Wave Simulation Based On Second-order Theory In Laboratory

The small-amplitude assumption of first-order wavemaker theory in laboratory will generate additional spurious free-wave which will affect the quality of the wave, while second-order wave generation is able to eliminate the spurious free-wave by attaching wave board movement and make a correction by means of keeping only bound harmonic waves. If we can simulate the wave precisely in laboratory, it is of great significance for studying wave propagation motion and effects of wave on structures.The paper establishes wave generation software in laboratory flume based on the second-order wavemaker theory derived by Schaffer in two-dimensional case. Using a piston-type wavemaker, a number of laboratory wave experiments for regular and irregular waves with first-order and second-order theory were conducted. The results verify the effectiveness of the second-order wave generation that it can suppress spurious free-wave effectively and get a more accurate waveform. In addition, the paper offers discussion of the problems in second-order wavemaker theory. This work will provide a reference for practical application.The paper makes a further expansion that the wave generation software in laboratory basin in three-dimensional case was established. Numerical simulation for oblique regular waves, oblique irregular waves, bichromatic and bidirectional waves and bidirectional irregular waves are conducted. After that, using a multidirectional piston-type wavemaker in the basin, a number of laboratory wave experiments for oblique reguar and irregular waves with first-order and second-order theory were conducted. The results verify the effectiveness of the second-order wave generation once again. The paper also offers discussion of the problems in the experiment in three-dimensional case, this work will provide a reference for practical application.In addition, based on the second-order wavemaker theory, the paper carries out the analysis on the change of dimensionless bound and free superharmonic wave height versus wave steepness, realtive water depth and wave propagation angle for regular waves. The results could provide scientific basis for wavemaker type selection when using first-order wave generation.