ESTUDO DO COMPORTAMENTO VIBRATÓRIO EM TUBOS RESSONANTES UTILIZANDO SÍNTESE MODAL DE COMPONENTES

The resonant cavities coupled in ducts, also known as Quarter-Wavelength Tube, perform their function as acoustic filters capable of significantly attenuating noise over wide frequency ranges. These filters can be used in various applications, especially in industrial tubular systems, buildings and vehicles. These resonant cavities have as their operating principle the sound reflection due to the change of cross section between the coupled structures, in this case, between the main duct and the quarter-wavelength tube. However, when it is introduced a new structural element into the original duct system, the vibration dynamics of the resulting system should be analyzed in order to guarantee structural integrity and thus avoid possible resonances. For this, the modal analysis is a classic and efficient tool for estimating natural frequencies and mode shapes. Tubular systems applied for heating, ventilation and air-conditioning (HVAC) purposes are generally large in both cross-sectional area and length. For modal analysis, experimental and numerical methodologies are the most used. Furthermore, in view of the complexity of these systems and especially of the large geometric dimensions, the Component Mode Synthesis (CMS) method appears as an alternative to the previous ones, mainly in terms of time reduction and computational effort. CMS works with reduced models of substructures from the original system, and later, these are synthesized in order to obtain the dynamics behavior of the complete system. In this context, the objective of this work is to implement the CMS technique in a quarter-wavelength tube silencer using finite element modeling. The validation of the synthesized model was done by modeling the complete system also in finite elements. The results obtained were satisfactory, demonstrating efficiency and reduction of time and computational effort using CMS.