Aero-acoustic Noise Control Of The Valve With The Help Of The Aero-Acoustic Numerical Simulation

Valves are essential parts of piping systems and their hydro-dynamic noise is one of main noise sources in ship's piping systems.The optimization of the valve's inner flow-field is an effective method to control the valve's hydro-dynamic noise.The noise reduction approaches with the help of hydro-acoustic numerical simulation have been extensively developed and applied in the engineering in these years.The hybrid CFD/CHA Approaches are applied in this paper,and the CFD software FLUENT and the acoustic software ACTRAN are used to numerically simulate and analyze the fluid-fields,equivalent aero-acoustical source fields and sound fields in a stop valve and its improved type with small hole muffler at several flow velocities.The noise reduction effects and mechanics of the aperture noise reduction device are calculated and analyzed quantitatively.The acoustic resonance characteristics of these two types of valve chambers are obtained by numerically simulating the acoustic responses of the valve chambers with a white noise plane source at the valve entrance or exit.And the influences of the acoustic resonance characteristics of valves' chambers on the valve noise are obtained by comparing between the sound pressure spectra with and without flow.It shows that the acoustic resonance has a crucial role to the valve noise.The 3D visualizations of equivalent aero-acoustical source fields in the valves,which are convenient for engineering applications,are obtained by adding UDF module to calculate the source term of Lighthill's equation in FLUENT.The mean flow and the velocity fields of POD modes are obtained by applying the Proper Orthogonal Decomposition(POD)analysis to the velocity fields projecting to the valves' main vertical section-plane.And the relationships between coherent structures of the flow and aero-acoustical sources are analyzed to clarify the noise generation mechanisms.