FLOW-INDUCED VIBRATION OF A LONG FLEXIBLE SHEET IN TANGENTIAL FLOW

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Date
2018
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ACAD SCI CZECH REPUBLIC, INST THERMOMECHANICS, DOLEJSKOVA 5, PRAGUE 8, 182 00, CZECH REPUBLIC
Abstract
During certain stages of the offset printing process, the paper sheet is conveyed by the blower air. Vibration and acoustic measurements confirmed that under certain circumstances the sheet undergoes flow-induced vibration with significant amplitudes, generating a serious noise source at the same frequency. In order to understand the fluid-structure interaction between the flexible paper sheet and air exiting the nozzles, and to assess the conditions when unstable paper vibration with large amplitudes is possible, a simplified analytical model was developed. The paper sheet, modeled as a flexible 1D chain, is fully coupled to quasi-1D inviscid flow. Under the assumption of small deflections, the coupled equations can be analytically solved in frequency domain, yielding complex eigenfrequencies of the system. For a given flow velocity (corresponding to a specific air pressure setting), the real and imaginary part of the eigenfrequency determines whether the system is stable or unstable.
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offset printing systems, flutter, fluid-structure interaction
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