Aeroelastic instability of paper sheet in an offset printing press

A simplified and efficient computational model of a thin flexible plate coupled to one-sided axial narrow-channel airflow is presented, modeling flow-induced vibration of a paper sheet transported by short pulses of compressed air encountered in the infeed system of offset printing press machines. The mathematical model is based on a discrete chain of masses, torsional springs, dampers and massless rigid rods. The linearized equations of motion coupled to inviscid flow equations are derived and solved analytically in frequency domain. The structural model is validated on the case of bending of a clamped-free beam under gravity and the elastic and damping constants are identified from measurements. Aeroelastic instability is investigated for three fluid-to-solid mass ratios ranging between 0.24 and 1.4, corresponding to three types of paper used in real offset printing machines. The growth rates and frequencies of the coupled system for supercritical flow velocities are reported and analyzed.