Structure of a rural atmospheric boundary layer near the ground.
Thesis DisciplineMechanical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
This thesis describes instrumentation and software developed to make detailed measurements of wind structure in the lower part of the planetary boundary layer. The instrumentation is based on a 190 mm diameter four bladed polystyrene propeller anemometer, designed to give a digital output. Arrays of three such instruments mounted orthogonally are used to measure the instantaneous wind vector as it varies with time. Data from up to 36 of the anemometers i.e. 12 arrays can be recorded simultaneously. The data is recorded onto a 7 track digital magnetic tape compatible with the University’s Burroughs 6712 Computer on which the data is analysed using software written in Algol. The limitations of the propeller anemometer as a sensor of atmospheric turbulence, the data recording method, and the computer analysis system used, are discussed in detail. The complete facility was found to work well. The results of the two field experiments using the instrumentation and software developed are presented. The first experiment was concerned in investigating the variation of the wind structure to a maximum height of 20 m. The measured results compared favourably with accepted values of the turbulence parameters from the literature. A limitation of the vertical component anemometer was observed as it filtered out high frequency velocity fluctuations when placed near the ground. Correlation functions were also found to be influenced greatly by non-stationarities in the flow. The second experiment was concerned with investigating the variation of the wind structure properties at a height of 10 m in a line perpendicular to the mean wind direction which had been chosen to study. From the appropriate horizontal space correlations, the integral length scales YL u,YLv and YLw were evaluated and found to be in good agreement with other similar full scale field measurements reported in the literature. It was found that YL u, , YLv and YLw  20 – 30 m and YLw  4 - 6 m.