Correlation Between Sound Pressure and Fluid Flow of Vacuum-Assisted Toilets*

Vacuum-assisted toilets are used in commercial aircraft and come with an unwanted stigma of being uncomfortable and loud. A quieter toilet design has been developed by modifying the waste tube geometry. The goal of this work is to understand quantitatively how this tube geometry modification to a vacuum-assisted toilet reduced its radiated noise. To better understand the noise reduction obtained using the modified waste tube, high-speed video of the flow passing through clear tubes of the same geometry has been recorded and analyzed. An open source Particle Image Velocimetry (PIV) MATLAB code called OpenPIV has been used to determine both the direction and speed of the flow. Correlations between the flow field and the noise reduction for the modified tube geometry will be shown.