| The traditional tests for ship hydrodynamics are usually carried out by means of scaled models in towing tanks.However,due to reasons such as the limitation of tank dimensions,unidirectional waves generated by wave-maker,scale effects,etc,characteristics of real ships cannot be fully reflected by such kind of model test.Although real ship sea trial is the most authentic testing approach,it cannot be generalized for ship research due to the long-time and high-cost consumed during the preparation and conduction of tests.A state-of-the-art ship hydrodynamic testing approach,proposed in this paper,is to perform tests in actual sea waves by using large-scale models.The novel testing approach combines both the advantages of tank test and full-scale trial.For example,the scale effects are reduced by using relative larger models.Moreover,the tests are performed in wind-generated sea waves,where all kinds of sailing headings can be tested in terms of ship seakeeping test.The main objective of this paper is to develop the novel measurement technique regarding large-scale model tests at sea.The following works are involved in the current paper:Firstly,characteristics of coastal waves are analyzed for the selection of testing area,where large-scale model tests are performed.Coastal wave measurements were carried out at different places in nearshore areas of Bohai Sea and Yellow Sea.The similarity between coastal waves measured and experiential spectra are verified by comparing their dimensionless spectral form.In addition,a coastal wave data-base project is planned,which includes monitoring the coastal waves in the experimental area perennially.The main objective of the wave data-base project is to improve operational efficiency of large-scale model test.Secondly,experimental setup and model design regarding scaled segmented model measurement are presented.This chapter firstly focuses on explaining how the backbone beam is designed and how to handle mode matching issues.Furthermore,details of large-scale model measurement technique are described,which includes model design,construction and assembly,testing apparatus components utilized and experimental campaign procedure.Thirdly,analyses of the large-scale model testing data are undertaken according to the following three aspects: 1)Investigation of motion and load response characteristics oflarge-scale model in three-dimensional sea waves;2)Comparison between experimental results of large-scale model at sea and small-scale model in the laboratory tank;3)Prediction of full-scale ship navigational responses in sea waves according to large-scale model measurement and numerical simulation.Lastly,large-scale model testing results are extended and applied to ship comprehensive performance evaluation by establishing a set of fuzzy comprehensive evaluation system.Comprehensive evaluation criteria are formed according to the knowledge of ship theory within multidiscipline.Then analytic hierarchy process(AHP)and entropy weighting based methods are applied to aggregate the evaluations of criteria weights.Finally the multilevel fuzzy comprehensive evaluation method is applied to assess the ship comprehensive environment adaptability.To summarize,the current paper describes the related technique in terms of large-scale model measurement thoroughly,includes analysis of coastal waves,experimental system setup,experiment implementation procedure,data analysis methods and potential application of the testing technique.The testing apparatus system assembled is reliable and capable enough as indicated by the field experiments conducted at Huludao harbor.According to the large-scale model testing data post-voyage analyses,as well as the comparisons among tank tests and numerical results,conducing large-scale model measurement in sea waves is insightful.Large-scale model measurements can be widely used for ship hydrodynamics research due to its combination of the advantages of both tank model and full-scale trial. |
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