Multi-Focused Wave Groups in Wave Flume

Abstract

Abstract People can simulate extreme hydrodynamic conditions in a laboratory facility by interfering a numbers of regular waves at a certain point in space and time, which is focused wave. It is obviously higher and steeper than any other wave, e.g. regular or irregular waves, within the propagating wave group. The focused wave occurs at a designed point both in space and time. It represents an event with a large return period which would take a long time to reproduce within a random wave sequence. The focused wave, representing of a large wave occurring in a random sea, is quite frequently used to investigate wave loading on marine or coastal structures. However, most research only employ one single focused wave group. Taking the randomness of the wave-structure interaction, repeated tests would be suggested by some textbooks or codes to eliminate the odd results. However, it would take more time to conduct those tests no matter in the laboratory or in the numerical simulations. In our present work, we use a novel method to experimentally generate several focused wave group with different focus time but same focus point at the same time to obtain multi-focused wave groups. The wave elevation and water particle kinematics are measured. The influence of peak frequency, frequency resolution and period of focused wave group are checked and discussed. The results show that present method can generate stable and repeatable focused wave groups in the wave flume.