The transient response characteristics of compliant coating to pressure fluctuations

Abstract

The amplitude and phase lag of surface deformation were determined for a compliant coating under the action of turbulent pressure fluctuations. For this purpose, pressure fluctuations were measured experimentally. The amplitude and duration of coherent wave train of pressure fluctuations were investigated using digital filtration. The transient response was calculated for stabilization of forced oscillations of the coating in approximation of local deformation. The response of coating was analyzed with considerations of its inertial properties and limited duration of coherent harmonics action of pressure fluctuations. It is shown that a compliant coating interacts not with the whole spectrum of pressure fluctuations, but only with a frequency range near the first resonance. According to the analysis, with increasing elasticity modulus Of the coating material E, deformation amplitude decreases as 1/E, and dimensionless velocity of the coating surface decreases as 1/root E. For sufficiently hard coatings, deformation amplitude becomes smaller than the thickness of viscous sublayer, while surface velocity remains comparable to vertical velocity fluctuations of the flow.