Numerical studies on the acoustic characteristics of the U-shaped corrugated pipes and application investigations

Abstract

This paper presents a numerical study on the effect of structural parameters on acoustical transmission loss of U-shaped corrugated pipe using the control variable method. Then, the interactions between the cutoff frequencies and structural parameters are modeled based on the dimension analysis method using the numerical results. An investigation into the application of the U-shaped corrugated pipe into a simple expansion chamber muffler is carried out using both numerical and experimental methods. The results show that the U-shaped corrugated pipes have unique acoustic characteristics in noise attenuation, which resembles a resonant muffler. Furthermore, the numerical results of the transmission loss of U-shaped corrugated pipes are in good agreement with experimental results, which indicates that the transmission loss results obtained by acoustic finite element method is accurate. In addition, the corrugation height, corrugation length, and corrugation internal diameter are the factors that affect the acoustical behavior of the corrugated pipe most significantly. Moreover, the proposed empirical formulas for predicting the cutoff frequencies of U-shaped corrugated pipes are verified with high accuracy and with a prediction error within ±3.0%. What is more, the application of U-shaped corrugated pipes in expansion chamber muffler can effectively reduce the noise in the mid- to high-frequency band, which is useful to reduce the muffler volume and the amount of sound-absorbing material. Hence, automobile mufflers can be designed in a much more environmentally friendly way. In conclusion, this work could provide a theoretical basis for the acoustical design of U-shaped corrugated pipes, and it initiates a new research and application field for corrugated pipes as well.