.9753/icce.v36v.currents.25.
Анотація:
The vorticity generation due to the ends of wave crests and its resultant rip current have been studied (Johnson and Pattiaratchi, 2006; Clark et al., 2012; Choi et al., 2015; Peregrine, 1998; Postacchini et al., 2014). Recently, a laboratory experiment was conducted to observe rip currents formed between the ends of breaking wave crests (Choi and Roh, 2020) by using the wave generation method of pseudo intersecting wave trains. In this method, regular waves were generated by running two parts of wave maker out of phase. Their pseudo intersecting wave trains was compared with the intersecting wave trains generated by regular waves having the same wave period and the slightly different two wave directions. However, the pseudo intersecting wave trains, i.e., out-of-phase wave trains, could be formed in the field by the transformation of long-crest waves propagating over a specific change of topography in an intermediate water depth, for example, a submerged semi-infinite straight seamount range parallel to the shoreline. The long-crest wave train can be divided into two wave trains with phase difference because of the different wave speeds over the end of the submerged structure. To understand the evolution process of nearshore currents generated due to transverse phase differences, a laboratory experiment was planned. This study showed the preliminary laboratory experiments in which two wave trains with phase differences and its resultant nearshore currents were observed using the optical flow method.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/SaMl6rspZmw
12
Li, Hong Wei, Yong Jie Pang, and Guo Cheng Zhang. "A New Control Method of Active Absorption Wave-Maker." Advanced Materials Research 591-593 (November 2012): 1748–52. http://dx.doi.org/10.4028/www.scientific.net/amr.591-593.1748.
Анотація:
The theory of 2D wave generation with active wave absorption is outlined. A new control method of active absorption wave-maker is established based on the S plane control (SPC) algorithm in this paper. Using SPC, a piston-type 2D numerical wave flume (NWF) simulation program for simultaneous wave generation and active wave absorption is developed with Boundary Element Method (BEM) and Mixed Eulerian-Lagrangian (MEL). The absorbing wave-making contrast simulation tests for regular wave are also carried out in NWF. Simulation results verify that the controller is robust and well effect for absorbing re-reflected wave is obtained in low reflect condition. Meanwhile, stable wave profile can be output by the absorbing wave-maker in a long time when acute reflected waves appear in the terminal of NWF.
13
Oliveira, Tiago C. A., Agustín Sánchez-Arcilla, and Xavier Gironella. "Simulation of Wave Overtopping of Maritime Structures in a Numerical Wave Flume." Journal of Applied Mathematics 2012 (2012): 1–19. http://dx.doi.org/10.1155/2012/246146.
Анотація:
A numerical wave flume based on the particle finite element method (PFEM) is applied to simulate wave overtopping for impermeable maritime structures. An assessment of the performance and robustness of the numerical wave flume is carried out for two different cases comparing numerical results with experimental data. In the first case, a well-defined benchmark test of a simple low-crested structure overtopped by regular nonbreaking waves is presented, tested in the lab, and simulated in the numerical wave flume. In the second case, state-of-the-art physical experiments of a trapezoidal structure placed on a sloping beach overtopped by regular breaking waves are simulated in the numerical wave flume. For both cases, main overtopping events are well detected by the numerical wave flume. However, nonlinear processes controlling the tests proposed, such as nonlinear wave generation, energy losses along the wave propagation track, wave reflection, and overtopping events, are reproduced with more accuracy in the first case. Results indicate that a numerical wave flume based on the PFEM can be applied as an efficient tool to supplement physical models, semiempirical formulations, and other numerical techniques to deal with overtopping of maritime structures.
14
Vasarmidis, Panagiotis, Vasiliki Stratigaki, and Peter Troch. "Accurate and Fast Generation of Irregular Short Crested Waves by Using Periodic Boundaries in a Mild-Slope Wave Model." Energies 12, no. 5 (February 26, 2019): 785. http://dx.doi.org/10.3390/en12050785.
Анотація:
In this work, periodic lateral boundaries are developed in a time dependent mild-slope equation model, MILDwave, for the accurate generation of regular waves and irregular long and short crested waves in any direction. A single wave generation line inside the computational domain is combined with periodic lateral boundaries. This generation layout yields a homogeneous and thus accurate wave field in the whole domain in contrast to an L-shaped and an arc-shaped wave generation layout where wave diffraction patterns appear inside the computational domain as a result of the intersection of the two wave generation lines and the interaction with the lateral sponge layers. In addition, the performance of the periodic boundaries was evaluated for two different wave synthesis methods for short crested waves generation, a method proposed by Miles and a method proposed by Sand and Mynett. The results show that the MILDwave model with the addition of periodic boundaries and the Sand and Mynett method is capable of reproducing a homogeneous wave field as well as the target frequency spectrum and the target directional spectrum with a low computational cost. The overall performance of the developed model is validated with experimental results for the case of wave transformation over an elliptic shoal (Vincent and Briggs shoal experiment). The numerical results show very good agreement with the experimental data. The proposed generation layout using periodic lateral boundaries makes the mild-slope wave model, MILDwave, an essential tool to study coastal areas and wave energy converter (WEC) farms under realistic 3D wave conditions, due to its significantly small computational cost and its high numerical stability and robustness.
15
Ni, Xing Ye, and Wei Bin Feng. "Numerical Simulation of Wave Overtopping Based on DualSPHysics." Applied Mechanics and Materials 405-408 (September 2013): 1463–71. http://dx.doi.org/10.4028/www.scientific.net/amm.405-408.1463.
