Application Of EFG Method To Acoustic Structure Coupling And Transient Heat Transfer Topology Optimization

In power engineering and automotive industry,key components such as engine exhaust manifold and catalytic converter have an important impact on the performance of structural noise reduction and heat transfer enhancement.At present,the common numerical methods in Computational Acoustics and numerical heat transfer are boundary element method(BEM),finite volume method(FVM)and finite element method(FEM).Among them,FEM is prone to dispersion errors when dealing with acoustic problems.At the same time,mesh based numerical methods often have problems such as sawtooth,checkerboard and mesh dependency in the topology optimization of heat transfer structures.Element free Galerkin(EFG)method is a mature element free method,which requires only node discrete information,does not need mesh generation,and has high calculation accuracy.In this paper,the EFG method is used to study the acoustic structure coupling analysis and the topology optimization of transient heat conduction,and the influence of relevant parameters and the optimal topology is discussed.The main research contents are as follows:The discrete governing equations of acoustic analysis are derived by EFG method,and the EFG calculation model of two-dimensional cavity problem is established.The influence of weight function,influence domain coefficient and penalty factor of EFG method on the calculation accuracy of two-dimensional acoustic problems is discussed,and the selection suggestions of weight function and the reasonable value range of influence domain coefficient and penalty factor are given;The computational accuracy and efficiency of EFG method and FEM in two-dimensional cavity problems are compared.The results show that both EFG method and FEM have good accuracy and stability at low wave number;However,at high wave number,EFG method has good advantages,its calculation accuracy is much better than FEM,and there will be no acoustic dispersion problem in FEM.The discrete control equation of acoustic structure coupling analysis is derived by EFG method considering the acoustic domain with simple harmonic wave and the structural domain subject to simple harmonic excitation force,and the meshless EFG method calculation model of acoustic structure coupling analysis is established.The correctness and effectiveness of the model are verified by programming.The results of acoustic field analysis and acoustic structure coupling analysis are compared.The effects of amplitude and wave number of harmonic exciting force on displacement and sound pressure distribution are discussed.Taking the transient thermal flexibility and the transient thermal dissipation efficiency as the objective functions,the transient heat transfer topology optimization model of orthotropic heat transfer structure is established by using EFG method.The effects of transient thermal load,transient heating time,anisotropic thermal conductivity factor and material orientation angle on the optimal transient heat transfer topology and objective function are discussed with relevant examples,and the reasonable range of relevant parameters is given;The results show that the transient effect of EFG topology optimization model with transient heat dissipation efficiency is much stronger than that of EFG topology optimization model with transient thermal flexibility.Based on the EFG method,this paper studies the coupling analysis of acoustic structure and the topology optimization of transient heat transfer.The results show that the EFG method has high accuracy of sound pressure and displacement,and the optimal topology of transient heat transfer has high resolution,clear boundary and is easy to manufacture.It has important theoretical guidance for the noise control of engineering structures and the lightweight design of transient heat transfer structures.