Research On Fluid-Coupled Motion Of Flexible Body Based On Immersed Boundary-Spectrum Element Method

With the latest development of computer technology,fluid-structure interaction simulation of scientific and engineering systems has become more and more complicated and difficult.The large deformation and non-linear characteristics in fluid-structure coupling and changes in the watershed topology during the coupling process bring challenges to physical modeling and numerical simulation.In addition,the fluidstructure interaction phenomenon is very common in the active movement of animals and the passive movement of plants in nature.The deformation of these elastic structures is generally the result of the combined action of fluid dynamics,elastic forces,and inertial forces.It is a complex fluid-structure coupling process and has research value.According to the coupling mechanism,fluid-solid coupling problems can be divided into two major categories.The first type of problems is characterized by the constitutive equations in the respective phase domains of fluids and solids.At the two-phase interface of fluid and solid,fluid-solid coupling is introduced by the equilibrium and coordination of the two-phase interface.The characteristic of the second type of problem is that the fluid-solid two-phase domains are partially or completely overlapped,and it is difficult to be clearly separated.The constitutive equation of the system needs to be established for specific physical phenomena,and its coupling effect is reflected by the constitutive equation.Such problems exist widely in the fields of civil engineering,petroleum development,and hydraulic geology.In order to simulate the dynamic behavior of the displacement of a large deformed flexible body in viscous fluid,a set of numerical simulation methods based on the immersed boundary spectral element method was developed here,and experiments related to the structure of a square cylinder with a flexible body were performed.By comparison,in this numerical method,the fluid motion is simulated in Euler coordinates using the spectral element method,and the flexible body motion is improved in the Lagrangian coordinate system using the finite difference method.The two are supplemented by the immersion boundary method.The main research contents here are as follows:(1)This paper studies the fluid-structure interaction vibration problem of a flexible plate attached to a cylinder under a low Reynolds number,analyzes the plate's vibration response and dynamic characteristics,and discusses the effects of stiffness displacement Strouhal number St and vibration response.The simulation results verify the accuracy of the numerical method.(2)The fluid-structure interaction vibration problem of a flexible cantilever beam attached to the opposite column is studied in this paper.The vibration response and dynamic characteristics of the cantilever beam are analyzed.The vibration characteristics of the structure and the vorticity distribution of the flow field under the medium Reynolds number are discussed.Pressure distribution characteristics.(3)The fluid-solid coupling experiment and numerical simulation of the flexible cantilever beam attached to the opposite column are compared in this paper.The effects of the vibration characteristics of the flexible plate attached to the column and the dynamic distribution characteristics of the flow field are explored.Reliability of solid supplementary calculation methods.