| In the case of a large number of cylindrical arrays at some specific critical wave frequencies,the hydrodynamic curves in the frequency domain show high peaks and a series of secondary peaks and valleys caused by the modes of near-captured waves.This capturing region shows huge hydrodynamic loads caused by the accumulation of wave energy,which is called "captured wave" phenomenon.In the remaining large range of wave number region of the hydrodynamic curve,the hydrodynamic curve presents regular fluctuations.Such periodic regular fluctuation load will cause fatigue failure of the structure.This region is generally referred to as the "non-captured region".Therefore,it is necessary to study its distribution and physical mechanism.In this thesis,a large number of seated and truncated cylindrical arrays are taken as the main research object.Under the framework of potential flow theory,diffraction theory and semi-analytic method based on characteristic function are used to simulate the distribution characteristics of hydrodynamic loads in frequency domain under wave action.The excitation conditions of near-captured wave modes and the influence laws of wave characteristics in noncaptured regions are studied around the single-row seated cylindrical arrays.On this basis,the hydrodynamic load characteristics of two-dimensional multi-row seated base array,single row truncated array and single row seated base array are analyzed successively.The main research contents include:(1)The conditions of excitation of near-captured wave modes in a single-row cylindrical array with a seated bottom under different parameter combinations and the numerical evidence of the generated near-captured wave phenomenon are given.Based on the wave characteristics of the non-captured region,the effects of different diameter-column spacing ratio a/d,the number of columns N,the position of columns k and the incidence Angle of waves on the wave characteristics of the hydrodynamic curve of the single-row cylindrical array were analyzed.(2)On the basis of the study of single-row seated base cylindrical array,in order to extend the phenomenon of single-row cylindrical array to two-dimensional rectangular array,the hydrodynamic curve and fluctuation characteristic changes presented by "single-row large number cylindrical array combined with a specific single column" and "single-row large number cylindrical array with characteristic multiple columns" in x and y directions were carried out in a simple and complex way.The distribution of hydrodynamic load and the differential effect of hydrodynamic curve of cylindrical array with multi-row sitting bottom are analyzed.(3)The excitation conditions of near-captured wave modes in a single row truncated cylindrical array under different parameter combinations and the numerical evidence of the phenomenon of captured wave generation are analyzed and given.Based on the wave characteristics of the uncaptured region and combined with the geometric characteristics of the truncated cylinder,the effects of different water depth to draft ratio b/h,diameter-column spacing ratio a/d,number of cylinders N and position k on the wave characteristics of the truncated cylinder array hydrodynamic curve were analyzed. |
