Research On Numerical Wave Tank And Method Of Active Wave Absorption

With the development of computer technology, numerical simulation method becomes an important route to solve tank test in the field of naval architecture and ocean engineering,which derived the numerical wave tank technology. Wave generating and absorption are important research projects both in numerical wave tank and physical basin. A well wave generating can ensure high quality of waves and an efficient absorption can decrease reflected waves to improve test precision. This thesis concerns on numerical wave generating and active wave absorption. The detailed illustration is as follows:Under the potential flow theory and based on Boundary Element and Mixed-Euler-Lagrange methods, the two dimensional numerical wave tank model was developed by using MALTAB software. Wave-maker was piston-type and flap-type to imitate physical wave making. These issues were solved in the process of model building:the free surface was updated by an explicit second order truncated Taylor expansion formula.Boundary shape was approached by cubic spline curve. In order to manipulate the integration singularity, two corresponding techniques were adopted. A Gauss type quadrature was employed in the calculation of singular source distribution integration,and another method was variable replacement The comer problem which occurred at the interaction point of the free surface and rigid boundaries was resolved by double node method. Method. The artificial damping zone was used to avoid wave reflecting. In order to test the performance of the model, a variety of waves were simulated, including linear progressive wave, irregular wave and solitary wave. The numerical results show that the model can simulate these waves steadily by long running test and accuracy kept in good rank., which illustrated that the numerical wave tank meet requirements.Research on active wave absorption was carried out from conventional theory and intelligent control. Methods of time-domain equation, frequency-domain filter and S plane controller were introduced, and then derivation and design were completed. Based on the numerical wave tank, numerical simulation of active wave absorption was accomplished forshallow water piston-type and deep water flap-type in cases of low and total reflection. The numerical simulation indicated that this three methods works well and reflected wave was absorbed effectively. According to frequency-domain filter method, a digital filter was achieved to realize the function of active wave absorption for non-linear wave (second order Stokes wave). For S plane controller method, results of active wave absorption were given in regular wave flume test.