The Simulation Of Water Entry Of Structures At High Velocity

As structures enter water at high velocity, they undergo distinct impacting force according to different conditions. In this thesis, structures' water entry is simulated by using ANSYS/LS-DYNA and two categories of curves in different conditions - angle and velocity of water entry - are obtained: curves of the structure's accelerations, curves of utmost loads. Change of free surface, as a structure enters water at high velocity, is also simulated in this thesis. All these results are significant and beneficial to design and safety of structures.This thesis starts from making sure if it is proper to simulate structures' water entry at high velocity by employing ANSYS/LS-DYNA. The author mainly analyses some parameters which affect if stable, impenetrable and convergent results can be obtained. A discussion of sensitive factors is shown in this thesis.Consequently, this thesis calculates elaborately the water entry of a structure with elliptic head. As a result, factors affecting on impacts of water entry and curves of correlative results are achieved and an expression of loads associating velocity of water entry at the same angle. In this section, the thesis also analyses functions of loads, fluid and characteristics of shock wave's transmission.This thesis simulates movements of underwater structures in vertical entry condition. The simulation shows several phenomenons such as cavity, changes of structures' direction and relationship between the deflection point and depth. Especially, this thesis simulates the pressures of deep closure and find out low pressure at the position of closure.At last, this thesis simulates function of airbag buffer in the process of water entry and elaborates the reason of reducing load. The author also simulates water entry by applying FE/SPH method.