Impact response characteristics of amphibious aircraft structure in internal flow field
Amphibious aircraft has some unique advantages in the field of aviation fire protection.However,when amphibious aircraft glides at high speed on the water surface to scoop water and fly to fight fire in the air,the moving liquid flow inside the body will bring the unsteady water impact effect.For the fluid-structure coupling characteristics of aircraft,previous studies have mainly focused on the interaction of the external flow field with rigid aircraft,and little attention has been paid to the effect of the internal flow field on the structural deformation and stress distribution.According to the mission mode of the amphibious aircraft in this paper,the coupling simulation of smoothed particle hydrodynamics and finite element method is adopted,the structural finite element modeling and internal flow field modeling of the main affected fields are established respectively,and the fluid-structure coupling method is used to solve the dynamic stress distribution of the structure in the process of high-speed water scooping and fire fighting in air.Results show that during the high-speed water scooping process of the aircraft,the structure is continuously excited by the water impact,the stress of each part of the structure is constantly changing,and there is great oscillation amplitude of the stress in some regions.The maximum transient stress of bulkhead at the typical moment reaches 0.38σb,and the maximum oscillation amplitude of stress is 0.42σmax.And when the aircraft drops water in the air by gravity,the water impact excitation on the structure is relatively weak,the maximum transient incremental stress of the end frame is 0.15σb,the maximum amplitude is 0.22σMax,so the incremental stress level of the structure is not high and the fluctuation range is not large.
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