Investigation On The Dynamic Characteristics Of Amphibious Aircraft Landing On Waves

The amphibious aircraft is widely used in maritime patrol,water rescue and forest fire fighting with its individual structure.The individual bottom structure of the amphibious aircraft is designed into hull type to make the aircraft take off and land on waters and lands.Accordingly,the amphibious aircraft takes off and lands on the waters frequently,which is about 4 to 10 times more than landing on lands.Thus it is meaningful to take a research in the mechanism of takeoffs and landings on waters.According to the wave situations where the aircraft land,especially the situations of landing on offshore waters,the amphibious aircraft may be hit by huge waves when landing in the terrible situation.The impact of aircraft hit by powerful waves with high speed leads to serious consequences including instantaneous draft,sliding resistance and impact load increasing,splash performance and stabilization reducing,which cause severe deformation of aircraft and affect the life and safety of aircraft.The numerical investigation on dynamic characteristics of amphibious aircraft landing on waves has great significance,which involves numerical wave-making and fluid-structure interaction(FSI).In this work,the system method of investigation on dynamic characteristics while amphibious aircraft landing on waves is established.This work aims to provide guidance for the experiment of water impact,airworthiness certification,formulation of operating regulations and structure design of amphibious aircraft.The main contents are as follows:1.This work introduced the ALE method to describe the fluid.Basing on linear wave theory,boundary on one side of water model is token as a plane wave-maker.The plane wave-maker with simple harmonic motion disturb the water to generate numerical wave in LS-DYNA,and verification of the consistency between theory and numerical results is created.With this method,progressive waves with different wave lengths and heights are modeled to simulate different actual wave situations when the aircraft landing.2.In actual cases,the water area is infinite and boundless.Wave absorbing region is introduced to simulate the boundless water.Mass damping is added into the elements of wave absorbing region.By this way,the energy of reflected wave from rigid boundary is absorbed,which reduces the effect of reflected wave on wave results.3.Utilize the penalty coupling method to simulate the interaction between water and aircraft structure.This work simulated varied cases of amphibious aircraft with different initial velocities and different relative positions to the wave crest when landing.The change of attitude,the change of the overload causing by heave motion and pressure distribution of lower fuselage are computed.4.The calculation models where wave with different wave lengths and heights are established to investigate the dynamic characteristics of amphibious aircraft landing on different wave situations in actual cases.According the calculation results,we discuss the attitude changing,the overload changing causing by heave motion and the pressure distribution of lower fuselage of amphibious aircraft.