On Modeling Structural Excitations by Low Speed Turbulent Boundary Layer Flows

Abstract : This report documents the results of an investigation on the modeling of structural excitations by low speed turbulent boundary layer flows. This work critically examines various spectral models, both wave vector-frequency spectra and cross-spectra. Many of these models became available after the publication of the monograph by Blake (1986). These models are used to predict the pressure spectra measured by flush-mounted hydrophones of various size and location on buoyantly propelled vehicles. Predicted hydrophone responses are compared with experimental data. Recent publications by Chase (1991, 1993) and Dowling (1998) demonstrate that near wall viscous shear stress contributions to the low-wave number pressures need to be included. By combining the Chase 1987 inviscid flow model with his 1993 semi%empirical shear stress model at low wave numbers, a so called Combined Chase Spectrum is developed and presented as the most comprehensive model for underwater applications.