Parametric studies on acoustics of corrugated tubes using large eddy simulation (LES)

Airflow through a corrugated tubing can generate loud tonal sounds. The production of these tones, sometimes called as whistling, in a corrugated tubing is an interesting phenomenon because the presence of corrugations in a straight tube transforms the tube into an aerodynamic sound source that may produce significant tones and resonance responses. Corrugations add flexibility to both metallic and non-metallic tubings, making them useful in many engineering, industrial and household applications. Even though corrugations can be used to produce pleasant musical tones in a children's toy called “Magic Whistle,” it can cause noise problems in vacuum cleaners and also results in severe structural failure in “singing risers” on off-shore gas platforms, HVAC ducts and air-conditioning system pipe lines used in aircraft and automotive applications. In this study, interaction of flow with corrugations is modeled with CFD-LES using ANSYS-FLUENT. The predicted whistling frequencies are then compared with experimental values. It is observed that there is a good agreement between experiment, theoretical and numerical analysis. The work also presents a parametric study of eight types of corrugated tubes with different cavity length, width and pitch on their acoustical behavior. The study indicates that decreasing cavity depth and increasing number of corrugations per given length would result in reduced noise level.