Research On Ventilated Super-cavitating Ballistics Of Underwater Body

Coupling with triple-phase interactions, the ventilated super-cavitating ballistics of anunderwater body is very complex. It has attracted increasing concern in relative fields. Inthe present work, the flow field structures inside the ventilated super-cavitation have beenresearched by experimental and numerical methods. Furthermore, the dynamicsmechanisms of gas-liquid coupling and dynamics behavior of gyrodial body in ventilatedsuper-cavitating flow field are all studied. And then a ballistics model of gyrodial body inventilated super-cavitating flow would be developed.Experimental, theoretical and numerical studies are adopted in this paper, the maincontents and conclusions are as follows:(1) Experimental study on the flow field in ventilated cavity by DPIV.On the one hand, the DPIV experimental technology is modified to apply for theinternal flow field study of ventilated cavity. An appropriated type of tracer particle ischosen, and also the way to seed is solved. In order to avoid the influences of the strongreflection and diffraction by the gas-water interface as well as the particles on the realimages, a revivification-correction method is proposed which can transform theexperimental images and data to real ones. In addition, a corresponding program isdesigned to process the recorded images and date by DPIV.On the other hand, DPIV experimental studies are carried out. Two typical bodys aretested with16kinds of ventilated super-cavitating conditions. These enormousexperimental data are of great value, which help to shed light on the internal structure andflow pattern.(2)3D numerical simulation on the internal flow field of ventilated super cavity.36kinds of flow conditions are simulated by CFD software FLUENT. The simulatedresults agree well with the DPIV measurement results, which prove that both the DPIV andthe numerical method are suitable for studying the flow field inside ventilated super cavity.The flow field is characterized by injection flow zone and reentrant jet zone by numericalsimulation method. The structure of ventilated super cavity is conducted by3D numerical simulation. The influence of multiple parameters, such as ventilation rate, ventilationdirection, inlet velocity, inlet direction and air deflector, on the structure of ventilatedcavitating flow is studied. Furthermore, the influences of these parameters on the velocityfield, pressure field and gas-water interface inside the ventilated cavity are studied, and theshear layer near the cavity wall is also analyzed.(3) The dynamic behavior of the ventilated cavity surface.When the gas dynamic effect inside ventilated cavity is considered, the boundaryconditions of pressure and impact are obtained by combined experimental and numericalmethods. The oscillation mathematical model of cavity surface is established byconsidering the gas energy and pressure distributio n inside ventilated cavity. Theexperimental study on the ventilated super cavity is carried out by high speed camera, andthe empirical formula of cavity oscillation is established by spectrum analysis. Thenumerical results obtained by the proposed mathematical model agree well with thosecalculated by the empirical formula.(4) Ballistic equations of ventilated underwater body.The mathematical model of gyrodial body load is established when taking theinfluence of ventilated cavity on the vehicle into account, including impact of gas boundarylayer, reentrant flow of gas and radial oscillation of water. Furthermore, the ballisticequations are established by considering the unsteady multiphase field of ventilatedcavitating flow.