Elastic near-field wave energy radiated by a spherical cavity

1994 ◽  
Vol 66 (1) ◽  
pp. 241-247 ◽  
Author(s):  
Václav Vavryčuk
Keyword(s):  
Wave Energy ◽  
Spherical Cavity ◽  
Near Field ◽  
Field Wave

scholarly journals Benchmark Modeling of the Near-Field and Far-Field Wave Effects of Wave Energy Arrays

2013 ◽  
Author(s):  
Kenneth E Rhinefrank ◽  
Merrick C Haller ◽  
H Tuba Ozkan-Haller
Keyword(s):  
Wave Energy ◽  
Near Field ◽  
Far Field ◽  
Wave Effects ◽  
Field Wave

scholarly journals Coupling Methodology for Studying the Far Field Effects of Wave Energy Converter Arrays over a Varying Bathymetry

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2899 ◽  
Author(s):  
Gael Verao Fernandez ◽  
Philip Balitsky ◽  
Vasiliki Stratigaki ◽  
Peter Troch
Keyword(s):  
Numerical Simulations ◽  
Wave Energy ◽  
Near Field ◽  
Coupled Model ◽  
Propagation Model ◽  
Irregular Waves ◽  
Computational Time ◽  
Far Field ◽  
Field Effects ◽  
Numerical Tool

For renewable wave energy to operate at grid scale, large arrays of Wave Energy Converters (WECs) need to be deployed in the ocean. Due to the hydrodynamic interactions between the individual WECs of an array, the overall power absorption and surrounding wave field will be affected, both close to the WECs (near field effects) and at large distances from their location (far field effects). Therefore, it is essential to model both the near field and far field effects of WEC arrays. It is difficult, however, to model both effects using a single numerical model that offers the desired accuracy at a reasonable computational time. The objective of this paper is to present a generic coupling methodology that will allow to model both effects accurately. The presented coupling methodology is exemplified using the mild slope wave propagation model MILDwave and the Boundary Elements Methods (BEM) solver NEMOH. NEMOH is used to model the near field effects while MILDwave is used to model the WEC array far field effects. The information between the two models is transferred using a one-way coupling. The results of the NEMOH-MILDwave coupled model are compared to the results from using only NEMOH for various test cases in uniform water depth. Additionally, the NEMOH-MILDwave coupled model is validated against available experimental wave data for a 9-WEC array. The coupling methodology proves to be a reliable numerical tool as the results demonstrate a difference between the numerical simulations results smaller than 5% and between the numerical simulations results and the experimental data ranging from 3% to 11%. The simulations are subsequently extended for a varying bathymetry, which will affect the far field effects. As a result, our coupled model proves to be a suitable numerical tool for simulating far field effects of WEC arrays for regular and irregular waves over a varying bathymetry.

Mean-Flow Measurements in the Boundary Layer and Wake and Wave Field of a Series 60 CB = 0.6 Ship Model—Part 2: Scale Effects on Near-Field Wave Patterns and Comparisons with Inviscid Theory

1993 ◽  
Vol 37 (01) ◽  
pp. 16-24
Author(s):  
J. Longo ◽  
F. Stern ◽  
Y. Toda
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Scale Effects ◽  
Near Field ◽  
Wave Profile ◽  
Wave System ◽  
Mean Flow ◽  
Wave Elevation ◽  
Wave Patterns ◽  
Field Wave

Part 2 of this two-part paper presents additional results from a towing-tank experiment conducted in order to explicate the influence of wavemaking by a surface-piercing body on its boundary-layer and wake and provide detailed documentation of the complete flow field appropriate for validating computational methods. In Part 1 (Journal of Ship Research, Dec. 1992), wave profile, local and global wave-elevation, and mean-velocity and pressure field measurements for Froude numbers 0.16 and 0.316 for a 3.048 m Series 60 CB = 0.6 hull form are presented and discussed to point out the essential differences between the flows at low and high Froude number and to assess the nature of the interaction between wavemaking and the boundary layer and wake. In Part 2, scale effects on the near-field wave patterns are examined through wave profile and local and global wave-elevation measurements for 1.829 and 3.048 m models and Froude numbers 0.316, 0.3, and 0.25. The bow-wave amplitude and divergence angle are larger and the stern waves smaller for the smaller model. The latter scale effect is well known, but the former one is a new and unexpected result. Also, comparisons are made between the experimental results and those from a wavy inviscid-flow method, which provides an evaluation of the capabilities of the computational method. Although the computations predict the gross features of the wave system and velocity and pressure fields, they do not simulate the complex details of either the wave system or the flow field, especially close to the hull and wake centerplane.

