The Response of Elastic and Viscoelastic Surfaces to a Turbulent Boundary Layer

Abstract

The unstable response of elastic and viscoelastic surfaces to a turbulent boundary layer was experimentally investigated in an 18-m towing tank. The compliant surface deformation was measured using a remote optical technique. The “Laser Displacement Gauge” employs a Reticon camera equipped with a linear array of 256 photodiodes spaced 25 microns apart. The device was used to measure the characteristics of two classes of hydroelastic instability waves that form on elastic or viscoelastic surfaces as a reuslt of the interaction with a turbulent boundary layer. The instability waves developing on an elastic surface are symmetric and have a relatively high phase speed and a small wavelength, as compared to the slow and highly nonlinear “static-divergence” waves observed on the viscoelastic surface. The experimentally determined wave characteristics are compared to existing theories on compliant surface instabilities.