Numerical investigation of cavity noise from a complex outflow-valve pipe

During flight, in order to ensure the comfortable environment for passengers and the stable pressure in the cabin, the aircraft needs to provide fresh air continuously through the environmental control system. Therefore, there must be a valve connecting the interior and exterior of the cabin on the aircraft, which is usually called outflow valve. The outflow valve is connected to the aircraft through pipelines, thus forming a cavity structure on the surface of the aircraft. When the high-speed air flows pass over the cavity structure, vibration and noise are generated. The vibration and noise affect the comfort of passengers and cause damage to the aircraft structure in severe cases. In this paper, the noise characteristics of the closed and open configuration of the outflow valve are analyzed by unsteady numerical simulation. The study found that the fundamental frequency of the cavity does not change under the closed and open configurations of the valve. The noise of the closed configuration is higher than that of the open configuration at fundamental frequency, but at high frequency range the noise of the open valve configuration is higher. When the valve is open, there is additional high frequency tonal noise in the downstream of the valve.