A new technique for rapidly obtaining vertical profiles of
vertical velocity and temperature in a thermally stratified
turbulent shear flow has been developed. The technique consists of
a cold-wire probe for temperature measurements and a hot-wire
probe for velocity measurements propelled vertically through a
thermally stratified wind tunnel by a pneumatic piston. Speeds of
nearly 15 m/s are reached as it traverses the central part of the
tunnel. This speed is sufficient to freeze the flow structure
sampled by the sensors, so the measured profiles are effectively
instantaneous. The ultimate purpose of these experiments is to
gain a better understanding of what effectively instantaneous
measurements along a vertical line, as in measurements of oceanic
turbulence and microstructure, can tell us about the mixing
characteristics of the turbulence.
The focus of this thesis is the development of the controls, data
acquisition and analysis associated with the rapid vertical
profiling system. The methods to control the traverse system, to
measure its position and velocity, and to obtain samples equally
spaced in height using triggered data acquisition are described.
The entire system is controlled by a computer program coded in
LabVIEW. Due to the high acceleration of the traverse, the
acceleration effects must be taken into account for calibrating
the hot-wire. A new dynamic insitu calibration method for
the hot-wire is described.
Preliminary experiments were performed to evaluate the performance
of the new rapid vertical profiling system. Ensemble-averaged
measurements of the vertical velocity and temperature profiles are
presented and compared with stationary fixed point time-averaged
measurements.