A new wave energy dissipation structure is proposed, aiming to optimize the dimensions of the structure and make the reflection of the structure maintain a low level within the scope of the known frequency band. An optimal extended ANFIS model combined with the wave reflection coefficient analysis for the estimation of the structure dimensions is established. In the premise of lower wave reflection coefficient, the specific sizes of the structure are obtained inversely, and the contribution of each related parameter on the structural reflection performance is analyzed. The main influencing factors are determined. It is found that the optimal dimensions of the proposed structure exist, which make the wave absorbing performance of the structure reach a perfect status under a wide wave frequency band.
Based on phase focusing theory, focusing waves with different spectral types and breaking severities were generated in a wave flume. The time series of surface elevation fluctuation along the flume were obtained by utilizing 22 wave probes mounted along the mid-stream of the flume. Based on the wave spectrum obtained using fast Fourier transform(FFT), the instability characteristics of the energy spectrum were reported in this paper. By analyzing the variation of total spectral energy, the total spectral energy after wave breaking was found to clearly decrease, and the loss value and ratio gradually increased and tended to stabilize with the enhancement of breaking severity for different spectral types. When wave breaking occurred, the energy loss was primarily in a high-frequency range of f/fp>1.0, and energy gain was primarily in a low-frequency range of f/fp<1.0. As the breaking severity increased, the energy gain-loss ratio decreased gradually, which demonstrates that the energy was mostly dissipated. For plunging waves, the energy gain-loss ratio reached 24% for the constant wave steepness(CWS) spectrum, and was slightly larger at approximately 30% for the constant wave amplitude(CWA) spectrum, and was the largest at approximately 42% for the Pierson-Moskowitz(PM) spectrum.
With the unstructured grid, the Finite Volume Coastal Ocean Model(FVCOM) is converted from its original FORTRAN code to a Compute Unified Device Architecture(CUDA) C code, and optimized on the Graphic Processor Unit(GPU). The proposed GPU-FVCOM is tested against analytical solutions for two standard cases in a rectangular basin, a tide induced flow and a wind induced circulation. It is then applied to the Ningbo's coastal water area to simulate the tidal motion and analyze the flow field and the vertical tide velocity structure. The simulation results agree with the measured data quite well. The accelerated performance of the proposed 3-D model reaches 30 times of that of a single thread program, and the GPU-FVCOM implemented on a Tesla k20 device is faster than on a workstation with 20 CPU cores, which shows that the GPU-FVCOM is efficient for solving large scale sea area and high resolution engineering problems.
The wave parameters(the wave height and period)are important environmental factors in the ocean engineering design.General numerical wave models,such as SWAN and WAVEWATCH,are widely employed to simulate the wave conditions.However,significant differences were observed between the measurement and the simulation for both the wave height and period,which asks for wave model improvements.The differences are mainly due to the uncertainty of parameterizing various physical processes,including the wave breaking.The energy transfer and loss during the wave breaking involves an important physical mechanism,and the energy dissipation and the period changes are not well studied.This paper studies the deep and shallow water wave breaking using the wave focusing and the slope platform random wave experiments.The characteristics of the wave periods under different conditions are studied in detail,including the period variation.The results show that the periods change during the wave propagation and breaking processes.The energy transfer caused by the strongly nonlinear interaction between the wave components,as well as the energy loss caused by the wave breaking,are the primary causes.The corresponding relationships are established by fitting the data.For the deep water breaking waves induced by the wave focusing,the spectrally averaged period(SAP)increases,and a positive correlation between the rate of change and the wave steepness is found.In the shallow water,the nonlinear interactions are stronger than in the deep water,the wave periods are significantly reduced,and a negative correlation between the rate of change and a nonlinear parameter is found.The inherent mechanism of the period variation is analyzed based on the energy spectrum distribution variations.The contributions of the nonlinear interactions and the wave breaking to the SAP evolution are discussed.
