Analysis on the Characteristics of the Infra-Gravity Waves inside and outside Pohang New Harbor using a Transfer Function Model

摘要

Infra-gravity waves (IGWs) with a period of 1~3 minutes are a factor that directly influences the motion analysis of moored ships inside a harbor and longshore sediment transport analysis.If significant levels of IGWs from far seas are transferred to a harbor and amplified,they may cause downtime of large ships and induce economic loss.In this study,transfer characteristics of the IGWs intruding from outside to inside Pohang New Harbor were analyzed using statistical analysis and transfer function of wave data measured at both outside and inside the harbor for around 5 years.Transfer characteristic analysis was limited to events where IGWs had wave heights above 0.1 m.The wave height distribution of inside the harbor was similar to that of outside the harbor,while the wave period variance of the former was larger than that of the latter.The parameters of the transfer function was optimally estimated according to each event.The estimated average RMS error of the wave height inside the harbor was around 0.013 m.The estimated parameters had a strong correlation with the linear combination information of IGW wave height,period,and direction (R = 0.95).The transfer function suggested in this study can quickly and easily estimate information on IGWs inside the harbor using IGW information predicted beforehand,and is expected to reduce damage due to unexpected restrictions on harbor usage.