| With the development of Marine resources and the increasing demands of the military,the application of the submersible in the field of scientific research and military has attracted much attention.Submersible can dive to a certain sea area to monitor the complex ocean environment and the living things,and complete the tasks of hydrographic survey,scientific sampling,searching at the bottom of sea and underwater mining.It has a good application prospect.AUV,a kind of water submersibles,is small in size and light in weight.It is susceptible to currents and vortices when sailing in the water,which will interfere its sailing state and underwater operation.In order to study the hydrodynamic performance of AUV in complex flow field,the CFD numerical simulation method has been adopted in this paper.The specific contents are as follows:(1)Firstly,to verify the reliability of CFD numerical calculation and select the appropriate turbulence model and grid numbers,the AUV with no tail fins is numerically calculated.According to the comparison between the calculated values of turbulence models of Standard k-??RNG k-??SST k-?,RNG k-? has been to the optimal turbulence model;Then the independence of grid numbers has been analyzed,and the appropriate number of grid is about 500,000 for saving time and meeting precision requirements.(2)The 40 different working conditions,which considering the AUV with or without tail fins,the speed and drift angles from 1.4m/s to 2.2m/s,0°to 15°respectively,have been calculated.The analysis of chart and the results shows that the change of drift angle and velocity has a great influence on the friction resistance of AUV,but little influence on the pressure resistance,therefore,the influence of drift Angle and velocity on the friction resistance is the main reason for the change of the total resistance of AUV.In addition,the influence of drift angles and velocity on the hydrodynamic performance of AUV with tail fins is greater than that of AUV without tail fins.The analysis of variance analysis of IBM SPSS software demonstrate that the significant value of the tail fins is very close to the given significance level,which indicates that the tail fins of AUV has little effect on the total resistance.During the given range of velocity an drift angle,the sequence of three factors,which make a difference to the hydrodynamic performance of AUV is velocity,than drift angle,and the minimum tail fins.(3)To study the influence of free surface on the hydrodynamic performance of AUV,the resistance values of AUV sailing near the free surface have been calculated by two-phase flow simulation,and the results are compared with the infinite water.The results reveal that the effect of free surface on hydrodynamic performance of AUV can not be ignored,and the change of pressure resistance is the main reason for the changing of total resistance,when the AUV navigates near the free surface.Through numerical results and cloud image analysis,the conclusion can be drawn that when the Froude number is in the range of 0.278~0.437,wave interference will be generated in the aft of AUV.Through numerical simulation of AUV in infinite waters and nearly free surface while sailing,the influence of different parameters and free surface on the hydrodynamic performance of AUV have been analyzed,which can provide reference for the subsequent research and practical engineering application. |
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