Анотація:
To obtain a more detailed description of wave overtopping, a 2-D numerical wave tank is presented based on an open-source SPH platform named DualSPHysics, using a source generation and absorption technology suited for SPH methods with analytical relaxation approach. Numerical simulation of regular wave run-up and overtopping on typical sloping dikes is carried out and satisfactory agreements are shown between numerical results and experimental data. Another overtopping simulation of regular wave is conducted against six different types of seawalls (vertical wall, curved wall, recurved wall, 1:3 slope with smooth face, 1:1.5 slope with smooth face and 1:1.5 slope with stepped-face), which represents the details of various breaking waves interacting with different seawalls, and the average deviation of wave overtopping rate is 6.8%.
16
Chitale, Kedar, Casey Fagley, Ali Mohtat, and Stefan Siegel. "Numerical Evaluation of Climate Scatter Performance of a Cycloidal Wave Energy Converter." International Marine Energy Journal 5, no. 3 (December 19, 2022): 315–26. http://dx.doi.org/10.36688/imej.5.315-326.
Анотація:
Ocean waves offer an uninterrupted, rich resource of globally available renewable energy. However, because of their high cost and low power production, commercial wave energy converters are not operational at present. In this paper, we numerically evaluated the performance of a novel feedback-controlled lift-based cycloidal wave energy converter (CycWEC) at various sea states of the Humboldt Bay wave climate. The device comprised of two hydrofoils attached eccentrically to a shaft at a radius, submerged at a distance under the ocean surface. The pitch of the blades was feedback-controlled based on estimation of the incoming wave. The simulations were performed for regular waves and irregular waves approximated with a JONSWAP spectrum. Climate data from Humboldt Bay, CA was used to estimate the yearly power generation. The results underline the importance of a well-tuned control algorithm to maximize the annual energy production. The estimated annual energy production of the CycWEC was 3000MWh from regular wave simulations and 1800MWh from irregular wave simulations, showing that it can be a commercially viable means of electricity production from ocean waves.
17
Hu, Xiaozhou, Daojun Cai, and Yiyao Jiang. "A Numerical Approach to the Dynamic Response of the Deployment System during a Circular Cylinder Crossing through the Wave Zone." Shock and Vibration 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/7974057.
Анотація:
The dynamic response of the deployment system while deploying a circular cylinder crossing wave surface and the following submerging process are investigated numerically. The present numerical approach is based on the combination of solution methods of cable dynamics and computational fluid dynamics (CFD). For the implementation of the numerical approach, a cosimulation platform based on a CFD code and MATLAB is developed to study the fluid-solid interaction problem in the process. To generate regular waves, a numerical wave tank is built based on a piston-type wave generation method and a wave damping method applying porous media. Numerical simulations are performed based on the cosimulation platform. The sensitivities of cable tension, velocity, and acceleration of deployed body to different input parameters are investigated, including phase angles, wave heights, and periods of regular waves and deploying velocities, and the effects of those input parameters on dynamic responses of the deployment system are also discussed.
18
ZHU, Q., Y. LIU, A. A. TJAVARAS, M. S. TRIANTAFYLLOU, and D. K. P. YUE. "Mechanics of nonlinear short-wave generation by a moored near-surface buoy." Journal of Fluid Mechanics 381 (February 25, 1999): 305–35. http://dx.doi.org/10.1017/s0022112098003826.
Анотація:
We consider the nonlinear interaction problem of surface waves with a tethered near-surface buoy. Our objective is to investigate mechanisms for nonlinear short surface wave generation in this complete coupled wave–buoy–cable dynamical system. We develop an effective numerical simulation capability coupling an efficient and high-resolution high-order spectral method for the nonlinear wave–buoy interaction problem with a robust implicit finite-difference method for the cable–buoy dynamics. The numerical scheme accounts for nonlinear wave–wave and wave–body interactions up to an arbitrary high order in the wave steepness and is able to treat extreme motions of the cable including conditions of negative cable tension. Systematic simulations show that beyond a small threshold value of the incident wave amplitude, the buoy performs chaotic motions, characterized by the snapping of the cable. The root cause of the chaotic response is the interplay between the snapping of the cable and the generation of surface waves, which provides a source of strong (radiation) damping. As a result of this interaction, the chaotic buoy motion switches between two competing modes of snapping response: one with larger average peak amplitude and lower characteristic frequency, and the other with smaller amplitude and higher frequency. The generated high-harmonic/short surface waves are greatly amplified once the chaotic motion sets in. Analyses of the radiated wave spectra show significant energy at higher frequencies which is orders of magnitude larger than can be expected from nonlinear generation under regular motion.
19
Conde, J. M. P. "COMPARISON OF DIFFERENT METHODS FOR GENERATION AND ABSORPTION OF WATER WAVES." Revista de Engenharia Térmica 18, no. 1 (June 3, 2019): 71. http://dx.doi.org/10.5380/reterm.v18i1.67053.
Анотація:
The knowledge of water wave characteristics (generation, propagation, transformation and breaking) is fundamental for hydrodynamic studies and the design of ocean, coastal and port structures. In addition to the small-scale experimental studies, the use of numerical models is also a very important tool in hydrodynamic studies. To have reliable numerical results a proper validation is required. The main objective of this paper is to compare different methods of wave generation and wave absorption in a numerical flume, and to find what is the most suited to simulate non-breaking regular wave propagation in a two-dimensional flume in deep water condition. The numerical simulations were made using the OpenFOAM® software package. Two solvers, waves2Foam and IHFoam/OlaFlow, the utility GroovyBC and a mesh stretching technique are compared. These numerical codes solve the transient Navier-Stokes equations and use a VoF (Volume of Fluid) method to identify the free surface. A solution dependence study with the methods of wave generation and wave absorption is presented. The results are also compared with the theoretical wave and experimental data. The results show that the different methods of generation produce waves similar to the theoretical and the experimental ones, only slightly differences were visible. The three method of wave dissipation considered produce very different results: IHFoam/OlaFlow is not able to dissipate the wave tested; the mesh stretching technique is able to dissipate the waves but produces a water level rise; the waves2Foam solver is able to dissipate properly the wave tested.
