Research Of SES Upsizing Basing On Resistance Performance

Combining many advantages of the ordinary catamaran and the air cushion vehicle,SES has some virtues such as high speed,good stability,low consumption.And because of large deck area and small propeller size,it's easier to upsize.But in the process of SES upsizing,we have encountered some difficulties.First of all,sharp increased seal resistance caused by upsizing will seriously influence SES's resistance performance.Furthermore,because of hull length after upsizing,the SES may not pass resistance peak for a reduced Fr number.Water may blocking and splashing seriously in the stem.Meanwhile,because of an acute coupled motion,stability turns bad.Last,uneven distribution of the pressure may happen because of an increased air-bag volume.To solve these problems,following changes have been made on the basis of traditional SES.Remove the stem air bag to prevent the sharp increased seal resistance;then,a vertical segmentation wing has been added on the bottom of the hull,the wing can provide part of pitch moment to ensure the stability.At the same time,it can reduce the leakage of the gas in air cushion is reduced.Thus,additional resistance can be avoided.Lastly,pumping chamber has been added into lift system to let air get through.By doing this,enough pressure and flow reserve storage can be ensred.Comparing with traditional type,this new SES has changed greatly.To analyze its resistance performance,the following tasks have been done in this paper:Firstly,based on the research of traditional sidewall hovercraft,the influence of different hull parameters to ship resistance has been analyzed.Theoretical method has been used to calculate the relationship between length-width ratio and resistance performance.According to this ship optimization has been made.Secondly,it designs a test method which applies to the ship,resistance,sinkage,pitch.the pressure in pumping chamber and lift cabin in different situation has been recorded.The effect of the vertical separator and lift systems to the resistance performance has also been analyzed.By changing corresponding factors(gas flow rate,gas area,etc.),it gets the law of resistance performance influenced by pressure ratio of the air cushion.Lastly,to analyze more about resistance performance of this new SES,CFD method is used in this paper.By observing the details of the flow field,and comparing numerical values with the experimental values,the accuracy and feasibility of the numerical calculations has been verified.Based on this,a changing of stem air sealing device form from flexible material to a bunch of high speed gas has been applied to reduce resistance and cut down its peak value.At the same time,the impact of different nozzle area,the jet angle,nozzle position and the flow velocity on the drag reduction ability has also been investigated which can be a reference to the further analysis of the ship.