The Dynamical Analysis Of Fluid-Structure Interaction In An Oil Pipeline Of Aircraft

Aerospace industry plays a very important role on military affairs and people's daily life.When an aircraft's speed is very high,there are always something wrong with its pipelines caused by interactional vibration.Avoiding the sympathetic vibration is always a designer's strong pursuit.For safer pipelines or even a safer aircraft structure,the vibration problem is needed to be researched.In this paper,a finite element method(FEM)program written in MATLAB language is used to do statics analyses,modal analyses and dynamics analyses about time or frequency to solve the fluid-solid interaction(FSI)problem.Firstly,accoeding to the structure's geometry dimensions,material properties and constraint conditions etc.are needed,a FEM mode is built with a proper element division method(along axis,radius and loop respectively),for all nodes' coordinates and all elements' topology.Then according to characteristics of its FSI FEM equation,its mass matrix,stiffness matrix,interaction matrix,damping matrix and load column vector etc.are built respectively.Finally,according to different working conditions,whether a wavepipe exists,whether the pipe is filled up with oil,whether damping exists and what its load's kind is etc.,these corresponding different FEM equations are solved respectively.Besides,CAE software of ANSYS Workbench 14.5 is used to simulate the cases with some working conditions and check their results gained above.Some main results gained through the non-viscous FSI theory are as follows:(1)If the pipeline is oil-filled,its natural frequencies decrease 8% averagely.(2)If the pipeline has a wavepipe part,its natural frequencies decrease 26% averagely.(3)The measure,which is filling oil to the pipeline,doesn't work well.(4)Under a harmonious load with damping,if the pipeline has a wavepipe part,its displacement resonse amplitude increases 46.8% and its equivalent stress resonse amplitude decreases 13.5%.(5)The damping can reduce the resonant amplitude greatly,but has little influence on the vibration whose frequency is far away from any natural frequencies.(6)If a 28 MPa oil pressure is considered,the natural frequencies of the pipeline with or without a waveline part increase average 9% and 17% respectively.The aircraft pipeline's natural frequencies and the dynamical response curves and other data from this paper can be used to instruct and check aircraft designs.