20
Chandrasekaran, Srinivasan, and Harender. "Power Generation Using Mechanical Wave Energy Converter." International Journal of Ocean and Climate Systems 3, no. 1 (March 2012): 57–70. http://dx.doi.org/10.1260/1759-3131.3.1.57.
Анотація:
Ocean wave energy plays a significant role in meeting the growing demand of electric power. Economic, environmental, and technical advantages of wave energy set it apart from other renewable energy resources. Present study describes a newly proposed Mechanical Wave Energy Converter (MEWC) that is employed to harness heave motion of floating buoy to generate power. Focus is on the conceptual development of the device, illustrating details of component level analysis. Employed methodology has many advantages such as i) simple and easy fabrication; ii) easy to control the operations during rough weather; and iii) low failure rate during normal sea conditions. Experimental investigations carried out on the scaled model of MWEC show better performance and its capability to generate power at higher efficiency in regular wave fields. Design Failure Mode and Effect Analysis (FMEA) shows rare failure rates for all components except the floating buoy.
21
Liu, Zhigang, Wei Huang, Shi Liu, Xiaomei Wu, Chun Sing Lai, and Yi Yang. "An Improved Hydraulic Energy Storage Wave Power-Generation System Based on QPR Control." Energies 16, no. 2 (January 5, 2023): 647. http://dx.doi.org/10.3390/en16020647.
Анотація:
According to the inherent characteristics of the hydraulic power take-off (PTO) system, the output power of a generator tends to be intermittent when the wave is random. Therefore, this paper aims to improve the effective utilization of wave energy and reduce power intermittency by constructing a topology with two branches to transmit electrical energy. Firstly, the wave-to-wire (W2W) model of the system is constructed. Secondly, the W2W model is simulated by using synovial and quasi-proportional resonance (QPR) control with regular and irregular incident waves, and the results of PI control are compared. Then, the control strategy in simulation is verified by experiments. The simulation and experimental results show that the control strategy has better performance, and the stability of the system output power is greatly improved.
22
Sarmento, A. J. N. A., and A. F. de O. Falcão. "Wave generation by an oscillating surface-pressure and its application in wave-energy extraction." Journal of Fluid Mechanics 150 (January 1985): 467–85. http://dx.doi.org/10.1017/s0022112085000234.
Анотація:
A two-dimensional analysis, based on linear surface-wave theory, is developed for an oscillating-water-column wave-energy device in water of arbitrary constant depth. The immersed part of the structure is assumed of shallow draught except for a submerged vertical reflecting wall. Both the cases of linear and nonlinear power take-off are considered. The results show that air compressibility can be important in practice, and its effects may in general be satisfactorily represented by linearization. The analysis indicates that using a turbine whose characteristic exhibits a phase difference between pressure and flow rate may be a method of strongly reducing the chamber length and turbine size with little change in the capability of energy extraction from regular waves. It was found in two examples of devices with strongly nonlinear power take-off that the maximum efficiency is only marginally inferior to what can be achieved in the linear case.
23
SAGUÉS, F., S. ALONSO, and J. M. SANCHO. "WAVE PATTERN DYNAMICS IN FLUCTUATING MEDIA." International Journal of Modern Physics C 13, no. 09 (November 2002): 1243–52. http://dx.doi.org/10.1142/s0129183102004091.
Анотація:
Analytical and numerical results on the ordering role of external random fluctuations in excitable systems are presented. Our study focuses on a simple model for excitable systems. Regular waves are created and sustained out of noise when the system is forced with random perturbations. Explicit results for the generation and dynamics of rings and targets are presented.
24
Meng, Zhongliang, Yanjun Liu, Jian Qin, and Shumin Sun. "Mooring Angle Study of a Horizontal Rotor Wave Energy Converter." Energies 14, no. 2 (January 9, 2021): 344. http://dx.doi.org/10.3390/en14020344.
Анотація:
The horizontal rotor wave energy converter is a newly designed wave energy converter. While the mooring system plays a vital role in keeping the device floating stably, the selection of the mooring angle has immediate effects on the device’s floating stability and energy generation efficiency. Given the properties of wave energy along the coast in Shandong Province, this study combines wave statistics gathered from field measurements of a certain area in the Bohai Sea with hydrological data obtained in a field test in the same sea area and adopts Stokes’ fifth-order wave theory to theoretically design and simulate the mooring system for the new type of power generating device. With the help of AQWA software, data on the dynamics of the device at various angles are obtained to construct models and carry out regular wave experiments according to the most appropriate mooring angles to show the validity of the selected mooring angles. The consistency of the results between the experiment and simulation confirms that under the same working conditions of regular waves, as the mooring angle increases, the roll angle decreases first and then increases, the pitch angle barely varies, and the yaw angle decreases first and then increases. The adoption of this simulation method and the gathered experimental data help to provide theoretical and practical bases for choosing the mooring method for the engineering prototype and obtaining a reliable supply of power.
25
Meng, Zhongliang, Yanjun Liu, Jian Qin, and Shumin Sun. "Mooring Angle Study of a Horizontal Rotor Wave Energy Converter." Energies 14, no. 2 (January 9, 2021): 344. http://dx.doi.org/10.3390/en14020344.
