高速船迎波中運動之非線性壓力變化特性分析

Analysis on Nonlinear Pressure of a High-Speed Vessel in Regular Head Waves

船舶高速航行於波浪中，其運動及壓力反應皆呈現非線性行為，因此線性統計理論將不足以對不規則波中的統計特性準確預估；另一方面，三階Volterra模式已被確認可應用於船舶非線性運動及波浪彎矩的不規則波中統計特性分析。因此本文旨在以非線性截片法所建構之理論基礎，並經由非線性Volterra模式所架構之平台，萃取出規則波試驗所得之系統特性參數相互比較，來評估該理論未來預測不規則波統計特性之可行性。為此規劃一系列以RD200船型為對象之迎波中曳航試驗，量測項目包含起伏及縱搖二個運動、垂向加速度及船殼25點的水壓等，其結果驗證了該理論分析可掌握運動、加速度及大部分壓力的非線性特性，但對於船舫底壓力的描述則不盡理想，此乃今後需再進一步探討的課題。 It's commonly known that the hydrodynamic responses of a ship traveling in waves at high speed can show a significant nonlinear behavior even the wave is moderate, and the linear statistical techniques become insufficient for predicting the statistics of response in irregular waves. On the other hand, it has been shown that the approximate third-order Volterra modeling is applicable to analyze the statistics of some nonlinear seakeeping problems, such as vertical hull girder loads. Thus, the objective of this paper focuses on the frame of nonlinear strip synthesis to assess its' capability in analyzing pressure acting on ship hull in irregular waves. Based on the results in regular wave tests, the validity of nonlinear strip synthesis is investigated by comparing with the intrinsic parameters of system obtained from Volterra modeling. To accomplish this objective, a series of model tests of a high-speed mono-hull, RD-200, traveling in waves at speed of Froude number of 0.31 and 0.42 had been carried out. The nonlinearity of vertical motions, accelerations and water pressure at 25 locations are investigated. The validity of using nonlinear strip synthesis to reproduce the nonlinear vertical motions, accelerations and most pressures has been confirmed. However, it's also confirmed that to reproduce the pressure acting on hull surface near bow keel, the nonlinear strip synthesis may induce significant error.