A Study On The Typhoon Prevention Ability Of Fishing Port Anchorage Based On The Example Of Wenling Shitang Port

In recent years,researchers of marine numerical models in engineering field have carried out productive research on the design of storm surge disaster micro-scale engineering.However,the rationality of storm surge disaster assessment methods for fishing ports with small water area and shallow water depth has not been determined.The Technical Guideline for Typhoon Prevention in Fishing Ports of Zhejiang Province is the first national evaluation guideline for storm surge disaster in fishing ports.The numerical model is a tool for evaluating the safety of fishing ports under typhoons at all levels by calculating the results of storm surge,current velocity and wave of virtual typhoon grade.The guideline are the first in China and59 fishing ports with better shelter in Zhejiang Province are being tested firstly,the guideline need to be revised and promoted.Shitang Fishing Port as an example,this paper obtains hydrometeorological data from local and nearby fishing ports in Wenling County,Zhejiang Province.Based on the results of ADCIRC and SWAN two-way coupled ocean model,the coastline facilities,breakwaters and anchorage sites of storm surge hazards in fishing ports are analyzed.The hydrological factors in anchorage sites and the anchorage conditions of fishing vessels themselves are taken into account,and the anchorage stability of fishing vessels is studied.The main purpose of this paper is to study and discuss the anchorage in fishing harbor.The results show that the numerical model validates the astronomical tide level well.In the evaluation of mooring platform in fishing harbor,the anchor grip field experiment is used.The experimental results are in good agreement with the theoretical results.The purpose of this paper is to provide a conclusion on the assessment level of typhoon defense capability for Shitang Fishing Port,and to provide a reference for fishing vessel mooring under typhoon shelter in Zhejiang Fishing Port mooring site.The specific contents of this paper are as follows:ADCIRC+SWAN ocean coupling model constructs virtual typhoon path based on historical typhoon data,obtains the calculation results of wind wave and current elements under different typhoon grades,evaluates three single assessments of shoreline facilities,breakwaters and mooring sites of Shitang fishing port in Wenling,and determines the comprehensive grade of fishing port according to the guideline.The coastline facilities are calculated according to the superimposed tide level and effective wave height of storm surge,the breakwater is classified according to the ratio of wave height in fishing harbor to wave height outside harbor,and the design data of Engineering buildings;the single evaluation of mooring land first designs the representative ship type,calculates the windcurrent load resultant force according to the flow speed and wind speed of each grade,and takes into account the single-vessel and multi-vessel situations.In the evaluation of mooring land,the data of Wenling fishing vessel are statistic.The data conform to normal distribution.There is a good linear relationship between the width of fishing vessel and length.The average length is 37.42 m and the width is 6.78 m.In Shitang fishing harbor,the field anchor grip towing cable experiment was carried out.The experimental results show a greater degree of dispersion due to the fewer experimental points.The experimental results are close to the theoretical values of anchor grip.In the calculation of mooring force,the parameters of wind load are discussed.In addition to the influence of wind speed,the results show that the calculation of transverse wind area by empirical equations of different types of ships in the Code for Port Engineering Load differs greatly,while the longitudinal wind area does not change much.Because there is no formula for wind area of fishing vessel,the wind load is evaluated by the formula of wind area of cargo vessel.Wind area directly affects the force result of the final wind load.This parameter is very important for the determination of the final anchorage grade.Therefore,it is necessary to determine the selection and calculation method of wind load area in the guideline.The calculation results of anchorage not only take into account the force analysis of fishing vessels and the judgment of typhoon grade,but also the anchorage area and the number of anchorage under the avoidable typhoon grade are very important for the evaluation of fishing ports and the command and dispatch of local fishery departments when sheltering from wind.The factors of water depth and wave height should be taken into account in determining the suitable anchorage area.There is a great difference between the mooring mode of multi-vessel and the final number of single vessel.The mooring capacity decreases from 187 to 182 in the case of single vessel,and from 632 to 612 in the case of multi-vessel mooring.According to the model wave results,the berthing capacity and area of fishing vessels do not change much under the avoidable typhoon grade.In Shitang Fishing Port,there are many ships and single ship mooring in the fishing port,and most of them are Multi-ship mooring.The stochastic simulation method is used to simulate the shelter area of Shitang Fishing Port,which is between [503,572] vessels and the actual situation of about 600 typhoon mooring in Shitang Fishing Port.