Анотація:
The horizontal rotor wave energy converter is a newly designed wave energy converter. While the mooring system plays a vital role in keeping the device floating stably, the selection of the mooring angle has immediate effects on the device’s floating stability and energy generation efficiency. Given the properties of wave energy along the coast in Shandong Province, this study combines wave statistics gathered from field measurements of a certain area in the Bohai Sea with hydrological data obtained in a field test in the same sea area and adopts Stokes’ fifth-order wave theory to theoretically design and simulate the mooring system for the new type of power generating device. With the help of AQWA software, data on the dynamics of the device at various angles are obtained to construct models and carry out regular wave experiments according to the most appropriate mooring angles to show the validity of the selected mooring angles. The consistency of the results between the experiment and simulation confirms that under the same working conditions of regular waves, as the mooring angle increases, the roll angle decreases first and then increases, the pitch angle barely varies, and the yaw angle decreases first and then increases. The adoption of this simulation method and the gathered experimental data help to provide theoretical and practical bases for choosing the mooring method for the engineering prototype and obtaining a reliable supply of power.
26
Maciel, Rafael P., Cristiano Fragassa, Bianca N. Machado, Luiz A. O. Rocha, Elizaldo D. dos Santos, Mateus N. Gomes, and Liércio A. Isoldi. "Verification and Validation of a Methodology to Numerically Generate Waves Using Transient Discrete Data as Prescribed Velocity Boundary Condition." Journal of Marine Science and Engineering 9, no. 8 (August 19, 2021): 896. http://dx.doi.org/10.3390/jmse9080896.
Анотація:
This work presents a two-dimensional numerical analysis of a wave channel and a oscillating water column (OWC) device. The main goal is to validate a methodology which uses transient velocity data as a means to impose velocity boundary condition for the generation of numerical waves. To achieve this, a numerical wave channel was simulated using regular waves with the same parameters as those used in a laboratory experiment. First, these waves were imposed as prescribed velocity boundary condition and compared with the analytical solution; then, the OWC device was inserted into the computational domain, aiming to validate this methodology. For the numerical analysis, computational fluid dynamics ANSYS Fluent software was employed, and to tackle with water–air interaction, the nonlinear multiphase model volume of fluid (VOF) was applied. Although the results obtained through the use of discrete data as velocity boundary condition presented a little disparity; in general, they showed a good agreement with laboratory experiment results. Since many studies use regular waves, there is a lack of analysis with ocean waves realistic data; thus, the proposed methodology stands out for its capacity of using realistic sea state data in numerical simulations regarding wave energy converters (WECs).
27
Ting, Chao-Lung, Wei-Ting Chao, and Chih-Chieh Young. "Experimental investigation of nonlinear regular wave transformation over a submerged step: Harmonic generation and wave height modulation." Coastal Engineering 117 (November 2016): 19–31. http://dx.doi.org/10.1016/j.coastaleng.2016.07.005.
28
Zhang, Haiming, Aifeng Tao, Junhao Tu, Junwei Su, and Shuya Xie. "The Focusing Waves Induced by Bragg Resonance with V-Shaped Undulating Bottom." Journal of Marine Science and Engineering 9, no. 7 (June 27, 2021): 708. http://dx.doi.org/10.3390/jmse9070708.
Анотація:
Intensive wave reflection occurs when the wavelengths of the incident waves and bottom undulations are in a 2:1 ratio. Existing studies have included the Bragg resonance phenomenon of waves passing over a continuous undulating bottom parallel to and oblique to the shoreline. More generally, the Bragg resonance mechanism is used as a means of coastal protection, rather than wave power generation. To focus the wave energy in a specific area, here, we propose sinusoidal sandbars of a horizontal V-shaped pattern, which is formed by two continuous undulating bottoms inclined at an angle to each other and the center axis of the angle is perpendicular to the shoreline. Based on the high-order spectral (HOS) numerical model, both the characteristics of Bragg resonance induced by the regular waves and random waves are investigated. In the scenario of regular waves, it shows that the wave-focusing effect is related to the angle of the V-shaped undulating bottom, and the optimal angle of inclination for the V-shaped undulating bottom is 162.24°. On that basis, considering the interactions between the random waves and the V-shaped undulating bottom of 162.24°, the Bragg resonance characteristics of random waves are studied. The BFI factor combining wave steepness and spectrum width can evaluate the focusing intensity of the Bragg resonance of the random waves. For BFI, in the range of 0.15–1.0, the values of Hsmax/Hs0 linearly increase with the increase of BFI.
29
Mohtat, Ali, Casey Fagley, Kedar C. Chitale, and Stefan G. Siegel. "Efficiency analysis of the cycloidal wave energy convertor under real-time dynamic control using a 3D radiation model." International Marine Energy Journal 5, no. 1 (June 14, 2022): 45–56. http://dx.doi.org/10.36688/imej.5.45-56.
Анотація:
Ocean waves provide a vast, uninterrupted resource of renewable energy collocated around large coastal population centers. Clean energy from ocean waves can contribute to the local electrical grid without the need for long-term electrical storage, yet due to the current high cost of energy extraction from ocean waves, there is no commercial ocean wave farm in operation. One of the wave energy converter (WEC) device classes that show the potential to enable economic energy generation from ocean waves is the class of wave terminators. This work investigates the Cycloidal Wave Energy Converter (CycWEC), which is a one-sided, lift-based wave terminator operating with coupled hydrofoils. The energy that the CycWEC extracted from ocean waves was estimated using a control volume analysis model of the 3D wave field in the presence of the CycWEC. The CycWEC was operated under feedback control to extract the maximum amount of energy possible from the incoming waves, and the interaction with different incoming regular, irregular, and short crested waves was examined.
30
Katafuchi, Masaki, Hideyuki Suzuki, Yuya Higuchi, Hidetaka Houtani, Edgard B. Malta, and Rodolfo T. Gonçalves. "Wave Response of a Monocolumn Platform with a Skirt Using CFD and Experimental Approaches." Journal of Marine Science and Engineering 10, no. 9 (September 9, 2022): 1276. http://dx.doi.org/10.3390/jmse10091276.