scholarly journals Irregular Wave Validation of a Coupling Methodology for Numerical Modelling of Near and Far Field Effects of Wave Energy Converter Arrays

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 538 ◽  
Author(s):  
Gael Fernández ◽  
Vasiliki Stratigaki ◽  
Peter Troch
Keyword(s):  
Experimental Data ◽  
Wave Field ◽  
Wave Energy ◽  
Near Field ◽  
Coupled Model ◽  
Propagation Model ◽  
Irregular Waves ◽  
Far Field ◽  
Engineering Research ◽  
Field Effects

Between the Wave Energy Converters (WECs) of a farm, hydrodynamic interactions occur and have an impact on the surrounding wave field, both close to the WECs (“near field” effects) and at large distances from their location (“far field” effects). To simulate this “far field” impact in a fast and accurate way, a generic coupling methodology between hydrodynamic models has been developed by the Coastal Engineering Research Group of Ghent University in Belgium. This coupling methodology has been widely used for regular waves. However, it has not been developed yet for realistic irregular sea states. The objective of this paper is to present a validation of the novel coupling methodology for the test case of irregular waves, which is demonstrated here for coupling between the mild slope wave propagation model, MILDwave, and the ‘Boundary Element Method’-based wave–structure interaction solver, NEMOH. MILDwave is used to model WEC farm “far field” effects, while NEMOH is used to model “near field” effects. The results of the MILDwave-NEMOH coupled model are validated against numerical results from NEMOH, and against the WECwakes experimental data for a single WEC, and for WEC arrays of five and nine WECs. Root Mean Square Error (RMSE) between disturbance coefficient (Kd) values in the entire numerical domain ( R M S E K d , D ) are used for evaluating the performed validation. The R M S E K d , D between results from the MILDwave-NEMOH coupled model and NEMOH is lower than 2.0% for the performed test cases, and between the MILDwave-NEMOH coupled model and the WECwakes experimental data R M S E K d , D remains below 10%. Consequently, the efficiency is demonstrated of the coupling methodology validated here which is used to simulate WEC farm impact on the wave field under the action of irregular waves.

scholarly journals LARGE SCALE EXPERIMENTS ON FARMS OF HEAVING BUOYS TO INVESTIGATE WAKE DIMENSIONS, NEAR-FIELD AND FAR-FIELD EFFECTS

2012 ◽  
Vol 1 (33) ◽  
pp. 71 ◽  
Author(s):  
Vasiliki Stratigaki ◽  
Peter Troch ◽  
Timothy Stallard ◽  
Jens Peter Kofoed ◽  
Michel Benoit ◽  
...  
Keyword(s):  
Wave Energy ◽  
Energy Demand ◽  
Large Scale ◽  
Renewable Energy Sources ◽  
Near Field ◽  
Experimental Studies ◽  
Far Field ◽  
Power Absorption ◽  
Field Effects ◽  
Wave Basin

The shrinking reserves of fossil fuels in combination with the increasing energy demand have enhanced the interest in renewable energy sources, including wave energy. In order to extract a considerable amount of wave power, large numbers of Wave Energy Converters will have to be arranged in arrays or farms using a particular geometrical layout. The operational behaviour of a single device may have a positive or negative effect on the power absorption of the neighbouring WECs in the farm (near-field effects). Moreover, as a result of the interaction between the WECs within a farm, the overall power absorption and the wave climate in the lee of the WECs is modified, which may influence neighbouring farms, other users in the sea or even the coastline (far-field effects). Several numerical studies on large WEC arrays have already been performed, but large scale experimental studies on near-field and far-field wake effects of large WEC arrays are not available in literature. Within the HYDRALAB IV European programme, the research project WECwakes has been introduced to perform large scale experiments in the Shallow Water Wave Basin of DHI, in Denmark, on large arrays of point absorbers for different layout configurations and inter-WEC spacings. The aim is to validate and further develop the applied numerical methods, as well as to optimize the geometrical layout of WEC arrays for real applications.

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