| Improving the speed of underwater vehicles is always the goal gone in the field Military and ocean engineering at home and abroad,the development of supercavitation technology make a new method of improving the speed of underwater vehicles.,supercavitation technology can decrease the 90 percent of drag of underwater vehicles.Russia's "the storm" torpedo has the strong capabilitie of charter flights.After Russia's "the storm" torpedo was first published,supercavitation weapons became the hot field in military researchs of many countries.But because there are difficult problems of phase transitions,turbulent flows and interactions in gas phase and liquid phase,the research of rules in cavitation flow fields is particularly important.in both academic meanings and application values.In this paper,I make predictions and simulations of cavitating flow field around underwater vehicles by the Fluent numerical software,and make numerical simulation of the projectile and the hydrofoil respectively.The main contents are as follows:To know shapes and hydraulic characteristics of underwater vehicles in cavitation flow fields,this paper use the numerical software with cavitations models and multiphase models to predict and analyze the phenomena of the cavitation flow field.The general process of numerical simulations in cavitation flow fields is introduced,and the theoretical basis in cavitation flow fields is discussed.Meanwhile,the main control equations,turbulence models,cavitation models,some dimensionless parameters and so on have been listed.By multiphase models,cavitation models and turbulence models,numerical simulation analysises in underwater axisymmetrical vehicles have been conducted,and cavitation shapes and hydraulic characteristics of underwater axisymmetrical vehicles in cavitation flow fields have been analyzed.Firstly,surface pressure coefficients of the underwater vehicle with round head under different cavitation numbers have been calculated,and these results have been comparised with experimental datas from Ross et al,through above way,correctness of the numerical way for simulating in this paper has been validated.Change laws for influences from cavitation numbers,acceleration and attack angles have been calculated and researched.The prediction of unsteady cavitation flow phenomenon computed by RNG k-?turbulence model have been contrasted with the prediction by LES turbulence model,and the cavitation flow field of hydrofoil is analyzed by Zwart-Gerber-Belamri cavitation model and Schnerr and Sauer cavitation model.And hydraulics characteristic parameters and the periodic shedding process of cloud cavitation have been analyzed.In conclusion,directing at the experiment done by Rouse et al,I make the verification of computation in the underwater vehicle with round head with the above algorithm in this paper,and distributions of surface pressure coefficient have been received,for example,the way of the numerical simulation is proved favorable in cavitating flow fields.And the result in this paper is basically the same in the comparison with unsteady images of the experiment.This paper get the cavitation shapes when the speed is 50m/s with a acceleration from the speed of 30m/s.When the underwater vehicle has the same velocity with a plus acceleration,the length and the thickness of cavitation is littler than them in the steady state.This paper explores and researches the rule of the cyclical cloud cavitation of the airfoil with Large Eddy Simulation turbulence model.As an elevation of cavitation number,the lift-to-drag ratio elevates at the same time.When ?=0.6,?=0.9 and ?=1.2,average lift-to-drag ratios are 4.357,7.367 and 17.2,and the trend is rising.There is re-entrant jet in the tail region of the underwater vehicle,and because the shock of the re-entrant jet,the cavitation from the front region of the underwater vehicle is cut off,and the phenomenon of cloud cavitation with greatly unsteady state happens. |
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