Анотація:
This paper aims to investigate the nonlinear motion characteristics of a monocolumn type floater with skirts numerically and experimentally. Wave calibration, free decay, and regular wave tests were simulated using a computational fluid dynamics (CFD) code OpenFOAM. The experiments were carried out in a wave tank to validate the CFD results. First, wave calibration tests were performed to investigate wave generation, development, propagation, and absorption in the numerical wave tank. Second, the simulation input parameters were calibrated to reproduce the waves generated in the tank experiment. Third, free decay tests of heave and pitch were conducted to examine the natural period and the linear and quadratic damping of the floater. A verification and validation study was performed using experimental data for free decay tests. Finally, regular wave tests were performed to investigate the motion characteristics of the floater. The results were processed to obtain the response amplitude operator (RAO) for the heave and pitch motions. The RAOs of the floater was compared with the experimental data and numerical simulations based on the linear potential theory code WAMIT to investigate the performance of the CFD simulations. The comparisons made in this work showed the potential of the CFD method to reproduce the motion characteristics of a shallow-draft floating object with a skirt in waves and to visualize the nonlinear phenomena behind the oscillation of the floating object.
31
Gheni, Mamtimin, X. F. Wang, and Masanori Kikuchi. "Study on Self-Consistent Mesh Generating Method of Hexahedron Element Based on the Local Waveform Method with Damping." Key Engineering Materials 306-308 (March 2006): 607–12. http://dx.doi.org/10.4028/www.scientific.net/kem.306-308.607.
Анотація:
Three-dimensional finite element method (FEM) is widely used as an effective numerical simulation technique to solve the complex engineering problem. In the FEM simulation technique at first it needs to discrete the problem. However, the almost all of the engineering problem have very complicated structure and shape, so that the mesh generation also have much difficulty. Furthermore, the correct generation of mesh is one of the most significant issues that directly affect to the accuracy of the FEM simulation. Though in extensive commercial software have an excellent automatic mesh generating system, however the problem of hexahedral automatic mesh generation and its adaptation are not enough to solve for practical applications, because for the mesh generation of complex shape is very difficult and still intensive labor work by hand. In this paper we present a new method to generate an appropriate mesh using existing regular hexahedral mesh and hexahedron mesh generation technique. This technique based on the wave transmits theory with damp named Waveform Mesh Generating (WMG) method. The results shown that the complex shaped FEM discrete hexahedral mesh model generated when shape of the side apply to regular mesh side as a waveform constraint.
32
Zhang, Guanyu, Xiang Chen, and Decheng Wan. "MPS-FEM Coupled Method for Study of Wave-Structure Interaction." Journal of Marine Science and Application 18, no. 4 (October 15, 2019): 387–99. http://dx.doi.org/10.1007/s11804-019-00105-6.
Анотація:
Abstract Nowadays, an increasing number of ships and marine structures are manufactured and inevitably operated in rough sea. As a result, some phenomena related to the violent fluid-elastic structure interactions (e.g., hydrodynamic slamming on marine vessels, tsunami impact on onshore structures, and sloshing in liquid containers) have aroused huge challenges to ocean engineering fields. In this paper, the moving particle semi-implicit (MPS) method and finite element method (FEM) coupled method is proposed for use in numerical investigations of the interaction between a regular wave and a horizontal suspended structure. The fluid domain calculated by the MPS method is dispersed into fluid particles, and the structure domain solved by the FEM method is dispersed into beam elements. The generation of the 2D regular wave is firstly conducted, and convergence verification is performed to determine appropriate particle spacing for the simulation. Next, the regular wave interacting with a rigid structure is initially performed and verified through the comparison with the laboratory experiments. By verification, the MPS-FEM coupled method can be applied to fluid-structure interaction (FSI) problems with waves. On this basis, taking the flexibility of structure into consideration, the elastic dynamic response of the structure subjected to the wave slamming is investigated, including the evolutions of the free surface, the variation of the wave impact pressures, the velocity distribution, and the structural deformation response. By comparison with the rigid case, the effects of the structural flexibility on wave-elastic structure interaction can be obtained.
33
Conde, J. M. P., P. T. S. Roberto, and C. J. E. M. Fortes. "WAVE PROPAGATION ON A FLUME: NUMERICAL SIMULATION." Revista de Engenharia Térmica 14, no. 1 (June 30, 2015): 95. http://dx.doi.org/10.5380/reterm.v14i1.62120.
Анотація:
This paper presents the numerical simulations done by using the waves2Foam, an OpenFOAM® library, to simulate the propagation of regular waves without breaking in a three-dimensional flume. The numerical code solves the unsteady Navier-Stokes equations and uses a Volume-of-Fluid (VoF) method to identify the free-surface. A regular incident wave with a 1.5s period and 0.1m wave height was considered. This is one of the conditions, from the wide range of wave flume tests conducted at the National Laboratory for Civil Engineering (LNEC), whose objective was to analyze the hydrodynamics of wave transformation and wave breaking for different incident conditions over a variable bathymetry. Comparisons are made between the numerical and the experimental results. These comparisons include time-series of wave-gauges records at several locations along the flume and the corresponding amplitude spectra; significant wave height and average period evolution along the flume; time-series of the velocity components at one section of the flume, measured at the middle of the water column; and hodograph representation of the velocity components, in the middle of the water column, in the xy, xz, and yz planes, along the flume. It was found that the numerical results obtained are close to the experimental data. The observed differences are attributable to numerical inaccuracies as well as the differences between the wave generation method in the numerical and experimental tests.
