Computation of Flow-induced Sound from Gust Interacting with a Vibrating Cascade Using Body Force Model
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[Abstract] Nonlinear Euler equations are solved to study the radiated sound from a vibrating 2-D cascade with one transverse degree-of-freedom in a subsonic flow. To consider the cascade motion, an inviscid and compact body force model, on the basis of immersed boundary method, is utilized to model moving walls on an orthogonal Cartesian grid. The vibration-induced Parker’s β acoustic resonance mode is numerically found using our in-house high-order computational aeroacoustics solver combined with the inviscid body force model. Furthermore, to find the possibility of exciting the Parker’s mode from gust-induced vibration and sound of the cascade, the fluid-structure coupled equation is solved in our present simulation without updating the background grid due to the adoption of body force model. It is the acoustic anti-resonance, rather than Parker’s resonance mode, is observed for the first time at the frequency ratio (cascade natural frequency/gust frequency), 1.0, although the current parameters, such as cascade configuration, excitation frequency and inter-blade-phase-angle of the cascade, are originally set to excite the resonance. The anti-resonance obviously causes the approximate zero unsteady loading on the cascade and silent sound field. Besides, the conducted numerical experiments also indicate the significance of flow-structure-sound coupled prediction methods and that it is probably inappropriate to utilize low-fidelity CFD tools combined with acoustic analogy theory to calculate the turbomachinery noise when the strong interference happens in the adjacent blades, especially near resonant status