Study On Multiphase Flow Of Typical Body During Water Entry

Water-entry cavity due to the free surface impact of solid objects related to thesolid, gas, and liquid at the same time is very complicated. This canonical problemcomprises a complicated series of events, which related to impact force, water-entrycavity, and hydroballistics, is applied on naval hydrodynamics, float-plane impact,ship slamming, oil platforms, and industrial, and biology. This thesis based onnumerical simulation and experimental study to discover underlying physics andfurther our understanding of water-entry phenomena through improvements toanalytical solutions.The main works are as follows:A comprehensive computational methodology is development for turbulentwater-entry cavity flows. The RANS(Reynolds-averaged Navier-Stocks) equations,along with volume of fluid model and a volume fraction transport model, areemployed for free surface and multiphase transportation. Dynamic mesh method isapplied for the numerical solving of the water-entry history. The validation ofnumerical model is examined through comparing with experimental andbibliography resealts.Numerical simulations based on VOF(Volume of fluid) model of axisymmetricvertical water-entry cavity for cylinder in constant speed are performed, to study theformation and development of the vertical water-entry cavity, study the velocity andpressure distribution in vertical water-entry cavity. Examines the effects of severalkey parameters on the vertical water entry physics of cylinder bodies at constantspeed including: with and without afterbody and the lengths of afterbody, entryspeed, cones of cylinder body nose and atmospheric pressure. The forces acting onthe cylinder bodies during the vertical water entry at constant speed are discussed,furthermore the effect of cones and entry speed on forces of vertical water entry arediscussed.Numerical simulations based on VOF model for three dimensional water entryfreely in vertical are performed for the formation and development of verticalwater-entry cavity. Numerical studies on the effect of diameter of cylinder bodies,initial water-entry speed, cones of cylinder body nose, and the density of entrybodies on the vertical water entry physics are also executed. The numericalsimulations of two cylinder bodies in parallel water entry are executed for thedevelopment of cavity, and for the effect of the distance between the two cylinderbodies on the cavity formation. Furthermore, the forces acting on the cylinderbodies during the vertical water entry freely are discussed, as well as the effect of cones, density of cylinder bodies, and entry speed on forces on freely vertical waterentry.Experimental facility for vertical and oblique water-entry has executed. Thespheres vertical water-entry experiment has performed. Investigated the effect ofthe surface wetting conditions and initial entry speed on the formation ofwater-entry cavity. The discussion continues with the experiment study of waterentry of cylinder bodies, for the formation and development of vertical and obliquewater-entry cavity. And the effect of nose shapes and density on the cavity shape areinvestigated through experimentation. The stability of cavity due to tail snap aftervertical and oblique entry, and the effect of deep seal of water-entry cavity on thestability of cavity are analyzed through experimentaion. Coefficient of drag for thevertical impact of sphere and cylinder are discussed.