Research On Numerical Analysis Method Of High-speed Underwater Vehicles With Supercavity Flow

With the rapid development of science,technology and marine military in the world,supercavitation technology was applied to the design of underwater vehicle in order to increase the speed of underwater vehicle extremely,it has been paid close attention by hydrodynamic field at home and abroad widely.Supercavity flow can be divided into two styles,namely natural supercavity flow and ventilated supercavity flow,the former can be obtained only when the vehicle reaches a high speed(higher than 50m/s or higher),the latter can be obtained when the vehicle’s speed is low by adjusting the ventilation pressure in supercavity flow. This paper uses the commercial numerical calculation software Fluent to simulate the two-dimensional natural supercavity flow,three-dimensional natural supercavity flow,three-dimensional ventilated supercavity flow,three-dimensional parallel and tandem natural supercavity flow,the detail research work is as follows:Study the natural supercavity size for two-dimensional and three-dimensional underwater high-speed vehicles with blunt cavitator at cavitation number 0.319、0.264、0.222、0.189,verify the three-dimensional result is closer to the real situation by combining with the result obtained by empirical formula,give the exterior pressure distribution and resistance coefficient for two-dimensional and three-dimensional vehicles, study the difference of internal mechanism for exterior pressure distribution and resistance coefficient between two-dimensional and three-dimensional vehicles by combining with supercavity size. The results show that the length and diameter of supercavity increase with the decrease of cavitation number,but the frictional resistance and pressure resistance decrease with the decrease of cavitation number,when the cavitation number reaches 0.189,the length and diameter of supercavity reaches 2.14 and 1.59 times larger than those for cavitation number 0.319,but the frictional resistance and pressure resistance occupies 95% and 91% of those for cavitation number 0.319.So the faster the vehicle is,the larger the supercavity shape is,the less resistance is.On this basis, study the natural supercavity for three-dimensional underwater high-speed vehicles with blunt and coin cavitator at cavitation number 0.125、0.080、0.055、0.041,focus on the effect of cavitation number and cavitator parameter on supercavity shape and resistance reduction,and do research about the natural supercavity evolutionary process. The results show that the blunt cavitator is more conducive to create supercavity than coin cavitator,and the length and width of supercavity is in direct proportion to the diameter of blunt cavitator and coin angle of coin cavitator,when the cavitation number reaches 0.041,the length of supercavity obtained by blunt cavitator with diameter 4mm is 1.56 times larger than that by blunt cavitator with diameter 3mm,the length of supercavity obtained by coin cavitator with coin angle 120°is 1.07 times larger than that by coin cavitator with coin angle 90°,however,the resistance coefficient of coin cavitator is smaller and in direct proportion with coin angle,when the cavitation number reaches 0.041,the total resistance coefficient of vehicle with 90°coin angle cavitator occupies 83.2% of that with blunt cavitator.On the basis of the study for natural supercavity,simulate the ventilated supercavity for three-dimensional underwater high-speed vehicles with blunt and coin cavitator at cavitation number 0.125、0.080、0.055、0.041,focus on the effect of cavitation number、ventilation rate and cavitator parameter on supercavity shape and resistance reduction,do research about the internal mechanism and analyze contrast with natural supercavity. The results show that the ventilated supercavity size is larger than natural supercavity size,and the length and diameter of supercavity increase with the increase of ventilation rate,but the frictional resistance and pressure resistance decrease with the increase of cavitation number,when the cavitation number reaches 0.041 and ventilation rate 4,the length and diameter of supercavity reaches 1.26 and 1.13 times larger than those for ventilation rate 1,but the frictional resistance and pressure resistance drops 68% and 6.08% of those for ventilation rate 1, it means ventilation rate plays an important role on resistance reduction.Simulate the natural supercavity for parallel and tandem vehicles with blunt cavitator at cavitation number 0.041,analyze the effect of distance for vehicles on supercavity shape and resistance reduction,and contrast with those for single vehicle. The results show that the frictional resistance for parallel vehicle is smaller than that for single vehicle,this is resulted with distance,when the distance between the parallel vehicles reaches 3.5 times longer than the diameter for the vehicle,the frictional resistance drops 8.37%;but the pressure resistance for the after tandem vehicle is smaller than that for single vehicle,this is resulted with the front vehicle and supercavity shape change,when the distance between the tandem vehicles reaches 5 times longer than the diameter for the vehicle, the pressure resistance for the after tandem vehicle occupies 87.23% of that for single vehicle.