A pure tone phenomenon has been observed at 460 Hz in a PWR steam line. The acoustical energy has been identified to be generated in an open gate valve and to be of cavity noise type. The objective here is to understand the flow acoustic coupling in the cavity and in the duct. Both experimental and numerical investigation ways are used. The flow acoustic phenomena are modeled by computing the Euler equations. Two different computations are carried out: in the first one, a pure Euler modeling is used, in the second one, a boundary layer obtained from experimental data is introduced in the computation in order to have a realistic flow profile upstream the cavity. In the first computation, the acoustic excitation due to the cavity is qualitatively retrieved but the frequency is too high compared to the experimental one and no cavity duct coupling is detected. In the second computation, the frequency of the cavity oscillation is very close both the theoretical one and the experimental one. As it is also very close the frequency of the first transverse mode of the duct, the two modes of oscillation (the cavity one and the duct one) are coupled.
This paper presents a computational tool for industrial aero-and hydroacoustic applications. This tool solves the three dimensional linearized Euler equations with using a dispersion-relationpreserving scheme in space associated with a fourth order Runge-Kutta algorithm in time. An image method provides precise boundary conditions and may be used to exactly specify a zero normal velocity at a wall. An original implementation of an artificial selective damping limits the attenuation of the signal without loosing its efficiency on spurious numerical modes. Three industrial applications of this tool are then presented : • The first one concerns the propagation of a depressurization wave in a nuclear reactor. This study allows an improved description of the process than that obtained from a global dimensional model. • The study of the propagation and of the generation of noise in a butterfly valve is then presented. Numerical results match the experimental data both for the transfer matrix and the acoustic source. • The acoustic study of a 216 MW gas turbine exhaust duct constitutes the third illustration of the method.
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