| With the rapid development of hypersonic technology,the new generation of hypersonic vehicles is gradually moving towards the field of low altitude and high speed.The complex hypersonic fluidthermal-structural multi-field coupling problem caused by the interaction between the thermal structure of the hypersonic vehicle and the external aerodynamic pressure/ thermal loads has become increasingly prominent.It seriously affects the flight performance and structural safety of the aircraft,which greatly restricts the further development of the hypersonic vehicle and has become one of the research hotspots in various countries.Therefore,accurately simulating the hypersonic fluid-thermal-structural multi-field coupling problem is of great significance to the overall design and structural safety assessment of hypersonic vehicles.In this paper,aiming at the problems of the coupling between aerodynamic heating and structural heat transfer,as well as the problems of static aerothermoelasticity,some shortcomings of the existing calculation methods for the hypersonic fluid-thermal-structural analysis of hypersonic vehicles are analyzed in detail.The researches on key calculation methods,such as flow-field calculation method based on improved FVM-LBFS method,structural heat conduction calculation method based on FVMTLBFS method,structural thermal stress-strain calculation method based on isoparametric-finite element method,are carried out.Based on the hybrid FVM-LBFS method,the integrated simulation method for the coupling between aerodynamic heating and structural heat transfer is established,and a new integrated static thermal-aeroelasticity calculation method is further developed.The integrated analysis and prediction technology for the complex force-heat-structure coupling property hypersonic vehicle is formed,which provides theoretical support and calculation means for the thermal structure and thermal protection designs of advanced hypersonic vehicle.Firstly,this article describes in detail the basic characteristics of the flow field,structural temperature field,and structural stress\strain field involved in the fluid-thermal-structural multi-physics coupling problem of hypersonic vehicles.From the perspective of mathematics,the internal relations and the master-subordinate relationship between the physical quantities are analyzed,and the actual physical problems are reasonably simplified.Based on the theoretical analysis,an improved integrated synchronous solution method and time coupling strategy are proposed.Compared with the tightly coupled and loosely coupled time advancement strategies of traditional partitioned coupling methods,the proposed method does not require additional data interpolation processes and complex data exchange strategies,which can greatly save coupling calculation time and improve calculation efficiency.At the same time,it can also efficiently solve the steady-state multi-field coupling problem,which lays a theoretical foundation for the establishment of hypersonic fluid-thermal-structural multifield coupling numerical simulation method.Secondly,an improved FVM-LBFS method was developed for the numerical simulation of hypersonic flow.With the new improved switch control function based on the pressure and temperature,this method realizes the precise control of numerical dissipation of inviscid flux in LBFS method,and extends the application scope of non-uniform grid by introducing the slenderness ratio correction coefficient of grid cell,which overcomes the shortcomings of the existing lattice Boltzmann method in simulating hypersonic flow.A series of numerical calculations show that the improved FVM-LBFS method can simultaneously capture complex strong flow and accurately predict the aerodynamic thermal parameters of the thermal boundary layer in the hypersonic flow numerical simulation,and there will be no shock instability such as “carbuncle phenomenon”.This method is simple and efficient,and its stability and accuracy are reliable.It extends the application of the lattice Boltzmann model in the field of hypersonic flow,and provides calculation basis for the research of hypersonic fluid-thermalstructural multi-field coupling numerical simulation method in subsequent chapters.Thirdly,we explored and established a calculation method of structural heat conduction based on the FVM-TLBFS method.This method successfully constructed 2D and 3D TLBFS flux solvers using the existing efficient LBE model to solve the numerical flux of structural heat conduction equation,and the corresponding numerical examples are verified.The FVM-TLBFS method is simple and efficient in solving structural heat conduction,and can be applied to complex real and complex geometric shapes.It improves the traditional first-order accuracy of heat transfer calculation based on the finite volume method to second-order accuracy,which provides theoretical basis and method support for the study of the integrated method for the problems of the coupling between aerodynamic heating and structural heat transfer.In addition,the finite element method of structural thermal stress-strain based on isoparametric element is introduced in detail,which provides technical support for the subsequent analysis of hypersonic static aerothermoelasticity.Numerical calculations show that the different numerical solutions of linear equations have a great influence on the computational efficiency of the finite element method.Compared with the generalized minimal residual method,the conjugate gradient method has superlinear convergence characteristics with less storage and convenient calculation.Fourthly,based on the above research foundation,a new integrated calculation method for the multi-physical coupling of hypersonic flow field and structure heat transfer based on hybrid FVMLBFS method is established.In the method,the macroscopic Navier-Stokes(N-S)equations and structural heat transfer equation are unified into the same control equtions and uniformly discretized by the finite volume method;and the mixed lattice Boltzmann flux solver is used to calculate the flow field flux and structural energy equation flux,respectively.At the same time,a new dual thermal resistance model is proposed to calculate the thermal properties at the fluid-solid interface.The flow field calculation is synchronized with the structure heat conduction to advance in time.In order to improve the efficiency of unsteady calculation,the adaptive time step based on PID control is used instead of the fixed time step.The numerical results show that,compared with the traditional partitioned coupling method,the integrated method can quickly solve the problem of steady coupling of aerodynamic heating and structural heat transfer steady,which improve the calculation efficiency.And this method has better calculation stability with less dependence on grid scale and time scale.The present solver can predict accurately the thermal properties of hypersonic fluid-thermal-structural problems and has the great potential for solving fluid-thermal-structural problems of long-endurance high speed vehicles.Then,to solve the problem of static aerothermoelasticity of hypersonic vehicle,a new integrated method of static thermal aeroelasticity is established.This method integrates aerodynamics,aerodynamic heat,structural heat conduction,and structural displacement in an integrated synchronous solution.The solution simplifies the static aerothermoelasticity calculation process,and does not require additional complicated data interpolation and data exchange strategies,which saves coupling calculation time and improves the steady-state analysis efficiency.The static aerothermoelasticity calculation and analysis of the high-speed two-dimensional hollow wing and the three-dimensional solid wing are carried out respectively.The calculation results show that,the static thermalaeroelasticity and the static aeroelasticity have a greater bending deformation effect on the twodimensional hollow wing,and the bending deformation has a significant effect on the aerodynamic performance of the wing,which cannot be ignored;compared with the synchronous iteration method(IFHS),the static thermal-aeroelastic calculation method(FH-S)at a steady-state structure temperature is not accurate enough,resulting in errors in the prediction of the structural static aerothermoelasticity;The static aerothermoelasticity will produce a strong force-heat-structure coupling nonlinear effect on the wing structure,resulting in a significant amplification effect of the structural deformation,which will have a serious negative impact on the flight performance and structural safety of the aircraft.In summary,it is of great significance for the overall design and structural strength analysis of hypersonic vehicle to accurately predict the static aerothermoelasticity of the structure.Finally,the main research contents and innovations points of the thesis are summarized,and the subsequent development of design techniques is prospected. |
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