Low-wavenumber turbulent boundary layer wall-pressure measurements from vibration data over smooth and rough surfaces in pipe flow

Open Access
Author:
Evans, Neal
Graduate Program:
Acoustics
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 08, 2011
Committee Members:
  • Dean Capone, Thesis Advisor
Keywords:
  • low-wavenumber
  • turbulent boundary layer
  • surface roughness
Abstract:
The vibration response of a thin cylindrical shell excited by fully-developed turbulent pipe flow is measured and used to extract the fluctuating pressure levels generated by the boundary layer. Parameters used to extract the turbulent flow pressure levels are determined via experimental modal analyses of the water-filled pipe and measured vibration levels from flow through the pipe at 5.8 m/s. Measurements are reported for hydraulically smooth and fully rough surface conditions. Smooth wall-pressure levels are compared to the turbulent boundary layer pressure model of Chase (1987) and the measurements of Bonness, et al. (2010). Results for the smooth pipe match the predicted smooth wall-pressure spectrum and correspond to a normalized low-wavenumber-white level of -41 dB. Pressure levels from the fully rough condition display a low-wavenumber-white level of -28 dB for a surface with uniformly distributed roughness elements, suggesting a 13 dB correction factor for a fully rough surface over a hydraulically smooth surface.