34
Meng, Zhongliang, Yi Ding, Yun Chen, and Shizhen Li. "Experimental study on heave performance of a new wave energy power generation device based on regular waves." Ocean Engineering 252 (May 2022): 111099. http://dx.doi.org/10.1016/j.oceaneng.2022.111099.
35
Li, Mengyu, Xizeng Zhao, Zhouteng Ye, Weidong Lin, and Yong Chen. "Generation of regular and focused waves by using an internal wave maker in a CIP-based model." Ocean Engineering 167 (November 2018): 334–47. http://dx.doi.org/10.1016/j.oceaneng.2018.08.048.
36
Ha, Taemin, Pengzhi Lin, and Yong-Sik Cho. "Generation of 3D regular and irregular waves using Navier–Stokes equations model with an internal wave maker." Coastal Engineering 76 (June 2013): 55–67. http://dx.doi.org/10.1016/j.coastaleng.2013.01.013.
37
Kazbegi, AZ, GZ Machabeli, and GI Melikidze. "The Nature of Pulsar Subpulse Drift." Australian Journal of Physics 44, no. 5 (1991): 573. http://dx.doi.org/10.1071/ph910573.
Анотація:
A possible mechanism for the explanation of pulsar subpulse drift is suggested. In the region of the open magnetic field lines the existence of an electron-positron plasma penetrated by a primary particle beam is assumed. There is a possibility of excitation of large-scale drift waves propagating transversely to the magnetic field lines. These waves can affect the fulfilment of the radio-wave generation conditions. If the pulsar angular velocity is near to the frequency of the drift waves one should observe regular drift phenomena.
38
Martins, J. C., M. M. Goulart, L. A. Isoldi, E. D. dos Santos, M. N. Gomes, and L. A. O. Rocha. "GEOMETRIC EVALUATION USING CONSTRUCTAL DESIGN OF A COASTAL OVERTOPPING DEVICE WITH DOUBLE RAMP CONSIDERING A REGULAR WAVE AND TIDAL VARIATION." Revista de Engenharia Térmica 18, no. 1 (June 3, 2019): 64. http://dx.doi.org/10.5380/reterm.v18i1.67051.
Анотація:
Concern for the environment and new ways of electricity generation, have led to studies of renewable energy sources, among these the Wave Energy Converters (WECs) are an option, however there are still many challenges to define how best to realize the conversion of the energy of the waves into electricity. In this work, a numerical study was carried out with the purpose of maximizing the available power (Pd) of a two-ramp overtopping device, considering the area fraction of ramps (ϕ1 and ϕ2) equal to 0.0006 and the ratio between height and length of the ramps (H1/L1 = H2/L2) equal to 0.3. The distance between the ramps (Lg) was varied in three values: 1.0; 1.5 and 2.0 m, besides three values for the free surface of water (h): 9.8; 10.0 and 10.2 m; simulating a tidal effect. The Constructal Design and Exhaustive Search methods were used, respectively, in the geometric evaluation (determination of a search field) and optimization. For the wave generation, the Second Order Stokes Theory was used, with wave period (T) of 7.5 s and wave height (H) 1.0 m. The results showed that there was no accumulation of water in the upper ramp of the device, in addition, with the increase of Lg there was an increase of Pd in h = 10.0 and 10.2 m, and Pd kept practically constant in h = 9, 8 m. And, as expected, with increasing of h, there was an increase in Pd.
39
Spinneken, Johannes, and Chris Swan. "Second-order wave maker theory using force-feedback control. Part II: An experimental verification of regular wave generation." Ocean Engineering 36, no. 8 (June 2009): 549–55. http://dx.doi.org/10.1016/j.oceaneng.2009.01.007.
40
Spinneken, Johannes, and Chris Swan. "Second-order wave maker theory using force-feedback control. Part I: A new theory for regular wave generation." Ocean Engineering 36, no. 8 (June 2009): 539–48. http://dx.doi.org/10.1016/j.oceaneng.2009.01.019.
41
Cho, Yong-Hwan, Tomoaki Nakamura, Norimi Mizutani, and Kwang-Ho Lee. "An Experimental Study of a Bottom-Hinged Wave Energy Converter with a Reflection Wall in Regular Waves—Focusing on Behavioral Characteristics." Applied Sciences 10, no. 19 (September 26, 2020): 6734. http://dx.doi.org/10.3390/app10196734.
Анотація:
The hybrid system of wave energy converters (WECs) using coastal structures is an attractive issue in terms of a decrease in construction costs and an improvement of the ability to capture wave energy. Most studies on the utilization of reflected waves from structures, which is one of the hybrid systems, are limited to mathematical analysis based on linear theories. Therefore, this paper presents fundamental experimental results in the presence of a reflection wall simplified as a coastal structure behind a bottom-hinged flap-type WEC under unidirectional regular waves. The behavioral characteristics and the power generation efficiency ke of the flap were investigated, focusing on wave steepness, initial water depth, and distance from the reflection wall. The results show that the condition of the initial water depth being smaller than the flap height is more effective in terms of avoiding unstable rotating of the flap. The maximum ke appeared slightly far from the node position of the standing waves because the flap shape and the power take-off (PTO) damping induce the phase difference between the reciprocating behavior of the flap and the period of the standing wave. The results imply that the optimum position of a WEC is dependent on WEC shape, PTO damping, and installation water depth.
42
Park, Min-Su, Seung-Heon Lee, and Sang-Cheol Ko. "Experimental Capture Width Ratio on Unit Module System of Hybrid Wave Energy Converter for Nearshore." Applied Sciences 12, no. 12 (June 8, 2022): 5845. http://dx.doi.org/10.3390/app12125845.
