Abstract:
An investigation of the fluctuating pressure in turbulent
shear flaws at low Mach numbers is described. The treatment is
both theoretical and experimental although, in the latter case,
present limitations of pressure transducer design have restricted
the experiments to surface measurements in wall shear flows over
rigid plane boundaries.
The turbulent flat-plate boundary layer is studied in detail.
Calculations from existing turbulent, velocity data show that the
ratio of the root-mean-square wall, fluctuating pressure to free
stream dynamic pressure is approximately twice the local skin friction
coefficient Cf. . The dependence on Cf has been verified
for the Reynolds number range 3 x 105 to 8 x 106. The factor of
proportionality was 2.2.
Although part of the test programme was performed in a low-noise
wind-tunnel, it was not possible to determine completely the pressure
power spectral density from laboratory measurements. This problem
has been resolved by full-scale flight measurements on the wing of
a high performance glider. The power spectral density of the
surface pressure fluctuations was found to vary as the square of
the frequency at low frequencies, a result in agreement with analysis
of the turbulence-mean shear contribution, to the wall pressure … [cont.].
