GPPS-2017-115 NUMERICAL INVESTIGATION OF NOISE CHARACTERISTICS FOR THE VORTEX-INDUCED VIBRATION OF A CIRCULAR CYLINDER

The noise characteristics for the vortex-induced vibration of a circular cylinder at low Reynolds number is investigated by utilizing a high-order in-house solver, which solves the compressible Navier-Stokes equations based on immersed boundary method. The benchmark problems about noise generation from a fixed and in-line oscillating circular cylinder are adopted to validate the in-house solver. Good agreements are obtained with the previous direct numerical simulation. Finally, the vortex-induced vibration of a circular cylinder at low mass ratio in a flow Re = 100 and 0.2 Ma  is simulated. It is found that noise amplification or attenuation in the far field highly depends on the vibration modes which are up to the reduced frequency in this paper. INTRODUCTION Vortex-induced vibration (VIV) is one of the most typical phenomena for fluid-structure interaction. It happens in many practical problems, such as cables in truss works, wind-induced vibration of buildings and current-induced vibration of ocean structures (Sarpkaya, 1979). Many works have been performed to investigate the fluid force on the bluff body and the body motion law in the past (Singh and Mittal, 2005; Blake, 1986). Little studies, however, have been performed to investigate the corresponding noise characteristics from the VIV. Only three kinds of methods are developed to evaluate the vibration influence on the farfield noise, that is, analytical method (Blake, 1986), hybrid method (Farassat, 2001) and direct computation (Inoue and Hatakeyama, 2002). It is difficult for the first two methods to consider the strong interference among the fluid, structure and sound, while the direct computation is identified a powerful tool to take into consideration all the interference effects. The present direct computation methods for the flowinduced noise problems are mostly based on the body-fitted grid. When flow-induced noise from moving boundaries is simulated, the locally moving-grid technique or dynamically overset grid is usually adopted. The confliction in the grid resolution and grid generation efficiency limits the bodyfitted-based method to be able to only consider the simple body and simple motion mode (Inoue et al., 2003), when low dissipation and low dispersion high-order numerical schemes in computational aeroacoustics (CAA) are adopted. To simulate the flow-induced noise from immersed bodies with complex motion modes, we conclude the following four optimal criteria “2H2U”, to develop the corresponding high-order computational models: (a) High-resolution grid for complex geometries; (b) High-efficiency treatment of the relative motion between moving boundaries and grid; (c) Unified high-order central schemes even near wall boundaries; (d) Unified large-stencils selective artificial damping or filtering even near wall boundaries. It is found that only Cartesian-type methods are possible to satisfy the above “2H2U” criteria. Among the Cartesiantype methods, the penalization method (Liu and Vasilyev, 2007) and influence matrix method (IMM) (Sun et al., 2012) belong to the immersed boundary (IB) method (Peskin, 1972). They are promising to satisfy the “2H2U” criteria, due to the suitable body force model. The present high-order inhouse solver is established on the extended IMM and prediction-correction time marching scheme. And it can keep high-order quality away from the wall boundaries and keep formally high-order quality near the wall boundaries. Besides that, it achieves a high parallel efficiency due to the adoption of Cartesian grid and the message passage interface (MPI). The paper is organized as follows. In Section 2, the adopted in-house solver is introduced. In Section 3, validation is performed for two benchmark problems. One is sound generation by a fixed circular cylinder in a laminar flow. The other is the inline oscillation of a circular cylinder in a static fluid. In Section 4, the VIV of a circular cylinder at small mass ratio 10 in a laminar flow is simulated. The noise characteristics for different reduced frequencies are analyzed.