A systematic study has been carried out on the interaction effects of 3-D wave forces on vertical pile arrays by using wave source distribution method. Not only can the properties of hydrodynamic interaction of single row piles be got, but also some new discoveries are found for the pile arrays of multiple rows. It is found that the shielding effect of multiple rows is larger than that of the single one. There is a sensitive wave frequency range in which the variation of the wave forces will probably much larger than those in the other frequency range. The mechanical characteristics for the matrix pile arrays are found different from those for the staggered pile arrays. The discoveries may give important guidance to the design of the super-large offshore structures.
It is known that complex hydrodynamic interactions may occur for a super-large marine structure in waves due to the combinations of a large number of single blocks. From view points of engineering and application, it is of great importance to study hydrodynamic interactions upon multiple objects. This hydrodynamic problem can be tackled by using 3-D source distribution methods (Liu and Miao, 1987), which, however, may not predict efficiently the interactions of dozens (even hundreds) of objects due to the limitation of the capacity of commonly available computers. Maniar and Newman (1996) investigated the wave forces on single-row vertical pile arrays, being bottom mounted and water surface piercing, of 100 and 101 piles with equal circular sections in regular waves with spline-Galerkin method. It is interesting in their results that the in-line wave loads upon piles in the middle part of the array may increase significantly at a certain frequency when the wave train is collinear with the pile row (referred as head sea condition hereafter).