Анотація:
This study proposes a new hybrid wave energy converter composed of a horizontal cylinder and a swing plate to improve the capture width ratio. The horizontal cylinder generates electrical energy by using the potential energy of the incident wave, whereas the swing plate produces electrical energy by using the kinetic energy of the water particles. The converter can improve the capture width ratio of the wave energy by efficiently combining the energies generated by these two different sources. The power-generating performance of the proposed hybrid wave energy converter is evaluated experimentally through a hydraulic model test at a scale ratio of 0.3 in a two-dimensional wave tank using direct conversion by a dynamo PTO (Power Take-Off) system. The dynamic power-generation characteristics of the hybrid wave energy converter are analyzed with respect to the eventual regularity of the incident wave (regular and irregular wave conditions), and the data necessary for the design of the generator and control system are acquired.
43
Oliveira, Tiago C. A., Agustín Sanchez-Arcilla, Xavier Gironella, and Ole S. Madsen. "On the generation of regular long waves in numerical wave flumes based on the particle finite element method." Journal of Hydraulic Research 55, no. 4 (February 22, 2017): 538–56. http://dx.doi.org/10.1080/00221686.2016.1275047.
44
Dermatis, Athanasios, Dimitrios Ntouras, and George Papadakis. "Numerical Simulation of Irregular Breaking Waves Using a Coupled Artificial Compressibility Method." Fluids 7, no. 7 (July 11, 2022): 235. http://dx.doi.org/10.3390/fluids7070235.
Анотація:
Wave breaking is widely recognized as a very challenging phenomenon to emulate using numerical/computational methods. On that condition, the transition from modelling regular to irregular breaking waves is not trivial. Even though some issues are surpassed in CFD simulations, there still are two substantial problems to account for. The first one entails the proper generation of irregular waves in a numerical wave tank, while the second is the introduction of the turbulent regime of breaking in the solver. The present work addresses these two problems by employing the Stabilized k−ω SST model for turbulence closure and by proposing an efficient and accurate method for irregular wave generation. Apart from that, an artificial compressibility method is used for coupling the system of equations, which solves these equations in a non-segregated manner and overcomes problems pertaining to the existence of the interface in free-surface flows. The methodology is validated through the test case of irregular wave propagation over a submerged breaker bar and a piecewise sloped bottom, indicating the ability of the method to capture irregular breaking wave phenomena. Simulations are in fair agreement with experimental data regarding energy spectra and free surface time-series, while results suggest that the known over-prediction of turbulent kinetic energy (TKE) is significantly constrained by the stabilized k−ω SST model.
45
Derzho, Oleg G. "Large internal solitary waves on a weak shear." Chaos: An Interdisciplinary Journal of Nonlinear Science 32, no. 6 (June 2022): 063130. http://dx.doi.org/10.1063/5.0078975.
Анотація:
Large amplitude solitary internal waves of permanent form propagating in a stratified shallow fluid between the free surface and a horizontal bottom are described by the amplitude equation obtained by a regular asymptotic procedure, which incorporates a complicated nonlinearity and Korteweg–de Vries (KdV) dispersion. It is discussed how the structure of stratification and shear affects wave properties. The particular case of a constant buoyancy frequency and a quadratic polynomial for the ambient shear for the flow under free surface is considered in detail analytically. It is shown that for such profiles, the equation for the wave amplitude reduces to the mixed-modified KdV equation and finite amplitude waves obey it up to the breaking level. Rogue waves could appear in this case, and the condition for their generation is identified. More complicated shear profiles lead to higher-order nonlinearities, which produce the multiscaled pyramidal wave patterns, asymmetric bores, and various instabilities. Such wave structures are studied numerically. An analytical bore-like solution having both exponential and algebraic asymptotes is presented.
46
Mukhlas, Nurul 'Azizah, Noor Irza Mohd Zaki, Mohd Khairi Abu Husain, and Gholamhossein Najafian. "Comparison of Extreme Surface Elevation for Linear and Nonlinear Random Wave Theory for Offshore Structures." MATEC Web of Conferences 203 (2018): 01021. http://dx.doi.org/10.1051/matecconf/201820301021.
Анотація:
For offshore structural design, the load due to wind-generated random waves is usually the most important source of loading. While these structures can be designed by exposing them to extreme regular waves (100-year design wave), it is much more satisfactory to use a probabilistic approach to account for the inherent randomness of the wave loading. This method allows the statistical properties of the loads and structural responses to be determined, which is essential for the risk-based assessment of these structures. It has been recognized that the simplest wave generation is by using linear random wave theory. However, there is some limitation on its application as some of the nonlinearities cannot be explained when higher order terms are excluded and lead to underestimating of 100-year wave height. In this paper, the contribution of nonlinearities based on the second order wave theory was considered and being tested at a variety of sea state condition from low, moderate to high. Hence, it was proven that the contribution of nonlinearities gives significant impact the prediction of 100-year wave's design as it provides a higher prediction compared to linear wave theory.
47
Yao, Jianxi, Xide Cheng, Xuemin Song, Chengsheng Zhan, and Zuyuan Liu. "RANS Computation of the Mean Forces and Moments, and Wave-Induced Six Degrees of Freedom Motions for a Ship Moving Obliquely in Regular Head and Beam Waves." Journal of Marine Science and Engineering 9, no. 11 (October 26, 2021): 1176. http://dx.doi.org/10.3390/jmse9111176.
