Velocity and temperature scaling in a rough wall boundary layer
Measurements of the three velocity fluctuations u, v, w and of the temperature fluctuation straight theta have been made in a turbulent boundary layer roughened by wall-mounted spanwise cylindrical rods regularly spaced in the streamwise direction. Power-law exponents have been estimated for spectra, cospectra, and the corresponding structure functions associated with u, v, w, and straight theta at various locations across the layer. In the scaling range, the u and v spectra exhibit the largest and smallest slopes, respectively. The slope of the temperature spectrum is quite close to that of the spectrum corresponding to the mean turbulent energy <q(2)>. The scaling range slope of the ustraight theta cospectrum is greater than that of the uv cospectrum which, in turn, is slightly larger than that of the vstraight theta cospectrum. These observations are fully supported by the relative behavior of the structure functions. The magnitudes of the scaling exponents decrease as the wall is approached while those of the intermittency exponents increase.
Antonia
RA
Department of Mechanical Engineering, University of Newcastle, New South Wales 2308, Australia.
Smalley
RJ