Research On Response Induced By Springing Vibrations And Whipping Vibrations Of River-sea-going Ship

As country intensifies the development of inland river "golden waterway" and the advancement of standardization of inland river ships,the development of a new generation river-sea-going ship is necessary.With the simultaneously considered of shipping efficiency and the limited conditions of the inland waterway,flat and small draught with double-tailed ship become the preferred type for river-sea-going ship,it is bad to the the vertical stiffness and structural strength of the ship.Flat bottom and large flare lead to the serious slamming phenomena when ships sail on bad sea conditions,which will induce the whipping vibrations of the ship.Meanwhile wide hatch openings of river-sea-going ship will make the stiffness further weaken.When springing vibrations occur to the "softer" hull,because of the frequency of section load of higher order being more likely to close to the natural frequency of the hull girder,section load will increase further,which will induce the extreme load and cause damage to the hull.Because of wide hatch openings,more attention should be paid to the non-linear torque moment problems which induced by springing vibrations and whipping vibrations.It is necessary to verify the accuracy of theoretical calculation about section load of river-sea-going ship and it is difficult to get the right section load through theoretical calculation and rules,so it is necessary to study the wave load characteristics of new river-sea-going ship.The main research contents and achievements are as follows:1.Experimental study of the different working conditions is carried out in a towing tank through a independently designed equipment which can control the motion of the hull.The model ship is divided into four sections,a U-shaped beam is used to make them together.The experiment mainly stutied the law of the motion response and section load of hull girder under different working conditions.2.High frequency section load of different working conditions will be separated from the low one by Using FFT filtering method.The changing rule of the high and low frequency components of section load along with the speed and wave diretion will be studied,and then both FFT filtering method and mode shape identification method will be both used to analyse the torque moment components induced by hullmotion in the oblique seas.At last changing law along with the wave length of high frequency section load induced by springing vibrations and whipping vibrations will be studied respectively.3.Simulation study will be carried out according to the working condition of the experient by using Wasim to testify the reliability of the simulation method at first.Then the impact of speed,wave direction and wave height to the response on bending moment of river-sea-going ship has been studied.Finally,compared the simulation results with the calculated value according to the rules,modification opinions to the design load value have been put forward...