Wind flow and structure over Gebbies Pass, New Zealand: A comparison between a wind tunnel simulation and field measurements
Thesis DisciplineMechanical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
This thesis presents the result of a study to show the validity of using wind tunnel modelling to predict the wind flow over a complex terrain situation. A wind tunnel traversing system which is particularly suitable for flow measurements over topographical models, is described. A 1:4000 undistorted geometric scale model of Gebbies Pass in the South Island of New Zealand was prepared. The required approach flow boundary layer was simulated in the boundary wind tunnel in the Department of Mechanical Engineering. This was confirmed by field measurements on the approach terrain with the Department's instrumented 20m tower and TALA kite equipment. The model was tested in three forms of construction; terraced, contoured (terraces filled with Polyfiller), and with shelterbelts and scrub areas added. The results of the wind tunnel tests are presented in the form of isotach and isoturb contours for lateral and longitudinal cross sections through the models. The longitudinal component of the energy spectrum, autocorrelation function, pūw Reynolds stress profiles and integral length scales LUX were also measured. They are presented and compared, where possible, with measured and theoretical values. The results for the various forms of construction are correlated and show that the terraced form of construction differs significantly from the other forms. On six days when strong south-west wind events prevailed, teams of investigators surveyed field sites in the area, measuring wind speeds at a height of 10m. The results for this of the field programme are presented and correlated with the results obtained from the models. Detailed wind structure measurements of the velocity, turbulence intensity and pūw Reynolds stress profiles, autocorrelation function and the u, v and w components of the energy spectrum were made at two field sites up to a height of 20m. One site was on the level approach terrain to the region and the other was on top of the Gebbies Pass saddle. The results are presented and compared with the wind tunnel results and theoretical predictions, where possible, and show good agreement.