|dc.description.abstract||An experimental and theoretical investigation of the turbulent free
convection boundary layer on a vertical plane surface in air has been
The experimental investigation comprised observations of both the
streamwise development from a laminar state to a 'fully developed' turbulent
flow and the lateral structure of the turbulent flow at Grashof numbers
up to 7x 1010. Measurements were taken of the probability density
distributions of temperature and streamwise velocity as well as power
spectra of these quantities. The results show that a periodic flow
structure, present in the early stages of the transition, disappears as the
intensities of temperature and velocity increase to a maximum in the midstage
of the transition and then decay.
Observations in the 'fully turbulent' flow suggest that the flow has a
lateral structure similar to that of a forced convection flow: a viscous
sublayer with mean temperature profiles linearly dependent on the distance
from the plate, a buffer layer which includes the maximum of mean velocity
profiles, and a turbulent layer where the power spectra of temperature and
velocity contain an inertial subrange.
The theoretical investigation comprised a study of the governing
equations and the application of several turbulence hypotheses to the
prediction of the boundary layer flow. Solutions for lateral profiles and
for the streamwise development of velocity and temperature fields agreed
reasonably well with experimental data although there was some disagreement
on the heat-transfer rates. Energy balances of the mean kinetic energy
and turbulence kinetic energy of the turbulent flow were also predicted.
Measurements of the flow were performed with a hot-wire anemometer
and thermocouple sensor in conjunction with digital data processing.
A large part of the work was devoted to the development of suitable data