Study On The Sound Field Characteristics Of Muffler Based On Meshfree Weak-strong Method

Meshfree method was started at the end of the 20 th century.Since meshfree method has high computational efficiency and does not need grid division compared with numerical methods such as finite element and boundary element,it has become a research hotspot in recent years.Meshfree method has been widely used in the fields of fluid mechanics,dynamics and solid mechanics.However,the application of mesh-free method in the field of acoustics is still rare.Muffler is widely used to reduce noise pollution in engineering practice,and its acoustic performance is used to measure the effect of the muffler.As finite element method and other numerical methods rely on the division of the mesh,this thesis uses meshfree method to calculate and analyze the acoustic performance of the muffler.This thesis systematically introduces the solving process of weak-form meshfree method and strong-form meshfree method in acoustic performance calculation of muffler,including the construction of shape function,the discretization of system equation and the derivation of eigenequation,and the application of collocation technique to solve transmission loss.The weak-form meshfree method program is designed to solve the eigenvalue of circular cross section,irregular quadrilateral cross section and perforated cross section.A strong-form meshfree method program is designed to study the influence of the parameters of radial basis function,the size of support domain and the number of nodes on solving the eigenvalue of circular cross section.Based on the advantages of strong-form meshfree method and weak-form meshfree method,a new meshfree weak-strong method is proposed.The programs of strong-form meshfree method,weak-form meshfree method and meshfree weak-strong method are written.The calculation results of the three meshfree methods are compared and analyzed,and the calculation accuracy and efficiency of the weak-strong meshfree method are verified.Compared with the finite element method,the weak-form meshfree method has higher calculation accuracy and efficiency.The strong meshfree method has higher computational accuracy and does not depend on the background grid,so its computational efficiency is higher than that of the weak-form method.Weak-strong meshfree method has higher calculation accuracy and efficiency when solving expansion cavity muffler and perforated pipe muffler.When designing the muffler with expansion cavity,the acoustic performance of the muffler can be improved by choosing the appropriate length of the cannula and the expansion cavity.However,the influence of aperture,perforation rate and sound-absorbing material of perforated pipe muffler is mainly concentrated in medium and high frequency,so it is necessary to select appropriate parameters to improve the silencing effect of muffler.