DID YOU KNOW? DTIC has over 3.5 million final reports on DoD funded research, development, test, and evaluation activities available to our registered users. Click HERE
to register or log in.
Microscale Pressure Fluctuations Measured within the Lower Atmospheric Boundary Layer,
BRITISH COLUMBIA UNIV VANCOUVER INST OF OCEANOGRAPHY
Pagination or Media Count:
An instrument was developed to measure the static pressure fluctuations within the turbulent flow of the atmospheric boundary layer. This instrument was used to measure some of the properties of pressure fluctuations over a flat boundary and over water waves and has provided the first reliable pressure data within a turbulent boundary layer. For all observations over a flat boundary the root-mean-square pressure produced by the boundary layer turbulence was about 2.6 times the mean stress. The spectra had a power law behaviour with a mean slope of -1.7 for scales above the peak of the vertical velocity spectrum. Pressure fluctuations were approximately spherical in shape, and propagated downstream at a rate equal to the local mean wind. Pressure measurements near wind generated waves showed a large spectral hump at the wave frequencies. The amplitude of this hump increased, and its vertical rate of decay decreased, as the mean wind speed increased. The phase difference between pressure and waves during active generation was found to be about 135 degree, pressure lagging waves. This did not change vertically. Author
APPROVED FOR PUBLIC RELEASE