2D Numerical Wave Tank Research

The simulation of wave environment by experiment or numerical method is an essential topic in thefield of Naval Architecture and Ocean Engineering. The fast development of modern computer science hasempowered the researchers to, at least partly, substitute numerical simulation for experiment study, whichis called Numerical Wave Tanks (NWT) technique. Some fundamental research has been conducted in twodimensional situation:A two dimensional NWT was developed based in Boundary Element Method (BEM) and MixedEulerian-Lagrangian (MEL) method, using MATLAB software. The wave-maker is piston-type orflap-type. The free surface is updated by an explicit2ndorder truncated Taylor expansion formula, and itsshape is approached by fitting the x and y coordinates using3rdsipline separately. In order to manipulatethe integration singularity, two corresponding techniques were adopted. Specially, A Gauss type quadraturewas employed in the calculation of singular source distribution integration, and the normal derivative oflogarithmic function was changed into the derivative of an angle to remove the singularity of dipoledistribution integration. The so-called “corner problem” which occurred at the interaction point of the freesurface and rigid boundaries was manipulated by double node method. The artificial damping zone wasused to avoid wave reflecting.In order to test the performance of the NWT, a variety of waves were simulated, including2ndorderStokes waves, irregular wave (P-M spectrum), solitary wave, transient overtopping wave and transientfocus wave. The numerical results show that this NWT can work steadily for quite a long time even whenthe wave-maker moves rapidly, high-frequency or sharply. And the numerical results also mach thecorresponding analytical results well in all the simulated cases. The convergence rate is good according thecalculation with different node density and time intervals.With the CFD software FLUENT, a viscous NWT was established to investigate the attenuationfeature the wave propagation. This dimension of the viscous NWT was chosen according to the physicaldimension of the general deepwater basin. Structural and dynamic mesh technique was adopted to ensurethe fluent movement of the rocker. At the end of the basin, an artificial damping zone was distributed toabsorb the incident wave.After simulating a wide range of regular wave (ω=5.5rad/s～1.8rad/s, H=0.1m~0.4m), the waveattenuation character can be represented by logarithmic function. And the corresponding coefficients werealso obtained.The Active Reflection Compensating (ARC) Technique was investigated by this viscous NWT. Thesystem transformation function was obtained by using the so-called “frequency domain” method. Thenumerical simulation indicate that this function works well i.e. the re-reflecting wave was absorbedeffectively.