I graduated Tohoku University in 2001. I received a Master’s degree in Aerospace Engineering from Tohoku University in 2003; a Ph.D. from Tohoku University in 2006. I have been working at Acoustic Analysis Solution Group of Mechanical CAE Division in Cybernet Systems since 2006. I am a Sales and Support Engineer of Acoustic, Fluid Dynamics and Structure Analysis Software. Currently, he has been studying Flow‐Induced noise and Vibration.
Heat exchangers and boilers are widely used in various plants such as power plants and chemical plants. In the heat exchanger and the boiler, a high level sound is sometimes generated from the tube bank installed in a duct. In tube banks, warm gas flows outside of the tube, and due to the external flow around tube banks, the Karman vortex shedding occurs. At a certain frequency of the Karman vortex shedding that depends on the flow velocity, the resonance phenomenon called the self-sustained tone occurs. The self-sustained tone might cause noise problems in the surroundings, losses due to plant shutdown, etc. For suppression of the self-sustained tone, insertion of baffle plates in the tube bank is generally used. Although the insertion of baffle plates has been adopted for a long time, it is difficult to decide the effective insertion positions. On the other hand, a method using perforated plates has been proposed for the suppression of the self-sustained tones. In this chapter, we review the generation mechanism of the self-sustained tone clarified experimentally and numerically, and the methods for suppressing a self-sustained tone using baffle plates and perforated plates.
Part of the book: Noise and Vibration Control
In many engineering applications, obstacles often appear in the wake of obstacles. Vortices shed from an upstream obstacle interact with downstream obstacle and generate noise, for example blades in a turbomachinery, tubes in a heat exchanger, rotating blades like a helicopter and wind turbine and so on. This phenomenon is called wake-body interaction or body-vortex interaction (BVI). The rod-airfoil and airfoil-airfoil configurations are typical models for the wake-body interaction. A rod and an airfoil are immersed upstream of the airfoil. In this chapter, we review the noise mechanism generated by the wake-body interaction and show the numerical results obtained by the coupling method using commercial CFD and acoustic BEM codes. The results show that depending on the spacing between the rod or airfoil and the airfoil, the flow patterns and noise radiation vary. With small spacing, the vortex shedding from the upstream obstacle is suppressed and it results in the suppression of the sound generation. With large spacing, the shear layer or the vortices shed from the upstream obstacle impinge on the downstream obstacle and it results in the large sound generation. The dominant peak frequency of the generated sound varies with increase in the spacing between the two obstacles.
Part of the book: Vortex Dynamics Theories and Applications