Variation of the peak gust speed over an isolated hill

Abstract

This thesis describes the behaviour of the peak-gust speed over an isolated hill by studying wind tunnel models. A brief description of relevant background theory from literature has been summarised. The Askervein Hill model which had been used previously in several tests for the Askervein Hill Project was reused in this project. Measurements of the mean wind speeds, RMS velocity and the gust factors at different averaging time were made over the Askervein Hill model at 10 metres height and 1, 2 and 3 hill heights. Experimental evidence shows that the gust factors in the attached flow over a simple isolated hill are directly related to the local turbulence intensity and are largely independent of special hill effects. The values indicated by the New Zealand and Australian Draft Building Codes for the variation in mean wind and gust speed topographic multipliers over a low isolated hill were compared with the experimental data. It shows that both Codes appear adequate for the example considered.