Анотація:
Ship maneuvering performance in waves has attracted much attention in recent years. One of main research efforts for this problem has been devoted to the high-accuracy computation of hydrodynamic forces and moments, as well as wave-induced motions, for ships performing maneuvering motions in waves. The objective of this article is to present a numerical study on the computation of the mean forces and moments, and wave-induced six degrees of freedom motions for a ship moving obliquely in regular head and beam waves. The RANS (Reynolds-Averaged Navier-Stokes) solver based on OpenFOAM is used for this purpose. The RANS computations herein are carried out in a horizontal coordinate system. The numerical wave maker with prescribing values of flow variables on the domain boundaries is applied for the wave generation in the computational domain. However, in order to prevent wave reflection, relaxed zones adjacent to the wave maker boundaries are set up. A new program module is inserted into OpenFOAM to update the flow velocity and wave evaluation on the wave-maker boundaries and in the relaxed zones during the RANS computation. The mesh deformation method is employed to allow the ship to perform motions in space. However, a virtual spring system is attached to the ship so as to restrain the surge, sway and yaw, while heave, pitch and roll are completely free, so that the ship is able to oscillate periodically around a certain position in space. The computed mean forces and moments with the inertia effects agree fairly well with the experimental data, and the computed wave-induced motions are also in quite reasonable agreement with the experimental data. This study shows a very successful computation, as well as the procedure of the RANS results processing.
48
Martinelli, Luca, Matteo Volpato, Chiara Favaretto, and Piero Ruol. "Hydraulic Experiments on a Small-Scale Wave Energy Converter with an Unconventional Dummy Pto." Energies 12, no. 7 (March 29, 2019): 1218. http://dx.doi.org/10.3390/en12071218.
Анотація:
This paper investigates on a Wave Energy Converter (WEC) named Energy & Protection, 4th generation (EP4). The WEC couples the energy harvesting function with the purpose of protecting the coast from erosion. It is formed by a flap rolling with a single degree of freedom around a lower hinge. Small-scale tests were carried out in the wave flume of the maritime group of Padua University, aiming at the evaluation of the device efficiency. The test peculiarity is represented by the system used to simulate the Power Take Off (PTO). Such dummy PTO permits a free rotation of two degrees before engaging the shaft, allowing the flap to gain some inertia, and then applying a constant resistive moment. The EP4 was observed to reach a 35% efficiency, under short regular waves. The effects, in terms of coastal protection, are small but not negligible, at least for the shortest waves.
49
Perrard, Stéphane, Adrián Lozano-Durán, Marc Rabaud, Michael Benzaquen, and Frédéric Moisy. "Turbulent windprint on a liquid surface." Journal of Fluid Mechanics 873 (June 28, 2019): 1020–54. http://dx.doi.org/10.1017/jfm.2019.318.
Анотація:
We investigate the effect of a light turbulent wind on a liquid surface, below the onset of wave generation. In that regime, the liquid surface is populated by small disorganised deformations elongated in the streamwise direction. Formally identified recently by Paquier et al. (Phys. Fluids, vol. 27, 2015, art. 122103), the deformations that occur below the wave onset were named wrinkles. We provide here a theoretical framework for this regime, using the viscous response of a free liquid surface submitted to arbitrary normal and tangential interfacial stresses at its upper boundary. We relate the spatio-temporal spectrum of the surface deformations to that of the applied interfacial pressure and shear stress fluctuations. For that, we evaluate the spatio-temporal statistics of the turbulent forcing using direct numerical simulation of a turbulent channel flow, assuming no coupling between the air and the liquid flows. Combining theory and numerical simulation, we obtain synthetic wrinkles fields that reproduce the experimental observations. We show that the wrinkles are a multi-scale superposition of random wakes generated by the turbulent fluctuations. They result mainly from the nearly isotropic pressure fluctuations generated in the boundary layer, rather than from the elongated shear stress fluctuations. The wrinkle regime described in this paper naturally arises as the viscous-saturated asymptotic of the inviscid growth theory of Phillips (J. Fluid Mech., vol. 2 (05), 1957, pp. 417–445). We finally discuss the possible relation between wrinkles and the onset of regular quasi-monochromatic waves at larger wind velocity. Experiments indicate that the onset of regular waves increases with liquid viscosity. Our theory suggests that regular waves are triggered when the wrinkle amplitude reaches a fraction of the viscous sublayer thickness. This implies that the turbulent fluctuations near the onset may play a key role in the triggering of exponential wave growth.
50
Seki, N., and H. Suzuki. "Electrical properties of smooth muscle cell membrane in renal pelvis of rabbits." American Journal of Physiology-Renal Physiology 259, no. 6 (December 1, 1990): F888—F894. http://dx.doi.org/10.1152/ajprenal.1990.259.6.f888.
Анотація:
Intracellular recordings were made to study the electrical properties of smooth muscle cells in the rabbit renal pelvis. The muscle cells exhibited spontaneous oscillation in the membrane potential (slow wave). The slow waves were regular and were resistant to tetrodotoxin and sympathomimetic or parasympathomimetic antagonists, findings indicative of myogenic activity. The membrane was depolarized by an increase in extracellular concentration of K+ ([K+]o), decrease in [Na+]o, inhibition of the electrogenic Na(+)-K+ pump by ouabain or K(+)-free solution, and the application of norepinephrine (NE, greater than 10(-6) M). The maximum slope of the membrane depolarization produced by a 10-fold increase in [K+]o was approximately 48 mV. Reductions in [Ca2+]o inhibited the generation of slow waves with no marked change in the membrane potential. Depolarizations produced by any given method increased the frequency and decreased the amplitude of the slow wave, and NE had the most potent accelerating action on the frequency. Hyperpolarization of the membrane by 1-5 mV with extracellularly applied current stimuli reduced the frequency, and a strong hyperpolarization (greater than 5 mV) blocked the generation of slow waves. Electrophysiological properties of the slow waves obtained with tissues of the renal pelvis and intestinal smooth muscles were compared.