The Study On Resistance Prediction Method And Resistance Characterristics Of Partial Air Cushion Supported CATamaran(PACSCAT)

PACSCAT(Partial Air Cushion Supported Catamaran)is a new concept composite ship,which is based on the wide-bodied catamaran and supported by air cushion partially.For its characteristics,such as shallow draught,high speed,and flexible maneuverability,PACSCAT has a broad application prospect in both military and civil areas.Due to its special cushion system and seal system,the hydrodynamic performance of PACSCAT,with a wide range of resistance components intervened with each other,is different from conventional vessels.And its resistance,corresponding resistance laws and sailing attitude,will vary from lower static state to high speed state.To design PACSCAT with excellent drag performance,it is necessary to know resistance components change regularity and interaction mechanism between them.The bodies and the displacement proportion of PACSCAT have significant differences from SES(surface effect ship),and making the theoretical simulation much more difficult than the latter.The existing theoretical methods are very hard to be used for finding rules or making detail analysis of resistance performance provided by PACSCAT.In this paper,the resistance predication method and resistance characteristics of PACSCAT are exploited with a combined method of principle experiments and model tests in order to provide reference for the hull form development and analysis.The author has thus conducted the following works.1.Because of the novelty,there are less referential materials for PACSCAT.The research progress on resistance components and resistance predication methods of SES was then reviewed in three aspects,namely the experiments,analytical analysis and numerical simulations.The major defect and difficulty in existing wavemaking resistance predication methods and seal resistance predication methods to calculate the PACSCAT resistance was analyzed,after which the research methodology and the experiment are proposed.2.A resistance experiment method for PACSCAT is proposed.The complete testing scheme and equipment operational process is established to solve the problems i.e.complicated experiment system and sensitive seal systems.And the feasibility and reliability of the experiment method are verified by the repeated tests.Then this method was employed to explore the resistance characteristics and the rules of resistance,trim,sigkage and exhaust followed the speed were made.On this basis,the effect of cushion flow on the PACSCAT resistance characteristics is analyzed with regard to the total resistance3.Based on the Neumann-Michell theory,the waterline integration of the existing SES wavemaking resistance predication method was removed to avoid the errors from the differences between the waterline integration and surface integration.A wavemaking resistance calculation method of studying the near field waveform of both PACSCAT and SES was proposed and the local item of Green function was numerically solved through Chebyshev polynomial fitting method.Then the problems such as the integral limit,transom stern correction and stern resistance,were solved,the pressure distribution model of separate cushions is established and the effect of Green function local item on near field waveform was analyzed.4.Both the bow seal resistance calculation model and the stern seal resistance calculation model were established based on experimental phenomena.In the bow seal model,the wetted part of seal was expressed by cubic curve.Then the deformable model of bow was built according to the balance between the hydrodynamic force and cushion force.In the stern seal model,the rotational deformation around the connection points was assumed as spring sheet with stiffness coefficients without consideration of the Slight shrinkage.And the influences of immersion height,velocity and cushion pressure(or pressure ratio)were investigated.5.By comprehensively utilizing the model experiment and theoretical methods,the resistance components and resistance characteristics of PACSCAT are studied.In the meanwhile,theoretical methods was verified by experiment results.Then the research investigates the wave making interference between bodies and cushion,the influence of cushion inside wave to wetted surface,the influences of cushion flow and "Partial Air Cushion" to the resistance components.