Title Of Dissertation:numerical Simulation Of Torpedo Water-entry Impact

The problem of torpedo water-entry is a very complicated physical process of interaction within gas,liquid and solid. the instantaneously of entry-water generated the strongest impact loads would produce negative effect for the torpedo and its internal parts, the most serious consequence would be depriving the torpedo system operational effect. In this paper, the analysing process of the numerical simulation of torpedo entry-water, the models were set into vertical entry-water.The impact of the initial torpedo entry-water in response to various factors were considered, the results of numerical simulation will provide reference for torpedo overall structure design.Firstly,the present developing situation of torpedo and torpedo water-entry was introduced. Secondly, the structure and material properties of the torpedo was analyzed and compared the characteristic of MU90 torpedo with MK60 torpedo.Thirdly, the torpedo,regarded as the scaled structure based on theory of similitude, was studied by AUTODYN finite element analysis software, the results of numerical simulation show that the process of torpedo water-entry succefully.Finally, for each factor, the processing of the dynamic response of the intitial torpedo entry-water impact,was analyzed. Researches show that:(1)Defining three metallic material as shell material respectively(titanium alloy/alloy steel/aluminium alloy),the titanium alloy shows the best mechanical properties.On the conditon of velovity of 20m/s,only the shell of titanium alloy would not come on the irrversible deformation,combined with the result of numerical simulation : the titanium alloy would be applied in shell material.(2) Defining three head shape of torpedo,the results of numerical simulation show that the flat load impacted the most, then tapered cut, tapered torpedo the lest.(3)the more high the speed of the entry-water, the greater the impact surfacing loads. If the impact surfacing loads exceeds the yield strength of the shell material,the shell material of the torpedo come on deformed irreversibly and the internal parts of the torpedo suffered from the impacted loads become stronger.