CFD and aero-acoustic analysis of flush toilet in airplanes.

摘要

With the global expansion of air travel and increase in the fleet size of the aircraft with modern technology, the demand for the reduction of sound levels in the airplane toilet is increasing, as it causes discomfort to the passengers. During the cleansing process by air (vacuum), high level of acoustic noise is produced due to the turbulent vortex flow and boundary layer flow separation in the bowl. This study involves investigation of noise generation in a vacuum toilet during the evacuation of bowl in a flush cycle and to identify means to reduce the noise below a target level. In order to identify and present noise reduction concepts for vacuum flush toilets, a multi-physics CFD simulation analysis model is developed based on a representative CAD model of the actual toilet bowl and based on the actual flushing conditions that are typically used. The model involves coupled solutions of flow dynamics and noise generation/dissipation using a commercial code. CFD analysis is performed based on a selected acoustic noise model and results are compared with the experimental noise data. An effort was made to change the turbulence involved during the flow which resulted in being a positive approach. Different broadband noise source models were analyzed to understand the flow-induced noise generation. Sensitivity analysis is performed to evaluate the effect of variation in toilet throat design on the generation and dissipation of toilet flush noise, and identify ways to reduce noise generation.