| Infragravity waves have been shown to have important effects on a variety of nearshore processes since they were observed,typically such as sediment transport direction,excessive wave creep,dune erosion and overwash,including harbor resonance,which has received much attention in recent years.Therefore,understanding the characteristics of infragravity waves in the nearshore and their accurate prediction are of great engineering application.In this paper,we investigate the characteristics of nearshore infragravity waves based on the nearshore field measurement data and the XBeach-Surfbeat(XB-SB,below)numerical model in the southern Sri Lankan waters,and evaluate and integrate the existing empirical estimation formulas for nearshore infragravity waves,and propose a general form of empirical estimation method for nearshore infragravity waves,as well as for the XB-SB in simulating The performance of XB-SB in simulating infragravity in ports is also evaluated.The purpose of the study is to provide further understanding of the characteristics of infragravity wave activity in the nearshore,as well as to provide guidance and reference for the estimation of nearshore infragravity waves using empirical formulas,and for infragravity wave simulations using the XB-SB model.On this basis,the following studies are done in this paper:(1)The wave group resolving model XB-SB has been widely used in near-shore infragravity wave simulation studies,however,its performance in simulating infragravity waves inside a real port has not been investigated.In this study,the performance of XB-SB in simulating infragravity waves near the port gate and within the port,and in capturing the intrinsic period of the port is evaluated by comparing it with the field measurement data of Hambantota port in Sri Lanka.The results show that XB-SB can accurately predict the wave heights of short and infragravity waves near the port gate for a well-sheltered port like Hambantota Port.However,because XB-SB does not consider the bypassing and reflection of short waves,the short wave height in the port is greatly underestimated,while the infragravity wave height in the port is overestimated,while the intrinsic period of the Hambantota port can be well identified by the model.(2)The characteristics of the infragravity waves in the coastal waters of southern Sri Lanka were studied based on the field measurement data and XB-SB model.The results show that there is a strong correlation between the infragravity waves and the local short waves in the inshore waters of southern Sri Lanka;for the coastal direction of the inshore waters of southern Sri Lanka,the overall difference in the infragravity wave height is not large,but due to the greater water depth near the port gate compared with the shoreline on both sides,the short waves are not sufficiently shallow and broken,and there is a significant decrease in the infragravity wave height in this region;in the shoreward direction,the infragravity wave In the shoreward direction,the wave height of infragravity waves grows slowly in the deeper waters,and increases significantly near the shore as the water depth decreases,and the main infragravity wave energy is concentrated in the near shore area of about 3 km,which is not obvious in the port gate profile.(3)The existing empirical formulas for nearshore infragravity waves were sorted and categorized,and the applicability of the representative empirical formulas was evaluated using the field measurement data at the south coast of Sri Lanka.The results show that the empirical formulas perform well at the G2 measurement point,but the performance at the G1 measurement point shows a large variability,and the best performance in general is the empirical formulas of Jung and UKHC;on this basis,a general form of nearshore infragravity wave estimation method is proposed,which considers more comprehensive parameters and is simple and easy to use,and the reference range of each empirical coefficient is given. |
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